Astronomy

NASA's Perseverance rover stumbled upon a Mars rock. It seems to suggest evidence of ancient life on the Red Planet.

When the James Webb Space Telescope was launched it came with a fanfare expecting amazing things, much like the Hubble Space Telescope. One of JWST’s most anticipated target was TRAPPIST-1. This inconspicuous star is host to seven Earth-sized planets, with at least three in the habitable zone. The two inner planets are airless worlds but so far there has been no word of the third planet, the first in the habitable zone. The question is why and what makes it so tricky to observe?

TRAPPIST-1 is a red dwarf star about 41 light years in the constellation Aquarius. The interest in the planets in the habitable zone is that the conditions could allow for the existence of liquid water. The seven planets were discovered through transit photometry where tiny drops in brightness of the star are observed due to the passage of the planets in front of the star.  The planets that orbit the star all have fairly short orbital periods from 1.5 days to 20 days. The result of this is that their transits across the stellar surface often overlap. 

The launch of the JWST in 2021 reignited the interest in exoplanet studies. Its predecessor the Hubble Space Telescope was never expected to last as long to JWST was able to complement the famous telescope. Setting itself apart from Hubble by its advanced infrared capability, JWST was ideally placed to study exoplanet atmospheres. Fundamental to the operation of the JWST is a large, multi-segment mirror measuring 6.5 metres in diameter and a whole host of sophisticated instruments. 

Artist impression of the James Webb Space Telescope

A team of astronomers have been studying TRAPPIST-1 and its system of planets using JWST, exploiting its infrared capabilities. Using a technique known as transmission spectroscopy the starlight is explored as it passes through the planetary atmospheres as they pass in front of the star. Studying the light in this way can reveal the elements in the atmosphere. Three years in though and challenges have slowed them down. 

Now, a paper published in Nature Astronomy highlights the challenges they faced and proposes how to overcome them. Top of the list relates to the non uniformity of a star. Those interested in solar astronomy will already be familiar with sun spots, flares and other solar phenomenon. These are seen on stars too and regions where cooler regions form can often harbour water vapour, playing havoc with transmission spectra and making it difficult to identify elements in the planetary atmosphere rather than in the star. This is known as stellar contamination. 

Previous issues like this have been seen by astronomers studying exoplanet atmospheres using Earth based telescopes like the Magellan Telescope in Chile. Previously however, these issues were often simply ignored but the greater sensitivity of JWST causes more of a problem. There is a relatively simple work around however by observing the star as it rotates to build a picture of the stellar surface, allowing a more accurate analysis of the planetary atmosphere. 

Magellan Telescope

Using TRAPPIST-1 as a test bed, it is hoped that other challenges and their solutions can be tested before being applied to other, less easy to observe explanatory systems. The team propose that the exoplanet and JWST community work together on research projects to maximise efficiency in driving out solutions to other challenges in the road ahead. 

Source : Roadmap details how to improve exoplanet exploration using the JWST

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The extrasolar planet census recently passed a major milestone, with 5500 confirmed candidates in 4,243 solar systems. With so many exoplanets available for study, astronomers have learned a great deal about the types of planets that exist in our galaxy and have been rethinking several preconceived notions. These include the notion of “habitability” and whether Earth is the standard by which this should be measured – i.e., could there be “super habitable” exoplanets out there? – and the very concept of the circumsolar habitable zone (CHZ).

Traditionally, astronomers have defined habitable zones based on the type of star and the orbital distance where a planet would be warm enough to maintain liquid water on its surface. But in recent years, other factors have been considered, including the presence of planetary magnetic fields and whether they get enough ultraviolet light. In a recent study, a team from Rice University extended the definition of a CHZ to include a star’s magnetic field. Their findings could have significant implications in the search for life on other planets (aka. astrobiology).

The research team consisted of Anthony S. Atkinson, a graduate student with the Department of Physics and Astronomy at Rice University, Professor David Alexander, the director of the Rice Space Institute and member of the Texas Aerospace Research and Space Economy Consortium, and Alison O. Farrish, a NASA Postdoctoral Program Fellow at NASA’s Goddard Space Flight Center. The paper describing their findings, “Exploring the Effects of Stellar Magnetism on the Potential Habitability of Exoplanets,” appeared on July 9th in The Astrophysical Journal.

Artist’s impression of exoplanets orbiting different types of stars. Credit: NASA/W. Stenzel

On Earth, the presence of an intrinsic magnetic field has been vital to the emergence and evolution of life as we know it. Without it, our atmosphere would have been stripped away long ago by energetic particles emanating from the Sun – which was the case with Mars. In addition to Earth’s atmosphere, our planet’s magnetic field ensures that a limited amount of solar radiation and cosmic rays reach the surface. For this reason, astrobiologists consider a planetary magnetic field essential for determining whether or not an exoplanet is habitable.

Another factor is how the strength of a planet’s magnetic field and its interaction with its parent star’s magnetic field affect habitability. Not only does an exoplanet require a strong field to shield it against stellar activity (solar flares, etc.), but it must also orbit far enough to avoid a direct magnetic connection with its star. “The fascination with exoplanets stems from our desire to understand our own planet better,” said Prof. Alexander in a recent Rice University press statement. “Questions about the Earth’s formation and habitability are the key drivers behind our study of these distant worlds.”

