Astronomy

A small world in the outer solar system appears to have volcanic activity possibly spurred by liquid water

A new design competition, dubbed Project Hyperion, is calling for submissions for the design of a crewed interstellar generation ship.

Black holes are real. We see them throughout the cosmos, and have even directly imaged the supermassive black hole in M87 and our own Milky Way. We understand black holes quite well, but the theoretical descriptions of these cosmic creatures still have nagging issues. Perhaps the most famous issue is that of the singularity. According to the classical model of general relativity, all the matter that forms a black hole must be compressed into an infinite density, enclosed within a sphere of zero volume. We assume that somehow quantum physics will avert this problem, though without a theory of quantum gravity, we aren’t sure how. But the singularity isn’t the only infinite problem. Take, for example, the strange boundary known as the Cauchy horizon.

When you get down to it, general relativity is a set of complex differential equations. To understand black holes, you must solve these equations subject to a set of conditions such as the amount of mass, rotation, and electromagnetic charge. The equations are so complex that physicists often focus on connecting solutions to certain mathematical boundaries, or horizons. For example, the event horizon is a boundary between the inside and outside of a black hole. It’s one of the easier horizons to explain because if you happen to cross the event horizon of a black hole, you are forever trapped within it. The event horizon is like a cosmic Hotel California.

For a simple, non-rotating black hole, the event horizon is the only one that really matters. But for rotating black holes, things get really weird. To begin with, the singularity becomes a ring, not a point. And rather than a single event horizon, there is an outer and an inner horizon. The outer one still acts as an event horizon, forever trapping what dares to cross its boundary. The inner one is what’s often called the Cauchy horizon. If you cross the inner horizon, you are still trapped within, but you aren’t necessarily doomed to fall ever closer toward the singularity. Within the Cauchy horizon, spacetime can behave somewhat normally, though it is bounded.

Horizon structure for a rotating black hole. Credit: Simon Tyran, via Wikipedia

The Cauchy horizon can cause all sorts of strange things, but one of them is that the horizon is unstable. If you try to determine perturbations of the horizon, the calculated mass within the horizon diverges, an effect known as mass inflation. It’s somewhat similar to the way the singularity approaches infinite density in the classical model. While this is frustrating, physicists can sweep it under the rug by invoking the principle of cosmic censorship. It basically says that as long as some basic conditions hold, all the strange behaviors like singularities and mass inflation are always bounded by an event horizon. There may be an infinity of mathematical demons in a black hole, but they can never escape, so we don’t really need to worry about them.

But a new paper may have handed those demons a key. The paper shows that mass inflation can occur even without a Cauchy horizon. Without an explicit Cauchy horizon, those basic conditions for cosmic censorship don’t necessarily apply. This suggests that the black hole solutions we get from general relativity are flawed. They can describe black holes that exist for a limited time, but not the long-lasting black holes that actually exist.

What this means isn’t entirely clear. It might be that this impermanent loophole is just general relativity’s way of pointing us toward a quantum theory of gravity. After all, if Hawking radiation is real, all black holes are impermanent and eventually evaporate. But the result could also suggest that general relativity is only partially correct, and what we need is an extension of Einstein’s model the way GR extended Newtonian gravity. What is clear is that our understanding of black holes is incomplete.

Reference: Carballo-Rubio, Raúl, et al. “Mass inflation without Cauchy horizons.” Physical Review Letters 133.18 (2024): 181402.

The post We Understand Rotating Black Holes Even Less Than We Thought appeared first on Universe Today.

When we think of exoplanets that may be able to support life, we hone in on the habitable zone. A habitable zone is a region around a star where planets receive enough stellar energy to have liquid surface water. It’s a somewhat crude but helpful first step when examining thousands of exoplanets.

However, there’s a lot more to habitability than that.

In a dense stellar environment, planets in habitable zones have more than their host star to contend with. Stellar flybys and exploding supernovae can eject habitable zone exoplanets from their solar systems and even destroy their atmospheres or the planets themselves.

New research examines the threats facing the habitable zone planets in our stellar neighbourhood. The study is “The 10 pc Neighborhood of Habitable Zone Exoplanetary Systems: Threat Assessment from Stellar Encounters & Supernovae,” and it has been accepted for publication in The Astronomical Journal. The lead author is Tisyagupta Pyne from the Integrated Science Education And Research Centre at Visva-Bharati University in India.

The researchers examined the 10-parsec regions around the 84 solar systems with habitable zone exoplanets. Some of these Habitable Zone Systems (HZS) face risks from stars outside of the solar systems. How do these risks affect their habitability? What does it mean for our notion of the habitable zone?

