Astronomy Cast

It is arguable that humanity now has the technological ability to live on Mars. It would be done at enormous expense and sacrifice, and there are some tricky problems that we haven’t solved yet. Although we could live on Mars, should we? There is a famous quote from Jurassic Park: “Your scientists were so preoccupied with whether or not they could, they didn’t stop to think if they should.” This concept is played out across the sciences, and in planetary exploration, it requires us to ask, all because we can launch humans toward Mars, should we?

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Show Notes

• Framing
• Practical & environmental costs (Earth-side)
• Mission risks & human health
• Life on Mars: daily reality
• Reproduction & generational ethics
• Planetary protection & science first
• Timeframe & infrastructure argument

Transcript

[Fraser Cain]
Astronomy Cast, Episode 770, The Ethics of Living on Mars. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, I’m the publisher of Universe Today.

With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey Pamela, how you doing?

[Dr. Pamela Gay]
It is the most amazing fall day outside. It looks like a Hallmark special with cloudless blue skies, orange and red trees. I just want to go take photos during the golden hour, which is far too early because stupid daylight, time shifted.

[Fraser Cain]
Winter might have been cancelled here. Really? All of my fruit trees still have all of their leaves, still putting on new growth.

It is into November now. Yeah, they have not gotten the message. It has been surprisingly warm, but eventually I’m sure it’ll cool down.

Now I got a new piece of kit, new piece of gear, which I just want to talk about.

[Dr. Pamela Gay]
You did? What did you get?

[Fraser Cain]
I got a eight-inch Dobsonian telescope.

[Dr. Pamela Gay]
Those are the bestest.

[Fraser Cain]
I know, they are the bestest. So I was talking to a patron actually. They were telling me how they were on Facebook Marketplace and they bought a telescope for reasonably inexpensive.

I was like, oh, I should see what prices are like for Facebook Marketplace for telescopes. Just get a sense of the lay of the land out there. Boom, there’s a Skywatcher eight-inch Dobsonian telescope, which is like the perfect telescope.

It is not too small and it’s also not too big. The price was really reasonable, about less than half, maybe a third price of what you pay if you bought it new and shipping and taxes and all that kind of stuff. I was like, yeah, okay, I got to do this.

So I reached out to the seller and bought the telescope and brought it home. And of course we’ve had clouds. I got one quick look at the moon and where you go blind in one eye because it’s so bright.

And I was able to look at Andromeda and I was able to look at the double cluster in Perseus. And so a few things quickly before the clouds have set in, but what a great telescope. So just a reminder, every now and then if you’ve got sort of a telescope on your mind, just check and see what’s going on at Facebook Marketplace and see if someone is selling your dream telescope.

And so now I feel like with the Seastar and the Dobsonian, I have the perfect pair. I can look at Saturn and it’ll look glorious and I can see the bands across Jupiter and the moons, or I can take long exposure images of various nebulae and so on and so forth. So I think that’s the perfect pair now, Dobsonian with one of these new automated telescopes.

[Dr. Pamela Gay]
That is excellent.

[Fraser Cain]
Yeah. So it is arguable that humanity now has the technological ability to live on Mars. It would be done at enormous expense and sacrifice. And there are some tricky problems that we haven’t solved yet, although we could live on Mars.

Should we? All right, Pamela. So this is interesting because I think if there was one aspect of space exploration, of astronomy, of just like my entire career journey, my entire existence as a human being, something that I have evolved my thinking on more than almost any other aspect is human space exploration.

And my guess is that you have as well.

[Dr. Pamela Gay]
Yeah.

[Fraser Cain]
So let’s kind of like go back historically and think about sort of where we were, maybe even before we started AstronomyCast, like where were you with your sort of like becoming interested and excited in human space exploration and humanity living off planet?

[Dr. Pamela Gay]
So the X-Prizes that it was the Ansari X-Prize back when we were starting the show was looking to start the commercial space race with we’re going to accomplish multiple launches in a very short period of time. And this is going to start proving that it doesn’t have to be governments taking me to space. And my take was NASA has so few resources that we need to leverage NASA and governmental funds to do science, to send out the probes, to send out the rovers and the explorers and to not keep doing human exploration, but to leverage human beings as thumbs that can build things and fix things in space.

And I was like, we’ll just leave it to the commercial space agencies to go and take humans on the next step. Like the West Indian Trading Company took merchants on the next step once the government funded voyage of Columbus had found the new world. What I failed to think through in my ignorance was the trading companies led to all sorts of terrible working conditions, led to lots of pillaging of the ecosystem.

And I didn’t necessarily advance civilization. And I fear I was naive in what I thought. I foresaw commercial spaces like ecotourism, and it is absolutely not going to be that.

[Fraser Cain]
So for me, I was, you know, like, I think I grew up on a diet of science fiction. And so just a mainstay of science fiction is that humans are going to live on other planets, that this is just what we’re going to do. When you read the Pine Lines, you read all of the original science fiction books, they talk about humanity being across the solar system.

And it really kind of solidified for me, I read Red Mars, Green Mars, Blue Mars, not necessarily in that order. And that, you know, this was like the practical nitty gritty reality of living on Mars and humanity setting up its existence on Mars. And then that coincided with The Case for Mars by Robert Zubrin.

And then also, I was reading Pale Blue Dot by Carl Sagan. And together, those sort of books made this really compelling case that humanity actually has the technological capability now to live on Mars, we could do it, it’ll only cost about $10 billion. But with a live off the land approach, let’s get cracking.

And I was so inspired that I actually started Universe Today, that I wanted to play a part in sort of cataloging humanities, sort of moving out into space and participating in this dream. And it felt inevitable, and it felt right, and it felt like the right thing to do. And there was a lot of people who would argue with me and go like, it’s crazy, let’s just send robots to Mars.

That’s ridiculous. We don’t need to send humans. I’m like, yeah, but that’s not the point.

The point is not about the science. The point is about us living on another world, that this is our future, that we can explore out into the cosmos. And it starts with us living on Mars.

Once we lived on Mars, then we’ll be living on the cloud tops of Venus and the moon base and asteroids. And we will do asteroid mining, and we will eventually begin to move out to other star systems and so on and so forth, right? And then reality, just day after day after day of reporting, of sort of cataloging what has happened just in our reality compared to what the fantasy was, has brought me deeply back down to Earth, literally.

And now I kind of have this totally different perspective on sort of Mars exploration, both sort of the practical reasons why we may or may not want to do it. And then I think the core of what you’re saying is there’s a lot of ethical issues here that we haven’t even resolved and may never be able to resolve if this is the thing that we are set on doing. So, you know, I mean, obviously there are technical issues that need to be overcome in terms of the gravity, the radiation, the lack of atmosphere, the poison in the soil.

You know, the list goes on and on and on. The distance communication, the lack of resources available to the people living there, so on and so forth. So, you know, we’re approaching this now from a not can we, because I think, you know, I think we can both make the case that we can.

If we really want to have humans be on Mars and we’re willing to expend a lot of resources, we could pull this off.

[Dr. Pamela Gay]
And they’re willing to accept the high doses of radiation that they’re going to be. Oh, yeah.

[Fraser Cain]
Well, this comes to the ethical issue, right? So we’ll get into that. I mean, I think, you know, if we’re willing to spend hundreds of billions, if not trillions of dollars a year from the Earth’s economy, we could make some existence on Mars happen.

If the people who go will be experiencing high degrees of radiation, maybe that’s a personal choice. And then there are issues with future generations who might be born and try to live on Mars. So let’s kind of break down the ethical issues bit by bit by bit.

And I’m going to start with Earth, because I think that’s where this all starts, is that I think most people vastly underestimate what this is going to cost and what sacrifice planet Earth is going to need to make to have even just a handful of people live on Mars.

[Dr. Pamela Gay]
And I have to admit that last week I had a, oh, oh, no moment of doing back of the envelope calculations that turned into spreadsheet calculations. I noticed in the past couple of Starship launches that they talked about wanting to do up to 10 launches a day, that they were planning to produce a Starship every eight hours. And I was like, that is all ludicrous.

But I didn’t pay any real attention to it because SpaceX has lots of things and you wait for them to actually do it.

[Fraser Cain]
Yeah. And sometimes things actually happen.

[Dr. Pamela Gay]
Right. And then what got me was I saw someone post a picture of that jellyfish light pattern that appears in the sky when Starship is firing its engines. And underneath it was a clearly happy and cheerful and excited post along the lines of, just imagine when the sky is full of this happening every few minutes during the Mars windows.

And I was like, wait, what?

[Fraser Cain]
Wait, no, thank you.

[Dr. Pamela Gay]
And so I took a step back and I went to the SpaceX website and I was like, what are they planning here? And their plan is to launch literally thousands of Starships across multiple two month long launch windows to Mars. And if you do the back of the envelope math on 1,000 launches per two month window, for each of those windows, you have to do 25 launches per day to cover the, and the assumption I’m making is for each one Starship that goes to Mars, there is 19 Starships that’s needed to refuel it.

That is actually a completely middle of the estimation. There are people who have much higher estimations, a few people have lower estimations. So that’s just middle of the road.

So if you assume just to refuel each of the 1,000 that is departing, it’s 25 launches per day.

[Fraser Cain]
That’s 25,000 launches.