The magnetic interactions between planets and their parent stars are known as “space weather.” For their study, the team examined 1,546 exoplanets to determine if they orbited inside or outside their host star’s Alfvén radius – the distance where stellar wind decouples from the star. This consisted of characterizing the stars’ activity known using their Rossby number (Ro) – the ratio between a star’s rotational period to their convective turnover time.

Planets orbiting within this radius would directly interact magnetically with the star’s corona, leading to significant atmospheric stripping, ruling them out as viable candidates for habitability. This phenomenon has been observed with TRAPPIST-1 and its system of seven exoplanets. After examining the exoplanets in their study, they found that only two planets met all the conditions for potential habitability. These were K2-3 d and Kepler-186 f, two Earth-sized exoplanets 144 and 579 light-years from Earth (respectively).

Illustration of Kepler-186f, a possible Earth-like exoplanet that could be a host to life. Credit: NASA Ames, SETI Institute, JPL-Caltech, T. Pyle

These planets orbit within their stars’ CHZ, lie outside their Alfvén radius, and have strong enough magnetic fields to protect them from stellar activity. “While these conditions are necessary for a planet to host life, they do not guarantee it,” said Atkinson. “Our work highlights the importance of considering a wide range of factors when searching for habitable planets.”

These findings highlight the need for continuous observation when studying exoplanet systems and considering what factors have led to the emergence of life here on Earth. They are also indicative of current efforts among astronomers and astrobiologists to refine the definition of “Habitable Zone” and create a more nuanced understanding. In so doing, this research could help refine the search for extraterrestrial life by allowing scientists to further constrain where they should be looking.

Further Reading: Rice University, The Astrophysical Journal

The post Planetary Habitability Depends on its Star’s Magnetic Field appeared first on Universe Today.

Supermassive Black Holes are Nature’s confounding behemoths. It’s difficult for Earth-bound minds to comprehend their magnitude and power. Astrophysicists have spent decades studying them, and they’ve made progress. But one problem still baffles even them: the Final Parsec Problem.

New research might have solved the problem, and dark matter plays a role in the solution.

Supermassive Black Holes (SMBHs) can be billions of times more massive than our Sun. Evidence shows that they may reside at the center of all large galaxies. The Milky Way has one and it’s named Sagittarius A* (Sgr A*).

SMBHs grow so massive by merging with other SMBHs when their host galaxies merge. But there’s a problem. Astrophysicists don’t understand how the two SMBHs can close the final parsec that separates them.

When black holes merge, they begin as a binary object. They spiral around each other, each carrying their own momentum. To merge, the black holes need to shed energy. To do this, they shed energy to the surrounding gas and dust which then dissipates. But when they get about three light-years away from one another, or about one parsec, there simply isn’t enough gas and dust to absorb the necessary energy.

Yet SMBHs do merge, so somehow, nature overcomes the Final Parsec Problem (FPP).

New research published in the journal Physical Review Letters presents a solution to the FPP. The research is titled “Self-Interacting Dark Matter Solves the Final Parsec Problem of Supermassive Black Hole Mergers.” The first author is Gonzalo Alonso-Álvarez, a Postdoctoral Fellow in the Department of Physics at the University of Toronto, Canada.

“Our work is a new way to help us understand the particle nature of dark matter.”

Gonzalo Alonso-Álvarez, Department of Physics, University of Toronto

There’s no question that stellar-mass black holes can merge. LIGO/Virgo has sensed the gravitational waves coming from many mergers between stellar-mass black holes, which is direct evidence that black holes can merge. However, evidence for SMBH mergers is elusive.

In 2023, scientists announced the detection of a persistent background hum of gravitational waves. That detection came from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav.) NANOGrav gathered gravitational wave data for 15 years using pulsar timing.

Different groups of researchers hypothesized that the hum comes from the mergers of SMBHs. In one paper, researchers said the hum comes from hundreds of thousands of pairs of merging SMBHs. Somehow, these SMBHs are overcoming the FPP.

In their new paper, Alonso-Álvarez and his co-researchers show how dark matter allows SMBHs to merge despite the Final Parsec Problem. “We show that including the previously overlooked effect of dark matter can help supermassive black holes overcome this final parsec of separation and coalesce,” said Alonso-Álvarez. “Our calculations explain how that can occur, in contrast to what was previously thought.”

Astrophysicists have been working on the FPP for a long time. Different researchers have developed different models to try to explain how SMBHs merge, and those models include dark matter. However, previous merger models showed that the dark matter near the spiralling black holes is thrown clear of the merger area by the gravity created by the inspiralling holes. Without that dark matter to absorb energy, the pair of SMBHs can’t overcome the FPP.

But in this new research, dark matter interacts with itself and ‘spikes’ instead of being dispersed. Dark matter spikes are theoretical concentrations of dark matter around a black hole. As an SMBH grows, it draws regular matter towards itself. The same process could lead to a spike in dark matter around the black hole. Its density remains high enough that it can absorb enough energy for the pair of SMBHs to continue their inspiralling. Eventually, they overcome the FPP and coalesce into one.

