Astronomy

Researchers used a browser extension to reorder people’s X feeds, reducing their polarizing effect

The collision of supermassive black holes shakes the entire cosmos, hard

Four astronauts are on their way to this orbital space station. Docking is expected on Saturday

The Bronx Zoo is celebrating 15 years of its extremely popular Valentine’s Day “Name a Roach” program

Why the simple act of kissing—which can be traced back 21.5 million years—continues to confound evolutionary biologists

Avian enthusiasts around the world will identify and count birds from February 13 through February 16 as part of a massive community science project

Video: 00:02:36

Watch the liftoff of ESA astronaut Sophie Adenot to the International Space Station (ISS), aboard a SpaceX Falcon 9 rocket from Space Launch Complex 40 at NASA’s Kennedy Space Centre. Sophie flies as mission specialist. The other Crew-12 members are NASA astronauts Jessica Meir and Jack Hathaway, respectively commander and pilot of the mission, and Roscosmos cosmonaut Andrei Fedyaev, mission specialist.

Watch the full launch replay. 

Three planets await you in the western twilight, though low Venus is a toughie. The crescent Moon passes them and, for the lucky, occults Mercury. Dog and Hare accompany Orion. And can you find Kemble's Cascade?

The post This Week's Sky at a Glance, February 13 – 22 appeared first on Sky & Telescope.

We live in a cosmic shooting gallery. It’s not a matter of “if” but “when”! Dinosaurs, blah, blah, blah. You know the drill. But seriously, folks, it’s raining rocks & ice out there! How seriously should we take it? What happens when a variety of different objects hit the Earth? Different kinds of objects affect Earth very differently when they impact. Let’s discuss what makes an impactor more or less dangerous.

Show Notes

• What Is a Quasar?
• Discovery and Redshift Identification
• Supermassive Black Holes at Galactic Centers
• Active vs. Dormant Black Holes
• Accretion Disks and the Eddington Limit
• Why Quasars Turn On and Off
• Intermittent Jets and Radio Evidence
• Microquasars as Scaled Analogues
• Brightness Variability Across Timescales
• The Milky Way’s Past Black Hole Activity
• Galaxy Mergers as Quasar Triggers
• Quasar Feedback: Star Formation vs. Suppression
• Jets and Their Impact on Surrounding Galaxies
• Black Hole Interactions and Periodic Flares
• Human-Timescale Observations Near Black Holes
• Early Universe Quasars with JWST
• The Mystery of the “Little Red Dots”
• Direct Collapse Black Hole Formation Hypothesis

Transcript

Fraser Cain:

AstronomyCast, Episode 781, When Black Holes Awaken. 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 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 you doing?

Dr. Pamela Gay:

I am cold. This winter?

Fraser Cain:

Yeah.

Dr. Pamela Gay:

Like, it’s so cold that even the squirrels are struggling with the ice. I saw a squirrel fall out of the tree yesterday. It was the funniest thing.

Fraser Cain:

Wow.

Dr. Pamela Gay:

There’s this plop in the snow and then the walk of shame that the squirrel had to make.

Fraser Cain:

Or it jumped. It, you know, it knew this was the fastest way down. There was no jump involved.

Yeah.

Dr. Pamela Gay:

So, yeah. All right. How are you doing with this winter of arcticness?

Fraser Cain:

Warm. Are you kidding? We haven’t, we’ve barely seen below freezing.

We’re having 10 Celsius days right now here in Western Canada.

Dr. Pamela Gay:

Yeah, we’re minus 10 Celsius.

Fraser Cain:

I could be growing oranges. I could have orange trees. We are truly the Florida of Canada at this point.

But I want to shout out and encourage people to check out something that you do, Pamela. And I gave you a shout out in my most recent Space Bites, and I’m going to do it again here now, which is that, you know, for those of you who think that Pamela is merely a PhD astronomer who runs the very successful CosmoQuest and is a wonderful narrator, she is also a very established and skilled news presenter. And that is because she does a weekly show called Escape Velocity Space News on the CosmoQuest channel on Twitch, or I don’t know where you do this.

Dr. Pamela Gay:

It’s also on YouTube.