[Dr. Pamela Gay]
So you have 25 launches a day. This gets the eight Starships produced per day is what’s actually needed. The steel needed for only the 1,000 that go to Mars is a 10th of a percent of all US steel production, which doesn’t sound like a lot.

It’s a lot. But you’re taking what is a completely recyclable material and just sending it all to Mars. Sure.

Sure. And then on top of that, you have to have the cargo launches and you have to have the crew launches. So those are still in addition to the 25 per day, eight per hour that are getting produced.

And that is a number of launches that current research says our atmosphere cannot sustain.

[Fraser Cain]
Yes. Yeah. Yeah.

And I think like you’re taking them at their word and saying, yeah, what would it be if they did launch 1,000 per Mars window that they were planning on setting up a city of a million people on Mars. But even if you don’t take them at that point, like if you go the other end of the spectrum and say, what is the minimum viable resources required to have a colony on Mars that is permanently inhabited? Like maybe it’s a few hundred people.

Like maybe you’re looking at something like a McMurdo station in Antarctica, maybe 1,000 people. I mean, that costs hundreds of millions of dollars to sustain. And that’s here on planet earth.

You’re looking at tens of billions, if not trillions of dollars a year to sustain this. And that is money that could be spent on the economy in other ways. So as you said, you’re sending steel, you’re sending material, and those are relatively low.

Now, people are going to make the argument, well, the price is going to come down. Well, prove it. Right now, the cost to land a payload on the surface of the moon and not even bring it back is in the hundreds of millions of dollars, which is significantly cheaper than it used to be.

And then the Chinese are bringing missions back and they’re in the whatever low billions, hundreds of millions to bring stuff back from the moon. But to go to Mars is sort of next level. Right now, we’re looking at tens of millions of dollars per kilogram to land payloads onto the surface of Mars.

So we do not have the technology currently to deploy that stuff to the surface of Mars. And so right now, if you actually want to live up to that dream, you’re going to have to contribute a huge chunk of Earth’s resources to this process.

[Dr. Pamela Gay]
So while also being destructive to the environment, it’s both sides. Yeah.

[Fraser Cain]
While being destructive to the planet. Yes. Yeah.

And a bunch of those starships are going to burn up when they re-enter the Earth’s atmosphere. They’re going to contribute. It’s like a new worry that we actually didn’t even talk about or we didn’t even know about.

Now, it looks like there’s a high degree of catalytic metals that are being deposited in the Earth’s atmosphere that contribute to atmospheric chemistry and might actually, and that although, you know, we’re getting 100 tons of material from space, we’re producing, we’re putting a lot more of a very specific kind of metal into the atmosphere that is potentially harmful to the ozone layer. So exactly. So we are going to, if we try to live up to the dream, we are going to do, we’re going to have to sort of lose our economy to a certain extent and do damage to our natural environment to make this possible.

[Dr. Pamela Gay]
Yeah.

[Fraser Cain]
Right. And, and, and, and what we get from it is nothing. Right.

Except for some science and knowing that there are people now living on Mars, right? There’s no economy. There’s no value that has returned to Earth for this expense.

[Dr. Pamela Gay]
And it’s like data centers. It’s something that takes up a whole lot of resources without producing a whole lot of jobs. And the, the trade off between allowing people to improve their own state of life versus the notch down, it takes the entire world there.

There’s no way I’ve been able to find to balance those two, especially when you start factoring in, we’re talking about using methane fuels.

[Fraser Cain]
Yeah. So let’s now talk about the journey. And, you know, you brought this up a bit that, that you’re going to spend nine months just getting to Mars and you’re going to be in a radiation environment that is hundreds of times more damaging than what you experience just on a normal day, living down here on the surface of the earth, protected by the atmosphere and the magnetosphere.

You know, what are the implications of that?

[Dr. Pamela Gay]
The most concerning one is we know that being in outer space affects vision. It’s a combination of zero G does bad things to eyeballs. And just like taking a high energy ray to a CCD can blow out a pixel, constant radiation exposure to your eyeballs will ruin your eyeballs.

[Fraser Cain]
But that, I mean, just, I mean, radiation, the eyeballs is one thing, but you’re getting radiation over your whole body.

[Dr. Pamela Gay]
Right. But, but at a certain level, having a bunch of blind people on Mars trying to set up a colony, it seems like a really bad idea. So I’m just going to baseline it at let’s not disable people and then ask them to do the hardest thing possible.

[Fraser Cain]
Sure, sure. But I, I mean, yeah, if there’s a catastrophic, like if this is a really bad solar storm, they’re dead.

[Dr. Pamela Gay]
They’re all dead. Yeah.

[Fraser Cain]
Yeah. You’ve got a crew, you got a hundred people on board, bad solar storm. And it would, you know, if it moved in the direction of Mars, it would take out all thousands of starships.

[Dr. Pamela Gay]
The flare that went off, I think it was either yesterday or the day before would have been catastrophic. And the issue is these are vehicles that I, we’re not real great at, at protecting all of our electronics. And, and so we do have to harden things, but how are you going to harden that many electronics without something going wrong at some point?

[Fraser Cain]
Yeah.

[Dr. Pamela Gay]
The human body, you can’t just encase it in a Faraday cage.

[Fraser Cain]
Right.

[Dr. Pamela Gay]
And, and so it’s, it’s just layer upon layer of ways that things can go wrong and then factor in that we don’t have a clear understanding of what happens to Mars environment in high radiation.

[Fraser Cain]
Yeah. We’re going to get, we’ll get to that in a second, like just the journey there. I mean, the very worst case scenario is there’s a catastrophic solar storm.

Like we’ve seen these happen every couple of years and it takes out the entire fleet that everybody, like literally everybody dies.

[Dr. Pamela Gay]
Yes.

[Fraser Cain]
Right. Because, because everybody experiences a high radiation load.

[Dr. Pamela Gay]
That is not the worst case. The worst case is everyone, but one person dies.

[Fraser Cain]
Maybe. So, so, but, but so now then there is the kind of the inevitable stuff. As you said, there’s issues with the vision.

There’s just an increased radiation load. Like everybody is going to be getting a lifetime’s worth of radiation in a few months and that’s going to increase their chances of getting cancer. Cancer is going to be a very common.

[Dr. Pamela Gay]
Leukemia.

[Fraser Cain]
Yeah. Leukemia. These are going to be thyroid cancer.

These can be very common events on Mars that a much higher percentage of the population on Mars is going to come down with all these different diseases. And then there, and then whatever are the long term downsides of being in microgravity, you know, I think we, we know mostly and know how to deal with many of them. Like they’re going to be working out all the time to prepare themselves.

They’re going to probably have vision problems. Some percentage of people have vision problems downstream. They’ll wear glasses.

They’ll, you know, they’ll, they’ll, you know, so like these, you know, there’s a lot of stuff that we kind of know issues with your brain issues with some of your internal organs, liver, kidney. These are, these are changes in deep space memory. You know, we’ve never put people in deep space for longer than one week.

Right. Right. All of the longterm space exploration by humans so far has been under the protection of the Earth’s magnetosphere.

Only the Apollo missions have sent humans out beyond the magnetosphere and watch what happened to them. We just, we have not performed this experiment. We’ve not gathered enough data. Okay. So now people are landing on Mars and obviously some percentage of these starships are going to fail and they’re going to crash onto Mars. So that would be bad. A hundred people per starship that is fails its landing.

But then let’s, you know, let’s talk about the people that survive. You’ve got, you’ve got a Mars and this is their home. Now this is where they live.

Yes. What are the ethical issues for this now?

[Dr. Pamela Gay]
So, so you, you have three big things you have to worry about. One is people tend to be greedy and lazy. And how do you select a crew that is made up of people who won’t at some point decide, yeah, I’m just done.

[Fraser Cain]
And well, I mean, in theory, like basically it says there’s going to be return flights possible. So if you say you’re done, you hop in your return spaceship and you come home.

[Dr. Pamela Gay]
Okay.

[Fraser Cain]
And if you’re a bad person, they, they vote you off the Island. They put you in a starship and they send you home.

[Dr. Pamela Gay]
Like, I think that feels like, you know, I, I, I keep thinking back to the rules of the high seas, where if you didn’t do what was necessary, you were sent down the gangplank.

[Fraser Cain]
Sure. Yeah. If you’re a very bad person, they’d throw you overboard.

[Dr. Pamela Gay]
So, so you’re looking to put together a society of people who are in many cases, not going to fully comprehend how shockingly difficult it’s going to be, how shockingly unhealthy everyone is going to end up being. And the amount of never ending work is something we saw playing Oregon Trail growing up. If you are of the right age and you witnessed the dying of dysentery, but even the people on, on the Oregon Trail got to pause on Sunday and there’s no resting when you’re in an environment that’s trying to kill you constantly.

[Fraser Cain]
Yeah. I have a couple of kind of anecdotes on this. One is talking with astronauts about their life on the International Space Station and how much they have to work.

[Dr. Pamela Gay]
Yeah.

[Fraser Cain]
That, that they have to spend many hours every day just maintaining their strength and their, their cardiovascular system. They, they run nonstop and they lift weights. And I think they do two to three hours of exercise every single day.