This figure from separate research shows a spike in dark matter near a black hole. The vertical axis shows the dark matter’s density in solar masses per cubic parsec, and the horizontal axis shows the distance to the black hole center in parsecs. The black line shows the initial distribution of dark matter, and the pink line shows the spike that occurs due to adiabatic growth. Image Credit: Wierda 2023.

It all depends on dark matter self-interacting.

“The possibility that dark matter particles interact with each other is an assumption that we made, an extra ingredient that not all dark matter models contain,” said Alonso-Álvarez. “Our argument is that only models with that ingredient can solve the final parsec problem.”

Physicists aren’t certain that dark matter can interact with itself, though. The Standard Model says that dark matter interacts primarily through gravity. But newer evidence is accumulating that it can interact with itself, and physicists call this the Self-Interacting Dark Matter theory.

Other research has looked at dark matter spikes near merging black holes. According to that research, dynamical friction between the black holes and the DM spike could dissipate the spike. However, this new research argues that only SIDM can effectively move the heat outwards and replenish the DM spike. Contrary to collisionless dark matter, an SIDM spike maintains itself and allows the inspiralling black holes to shed enough energy and cross the final parsec problem.

More support for this hypothesis comes from the nature of the background gravitational wave hum that scientists announced in 2023. It was measured by pulsar timing and the waves displayed a softening at low frequencies. According to Alonso-Álvarez, their model predicts this phenomenon, lending credence to their work.

“A prediction of our proposal is that the spectrum of gravitational waves observed by pulsar timing arrays should be softened at low frequencies,” said co-author Professor James Cline from McGill University and the CERN Theoretical Physics Department in Switzerland. “The current data already hint at this behavior, and new data may be able to confirm it in the next few years.”

This research reaches beyond SMBH mergers to the nature of dark matter itself. The self-interactions the researchers modelled can help explain the shape of dark matter haloes around galaxies.

“Our work is a new way to help us understand the particle nature of dark matter,” said Alonso-Álvarez. “We found that the evolution of black hole orbits is very sensitive to the microphysics of dark matter and that means we can use observations of supermassive black hole mergers to better understand these particles.”

“Despite astrophysical uncertainties about their detailed nature, there is no doubt that dark matter spikes exist around supermassive black hole binaries and thus contribute to the dynamical friction accelerating the decay of their orbit,” the authors write in the conclusion of their paper.

“We found that the final parsec problem can only be solved if dark matter particles interact at a rate that can alter the distribution of dark matter on galactic scales,” said Alonso-Álvarez. “This was unexpected since the physical scales at which the processes occur are three or more orders of magnitude apart. That’s exciting.”

The post A Solution to the “Final Parsec Problem?” appeared first on Universe Today.

A rapidly spreading wildfire burns through part of the largest national park in the Canadian Rockies as satellites track its growth and movement.

Anticrepuscular Rays at the Planet Festival

In a global first, scientists working in the Clarion-Clipperton Zone in the North Pacific Ocean have found that metallic nodules on the seafloor produce their own oxygen, dubbed "dark oxygen."

Mouse pups have increased activity in certain neurons in the centre of their brains when they interact with their mothers, which is linked to them showing fewer signs of distress

Mouse pups have increased activity in certain neurons in the centre of their brains when they interact with their mothers, which is linked to them showing fewer signs of distress

The gamma ray burst known as GRB221009A is the biggest explosion astronomers have ever glimpsed and we might finally know what caused the blast

The gamma ray burst known as GRB221009A is the biggest explosion astronomers have ever glimpsed and we might finally know what caused the blast

The Euclid and XMM-Newton missions have combined to show the hidden, hot gas that fills an immense galaxy cluster 2.7 billion light-years away.

From left to right, NASA astronaut candidates Anil Menon, Deniz Burnham, and Marcos Berrios pose for a photograph in front of NASA’s Artemis I Space Launch System and Orion spacecraft at Launch Complex 39B at the agency’s Kennedy Space Center in Florida on Sept. 2, 2022.

Being immunised against shingles has been linked to a reduced dementia risk before and now a study suggests that the newer vaccine wards off the condition more effectively than an older one

Being immunised against shingles has been linked to a reduced dementia risk before and now a study suggests that the newer vaccine wards off the condition more effectively than an older one

Boeing moving toward a June 1 launch of its first-ever Starliner astronaut mission for NASA.

New analysis has revealed 21 Sun-like stars in mutual orbit around dark objects of neutron star–like masses — rare systems that have escaped destruction by supernova.

The post Astronomers Find 21 “Dark” Neutron Stars Orbiting Sun-like Stars appeared first on Sky & Telescope.

Citizen scientists have discovered what may be a brown dwarf racing through the cosmos at around 1.2 million miles per hour. Now astronomers want to know what launched it.

Boeing's Starliner does not have a landing date yet, but the troubleshooting is making progress. Engineers plan a "hot fire" test this weekend to see how the spacecraft does in orbit.

Starting this October, Marvel's core Star Wars line will move past Return of the Jedi and into a new era of storytelling set before The Mandalorian.