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Astronomers Have Found the Universe’s Missing Matter

Astronomers have finally found the last of the missing universe. It’s been hiding since the mid-1990s, when researchers decided to inventory all the “ordinary” matter in the cosmos—stars and planets and gas, anything made out of atomic parts. (This isn’t “dark matter,” which remains a wholly separate enigma.) They had a pretty good idea of how much should be out there, based on theoretical studies of how matter was created during the Big Bang. Studies of the cosmic microwave background (CMB)—the leftover light from the Big Bang—would confirm these initial estimates.

So they added up all the matter they could see—stars and gas clouds and the like, all the so-called baryons. They were able to account for only about 10 percent of what there should be. And when they considered that ordinary matter makes up only 15 percent of all matter in the universe—dark matter makes up the rest—they had only inventoried a mere 1.5 percent of all matter in the universe.

Now, in a series of three recent papers, astronomers have identified the final chunks of all the ordinary matter in the universe. (They are still deeply perplexed as to what makes up dark matter.) And despite the fact that it took so long to identify it all, researchers spotted it right where they had expected it to be all along: in extensive tendrils of hot gas that span the otherwise empty chasms between galaxies, more properly known as the warm-hot intergalactic medium, or WHIM.

Early indications that there might be extensive spans of effectively invisible gas between galaxies came from computer simulations done in 1998. “We wanted to see what was happening to all the gas in the universe,” said Jeremiah Ostriker, a cosmologist at Princeton University who constructed one of those simulations along with his colleague Renyue Cen. The two ran simulations of gas movements in the universe acted on by gravity, light, supernova explosions and all the forces that move matter in space. “We concluded that the gas will accumulate in filaments that should be detectable,” he said.

Except they weren’t — not yet.

“It was clear from the early days of cosmological simulations that many of the baryons would be in a hot, diffuse form — not in galaxies,” said Ian McCarthy, an astrophysicist at Liverpool John Moores University. Astronomers expected these hot baryons to conform to a cosmic superstructure, one made of invisible dark matter, that spanned the immense voids between galaxies. The gravitational force of the dark matter would pull gas toward it and heat the gas up to millions of degrees. Unfortunately, hot, diffuse gas is extremely difficult to find.

To spot the hidden filaments, two independent teams of researchers searched for precise distortions in the CMB, the afterglow of the Big Bang. As that light from the early universe streams across the cosmos, it can be affected by the regions that it’s passing through. In particular, the electrons in hot, ionized gas (such as the WHIM) should interact with photons from the CMB in a way that imparts some additional energy to those photons. The CMB’s spectrum should get distorted.

Unfortunately the best maps of the CMB (provided by the Planck satellite) showed no such distortions. Either the gas wasn’t there, or the effect was too subtle to show up.

But the two teams of researchers were determined to make them visible. From increasingly detailed computer simulations of the universe, they knew that gas should stretch between massive galaxies like cobwebs across a windowsill. Planck wasn’t able to see the gas between any single pair of galaxies. So the researchers figured out a way to multiply the faint signal by a million.

First, the scientists looked through catalogs of known galaxies to find appropriate galaxy pairs — galaxies that were sufficiently massive, and that were at the right distance apart, to produce a relatively thick cobweb of gas between them. Then the astrophysicists went back to the Planck data, identified where each pair of galaxies was located, and then essentially cut out that region of the sky using digital scissors. With over a million clippings in hand (in the case of the study led by Anna de Graaff, a Ph.D. student at the University of Edinburgh), they rotated each one and zoomed it in or out so that all the pairs of galaxies appeared to be in the same position. They then stacked a million galaxy pairs on top of one another. (A group led by Hideki Tanimura at the Institute of Space Astrophysics in Orsay, France, combined 260,000 pairs of galaxies.) At last, the individual threads — ghostly filaments of diffuse hot gas — suddenly became visible.

(A) Images of one million galaxy pairs were aligned and added together.
(B) Astronomers mapped all the gas within the actual galaxies.
(C) By subtracting the galaxies (B) from the initial image (A), researchers revealed filamentary gas hiding in intergalactic space.Adapted by Quanta Magazine

The technique has its pitfalls. The interpretation of the results, said Michael Shull, an astronomer at the University of Colorado at Boulder, requires assumptions about the temperature and spatial distribution of the hot gas. And because of the stacking of signals, “one always worries about ‘weak signals’ that are the result of combining large numbers of data,” he said. “As is sometimes found in opinion polls, one can get erroneous results when one has outliers or biases in the distribution that skew the statistics.”

In part because of these concerns, the cosmological community didn’t consider the case settled. What was needed was an independent way of measuring the hot gas. This summer, one arrived.

Lighthouse Effect

While the first two teams of researchers were stacking signals together, a third team followed a different approach. They observed a distant quasar — a bright beacon from billions of light-years away — and used it to detect gas in the seemingly empty intergalactic spaces through which the light traveled. It was like examining the beam of a faraway lighthouse in order to study the fog around it.

Usually when astronomers do this, they try to look for light that has been absorbed by atomic hydrogen, since it is the most abundant element in the universe. Unfortunately, this option was out. The WHIM is so hot that it ionizes hydrogen, stripping its single electron away. The result is a plasma of free protons and electrons that don’t absorb any light.

Fabrizio Nicastro used light from a quasar to track the missing gas.Courtesy of Fabrizio Nicastro

So the group decided to look for another element instead: oxygen. While there’s not nearly as much oxygen as hydrogen in the WHIM, atomic oxygen has eight electrons, as opposed to hydrogen’s one. The heat from the WHIM strips most of those electrons away, but not all. The team, led by Fabrizio Nicastro of the National Institute for Astrophysics in Rome, tracked the light that was absorbed by oxygen that had lost all but two of its electrons. They found two pockets of hot intergalactic gas. The oxygen “provides a tracer of the much larger reservoir of hydrogen and helium gas,” said Shull, who is a member of Nicastro’s team. The researchers then extrapolated the amount of gas they found between Earth and this particular quasar to the universe as a whole. The result suggested that they had located the missing 30 percent.