[Dr. Pamela Gay]
Yeah. And it’s a lot of elastic more than weights just because elastic is, is easier.

[Fraser Cain]
I mean, they have a weight machine. They literally have this sort of cool Smith, Smith machine they can, they can lift with. And then they spend hours maintaining the, the equipment that’s keeping them alive.

And then they perform a bunch of science experiments. And then if they’re lucky, they have a few minutes of personal time before they collapse and they begin the whole process all over again. And they know they’ve got a nine month, six month trip in space that, you know, they’re there for a reason.

They get it done. They come back home, but the people going to Mars, this is their whole life forever. Yeah.

Yeah. And then the other thing is this TV show called Alone, which is often filmed here on Vancouver Island where I live, which, you know, was recently voted as one of the best islands in the world. And, and they’re there in November when it’s kind of hard to, to find food and they’re alone by themselves trying to take care of themselves.

And they all go crazy. They all get sad, lonely, and they want nothing more than to return home. But when you’re on Mars, even if that starship is waiting, you’re looking at six months or so, whatever, before you can actually make that return journey.

So I think all the comforts of home, it’s exciting. They’re all excited in the beginning and then the reality sets in and they’re all really sad and wish they could, they could come home. And so there’s like this, just this cognitive load.

But I think, you know, one of the bigger issues that we’re not even dealing with is, yet, is what if they want to have kids?

[Dr. Pamela Gay]
Yeah. And, and so there’s two sides to that. One is we don’t know what additional biological issues there’s going to be because there is increasing evidence that once upon a time, long, long ago, Mars might’ve had microbial life.

We don’t know what it’s chemistry. We don’t know what it’s former biology. We don’t know what any of that will do in terms of influencing things like plant growth, anything like that.

This, this is an entirely new environment where for all we know, the specific chemistry that exists on Mars causes new kinds of birth defects that we don’t know about because that specific chemistry isn’t something that even in the most industrially polluted places people get attached to. Then add onto that, we already know that things don’t form right in lower gravity, in microgravity, in orbit on the international space station. They’ve had issues with embryos not forming skin and that will live rent-free in my brain with me forever.

That was an episode we did years ago, still lives rent-free in my brain.

[Fraser Cain]
Yes. And still nobody has done the next experiments.

[Dr. Pamela Gay]
Because it’s too scary and ethically wrong.

[Fraser Cain]
I know, but nobody’s done like, let’s set up a centrifuge and let’s see what happens in one sixth gravity. And let’s see what happens in simulated Mars gravity. Like we have literally no idea, none about what’s going to happen to human gestation in Mars gravity.

Might be fine, might be no skin.

[Dr. Pamela Gay]
And the problem with saying, oh, we’ll just mandate they don’t have children is human beings don’t work like that generally. And life finds a way. I mean, a lot of this goes back to a different Jurassic Park quote.

Your scientists were so preoccupied with whether or not they could, they didn’t stop to think if they should is another Ian, the Jeff Goldblum character.

[Fraser Cain]
The chaos mathematician. I mean, I think if you knew that there was a 100% chance that any child born on Mars would have such serious health issues that they would be non-viable or would live in pain and torment for their life, for their short lives, you would make it impossible. Everyone would have to be sterilized, I guess, going to Mars.

Like that’s crazy. Um, and if it was perfectly safe, then you would be like, okay, well, this is a problem, but the, but the problem is that we don’t know the answer to this question. Nobody has performed these experiments.

Nobody has, has taken mammals through gestation in various simulated versions of gravity. These are tests that need to be done. And we don’t know the answer to these questions.

And then the next issue is sort of like what life would be like. Now, we’re sort of giving this Mark Watney-esque from The Martian constant striving for basic survival. You’re probably living underground because you can’t be out on the surface to get more of that dose of the radiation.

You’ve already had a lifetime’s worth of radiation, so you’re going to spend every moment thinking about the time you spend outside. Probably you can’t grow food out in the open, even under a greenhouse.

[Dr. Pamela Gay]
It’s going to be moon is a harsh mistress style life where you’re underground in tubes. Your only source of light is artificial. Your only plants are grown in some sort of inside growing system.

[Fraser Cain]
Yeah.

[Dr. Pamela Gay]
Yeah.

[Fraser Cain]
Yeah. That’s your life. And so you sort of go back to that alone idea like you’re living underground.

You can’t go outside.

[Dr. Pamela Gay]
If you’re someone with seasonal affective disorder, not for you. Yeah.

[Fraser Cain]
You feed the algae bioreactor and you eat the slop that comes out. Yeah. So that is very tough.

Now, maybe people are going to think that this sounds like a great idea and maybe they’re going to want to do it. I don’t know. People have been able to weather hardships in exploration on Earth before, but often there’s another side to that.

It’s a tunnel and you get to come out the other side where now you’re living on a tropical paradise and you’re able to survive.

[Dr. Pamela Gay]
And this is where there’s so many post-apocalyptic sci-fi shows. Silo is one that I believe is on Apple TV that is the world has self-destroyed itself and everyone is living in underground silos where they have to completely match birth and death. And you see similar things in Fallout and all these different post-apocalyptic.

This would be that future without needing the apocalypse. You have chosen this future.

[Fraser Cain]
Yes. Self-inflicted sort of apocalypse.

[Dr. Pamela Gay]
And there’s another ethical side. Do we do this before the scientists have figured out all the things that we need to figure out before we pollute it with our own biology? Is there life on Mars?

Is there a fossil record we need to explore? I’m reminded of all the places that require a paleontologist and or an archaeologist to be on site during big digs to make sure that history isn’t destroyed. And do you see any of the commercial agencies planning that kind of, let’s make sure no fossil is destroyed?

[Fraser Cain]
Yeah. Yeah. I mean, I think this is a situation where finding life on Mars would be one of the most dramatic discoveries in human history.

And it would tell us a tremendous amount about how common life is in the universe, how it evolved separately, or if they’re related. And yet if we go without really thinking about our impact on the environment there, then we’re just going to release various kinds of bacteria into the environment that is going to attempt to colonize those places. Like, what do you know?

You dig down and you find water bears, right? Thanks for the trip. Thanks for the new environment.

So that is another issue that we may lose track of the life, the life that was there before humanity arrived. And that is a, you know, it feels like it’s kind of an inevitability. But it would be nice to have a chance to do lots of science before we bring the earth life.

And then, of course, people are thinking about if we can terraform it, right? That takes it to the next level. You’re turning this planet that was, you know, if it does have life, has this sort of set environment and you’re turning it into something completely different for us.

Yeah. And then a lot of people are like, I don’t care, whatever.

[Dr. Pamela Gay]
I want to be able to answer all the questions before I destroy the data.

[Fraser Cain]
Yeah. At the very least, let’s get the science done before we destroy the data. So I think, you know, there’s like a certain percentage of people who are going to go like, I never want to listen to Astronomy Cast again.

[Dr. Pamela Gay]
It’s true. It’s true.

[Fraser Cain]
Yeah. Which is fine, you know? And so for those of you who are like on the fence and they’re like, oh, I really hate what Fraser and Pamela are saying, I want to throw you a bone, which is that for me, and I don’t know about you, Pamela, but for me, this is not about whether or not we will or should colonize other worlds.

I think we should. And I think that we will. The issue is the timeframe.

The issue is where we are today on the technological curve towards this being a thing that we can do ethically and safely. And, you know, the analogy that I always use is, you look at a place like Phoenix, there’s whatever, 5, 3 million, 5 million people living in Phoenix in an environment that was never meant to support that many human beings. But we have infrastructure.

We have technology. We have highways. We have electrical grids.

We have air conditioning systems. We have transportation networks. Like we have, we have made it so that living in a place like Phoenix is eminently doable with our, with our level of technology.

We need that infrastructure. We need a way to safe. We need a way to safely transport people into space.

We need a way to safely transfer people through space to another world. We need to be able to make sure we can land on that other world. We need to be able to know the answer to the question of low gravity.

We need to be able to combat and stop radiation from space. We need to be able to manufacture resources that are required locally at scale. We need to be able to have new technologies that handle the temperature, the lack of atmosphere, the perchlorates in the soil, all of this kind of stuff.

It is infrastructure that we’ve not built yet. And that, that it, and so it’s not about whether or not this is going to happen for me. This is about when this is going to happen.

And I think a lot of people are getting very frustrated and angry that this isn’t happening tomorrow. And yet this humanity, as we continue to progress, we will inevitably reach this place where these are things that we do easily. We’re like, oh yeah, of course.

Hey, let’s just set up a city on Mars because that’s easy for us to do. We’ve got the, all the infrastructure. Let’s just do it.

And maybe we’re like, yeah, it sounds like a great idea. No problem. Right.

But we’re not there yet. And we get there by building infrastructure, developing our technology, understanding biology, understanding how, how, how close ecosystems work here on earth and in space as we live longer, close to earth, live on the moon, practice our techniques. Near earth asteroids.

Near earth asteroids, develop all of that infrastructure that then living on a place like Mars will be just the natural outcome of that. So I still believe that we will eventually live on Mars. I just think it’s going to happen in a few hundred years later than, than, you know, others who are a lot more enthusiastic to.

And that’s where I think my position has changed from the guy who was so excited about the case for Mars has now sort of tuned my enthusiasm to a more realistic timeframe.