Fraser Cain:

It’s also on YouTube. Yeah. And it’s so good.

And you’re writing it and you’re presenting it and you’re putting up graphics and you know what you’re talking about. And so as we live in this world with so much AI slop filling the channels and people looking for genuine human voices, don’t forget Pamela. And of course, you know, people tell me all the time, I’ll listen to your voice, I go to sleep.

I think that’s bananas because I speak quickly as I rise. Sometimes I’m yelling at you. Sometimes I’m very quiet.

I’m very manic. But Pamela has this beautiful, dulcet tones that just will help you go to sleep if that’s what you require. And so check out Escape Velocity Space News.

Thank you. One longstanding mystery in astronomy were the quasars, incomprehensible energy blasting out of a point like source billions of light years away. We now know these are actively feeding supermassive black holes, which can turn off and on in a startlingly short period of time.

Today, when black holes awaken, Pamela, let’s talk about quasars first because man, I always enjoy this. If you go and watch Cosmos, the original one with Carl Sagan, there’s right at the very beginning he is saying, there are these things called quasars and we don’t know what they are. And maybe they’re messages being, I’m not going to do a Carl Sagan impression anymore, but that maybe these are communications being sent by an advanced civilization in our direction.

And maybe these are black holes that are consuming material. Turns out it was the latter. So what are quasars?

Just to give people up to speed.

Dr. Pamela Gay:

It has been amazing to watch the evolution information about this. When I was an undergrad, we were still using overhead projectors with like this plasticky stuff that people would hand drawn and people would draw spiral galaxies with monsters in the center, here be dragons. And it was just awesome.

And the way they were discovered is these point sources were found in images that looked like stars. But when spectra were taken of them, they’re like, what the, none of these lines make sense. And I forget who it was specifically, sorry, I was not prepared for this specific question.

There was one guy who looked at it and was like, that’s redshifted a lot and was able to identify these were high redshift objects, not individual stars. These were galaxies, but they looked like stars. How was that?

It was deeply confusing. Right. And over the literally decades, we have gotten better and better equipment.

And the first thing they realized was these are mostly spiral galaxies that have in their core significantly more light being emitted than in the entire rest of the galaxy.

Fraser Cain:

Yes.

Dr. Pamela Gay:

And then we had to figure out how, and over time it was realized, okay, so this is an extremely small region in the center that is massively gravitationally strong. And there is a disk of material around this that is extraordinarily bright because it’s so compact that nuclear reactions are occurring in the disk. And over time, we started to also put together this unified idea that depending on the viewing angle, we are able to see different kinds of lines depending on where we’re looking in the disk.

And then finally, it was actually my graduate advisor, John Cormandy, and the team he was on, they were able to get spectra of the stars around the core of nearby galaxies and see in the redshifts of this material that the only way to explain the motions close in was if it was a supermassive black hole in the center.

Fraser Cain:

And, you know, the process of determining that there is a supermassive black hole at the heart of galaxies has become very mainstream, they’ve gotten very good at it. The best tool really is x-rays. So they will use telescopes like Chandra, they’ll be able to detect the presence of x-rays coming from the center of a galaxy and then use that to locate the position of the supermassive black hole.

Some of them are active, others are quiet. And so the natural question is, what makes them go from, when they’re active, what’s going on? And then what makes them go from active to quiet?

Are there just black holes that are always active and always putting out material? And are there black holes that are always quiet? Was the supermassive black hole at the heart of the Milky Way once active?

We have questions, Pamela. Answer them in whatever order you wish.

Dr. Pamela Gay:

OK, so, yes, our black hole has been active in the past. When we look at the core of the galaxy and the surroundings in x-rays and infrared, we’re able to see bubbles of material that was pushed out by the massive light pressure of some sort of a disk that was around it in the past. We see these bubbles, we see these high energy particles that are relics of past activity.

We don’t see relics of jets associated with our galaxy, so whatever occurred appears to have been short term, wasn’t highly active.

Fraser Cain:

Right.