“Among the 4,500+ exoplanet-hosting stars, about 140+ are known to host planets in their habitable zones,” the authors write. “We assess the possible risks that local stellar environment of these HZS pose to their habitability.”

This image from the research shows the sky positions of exoplanet-hosting stars projected on a Molleweide map. HZS are denoted by yellow-green circles, while the remaining population of exoplanets is represented by gray circles. The studied sample of 84 HZS, located within 220 pc of the Sun, is represented by crossed yellow-green circles. The three high-density HZS located near the galactic plane are labeled 1, 2 and 3 in white. The colour bar represents the stellar density, i.e., the number of stars having more than 15 stars within a radius of 5 arc mins. Image Credit: Pyne et al. 2024.

We have more than 150 confirmed exoplanets in habitable zones, and as exoplanet science advances, scientists are developing a more detailed understanding of what habitable zone means. Scientists increasingly use the terms conservative habitable zone and optimistic habitable zone.

The optimistic habitable zone is defined as regions that receive less radiation from their star than Venus received one billion years ago and more than Mars did 3.8 billion years ago. Scientists think that recent Venus (RV) and early Mars (EM) both likely had surface water.

The conservative habitable zone is a more stringent definition. It’s a narrower region around a star where an exoplanet could have surface water. It’s defined by an inner runaway greenhouse edge where stellar flux would vaporize surface water and an outer maximum greenhouse edge where the greenhouse effect of carbon dioxide is dominated by Rayleigh scattering.

Those are useful scientific definitions as far as they go. But what about habitable stellar environments? In recent years, scientists have learned a lot about how stars behave, the characteristics of exoplanets, and how the two are intertwined.

“The discovery of numerous extrasolar planets has revealed a diverse array of stellar and planetary characteristics, making systematic comparisons crucial for evaluating habitability and assessing the potential for life beyond our solar system,” the authors write.

To make these necessary systematic comparisons, the researchers developed two metrics: the Solar Similarity Index (SSI) and the Neighborhood Similarity Index (NSI). Since main sequence stars like our Sun are conducive to habitability, the SSI compares our Solar System’s properties with those of other HZs. The NSI compares the properties of stars in a 10-parsec region around the Sun to the same size region around other HZSs.

This research is mostly based on data from the ESA’s Gaia spacecraft, which is building a map of the Milky Way by measuring one billion stars. But the further away an HZS is, or the dimmer the stars are, the more likely Gaia may not have detected every star, which affects the research’s results. This image shows Gaia’s data completeness. The colour scale indicates the faintest G magnitude at which the 95% completeness threshold is achieved. “Our sample of 84 HZS (green circles) has been overlaid on the map to visually depict the completeness of their respective neighbourhoods,” the authors write. Image Credit: Pyne et al. 2024.

These indices put habitable zones in a larger context.

“While the concept of HZ is vital in the search for habitable worlds, the stellar environment of the planet also plays an important role in determining longevity and maintenance of habitability,” the authors write. “Studies have shown that a high rate of catastrophic events, such as supernovae and close stellar encounters in regions of high stellar density, is not conducive to the evolution of complex life forms and the maintenance of habitability over long periods.”

When radiation and high-energy particles from a distant source reach a planet in a habitable zone, they can cause severe damage to Earth-like planets. Supernovae are a dangerous source of radiation and particles, and if one were to explode close enough to Earth, that would be the end of life. Scientists know that ancient supernovae have left their mark on Earth, but none of them were close enough to destroy the atmosphere.

“Our primary focus is to investigate the effects of SNe on the atmospheres of exoplanets or exomoons assuming their atmospheres to be Earth-like,” the authors write.

The first factor is stellar density. The more stars in a neighbourhood, the greater the likelihood of supernova explosions and stellar flybys.

“The astrophysical impacts of the stellar environment is a “low-probability, high-consequence” scenario
for the continuation of habitability of exoplanets,” the authors write. Though disruptive events like supernova explosions or close stellar flybys are unlikely, the consequences can be so severe that habitability is completely eliminated.

When it came to the supernova threat, the researchers looked at high-mass stars in stellar neighbourhoods since only massive stars explode. Pyne and her colleagues found high-mass stars with more than eight solar masses in the 10-parsec neighbourhoods of two HZS: TOI-1227 and HD 48265. “These high-mass stars are potential progenitors for supernova explosions,” the authors explain.

Only one of the HZS is at risk of a stellar flyby. HD 165155 has an encounter rate of ?1 in 5 Gyr period. That means it’s at greater risk of an encounter with another star that could eject planets from its habitable zone.