[Dr. Pamela Gay]
I really want to see fossil hunting on Mars with high mass laboratories being possible, but I don’t care if there’s a human settlement tied to it. I just want to know if there’s actually fossils there. That’s what I want to know.

[Fraser Cain]
Sure. Yeah. Yeah.

Like we have all these scientific questions we’d love to know the answer to. And you know, people say, oh, should we live on Mars? I always have to distinguish like, should we have a research station on Mars?

Absolutely. Right away. Tomorrow.

Let’s get going on that. Should we have people living on the moon? A research station on the moon?

Yes, absolutely. Tomorrow. Let’s get going.

Should we have people like live and grow and, and, and live their whole lives on Mars only when it’s feasible and we won’t know until it’s feasible.

[Dr. Pamela Gay]
Yeah. Yeah.

[Fraser Cain]
All right. So hopefully that, yeah. So, so now we just, you may disagree with me, not you, Pamela, but you, the audience.

[Dr. Pamela Gay]
Yes.

[Fraser Cain]
You, the audience may disagree with me and that’s fine. But I, I hope that we can have an argument about timeframe and not about, you know, we’re not having an argument about whether or not it’ll happen and should happen. It’s about when it’s going to happen.

[Dr. Pamela Gay]
Yeah. Thanks Pamela. Thank you, Fraser.

And thank you so much to all of the folks out there on Patreon. This show is made possible by our community on patreon.com slash astronomy cast. This week.

We’d like to thank the following $10 and up patrons, Abraham Cattrell, Alex Rain, Andrew Stevenson, Arno DeGroot, Bart Flaherty, Benjamin Mueller, Bresnik, Bruce Amazine, Claudia Mastriani, Dale Alexander, David Bogarty, Diane Philippon, Dr. Jeff Collins, Iran Zegev, Felix Gut, Frodo Tanenbaugh, Glenn Phelps, Greg Davis, Hannah Tackery, Janelle, Jeanette Wink, Jim Schooler, Joe Holstein, John Thays, Justin Proctor, Katie and Ulyssa, Christian Golding, Laura Kettleson, Lana Spencer, Mark Schneidler, Matthew Horstman, Michael Purcell, Mike Dog, Nate Detweiler, Papa Hot Dog, Paul L. Hayden, Philip Walker, Robby the Dog with the Dot, Reuben McCarthy, Sandra Stanz, Scott Briggs, Zege Kemmler, Stephen Miller, The Brain, Tim Girish, Tushar Nakini, Will Feld, and Zero Chill. Thank you all so very much.

And we have, as of tomorrow, I think, for AstronomyCast, access to quips and all the new Patreon features. So check it out. You have to install Patreon on your mobile device, though.

[Fraser Cain]
All right. Thanks, everyone. And we will see you next week.

[Dr. Pamela Gay]
Bye-bye, everyone.

Live Show

New instruments bring new mysteries, and when James Webb came on line it uncovered a collection of strange, compact, bright objects shifted deeply into the red end of the spectrum. These were dubbed “Little red dots” or LRDs. And the astronomical community continues to puzzle over what they are. When JWST first peered into the distant past, it discovered the early universe had a rash of little red dots. Their existence just 450 million years after the big bang meant either galaxies were forming way faster than anyone predicted, or something unimagined had been found. 

Show Notes

• Excitement and anxiety astronomers feel when new telescopes like JWST come online.
• James Webb’s discovery of mysterious “Little Red Dots” — compact, bright, redshifted objects from the early universe.
• Possible explanations: active galactic nuclei (AGN), dust-enshrouded galaxies, or direct-collapse black holes.
• Debate over black hole growth limits, primordial black holes, and the Eddington limit.
• Theories on early galaxy and star formation, and what “Little Red Dots” reveal about cosmic dawn.

Transcript

Fraser Cain: 

AstronomyCast, Episode 769 Little Red Dots. Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, I’m the Publisher of the Universe Today.

With me as always is Dr. Pamela Gay, a Senior Scientist for the Planetary Science Institute, and the Director of CosmoQuest. Hey Pamela, how are you doing?

Dr. Pamela Gay: 

I am doing well. It is the most glorious of falls here in Southern Illinois. The leaves are falling, the sun is out, it is hoody weather, I am happy, and Halloween is almost upon us.

Fraser Cain: 

So are you ready to feel a little bit self-conscious?

Dr. Pamela Gay: 

I guess.

Fraser Cain: 

So I was interviewing one of my patrons, and the patron said, hey did you ever notice that when Pamela says, I am doing very well, I’m like, no, you just did it. So apparently every time I ask you how you’re doing, you say, I, I am doing very well.

Dr. Pamela Gay: 

That’s all right, I have habits.

Fraser Cain: 

Yeah, yeah, crazy, like you just like, by the numbers, you did exactly on, so I had to bring it up. But the funny thing is that when we started doing this podcast, you actually asked me how I was doing, and I had to give the answer every time, and I hated it, and people made compilations of you asking me how I was doing, and me answering, and it all just sounding exactly the same, and so at some point I just flipped it on you, and you never complained. And so now, um, you, you are the one who I ask how you’re doing, and you always answer, and we’ve, you’ve never gone, wait a minute, why am I always the one who has to say how, how I’m doing?

Dr. Pamela Gay: 

So I think the switch happened, uh, not too different in time from when we switched how we were doing so many other things. This show has evolved.

Fraser Cain: 

Yes.

Dr. Pamela Gay: 

We went from just the two of us on Skype, uh, with both of us recording locally to Google Hangouts, to Google Hangouts on air, with you producing and going through myriad different technologies to, at some point it switched to me producing, and there’s been so many evolutions in there. We’ve also changed how, how we do the opening music, um, yeah, yeah. We’re almost to 800 episodes.

Fraser Cain: 

Yeah, you do, you do this many times, and you just, you fall into ruts and patterns, and so I’m like, I’m just glad people aren’t sick of us yet, that this is still what they want to listen to. So thank you for listening to us, and I know for some of you, uh, hearing us fall into these standard patterns of speech is your comfy place. This is, this is what you want to hear.

This makes you feel like the world is going to be all right, and for those of you who are annoyed, I’m sorry, that’s a Canadian sorry, nothing we can do. Um, new instruments bring new mysteries, and when James Webb came online, it uncovered a collection of strange, compact, bright objects shifted deeply into the red end of the spectrum. These are dubbed Little Red Dots, or LRDs, and the astronomical community continues to puzzle over what they are.

All right, take us back to the history, actually, before we do this, I want to talk like philosophically about your experience watching new telescopes come online, and what it’s like to be an astronomer knowing that the presents are about to be opened up.

Dr. Pamela Gay: 

So there is a Schrodinger’s box of emotion when new telescopes are coming online, and I feel it very deeply because of my experiences with my dissertation where an X-ray satellite I was planning to use failed on launch, and the Javier Burley telescope that I was planning to use to take hundreds of spectra allowed me to take 18 spectra. I’m very much aware that the telescope can fail spectacularly, or, or, if you’re very lucky, which I am not, it will be the best thing ever, and amazing new things will be discovered. And so this dichotomy of emotions as you wait for enough data to come in to fully understand what’s going to be possible is, I don’t even know how to articulate the internal dichotomy of I’m trying not to get excited, I’m trying not to get excited, I want to be excited, this could be everything, or we just wasted billions of dollars.

Fraser Cain: 

Yeah, it was funny, when the next generation telescopes came out from the European Southern Observatory with a very large telescope, we got the announcement of a whole bunch of new planets, new dwarf planets, and that was due to just the capability of that instrument, that more powerful instrument, new things happen. Some of the things, you get answers to the old questions, the whole point of building the telescope is to answer a bunch of questions. But the part that I enjoy even more is the new questions that pop up.

And so with James Webb, we knew there were going to be new questions, and there have been a bunch, but this is the one that I think has sort of best encapsulated what James Webb was supposed to do. And I think the answer is becoming more interesting over time as we’re seeing this. So let’s go back and sort of talk about this discovery of these little red dots for the first time.

Dr. Pamela Gay: 

So JWST took a series of different images to showcase what it’s capable of. These images included really pretty nebula that filled the entire field, and also background fields that included galaxies that were doing gravitational lensing, and just blank fields. Blank fields by which I mean not a gravitationally lensing galaxy cluster there, nothing is blank in astronomy.

And in those images that allowed us to see the background universe, there were these small red luminous objects that when you took their light and figured out roughly what red shifts they’re at, what time in the universe they’re shining their light at is from, and you adjusted their spectra, their rainbow of light back to what it would look like where they are, their rest frame magnitudes. They became these objects that were super bright in rest frame reds that had all sorts of hydrogen bomber light emissions and seemed to be hot and massive and they looked kind of like AGNs and they were just confusing. And so everyone just sort of went, but there aren’t supposed to be galaxies then, and then started doing research.

Fraser Cain: 

Right. And it turns out galaxies have been found then and even earlier, like we’re seeing galaxies at times that are less than 300 million years after the Big Bang. We’re seeing super massive black holes at times when the universe is less than half a billion years old.

We’re seeing spiral galaxies when the universe is less than a billion years old. The universe was surprisingly evolved, but these little red dots, okay, so those features you mentioned, they’re very bright, they’re very compact, they’re now shifted into the red. What kind of light were they giving off back in the day?