Dr. Pamela Gay:

But these kinds of activities that we see early in the universe in large numbers and in decreasing numbers as the universe ages appear to be driven by some sort of an interaction between multiple galaxies that drives material, dust, gas, stars into the core where they get gravitationally locked into a death spiral with the supermassive black hole. And because of conservation of angular momentum, which is the enemy of all activities in astrophysics, as near as I can tell, as this material spirals in towards the core of the supermassive black hole, core of the galaxy rather, you end up with a disk building up, things keyed up in the disk, that disk and its light is what causes the quasar. It’s not the supermassive black hole, it’s the stuff trying to drop enough angular momentum to fall into that black hole.

Fraser Cain:

And the magnetic fields that are surrounding the black hole and its interactions. Those channel jets, yeah. That channel the jets.

And when you’re staring down the barrel of the jet, then you see a very bright center to the galaxy called the blazar. So the question I want to ask you is, are they forever? Are actively feeding galaxies always actively feeding or are they not sometimes?

Dr. Pamela Gay:

It turns out that they either run out of food naturally or fling their food away. So so actively feeding black holes, active galactic nuclei, quasars is what we call them when they’re sufficiently bright. That accretion disk generates a whole lot of light, and if it generates enough light, the pressure can start pushing away material that would want to be falling in.

Fraser Cain:

This sounds like the Eddington limit.

Dr. Pamela Gay:

Yeah. So there’s two different ways that black holes stop feeding. One is there’s just not enough stuff.

They run out of stuff to eat. And we’ve all been there. You open the refrigerator door and realize mistakes were made.

So it turns out, yeah, they can just run out of food sometimes. The other issue is they can have a disk that is so thick, so bright, it starts pushing material away, clears the region around it, and it goes hungry until the next time some sort of interaction occurs. And what’s so cool is we are starting to find these intermittent jets where you see dashed lines in the radio jets coming out of these systems.

Oh, that’s cool. Yeah.

Fraser Cain:

So where they turned off and turned on and you can actually see how long they’re off and how long they’re on.

Dr. Pamela Gay:

Exactly. Exactly.

Fraser Cain:

Yeah.

Dr. Pamela Gay:

And and we’ve we’d previously seen examples of quasars turning off. Hannes Vorwerp is an example of that. But the fact that we’re now finding these dashed jets of systems that turn on and off is just kind of awesome.

And I have to say, black holes at every scale are equally likely to do this kind of stuff. Stellar black holes and binary systems will steal material off of their companion, create accretion disks that light up, form jets. And when that companion either evolves to a different stage or just runs out of food in the gravitational Rocheleau limit, that feeding will turn off.

And so there are cataclysmic variables that include black holes out there doing their black hole things at stellar mass sizes.

Fraser Cain:

Yeah. Yeah, exactly. There’s this really interesting correlation that you can actually study relatively close to us, micro quasars, you know, I say tiny black holes, nearly with five times the mass of the sun, right, that are accreting material from some partner and have built an accretion disk and are firing out jets.

And they are in surprisingly similar ways, identical in terms of behavior to the ones where you’ve got a billion times the mass of the sun and can be used to study this for something that is much, much closer to home.

Dr. Pamela Gay:

Yeah. The laws of physics don’t care what scale it’s at.

Fraser Cain:

Yes. Yeah. Which is which is kind of surprising because you’d think there’d be a certain, you know, something would compound as these things get a lot more massive.

But but it all sort of works at different scales perfectly. So then, you know, you mentioned that you see this dotted line. Yeah.

How quickly does it appear that black holes can shut off and can shut on again?

Dr. Pamela Gay:

It’s millions of years. So so we it’s hard to tell exactly how long it takes them to turn off and turn back on. What we see is is gaps.

And and the example that is most recent is J1007 plus 3540. And it turned off as near as we can tell for about 100 million years and then turn back on. And we see that from the gap in its jet.

And we can see evidence in the jet of prior intermittency. And what’s amazing is this is a system that’s in a very thick galaxy cluster. And and so its poor jet is beat to its beat up by interacting with the surrounding intergalactic media or intercluster media, as the case may be.

Yeah, radio is starting to reveal some really cool stuff. The longer we have these high resolution systems like LOFAR and the new system in India online, the more of these kinds of things we’re going to discover.