The number also agrees nicely with the findings from the CMB studies. “The groups are looking at different pieces of the same puzzle and are coming up with the same answer, which is reassuring, given the differences in their methods,” said Mike Boylan-Kolchin, an astronomer at the University of Texas, Austin.

The next step, said Shull, is to observe more quasars with next-generation X-ray and ultraviolet telescopes with greater sensitivity. “The quasar we observed was the best and brightest lighthouse that we could find. Other ones will be fainter, and the observations will take longer,” he said. But for now, the takeaway is clear. “We conclude that the missing baryons have been found,” their team wrote.

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Astronauts may hibernate on trips to Mars

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Astronauts traveling to Mars in the near future may have to hibernate, according to a European Space Agency (ESA) scientist.

Astronauts may hibernate on trips to Mars

In interview with The Telegraph, Professor Mark McCaughrean, senior science consultant to the ESA Board of Science, revealed that hibernation could reduce the need for large amounts of food during the seven-month trip to Mars.

He explained:

The idea is that you sleep while traveling and use much less consumables.

Sleep is not the same as hibernation, because if you hibernate, it lowers your body temperature and reduces everything else, oxygen, and so on.

Placing astronauts in this state can also prevent fights between astronauts during the tiring journey, according to Professor McCaughrean.

He added:

If you have 100 people within a few hundred cubic meters for seven, nine months, you will have 20 people at the end, because they will do the Hunger Games. They will kill themselves.

While the idea of ​​hibernating astronauts may seem absurd, ESA is already conducting experiments on animals.

Professor McCaughrean said:

We are now experimenting with artificial hibernation to numb someone for seven months and not worry about food. We are talking about how we would do that. You do this with animal testing and we have programs to analyze how it would happen.

However, there are several obstacles to be overcome before these tests can be performed on humans.

He even said:

We are nowhere near that, because there are all ethical questions about how you would do it.

(Source)

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NASA will search for fossils on Mars

The Mars 2020 spacecraft will investigate an intriguing type of mineral deposit known to produce fossils on Earth.

NASA will search for fossils on Mars
Parts of this image of the Jezero crater have been enhanced to highlight the presence of certain minerals. Green areas indicate carbonate deposits.

And when you think of fossils, you probably imagine T. rex skulls and sauropod femurs. NASA’s Mars 2020 spacecraft will be searching for fossils on Mars, but not those fossils.

NASA highlighted a new study in the magazine Icarus this week pointing out some fascinating formations around the inner edge of the Jezero Crater, the spacecraft’s planned landing site. The agency compares these concentrated carbonate mineral deposits to a tub ring around what was once a lake 3.5 billion years ago.

NASA informed:

On Earth, carbonates help form structures that are tough enough to survive in fossil form for billions of years, including seashells, corals, and some stromatolites – rocks formed on this planet by ancient microbial life along ancient shorelines, where sunlight and water were abundant.

NASA does not expect to find sea shells, but the spacecraft will closely examine the stromatolites. Scientists would be thrilled to discover signs of past microbial life on the currently inhospitable planet. The Jeep’s investigation of carbonate deposits may also tell us more about how Mars made the transition from an aqueous to an arid place.

The probe jeep Mars 2020 is developing at NASA with a planned release mid-next year. If it stays on schedule, the spacecraft will reach the crater in February 2021.

Scientists do not know whether carbonates formed in the ancient lake or could have been deposited previously. We will have to wait to find out more. It will be a milestone worth waiting for.

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Site of NASA’s Mars 2020 Mission Could Contain Fossilized Signs of Life

The landing site selected for NASA’s upcoming Mars 2020 rover could well be one of the best chances we have of discovering whether the Red Planet was once home to life and whether it could be again.

The 28-mile (45km) wide Jezero crater was selected as the landing site for the new rover in late 2018, and has been found to contain vast deposits of hydrated silica and minerals called carbonates, according to a newly published study.

Once the site of a lake more than 3.5 billion years ago, scientists now believe that Jezero, thanks to its carbonate supplies, will likely contain structures that can survive for billions of years, such as shells, coral and certain types of rock formed by microbial life.

Deltas here on Earth are known to be hubs for preserved biomarkers and signs of life, and the presence of the hydrated silica suggests Mars is likely to be even better in this regard.

“Using a technique we developed that helps us find rare, hard-to-detect mineral phases in data taken from orbiting spacecraft, we found two outcrops of hydrated silica within Jezero crater,” said the study’s lead author, Jesse Tarnas, a PhD student at Brown University in Rhode Island, US.

We know from Earth that this mineral phase is exceptional at preserving microfossils and other biosignatures, so that makes these outcrops exciting targets for the rover to explore.

The intel about the site, and the surrounding delta, replete with mineral deposits, was provided by data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument that flies aboard NASA’s Mars Reconnaissance Orbiter.

“The material that forms the bottom layer of a delta is sometimes the most productive in terms of preserving biosignatures,” explained Jack Mustard, professor at Brown and study co-author.

“So if you can find that bottomset layer, and that layer has a lot of silica in it, that’s a double bonus,” he added.

The rover will land on Mars on February 18, 2021 when it will begin taking rock core samples that will be deposited in metal tubes on the Martian surface, waiting to be shipped back to Earth for analysis during a later mission.

RT

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