Dr. Pamela Gay: 

They were the moral equivalent. So James Webb Space Telescope is seeing them in colors our eyeballs can’t even see. If you take that light, shift it to what our eyeballs can see, they would literally be red galaxies, but they’re not galaxies.

Fraser Cain: 

Right. Well, we don’t know what they are yet.

Dr. Pamela Gay: 

Probably. So to give some context, if one of these was plopped into our local group, they’d be roughly the same brightness as the Triangulum Galaxy and 3% of Triangulum or 2% the size of the Milky Way Galaxy. So these are very bright, very small from what we can see.

Fraser Cain: 

And very red. Yeah. Yeah.

All right. So now think like an astronomer detective and put down all the pieces of evidence that we have so far that try to direct us towards what it is that these things might be.

Dr. Pamela Gay: 

So we’re seeing a bunch of different emission lines, which you get when you have a bright source shining its light through cooler gas that then has atoms that get excited into higher energy states. Nothing stays excited. And when they drop down to their lower energy level, they emit light.

Fraser Cain: 

Give us a sense of something that astronomers look at that has that phenomenon.

Dr. Pamela Gay: 

So, when you have cooler gas around very hot stars, you see emission lines. Active galactic nuclei quintessentially have this pattern of lines. It’s these scenarios where you have something very hot giving off light surrounded by gas and dust that allows you to have this kind of emission line.

Fraser Cain: 

Okay. So we’ve got an active galactic nuclei. Like.

Hold on. Active galactic nuclei, case closed. Right?

No. Okay. So why can’t you just say it’s an active galactic nuclei?

Dr. Pamela Gay: 

So there’s other colors of light. And while we see emission lines and this V-shape in their spectrum that reminds us of active galactic nuclei, active galactic nuclei have other things like hot corona of gas around them that give off x-rays. And as hard as we look, we’re not finding x-ray emission from these little red dots.

It’s just not there. And by the way, I just need to warn people, do not Google little red dots without adding the word cosmology or JWST. Cosmology.

Fraser Cain: 

You’re just going to get rashes. You’re going to get rashes. Yeah.

Yeah. Yeah. And perhaps a suggestion that you go see your doctor. Yeah. Right. And this is the key, which is that you can take an active galactic nuclei, an actively feeding supermassive black hole. It’s feeding so heavily.

There’s so much gas coming in that material is piling around it. You’ve got this shroud of gas and dust around this central core. And yet because the accretion disk heats up, it’s giving off x-ray radiation.

Astronomers have looked at each of these objects with the Chandra X-ray Observatory, for example, and they’re not seeing the kind of x-ray emissions that you would expect coming from an active galactic nuclei. So active galactic nuclei off the table, case closed.

Dr. Pamela Gay: 

So that means we have to come up with something else. And like I said, this is something, these are something, we’ve found over 350 of them now, that they exist in this window of time from about 300 million years after the Big Bang to about 1.2 billion years after the Big Bang. So this is a point in time where the diversity of elements in our universe wasn’t that great, when things were still in the process of forming.

And there’s a lot of problems that we want to solve with this era of the universe. And so people then go, I wonder if little red dots can solve this problem we have. And so the kinds of solutions that folks have looked at…

Fraser Cain: 

Well, what are the problems? Sorry, but you mentioned there’s a bunch of problems we’re trying to solve. What are those problems that we know of at the early universe?

Dr. Pamela Gay: 

So how do you get supermassive black holes that early? How big could stars get if they weren’t able to cool through metal lines? It turns out that heavy atoms provide ways for stars to do star things, and you can’t get massive stars if you have heavy elements in the stars.

So we have these two different problems that we’re trying to solve. We also have the, well, what if there were primordial black holes? What if things were happening with high turbulence in ways that we don’t think about in the early universe?

Fraser Cain: 

How did the dark ages end?

Dr. Pamela Gay: 

Right. And how did the dark ages end is something you can’t really solve with little red dots because it requires a lot of ultraviolet light. So the first thing we realized was, well, these don’t solve that.

And then the next question became, but what if they have a whole bunch of star formation? And then we started doing the weight. They’re like 3% the size of Triangulum, which is pretty small.

So where do you hide that much dust to enshroud star forming regions to hide the ultraviolet light? So that doesn’t work.

Fraser Cain: 

Well, hold on. So just like that line of thinking, right, is essentially you have stars compacted about as closely as you would see at the center of the Milky Way or in a globular cluster, and also with large amounts of dust and material all around them, like a super compact stellar nebula, like nothing we’ve seen in our nearby universe.

Dr. Pamela Gay: 

And one of the other problems that you run into with little red dots is they’re what’s called a super editing luminosity. This means that they aren’t in equilibrium between the amount of light going out and the amount of mass falling in. And so they don’t fit stars.

It’s this weird combination of things. So now we have to start saying, all right, so AGN is really, really close. It almost works.

We’re just missing the hot corona and some of the other details in the stellar spectra of a galaxy and the spectra of a little red dot don’t quite match. So is there a way to have essentially a naked AGN, something that doesn’t have that galaxy and that galactic halo around it? And that was the next place that people started looking.

Fraser Cain: 

And that would be weird. Yes. Right?

So you were talking about how instead of the traditional idea of a supermassive black hole at the heart of a galaxy, where it is maybe, I mean, right now the Milky Way’s black hole is only 10%. No, sorry. The Milky Way’s black hole is only 1%, maybe a 10th of a percent, I think, of the entire mass of the Milky Way.

Back in the early universe, they were more like 10%. So they were more dense, but still the black hole wasn’t the dominant mass in the Milky Way. It was the stars and the gas, the dust and the dark matter.

So, but in this case, we’re saying, well, maybe it was just a supermassive black hole and nothing else.

Dr. Pamela Gay: 

Well, a whole bunch of gas and dust.

Fraser Cain: 

Right.

Dr. Pamela Gay: 

Yeah. And so the idea here becomes, and people are getting at this from multiple different directions. So I’ve seen papers that are like, okay, so let’s just imagine for a moment you could get a supermassive population three star that like collapses down and then all the density of material falls in towards it.

Can we create through turbulent infall of material a situation where you have a rapidly growing into a supermassive star with turbulent infalling material? I’ve also seen, well, what if you start with primordial black holes and you have turbulent infall of material? Right.

However you get the black hole, the idea is you have this supermassive black hole in a universe that it’s able to be a seed for gas to flow inward. That material is turbulent and because of the turbulence, it’s able to give off momentum in ways that we don’t normally think about when we watch things like toilets flushing and bathtubs draining. Turbulence allows this chaotic buildup of material around that supermassive black hole and all that material is now glowing like the disc of a AGN.

And in this scenario, which don’t let us name things, astronomers should never be allowed to name things.

Fraser Cain: 

And yet they keep doing it.

Dr. Pamela Gay: 

Yeah, yeah. We need to like ask our kids, our spouses, our friends, just, yeah. I’ve seen two names pop up consistently.

One is quasistars where the idea is you don’t have, well, let me give both names. One name is quasistars and the other name, please don’t use this, please drop it forever, but you’re going to see it out there, is black hole stars, which is just leading people into a world of misunderstanding.

Fraser Cain: 

Isn’t a black hole a star?

Dr. Pamela Gay: 

No.

Fraser Cain: 

Gas?

Dr. Pamela Gay: 

So it’s a remnant.

Fraser Cain: 

It’s a remnant. Sure. Fine.

Dr. Pamela Gay: 

So stars, by definition, have nuclear reactions going on in their course.

Fraser Cain: 

What about a white dwarf?

Dr. Pamela Gay: 

A white dwarf?

Fraser Cain: 

Star. White dwarf star. What about a neutron star?

Dr. Pamela Gay: 

Yeah, so those are stellar remnants that have terrible names. Yeah, I know. That’s all I’m saying.

Fraser Cain: 

That’s all I’m saying. It’s just like this, this is a barn with a lot of horses that are already running free.

Dr. Pamela Gay: 

I know. I know. I’m just trying to keep the last horse in the barn.

Fraser Cain: 

You are wasting your time.

Dr. Pamela Gay: 

I usually do.

Fraser Cain: 

Black hole stars. That’s what’s for dinner. That’s what we’re going to talk about now.

So I want to just sort of go back and sort of re-describe what you’re saying here, which is that, you know, there’s these two mechanisms, both of which are, which most people don’t think work. One is that you have a giant cloud of gas and dust and something sets it off and the whole thing just turns into a big black hole. That’s not supposed to happen.

That as you heat up, as the black hole gets hotter and hotter, as the accretion just builds up around it, then the radiation starts to pour out of it and infalling material is prevented from happening. This is the Eddington Limit. And yet black holes have been seen beating the Eddington Limit.

And so maybe it is possible. And we have seen examples where perhaps black holes have formed directly. This idea of direct collapse.

You don’t need to go through star just, you know, accretion material until it’s fat. This other idea, as you say, primordial black holes, these might’ve formed in just ripples of space-time moments after the Big Bang. And then they got a headstart.

Yeah. You can have a black hole with, uh, 5 million times the mass of the sun early on in the universe. If it started at 4 million times the mass of the sun, right at the Big Bang and just kept on feeding from there and could be an explanation for dark matter.