Fraser Cain:

So I I think you might be wrong about the millions of years. Like, I think the period is faster than that in some cases that people are seeing these things.

Dr. Pamela Gay:

They turn on and off much faster. But the gap in time that this one is turned off.

Fraser Cain:

Yeah, right. Yeah. So that’s the so the turn off and turn on.

Dr. Pamela Gay:

So they turn on and off fairly quickly. We don’t know exactly how quickly, but they can have gaps in time that are hundreds of millions of years.

Fraser Cain:

Yeah. Yeah. And I think, you know, like part of this is that, you know, as you said, you have this accretion disk that’s around the black hole.

But there’s there’s this this idea that it’s actually really hard for material to kind of make that final drop down into the into the black hole. It’s got to shed all that final angular momentum and that it can just happily be spiraling around the black hole for longer periods of time before bits and blobs of it are being thrown in and sometimes requires some external interaction, another a new gas cloud giving a close star that causes turbulence that then throws in a new thing. And so so I think, you know, apparently we’ve seen quasars where they’ve noticeably brightened in the kinds of timescales that we can understand, like within a decade, within a couple of years, within you can see periodicities in their brightness over days.

Yes. Over days.

Dr. Pamela Gay:

Yeah. So it’s quite common to see that.

Fraser Cain:

Yeah. And so I think what was thought was, well, here’s the thing that this black hole is digesting, whatever, a thousand solar masses of material that it is piled up around it. And that’s going to take 10 million years to do.

No, you’re seeing variations that are happening on within human lifetimes.

Dr. Pamela Gay:

And what’s really cool is you can actually map out the accretion disk region by looking at the time scales of variations, because the time scale, the shortest possible time scale is dictated by how big or how small the area that’s emitting light will be, because you have to wait for the light from the entire object to reach you. And so the shorter the variations we see, the smaller the scale of the structure that’s doing that. And so when we see these variations, it’s a variation in the rate of consumption of the black hole.

We haven’t yet caught a black hole going entirely from active to completely turned off. And so we’ve only seen these variations in eating. And we’ve seen cases of like something gets nommed, but it was a quiet black hole that just suddenly ate something.

So it burped. And we’ve even seen that with the supermassive black hole at the Milky Way. In our black hole, yeah.

Fraser Cain:

Yeah, that there are, I mean, there’s a couple of masses worth of the Earth going into the black hole every year.

Dr. Pamela Gay:

Periodically, yeah.

Fraser Cain:

And and so you’ll get sort of a constant blast of X-rays and various radiation coming from the center of the Milky Way. And occasionally you get a little more.

Dr. Pamela Gay:

Yeah.

Fraser Cain:

Right. Yeah. So you hinted at this early on in the episode that that these jets, this activity has consequences for the galaxy that it is inside.

And around it. And around it. Yeah.

Like reaching out to other galaxies potentially within the cluster that it’s forming in. So so how does a actively feeding supermassive black hole and the jets and the material that it produces, how does that cause mayhem around it, both in the galaxy and nearby?

Dr. Pamela Gay:

So when this is occurring in a cluster environment, we have seen one case of a jet spearing a nearby galaxy and deforming it. So these these jets are carrying energy. They are carrying momentum.

They can push stuff around. And what’s amazing is as we look at more and more radio lobes, we can see them essentially forming fountain like ends as they interact with the significantly denser intra cluster media. So they’re pushing out on the media, creating dense places.

And when what they actually hit is another galaxy, they can trigger star formation.

Fraser Cain:

Or snuff it out.

Dr. Pamela Gay:

Or kill it. Yeah, that’s possible, too. They can just push out the material that would form.

Fraser Cain:

Yeah. Yeah. These jets and people need to understand these jets are last are going out tens of thousands, if not hundreds of thousands of light years long.

The material blasting out of these jets is going at relativistic velocity.

Dr. Pamela Gay:

Yeah.

Fraser Cain:

10 percent the speed of light, 20 percent the speed of light like this is serious business. And if you get caught, if your galaxy gets caught in the death beam of another galaxy’s actively feeding black hole, shenanigans ensue.