The team’s pair of indices, the SSI and the NSI, produced divergent results. “… we find that the stellar environments of the majority of HZS exhibit a high degree of similarity (NSI> 0.75) to the solar neighbourhood,” they explain. However, because of the wide variety of stars in HZS, comparing them to the Sun results in a wide range of SSI values.

We know the danger supernova explosions pose to habitability. The initial burst of radiation could kill anything on the surface of a planet too close. The ongoing radiation could strip away the atmospheres of some planets further away and could also cause DNA damage in any lifeforms exposed to it. For planets that are further away from the blast, the supernova could alter their climate and trigger extinctions. There’s no absolutely certain understanding of how far away a planet needs to avoid devastation, but many scientists say that within 50 light-years, a planet is probably toast.

We can see the results of some of the stellar flybys the authors are considering. Rogue planets, or free-floating planets (FPPs), are likely in their hapless situations precisely because a stellar interloper got too close to their HZS and disrupted the gravitational relationships between the planets and their stars. We don’t know how many of these FPPs are in the Milky Way, but there could be many billions of them. Future telescopes like the Nancy Grace Roman Space Telescope will help us understand how many there truly are.

An artist’s illustration of a rogue planet, dark and mysterious. Image Credit: NASA

Habitability may be fleeting, and our planet may be the exception. It’s possible that life appears on many planets in habitable zones but can’t last long due to various factors. From a great distance away, we can’t detect all the variables that go into exoplanet habitability.

However, we can gain an understanding of the stellar environments in which potentially habitable exoplanets exist, and this research shows us how.

The post Habitable Worlds are Found in Safe Places appeared first on Universe Today.

Nine years ago, Blue Origin revealed the plans for their New Glenn rocket, a heavy-lift vehicle with a reusable first stage that would compete with SpaceX for orbital flights. Since that time, SpaceX has launched hundreds of rockets, while Blue Origin has been working mostly in secret on New Glenn. Last week, the company rolled out the first prototype of the first-stage booster to the launch complex at Cape Canaveral Space Force Station. If all goes well, we could see a late November test on the launch pad.

The test will be an integrated launch vehicle hot-fire which will include the second stage and a stacked payload.

Images posted on social media by Blue Origin CEO Dave Limp showed the 57-meter (188-foot)-long first stage with its seven BE-4 engines as it was transported from the production facility in Merritt Island, Florida — next to the Kennedy Space Center — to Launch Complex 36 at Cape Canaveral. Limp said that it was a 23-mile, multiple-hour journey “because we have to take the long way around.” The booster was carried by Blue Origin’s trailers called GERT (Giant Enormous Rocket Truck).

#NewGlenn’s GS1 is on the move! Our transporter comprises two trailers connected by cradles and a strongback assembly designed in-house. There are 22 axles and 176 tires on this transport vehicle. It’s towed by an Oshkosh M1070, a repurposed U.S. Army tank transporter, with 505… pic.twitter.com/4Qq7Ofq2g2

— Dave Limp (@davill) October 30, 2024

“Our transporter comprises two trailers connected by cradles and a strongback assembly designed in-house,” said Limp on X. “There are 22 axles and 176 tires on this transport vehicle…The distance between GERT’s front bumper and the trailer’s rear is 310’, about the length of a football field.”

Limp said the next step is to put the first and second stages together on the launch pad for the fully integrated hot fire dress rehearsal. The second stage recently completed its own hot fire at the launch site.

An overhead view of the New Glenn booster heading to launch complex 36 at Cape Canaveral during the night of Oct. 30, 2024. Credit: Blue Origin/Dave Limp.

Hopefully the test will lead to Blue Origin’s first ever launch to orbit. While the New Glenn rocket has had its share of delays, it seems Blue Origin has also taken a slow, measured approach to prepare for its first launch. In February of this year, a boilerplate of the rocket was finally rolled onto the launch pad at Cape Canaveral for testing.  Then in May 2024, New Glenn was rolled out again for additional testing. Now, the fully integrated test in the next few weeks will perhaps lead to a launch by the end of the year.

New Glenn’s seven engines will give it more than 3.8 million pounds of thrust on liftoff. The goal is for New Glenn to reuse its first-stage booster and the seven engines powering it, with recovery on a barge located downrange off the coast of Florida in the Atlantic Ocean.

New Glenn boosters are designed for 25 flights.

Blue Origin says New Glenn will launch payloads into high-energy orbits. It can carry more than 13 metric tons to geostationary transfer orbit (GTO) and 45 metric tons to low Earth orbit (LEO).