So, you know, everything comes together nicely, except that we, we don’t see evidence really of, of either of these things, of direct collapse black holes or of, of primordial black holes.

Dr. Pamela Gay: 

So, so I’m not ready to say that these aren’t direct collapse black hole systems. Um, I’m just not ready to say we’ve disproven that there’s enough papers that are able to fit the pieces together. They’re able to model what the spectrum would look like and it matches.

And because the densities in the early universe were so different, it seems that for this moment in time, it may have been possible. And this idea that you have collapse coming in from multiple directions with a disc that is the bulk of the source of light, but it’s heating everything around it. It seems to fit the lack of variability in light that we’re seeing.

That’s another one of the differences is AGN flicker. It’s kind of awesome. It allows us to map out the sizes of accretion discs through echo mapping.

Um, the, the size of the disc and the size of the variations in time have to match. And, and so we don’t see any of that variability, but if you have a cloud of material all the way around that desk, you’re not going to be able to see into the core of the desk and see that variability. So there’s that enshrouding nature that’s getting answered.

The spectrum seems to match. And if this is the only case where these things would be observed, they’re rare enough that it could explain massive galaxies early on and everything else forms through hierarchical clustering, but it’s too early in the story. We’re going to have to come back to this in five years, but you need to know these exist.

Fraser Cain: 

Right, right. And there’s a couple of issues. One is where is what comes next?

So, you know, because James Webb and the other telescopes are time machines, they let us see little snapshots of the universe at different times. And so we’re seeing all of these little red dots at different ages, but within the first billion years of the universe, but you would expect to see objects that are now the next phase of whatever those started out as. And this has not been very well documented.

There’s a couple of papers where people are starting to propose that some objects that are actually giving off a lot of bluer light are a transition that maybe you’re getting this switch on of the visible light, the ultraviolet light, and you’re getting sort of turning into whatever comes next. You know, we’re seeing their baby Pokemon version with James Webb, and then hopefully we’re trying to find the larger versions. We’re looking for the Eevees.

Yeah. So that’s one sort of angle that we can watch is to look for the kinds of things that they turn into and that it gives you more information about what’s still there. Another paper that I was looking at that I found really interesting is that people simulated how big stars, how big that first generation of stars should be.

And the expectation is that they should be gigantic, but they simulated, in fact, they should be tearing off into small stars, just like normal-ish sized stars, and then exploding as well. And so maybe you just got a whole bunch of black holes clustered together that are in the process of coming together to maybe just like a ton of stars. And maybe, like, here’s my hope, is that these are globular clusters.

That maybe whatever it is, like right around the very beginning, they formed giant collections of stars, and we see them to this day. That would be really exciting to me. So yeah, it’s a wonderful mystery.

And hopefully, almost certainly, we will come back in a couple of years and go, okay, here’s what they are. And right now, it’s all in play.

Dr. Pamela Gay: 

And the wild thing is there’s so many different options. Like me, I’m kind of expecting the little red dots shut off as extremely dusty, extremely enshrouded disks or clouds of stars begin to light up, and they just haven’t produced the ultraviolet light yet necessary to clear out and make things visible. But we don’t know.

Fraser Cain: 

Yeah, we don’t know.

Dr. Pamela Gay: 

That’s the amazing part.

Fraser Cain: 

Yeah. And so you ask anybody, what I think is, you know, astronomers are going to have what they think is their most likely outcome. But if you showed them a piece of evidence that just proved that, they’d be like, yep, okay, that’s out.

They’re going to hold their ideas very loosely right now, because there’s still so much science to be done, and it’s an exciting mystery. So I look forward to that episode where we’re like, okay, here’s the boring explanation for what it is.

Dr. Pamela Gay: 

Just please call them quasi stars and not black hole stars. That’s the only thing I ask.

Fraser Cain: 

Good luck with that. I know. Thanks, Pebble.

Dr. Pamela Gay: 

Thank you, Fraser. And thank you to all of our patrons. You truly make this show possible.

This show wouldn’t exist without the amazing support of so many over on patreon.com slash astronomycast. This week, we would like to thank in particular Andrew Stevenson, Antisor, Arno DeGroot, Astro Bob, Bob Kale, Boogie Nat, Smansky, Daniel Schechter, David, David Rosetta, Dr. Whoa, Don Mundus, Dr. Jeff Collins, Elliot Walker, Father Prax, Frodo Tanenbaugh, Jeff McDonald, James Roger, Jim Schooler, J-O, Jonathan Poe, Kenneth Ryan, Kimberly Rake, Labrat Matt, Larry Dotz, Marco Yarasi, Mark Schneider, MHW1961 Super Symmetrical, Michael Hartford, Michael Prashada, Michael Regan, Nyla, Papa Hot Dog, Paul D. Disney, Paul Jarman, Philip Walker, Randall, RJ Basque, Robert Hundle, Robert Pelasma, Ron Thorson, Sam Brooks and his mom, Shersom, Semjan Torfason, Zeggy Kemmler, Steven Rutley, Thomas Gazzetta, Tiffany Rogers, Van Ruckman, Wanderer M101, Will Hamilton.

Thank you all so very much. That pause is where Rich is now going to drop in the previously recorded names.

Fraser Cain: 

I like this where we don’t do this live. This is great.

Dr. Pamela Gay: 

Oh, I know.

Fraser Cain: 

All right. All right. Thank you, Pamela. Thanks, everybody. And we will see you all next week.

Dr. Pamela Gay: 

Goodbye, everyone.

Live Show

So it’s been decades since we’ve seen a bright comet in the sky. And actually there was a pair — Hale-Bopp and Hyakutake. And then, silence! And unmet promises by the Universe to give us a bright comet. Comets are unpredictable, and they arrive precisely when they intend to. Is it time again for a bright comet? If you asked us in January if 2025 was going to have any outstanding comets would fly through the Solar System, we would have (and we did) say “no.” And we were wrong. Comets are fickle, unpredictable, and like to do exactly what we didn’t predict.

Show Notes

• What makes a great comet
• Why predictions are hard
• Historical highs & hopes
• Hyakutake & Hale-Bopp set the bar
• Halley’s best (1910) and next return in 2061
• Current/near-term watchlist (Fall 2025):
• C/2025 A6 (Lemon)
• 2025 R2 (SWAN)
• Big units: 2014 UN271 (Bernardinelli–Bernstein)

Transcript

Fraser Cain: 

This is a test. Welcome to Astronomy Cast, your weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, I’m the publisher of Universe Today.

With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmic Quest. Hey Pamela, how are you doing?

Dr. Pamela Gay: 

I am doing well. Our sights are still a bit on the struggle bus with the onslaught of scrapers, but I seem to have things running slow, but not crashing. And I’ll take slow and not crashing and continue to work on it.

So thank you everyone for your patience. Yeah, this was not what AI ever talks about doing to people.

Fraser Cain: 

Where are my Terminators? I would prefer Terminators over them slowly degrading our website service. Yeah, at least the Terminators are honest with you, as opposed to sneakily pretending to be Chrome browsers that are just browsing your website thousands of times a second.

So we did something unusual this week over on my YouTube channel. We released, instead of doing our normal news roundup with Space Bytes, we did a roundup of news about Comet 3i Atlas. And it was a very different episode, something unlike we’ve never done before, which was that I went very carefully through every single paper that has come out about 3i Atlas over the last three months.

Dr. Pamela Gay: 

There’s some doozies in there.

Fraser Cain: 

Yeah. The ones that I felt were scientifically valid, all of them in archive. Okay, fair.

Dr. Pamela Gay: 

Thank you.

Fraser Cain: 

And then we connected it all together into a video, but it’s just reference after reference. You could see us going through the paper, quotes. It was footnoted.

It was like an academic journal of its own. Normally, I’m very much fast and loose about the news. In this case, I was saying the names of the principal investigator.

We were providing a link to the paper on archive. We were showing it. We brought receipts for this episode.

Dr. Pamela Gay: 

That’s so important.

Fraser Cain: 

Yeah, because there’s so much AI slop out there. I think if you want a very science-based reference about 3i Atlas, definitely check out the episode that we did this week over on our YouTube channel, the Universe Today YouTube channel. But it’s also sent out in my newsletter.

We have it on the podcast in all the places, but I hope people really enjoyed that. It took me about four times as long as it normally takes me to do a Space Bytes because it was so carefully, meticulously researched. It felt very weird to do the episode.

I thought it was just going to be a disaster, but then Anton, our editor, he just nailed it. It’s a beautiful video, great graphics, lots of really cool stuff, and also really meaty scientifically. Definitely check that out.

I’m really proud of what we did.

Dr. Pamela Gay: 

Yeah. Some of the stuff you do is must watch. That one is getting added to the list of things that I must watch.

Fraser Cain: 

So it’s been decades since we’ve seen a bright comet in the sky. Actually, there was a pair, Hale-Bopp and Hyakutake, and then silence and unmet promises by the Universe to give us a bright comet. Comets are unpredictable, and they arrive precisely when they intend to.

Is it time again for a bright comet? We’ll talk about it in a second, but it’s time for a break, and we’re back. So, Pamela, is it time?

Are we due? Is this it? Is this our moment?