Dr. Pamela Gay:

And this is all a story of interactions. Quasars are created by having large amounts of material somehow triggered to fall into the center of a galaxy, which is most likely to occur when you look at these. The most common reason this happens is two galaxies interacted.

Two galaxies are merging and then you have the jets are going out and getting stabby with other galaxies, with the surrounding interstellar media. It is all a story of galaxies. I mean, we have all sorts of words.

It’s called galaxy harassment when they pass by each other too close. It’s ram pressure stripping when the inner cluster media decides to push material out of a galaxy. Quasars are often related with massive amounts of star formation that’s going on as dust and gas are getting compressed.

And once all of this chaos comes to an end, you’re often left with a red dead galaxy.

Fraser Cain:

Right. So you essentially are force feeding a galaxy its own gas. You’re causing all of its stars to form at once, burn through its reserves of gas.

And now it’s out. It’s done.

Dr. Pamela Gay:

Now it’s dead. Yeah.

Fraser Cain:

Yeah. And then all of the the red, all the stars just commonly evolve. Yeah.

Dr. Pamela Gay:

The blue ones go away supernova style as they do and tell this galaxy eat something else.

Fraser Cain:

Right. And then, you know, has fresh gas and then it all starts over. Right.

Dr. Pamela Gay:

Yeah.

Fraser Cain:

But but, you know, this is the effect that perhaps it can have on other galaxies. What what even effect can this have on the galaxy that the black hole is is within?

Dr. Pamela Gay:

Well, I mean, it’s deforming it by using its light to push things out. It is interacting with its media by pushing that around. It’s all a story of getting pushy, for lack of a better phrase.

Fraser Cain:

I mean, I think that I that I find kind of interesting is that you get this almost like a fountain in some cases. So the material is being blasted out. But then the gravity of the galaxy is dragging it back down.

And so it’s it’s sort of raining back down into the galaxy.

Dr. Pamela Gay:

That’s the innermost scale. We see this not in radio. This is something you study in other wavelengths.

Yeah. Yeah.

Fraser Cain:

And and that this could be seeding the galaxy with elements, with fresh material, with shock waves that are causing star systems, you know, causing gas clouds to collapse and begin the process of star formation and that that you get nucleosynthesis. You actually have heavier elements being formed in these accretion disks around the black holes. They’re like stars.

And then the material is being siphoned out of the accretion disk, jammed into the jets and then fountaining back down across the galaxy itself, enriching it with carbon, nitrogen, oxygen. Yeah. And so like, could we depend on a supermassive black hole for life?

Dr. Pamela Gay:

Oh, man. I wouldn’t depend on it, but it’s definitely a component, it’s a component. Yeah.

And as we look out across the interstellar media, we find really complex molecules. And these clouds of material have to get enriched somehow. And when you see them enriched, supernovae would deform them, would shock them.

And so this is a gentler way, in a way, to enrich the outer parts of the galaxy with material without causing the clouds of material to collapse.

Fraser Cain:

Right, right. So there’s one last thing that I wanted to talk about. I don’t know whether this needs to be a show on its own.

And I don’t know if this is in your mind, which is these transient, oh, man, transient luminance events.

Dr. Pamela Gay:

Yes. Yes, those those are cool. And yeah, and we need to do a show.

And I’m working on any of you who are on Patreon, drop me your ideas. I’m working on putting together the schedule for the rest of the season. Yes.

There’s a bunch of things that just like go flare in the night that we need to do a roundup of as we’re starting to get more and more understanding. Let’s go into this anyway.

Fraser Cain:

We’ll talk briefly about these because they’re related to the brightenings of galaxies and accretion disk and so on. But essentially, we now know that supermassive black holes can have other black holes in orbit around them. And as those black holes are passing through the accretion disk, plunging through the accretion disk, you get a flash coming out of the center of the galaxy.

Dr. Pamela Gay:

And so this flash is not the central supermassive black hole. It’s some other high density object, whether it be intermediate black holes or whatever. It just got hungry and stole food from its friends.

Right. And eventually that’s going to lead to emerging black hole. We’re just not seeing those yet.

We need more gravity wave detectors.