For the first flight, Blue Origin will be flying its own hardware as a payload, a satellite deployment technology called Blue Ring. Even though it doesn’t have a paying customer for the upcoming launch, it would be — if successful — the first of two required certification flights needed by the rocket by the U.S. Space Force so it could potentially be awarded future national security missions along with side SpaceX and United Launch Alliance (ULA.)

Additional details can be found at PhysOrg and NASASpaceflight.com.

The post New Glenn Booster Moves to Launch Complex 36 appeared first on Universe Today.

"[Now that I work for Safety and Mission Assurance,] it's really cool to read everything about the different types of the scenarios. I always get to see the task orders and the type of work that is going on to keep people safe on the ground and in the air.” — Miranda Meyer, Contract Specialist, NASA's Goddard Space Flight Center

A review of Netflix's new "The Man Who Loved UFOs," a film exploring a 1986 flying saucer hoax that captured the attention of a nation.

NASA astronauts can vote from space, but why can't they endorse political candidates? As it turns out, U.S. federal law specifically prohibits them from doing so.

While you can get good discounts during both shopping events, we take a look at which is better between Black Friday and the Christmas sales.

Matthew McConaughey narrates four new cinematic teaser trailers for out-of-this-world alien creatures in upcoming sci-fi role playing game "Exodus."

What created this huge space bubble?

Several downballot races in the 2024 presidential election will carry implications for climate policy far beyond state lines

Experts predict that the number of cancer cases around the world will skyrocket, resulting in millions more fatalities by 2050

Experts predict that the number of cancer cases around the world will skyrocket, resulting in millions more fatalities by 2050

Our ancestors probably used a wide range of plant-based tools that have since been lost to history. Now we're finally getting a glimpse of this Botanic Age

Our ancestors probably used a wide range of plant-based tools that have since been lost to history. Now we're finally getting a glimpse of this Botanic Age

"This is incredibly exciting, as up to now we have not had a tool for detecting plastics in coastal environments from space."

Torrential rainfall causing deadly flash floods has hit southern and eastern Spain in regions including the Costa del Sol, where the city of Malaga is located, and Valencia in the east. As these areas struggle to cope with the aftermath, satellite technology has played a crucial role in assessing the damages of the affected areas.

The article is being updated as new satellite images become available.

One thing we’ve learned in recent decades is that exoplanets are surprisingly common. So far, we’ve confirmed nearly 6,000 planets, and we have evidence for thousands more. Most of these planets were discovered using the transit method. though we there are other methods as well. Many stars are known to have multiple planets, such as the TRAPPIST-1 system with seven Earth-sized worlds. But even within known planetary systems there could be planets we’ve overlooked. Perhaps their orbit doesn’t pass in front of the star from our vantage point, or the evidence of their presence is buried in data noise. How might we find them? A recent paper on the arXiv has an interesting approach.

Rather than combing through the observational data trying to extract more planets from the noise, the authors suggest that we look at the orbital dynamics of known systems to see if planets might be possible between the planets we know. Established systems are millions or billions of years old, so their planetary orbits must be stable on those timescales. If the planets of a system are “closely packed,” then adding new planets to the mix would cause the system to go all akilter. If the system is “loosely packed,” then we could add hypothetical planets between the others, and the system would still be dynamically stable.

The seven planetary systems considered. Credit: Horner, et al

To show how this would work, the authors consider seven planetary systems discovered by the Transiting Exoplanet Survey Satellite (TESS) known to have two planets. Since it isn’t likely that a system has only two planets, there is a good chance they have others. The team then ran thousands of simulations of these systems with hypothetical planets, calculating if they could remain stable over millions of years. They found that for two of the systems, extra planets (other than planets much more distant than the known ones) could be ruled out on dynamical grounds. Extra planets would almost certainly destabilize the systems. But five of the systems could remain stable with more planets. That doesn’t mean those systems have more planets, only that they could.

One of the things this work shows is that most of the currently known exoplanetary systems likely have yet-undiscovered worlds. This approach could also help us sort systems to determine which ones might deserve a further look. We are still in the early stages of discovery, and we are gathering data with incredible speed. We need tools like this so we aren’t overwhelmed by piles of new data.

Reference: Horner, Jonathan, et al. “The Search for the Inbetweeners: How packed are TESS planetary systems?” arXiv preprint arXiv:2411.00245 (2024).

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The neutron star 4U 1820-30 is one of the fastest spinning bodies in the universe, spinning at 716 times a second and erupting like an atomic bomb, NASA's NICER telescope has found.