Dr. Pamela Gay: 

I don’t think we’re going to get a Hyakutake or Hale-Bopp, and this makes me sad because those two were my company at the end of undergrad, the beginning of graduate school. Yeah.

Fraser Cain: 

I mean, it’s sad that it’s been so long, 26 years?

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

27 years? There are people watching this episode, people listening to this podcast, that were not born when there was a bright comet in the sky.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

Yeah, but what about McNaught? What about Comet Swan? What about Comet Lemon?

Those are nothing. Those are garbage. Those are meaningless.

You don’t know what a bright comet looks like when you stand outside, and it has a tail that stretches for 20 degrees in the sky, that you can see it as the only object when the Sun has gone down, that it just is there night after night like a familiar companion. You go to dark skies, and you just marvel at it. You take pictures of it with a pocket camera, and it still looks amazing.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

The universe has just been, for a quarter century, nothing. I’m outraged.

Dr. Pamela Gay: 

I know. I know. Seriously, folks, unless you saw it, it’s impossible to imagine.

I was a baby grad student for Hale-Bopp, and the first night, I was using the McDonald Observatory 30-inch, which is kind of nestled into the side of the mountain. The person who was teaching me how to use it, Philip McQueen, he was like, just hold on until 5 a.m., because I had to drive all day, then I was going to observe with him all night. It was like being awake for 24 hours required for your education.

I was just melting into the desk. At 5 a.m., he’s like, okay, go outside and look. I opened the door from the dome, and straight in front of me, taking up a good 30 degrees of the sky, is Hale-Bopp.

Up to the left are the McDonald Observatory, 107-inch and 82-inch. They’re reflecting off of them the entire horizon of thunderstorms that are off in the distance. Then straight overhead, like you were in a planetarium, was the Milky Way.

It was this moment of, if you showed this in a planetarium, people wouldn’t think it was real. We saw that for months.

Fraser Cain: 

Months. Then we saw it again. I think it’s really important.

Pamela’s describing 30 degrees in the sky. Take your hand out at arm’s length, put your fingers out as far as they’re going to go, measure the bottom of your thumb to the top of your finger, and it’s more than that. That’s 25 degrees.

It’s bigger than that. Imagine that. Hold your arm out and imagine seeing a comet, bright comet, on the horizon, high up in the sky, that is just monstrous.

The problem is that we have to get pictures. People take amazing pictures with their telescopes, but that’s not what you see with your eyes. When Hakutake and Hale-Bopp were here, that’s what you saw with your eyes.

You didn’t need a camera. A telescope was of no benefit because it didn’t fit. It was so big.

It’s madness. Anytime people are like, yeah, but what about this comet? It is unacceptable.

The universe can do better. It knows it, and I accept nothing less than the best.

Dr. Pamela Gay: 

We need a comet 1729 P1. This was a comet that reached magnitude negative three. It is the brightest comet ever on record, although there are arguments that the Great Comet of 1882 might be even brighter.

Fraser Cain: 

You could read your newspaper to a comet that bright.

Dr. Pamela Gay: 

Yeah, and what’s amazing is because these are related to how close we were to them, there’s always that every single time we pass through the tail of a comet when there’s a shower, there’s this moment of, ah, but the comet could have just gone through and wouldn’t that be amazing? And this is what I want, but we don’t have any periodic comments that are due to do that anytime soon.

Fraser Cain: 

All right. So let’s set this up then. What is it going to take?

What are the confluence of factors that make a comet great versus one that is not great?

Dr. Pamela Gay: 

So a truly great comet has to have a number of different things. It has to be near the sun and the earth at about the same time, but not so close to the sun that we can’t see it. So you want this angle between looking from the earth to the comet to the sun, you want the comet earth sun angle to be greater than 20.

Fraser Cain: 

Right. And ideally you want the comet on the other side of the earth from the sun and close.

Dr. Pamela Gay: 

Yeah. Yeah. That is absolutely ideal.

But at least 30 degrees away. So greater so that it’s behind you.

Fraser Cain: 

And the, and the problem with that story is, is that comets get exciting. Comets get big tails when they’re close to the sun. It, and think about how hard it is to see mercury, right?

Mercury is close to this is always interior to us. We’re always having to look close to the sun to be able to see mercury. Very few people have even ever seen mercury because it’s close to the sun.

And so the comments are usually at their best when they’re close to the sun.

Dr. Pamela Gay: 

Right. Right. And so close to the sun, close to the earth at the same time, very important because you also want the object to have a lot of volatiles on its surface that can get exposed to the sun, form a bright coma, form the tails that we see both the ion tail and the tail of stuff and things.

So we’ve been seeing lately comments that have a lot of carbon in them and they become this amazing shade of green as they get ionized. And, and so the colors that we see are due to the composition. So having, it’s not a requirement, but it’s a bonus feature if they can have an interesting set of atoms in them.

Fraser Cain: 

Right.

Dr. Pamela Gay: 

And then you just want the sucker to be big, a little tiny comment that is like 90% volatiles and well-placed isn’t going to be able to put on as large a show as a significantly bigger object that may not have as many volatiles, but has a lot more surface area for those volatiles to be getting active on.

Fraser Cain: 

Give us a sense. What is a small comment versus a big comment? Like the size of the nucleus?

Dr. Pamela Gay: 

I mean, like the biggest comments can be measured in kilometers across. Generally they’re, they’re not going to be that big, but they can get that big.

Fraser Cain: 

Right. So hundreds of meters, two kilometers across. I think the largest comment that we’ve seen, we actually stopped fairly recently was in the tens of kilometers across.

It wasn’t very close. Unfortunately, even three eye Atlas is an interstellar object. It’s five and a half kilometers across.

Like it’s a big object.

Dr. Pamela Gay: 

Yeah. So 2014, I’m going to say this wrong. I, I am so sorry.

Comet 2014 UN 271 Bernard Nenilly Bernstein was a hundred kilometers, 62 miles across. And it is the biggest we know of so far, but we’ve only had the ability to measure their diameters very recently. So, so there’s that factor working against us.

Fraser Cain: 

All right. We’re going to talk about this some more, but it’s time for another break and we’re back. All right.

So we know that we want the comment to come close to the earth, but be on the opposite side of the sun. Ideally we want it to be large so that it’s going to be able to give off a lot of volatiles, be able to, uh, fire material out into space, the bigger, the coma, the longer the tail, the brighter it’s going to be. So then when comments are first discovered, there’s a lot of unpredictability.

Like, like we’ve done this quite a bit where a new comment has been discovered. And then we talk about whether or not it’s going to be great. Why can’t we be more certain?

Dr. Pamela Gay: 

So it turns out that when comments are struggling to stay in one piece, they get super interesting on the sky. So one of the things that can temporarily allow a comment to get super bright, super interesting is just when that sucker completely falls apart, which sometimes comments choose to do. We, we had one back in 2013 that opted to completely fall apart on Thanksgiving day.

So, uh, when you fall apart, you have many different pieces, all producing a lot of volatiles and very temporarily, uh, you can end up with a nice, cool, bright thing, but very temporarily. Uh, there’s also the issue that we don’t know when we first spot a comment, what its size is and what its composition is necessarily. And we make approximations based on how bright it appears.

And if you have a really big comment that has a lot of dark organic molecules on its surface, it will appear smaller than it actually is. If you have a little tiny comment that is super, super shiny, um, or asteroid in the case of the target for Hayabusa2, uh, if you have a small object that appears super shiny, you’re going to assume it’s much bigger. And there’s also the issue of sometimes we just don’t know that a comment is coming.

So when you and I make our predictions every December of what to look forward to the following year, we don’t know about comments that have never been seen before that are going to decide to show up. So, um, we can misidentify how interesting they’re going to be. They can decide, Hey, I’m just going to completely fall apart over here and become super bright.

Um, and then there’s all the ones we just didn’t know were coming.

Fraser Cain: 

And I think the most compelling ones are the ones that are most uncertain. They’re the ones that are going to do a close flyby of the sun. Um, you know, that trajectory you want is it falls down into the inner solar system, just scrapes past the sun and then goes into a trajectory that puts it on, as we mentioned on the opposite side of the earth from the sun, or at least 30 degrees away from the sun.

So you can see it in the, in the sky. The problem is the closer you get to the sun, the more dangerous a path you’re taking. And the sun will tear these comments apart in with its title forces into just a, uh, just a pile of dust.

And, and so you have to sort of thread that needle. You want to get really close to the sun so that you have a lot of volatile elements come off of it, but you don’t want to get so close that you get completely torn apart. And so there’s been examples where comments we’re watching for the comment to complete its, its flight past the sun, where if it survives, then it’s going to be one of the best comments we’ve ever seen.

It’s going to be super bright comment of the century. And we wait and we wait and we wait and no comment comes out the other side of comes around the back of the sun. It was destroyed.

It’s gone. It’s just, it’s, it’s, it’s smashed into little pieces. And then all the volatiles are blown away and maybe a debris cloud comes out the other side, but nothing that’s going to put on that big sky show.

It’s got to hold together and be able to make that journey. And so that’s one of the biggest unknowns is will it survive? It’s it’s travel around the sun.