Fraser Cain:

And it’s really impressive. Like there’s this flash, you get the X-rays, you get the visual confirmation, and there’s this periodicity where the astronomers are able to say, oh, it went up through one part of the disk and now it’s come back down through the other part of the disk. And we’re expecting to see it flash again in precisely 18 months.

Yeah. And then right on schedule flash as this black hole is is passing through the accretion disk of another black hole.

Dr. Pamela Gay:

And what I love is because the supermassive black hole has such huge mass, we can on human timescales see things orbiting it, including other black holes. And we’ve been seeing this with Andrea Goethe’s work, looking at the core of the Milky Way, watching stars and blobs of gas orbit around over decades. This is astronomy on human timescales.

This is the kind of thing that very rarely happens. And it’s really cool to get to see it with high energy events that get all the telescopes involved.

Fraser Cain:

Yeah, yeah, absolutely. And it really is interesting to me how, I mean, you hate to use this sort of anthropomorphization analogy that it’s all about the village, that no black hole is an island, that black holes evolve in galaxies, the galaxies are part of galaxy clusters, and that things that happen in one galaxy can reach out across millions of light years to the other galaxies that are around it and have an influence on it.

And so one bad apple can spoil the pie. Like, I’ll just keep making analogies here. But the point is, is that what you might have in terms of like, say, even the potential for life in your galaxy depends on what was the environment of the galaxies around your galaxy.

Were they all sort of feasting on material, blasting out jets? Was it like you’re trying to exist within all these death rays and you ended up in a red dead galaxy? Or were you far enough away that that didn’t happen or that there was a near miss that just enriched the galaxy with the heavier elements that are required for life, but not the death beam that caused it to die too young, too early.

And this is the kinds of stories that astronomers are still trying to pick apart. It absolutely plays a role, but we don’t know what role exactly yet.

Dr. Pamela Gay:

And what’s so cool is, I was so disenchanted with JWST before it launched because so much money and so many careers had been ended because their money was stolen for it. Do you feel better now, though? I’m still bitter, but it is living up to its potential.

And we are starting to be able to see in the early universe the way galaxies were clearing out the space around them using these jets. And there’s some really cool illustrations that are out there of this that end up looking like cells because you have these galaxies moving through the material around them. And I’m really enjoying watching the evolution in how people are trying to understand the little red dots.

There’s a couple of competing theories that have come out recently. The one that I like the best is that the very first stars, like all sets of stars, had an initial mass function where some of these stars were so big that they collapsed directly into intermediate black holes. And it is those massive, massive stars and their surroundings that led to these little red dots.

Fraser Cain:

My hope is that we’re seeing the formation of globular clusters.

Dr. Pamela Gay:

Okay.

Fraser Cain:

That’s my hope.

Dr. Pamela Gay:

Yeah, that’s another one of the theories.

Fraser Cain:

Because it’s so compact and tight. And yet, globular clusters are as old as the universe. Where do they come from?

So are they the stripped cores of dwarf galaxies or are they a separate thing that formed and then found their way into other galaxies? That’s my hope. That’s, yeah, direct collapse would be incredible.

Like we’re literally seeing the direct collapse of black holes because they’re gone within. But we did a whole episode on little red dots, didn’t we?

Dr. Pamela Gay:

So yeah, yeah, yeah, yeah.

Fraser Cain:

We don’t need to rehash that. Awesome. But that was super fun.

Thanks, Pamela.

Dr. Pamela Gay:

Thank you, Fraser. And thank you to all of you who support us through Patreon. You make it possible for us to do all the things we do and have other people help us.

So, yeah, this week I would like to thank the following people. This week, I’d like to thank the following $10 a month and up patrons. Don Mundus, Ed, Eric Lee, Father Prax, Frederick Salvo, G.

Caleb Sexton, Gerhard Schweitzer, Gold, Greg Vialt, Hannah Tackery, Jacob Houle, Jarvis Earl, Jeanette Wink, Jim McGeehan, Joanne Mulvey, John Muthis. And, uh, thanks, Fraser.

Fraser Cain:

Thanks, Pamela, and we will see you all next week.

Dr. Pamela Gay:

Bye-bye.

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