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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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Space

Extraterrestrial Life Could Feasibly Live in Salty Puddles on Mars

All Dried Up

Scientists found another possible place to look for extraterrestrial life on Mars. The Red Planet, recently discovered to have water just beneath its surface, could be dotted with puddles of mud with a high concentration of salts.

Investigating similar salty mud puddles on Earth, Wichita State University astrobiologists found that bacterial life could survive even after getting completely dried out, according to Space.com. The finding doesn’t by any means guarantee that there is or ever was life on Mars, but it does suggest that Mars is more hospitable than scientists previously assumed.

Puddle Pity

The scientists, who presented their research at an American Society for Microbiology conference on Friday, put bacteria in jars with a solution of saltwater similar to that found on Mars, per Space.com. They then left them to dry out and rehydrate as the water evaporated and condensed with changing temperatures, as it would on Mars.

“We have the first data showing the growth of bacteria after drying and then rehydration through humidity alone, in the presence of salts that absorb moisture from the air,” lead scientist Mark Schneegurt told Space.com.

Next up, Schneegurt told Space.com, is to get the experimental conditions closer and closer to those of Mars in order to better test the limits of these particularly resilient microbes.

READ MORE: How Martian Microbes Could Survive in the Salty Puddles of the Red Planet [Space.com]

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Scientists Think Black Holes Could Be Portals To Other Worlds

Very little is known about black holes, aside from the fact that they are the result of a dying star imploding on itself from the pressure of the gravity. One theory about the mechanics of black holes is that they might be portals to other galaxies, or other parts of a galaxy.

This is a relatively new theory, as scientists previously thought that attempting to travel through a black hole would destroy anyone who attempted it. In fact, some researchers still believe that the heat emanating from the black hole would entirely vaporize any spacecraft that would attempt to travel through it.

A team of scientists at the University of Massachusetts Dartmouth, believe that there are many different types of black holes, some of which would be easier to travel through than others. The team even believes that there are some black holes that a spacecraft would be able to pass through “gently.”

According to Gaurav Khanna, lead researcher on the team, “the reason that this is possible is that the relevant singularity inside a rotating black hole is technically “weak,” and thus does not damage objects that interact with it. At first, this fact may seem counter intuitive. But one can think of it as analogous to the common experience of quickly passing one’s finger through a candle’s near 2,000-degree flame, without getting burned.”

Scientists Think Black Holes Could Be Portals To Other Worlds 1

This illustration shows a black hole named Cygnus X-1, which is sucking the life out of a blue star beside it. Photo Credit: NASA/CXC/M.Weiss

Khanna’s team has been researching black holes for over 20 years, and they believe in this theory that some black holes would be possible to travel through.

“Under all conditions an object falling into a rotating black hole would not experience infinitely large effects upon passage through the hole’s so-called inner horizon singularity. This is the singularity that an object entering a rotating black hole cannot maneuver around or avoid. Not only that, under the right circumstances, these effects may be negligibly small, allowing for a rather comfortable passage through the singularity. In fact, there may no noticeable effects on the falling object at all. This increases the feasibility of using large, rotating black holes as portals for hyperspace travel,” Khanna says.

The researchers used a computer simulation to support their theory about calm black holes.

Scientists Think Black Holes Could Be Portals To Other Worlds 2

This graph depicts the physical strain on the spacecraft’s steel frame as it plummets into a rotating black hole. Photo Credit: Khanna/UMassD

For many years, scientists have only had theoretical models to help them imagine what a black hole looked like. No one had ever taken a photo of this phenomenon in space before, until earlier this year.

The images were captured thanks to a global network of telescopes called the Event Horizon Telescope.

Researchers found the apparent black hole in galaxy M87, according to Sheperd Doeleman, EHT Director and astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge.

The black hole is 55 million light-years from Earth in the constellation Virgo, and it’s about 1,000 times as large as the Milky Way’s giant, which weighs the equivalent of roughly 4 million suns.

Scientists Think Black Holes Could Be Portals To Other Worlds 3

Black Hole / Photo: Event Horizon Telescope

In another incredible discovery that happened this year, scientists detected a “dark impactor” that has some researchers believe has been “blasting holes in our galaxy.” This force is not visible, and may not be made up of matter. This may be made up of some type of material that humans aren’t even familiar with. Human telescopes haven’t even been able to detect this material yet, but it is leaving a mark and that is how we know it is out there.

Ana Bonaca, is the researcher from the Harvard-Smithsonian Center for Astrophysics, who discovered evidence for the impactor.

Bonaca presented her evidence to her peers for the first time on April 15, at the conference of the American Physical Society in Denver. Bonca says that whatever this mysterious force is, it is creating a series of holes in our galaxy’s longest stellar stream, GD-1.

If you are not familiar with the term, stellar streams are basically rows of stars that move together across galaxies. Many times, these streams originate in smaller clusters of stars that collided with the galaxy.

Bonaca managed to make this discovery by keeping an eye on data from the Gaia mission, a European Space Agency program that maps billions of stars in our galaxy and tracks their movements across the sky. Bonaca cross referenced the information from the Gaia mission with observations from the Multi Mirror Telescope in Arizona.

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Martian sand dune looks like Starfleet logo

Image Credit: NASA
The dune looks very similar to the Starfleet logo. 

New images taken by NASA’s MRO HiRise camera show a sand dune formation with a rather familiar shape.

The photographs, which were captured by NASA’s Mars Reconnaissance Orbiter, have prompted some rather tongue-in-cheek references to Star Trek’s iconic insignia.

“Enterprising viewers will make the discovery that these features look conspicuously like a famous logo,” the HiRise team at the University of Arizona wrote in a Tweet.

Star Trek references aside, this intriguing formation and others like it have been helping scientists to learn more about the Red Planet’s atmosphere, temperature and topography.

This, in turn, will also help NASA to better plan out future manned missions.

Source: IB Times

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