Dr. Pamela Gay: 

And one of the best apparitions that, uh, many of us heard about either from great grandparents or from music, it turns out was the 1910 apparition of Haley’s comment, uh, that particular year, all the right things occurred. And just after the comment went past earth’s orbit, passing through earth’s orbit, that’s how we get the meteor shower from it. Um, we basically flew through the tail.

And so if you can time it just right, so that it crosses the earth’s orbit as you are heading towards that crossing point. So it ends up behind you in the solar system. Um, you can get an amazing meteor shower that leads to really good music getting written.

Um, the stars fall over Alabama is the song I’m thinking of as well as an amazing comment to view at night. And that double whammy of shooting stars and comment to view is, is just the kind of thing. I for one dream of eventually seeing when some comment we don’t know about currently decides to grace our solar system with the passage.

Fraser Cain: 

All right. We’re going to take another break and we’re back. So you mentioned Halley’s and I wanted to sort of go into that a bit.

So, you know, we have now three classifications of comments. We have the interstellar comments of which we have seen three, maybe three.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

Well, I mean, was a moment, a comment was an asteroid.

Dr. Pamela Gay: 

Well, okay. That’s fair. We’ve seen three interstellar objects, right?

Yeah.

Fraser Cain: 

Boris Borisov was very much comment three. Alice is acting very much like a comment, but they come randomly at high velocity. They take whatever journey they’re going to take through the solar system and then they’re gone.

And so far they have not been very bright, hard to spot. Yeah. You have the long period comments, the ones that are entering the inner solar system for the first time in their entire experience that they’ve been out there for 4.5 billion years. They finally through some gravitational interaction, make the long journey. They take a million years to fall down into the inner solar system, zip through, and then they head back out.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

Random. We, we have no way to predict them, but we do have the periodic comments, the ones that are, that come on a regular basis. Comet Halley is the most famous of these.

Dr. Pamela Gay: 

Right.

Fraser Cain: 

So when can we expect a good, you know, can we know when there’s going to be good Halley’s comments and bad Halley’s comments to a certain degree?

Dr. Pamela Gay: 

I, a lot of us who were tiny children expecting to see a massive comment because so much went into educating children across at least America. I don’t know what you experienced in the Canadian. Yeah.

You had the same thing. It was just like all of this all of this prep and like kind of math. Yeah.

Yeah. I, I was not impressed and where it gets frustrating is at a certain point, the really cool stuff is also associated with stuff like landslides and disruptions, and we don’t know when those are going to occur. So like Rosetta got some amazing closeup images of Sherry Gary having outbursts related to disruptions of the comment.

And so we, we can run software and you can do this to a certain degree in Stellarium into the future and figure out when will we have passages of the earth right before or after a comment has crossed its orbit. And there’s, there’s none anytime soon. It’s kind of sad.

But at the same time, we keep finding comments that are the non-periodic ones. So currently the periodic ones, we’re going to get some, we’re not going to get anything like Yakutaki or Hale-Bopp from any of the periodic ones anytime soon.

Fraser Cain: 

I mean, our next Haley’s is 61.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

20, 2061, we’ll get another flyby. But, but as you said, we probably won’t get what we, what we got in 1910 where we went through the tail.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

Where it was very bright. It was, you know, it was a, it was a, it was like things worked out really well for that one. In this case, it’s going to be, I don’t know what the, what the kinematics are for this upcoming version, but, but in general, like there are a bunch of them, but they, but very few come even relatively close to the sky.

You can, you know, every year we get a couple that you can see in the telescope that are periodic comments. They come every 20 years, every thousand years. But it’s the, really, it’s the, the ones that have come from the Oort cloud that are the random, and they can be amazing or they can be mediocre.

Dr. Pamela Gay: 

And, and this is where, when we’re recording this in the fall of 2025, we’re looking at the surprise apparition of comets, Lemon, Swan, and then there’s a bunch of others that are just telescopic ones. But 2025 A6 Lemon is predicted to get maybe as bright as magnitude three by the end of October. Yep.

So I’m looking forward to being able to see that with my unaided eye.

Fraser Cain: 

Yeah, that you can see with your eye. And it’s been a while since we could even see a comet with our eyes. This one, and it’s also well-placed.

Dr. Pamela Gay: 

Yes.

Fraser Cain: 

So, and Swan as well. Swan is really well-placed.

Dr. Pamela Gay: 

2025 R2 Swan.

Fraser Cain: 

Yeah. So Comet Swan is, is up in, is going to sort of pass up through Hercules. So it’s a very high, very easy comet to spot.

Lemon is going to stay very close to the horizon.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

So you’re going to need a good view to the West to be able to see it. Both should be visible near the end of October and into early November. You just, you kind of need to know where to look and have some, have some clear skies, but really a pair of binoculars and a small telescope will get you to this place where you can see just a hint, but you should feel angry while you’re looking through the binoculars at these comets and going like really universe, this is the best you can do.

Dr. Pamela Gay: 

Fine. Yeah. Yeah.

And, and even though Hale-Bopp is a periodic one, it has an orbit of hundreds of years. So, uh, yeah, we’re not going to get to see it again.

Fraser Cain: 

Right. In our lifetime.

Dr. Pamela Gay: 

Right.

Fraser Cain: 

Unless we get a robot bodies. Yeah.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

But who knows? Right. You could be listening to this episode I’ll be here from now.

And there was the three great comments that happened in December.

Dr. Pamela Gay: 

Exactly. Exactly.

Fraser Cain: 

Right. The three great comments that happened in May and we’re all still talking about them. And that one time that the comet passed right through the atmosphere of the earth, that was scary is, is a thing that can happen.

Dr. Pamela Gay: 

Yeah. Yeah. And, and here’s the thing.

We suspect that perhaps the Tunguska event was, uh, a object that had a large volatile load. So it ended up having an air burst. Um, I’m not saying it’s a comment.

I’m not saying it’s an asteroid. I don’t think that debate will ever be solved, but it had enough volatiles in it to have this amazing air burst that flattened trees in spectacular ways. Um, there, there’s this, this hope that we can get a non-destructive really bright kind of event in our lifetime.

So I’m not saying please hit the earth. I’m saying please blow up in our atmosphere, uh, in places where there are monitoring cameras like they have out in Australia, but not a lot of life forms.

Fraser Cain: 

Are you sure you’re not a supervillain? No. Okay.

Dr. Pamela Gay: 

Um, it’s, it’s entirely possible. I’m also team. Please hit the moon for IR4.

Fraser Cain: 

Right. Yeah. But, but if YR4 hits the moon, causes debris that could take out a bunch of worth it maybe for the, for the mother of all meteor storms.

Dr. Pamela Gay: 

Well, and, and it’s like a 50 meter asteroid. So it will create a roughly one kilometer crater, which is right at the edge of what a human eye can, can make out. It’ll appear as a point source.

And I now need to figure out what will the phase of the moon be at the time of impact? Like, do we have enough information to know that? And if we do, then comes the question of if it’s in the shadow, can we see it?

And I’m actually working out the math for this. I meant to finish doing it yesterday, but we went down a neutron star rabbit hole. Um, so, so patrons, the $5 a month and higher level, we have a new, that takes math series that you can join me for.

Um, so yeah, I can consider doing that. Um, but comets, I mean, the real thing that we just haven’t hit on nearly enough is the more research we do, the more we’re realizing that things like landslides and other disruptions on the surface of these objects, cause them to form comas, cause them to periodically grow tails. It is one of these things where comments being not as structurally sound as one might hope for causes them to put on amazing light shows.

And if they’re big enough and the disruption is small enough, we get to enjoy the light show and have a tail later to see because the comment doesn’t fall apart completely.

Fraser Cain: 

Yeah. So, uh, you know, now we’ve reminded the universe what it’s, what it’s possible, what it’s capable of. It knows how it’s falling short of our expectations and we hope no demand demand demand, uh, better comments.

So how’s that coming universe? Thanks, Pamela.

Dr. Pamela Gay: 

Thank you, Fraser. And thank you to all the patrons who support this show. This show wouldn’t exist without the amazing support of so many of you over on patreon.com slash astronomy cast. This week, we would like to thank in particular, a pronounceable name, Alex rain, Astro Zets, Bart Flaherty, Bresnik, Brian Cagle, Cami Rassian, Cody Rose, Cooper, Daniel loosely, David Gates, Dwight ilk, evil milky, Frank Stewart, Hal McKinney, John Baptiste, Lamar, Jim of Everett, Joe Holstein, John Drake, John M. John days, Justin Proctor, Justin S. Christian Magerholt, Kinsaia Penflanko, Les Howard, Lou Zealand, Lona Spencer, Mark Phillips, Matt Rucker, Matthew Horstman, Matthias Hayden, Michael Wichman, Mike Heisey, Nick Boyd, Olga, Pauline Middlelink, Ruben McCarthy, Ryan Amory, Scott Bieber, Sean Matz, Sergei Monolov, Slug, Stephen Veidt, Stephen Miller, TC Starboy, the mysterious Mark, Time Lord Iroh, Travis C. Porco, Will Field, William Andrews. Thank you all so very much. I read your names pre-recorded.

Rich will insert them. And yeah, that’s a thing I do now.

Fraser Cain: 

Right. All right. Thanks, everybody.

Thanks, Pamela. And we’ll see you next week.

Dr. Pamela Gay: 

Bye-bye, Fraser. Bye-bye, everyone.

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