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What?! The Universe Appears to Be Missing Some Light

By Charles Q. Choi, Space.com Contributor

An extraordinary amount of ultraviolet light appears to be missing from the universe, scientists have found.

One potential source of this missing light might be the mysterious dark matter that makes up most of the mass in the cosmos. But a simpler explanation could be that ultra violet light escapes from galaxies more easily than is currently thought, according to the new research.

This puzzle begins with hydrogen, the most common element in the universe, which makes up about 75 percent of known matter. High-energy ultraviolet light can convert electrically neutral hydrogen atoms into electrically charged ions. The two known sources for such ionizing rays are hot young stars and quasars, which are supermassive black holes more than a million times the mass of the sun that release extraordinarily large amounts of light as they rip apart stars and gobble matter.

Infographic: Black holes are strange regions where gravity is strong enough to bend light, warp space and distort time.

Black holes are strange regions where gravity is strong enough to bend light, warp space and distort time.
Credit: Karl Tate, SPACE.com contributor

Astronomers previously found that ionizing rays from hot young stars are nearly always absorbed by gas in their home galaxies. As such, they virtually never escape to affect intergalactic hydrogen.

However, when scientists performed supercomputer simulations of the amount of intergalactic hydrogen that should exist and compared their results with observations from the Hubble Space Telescope‘s Cosmic Origins Spectrograph, they found the amount of light from known quasars is five times lower than what is needed to explain the amount of electrically neutral intergalactic hydrogen observed.

“It’s as if you’re in a big, brightly-lit room, but you look around and see only a few 40-watt lightbulbs,” lead study author Juna Kollmeier, a theoretical astrophysicist at the Observatories of the Carnegie Institution of Washington in Pasadena, Calif., said in a statement. “Where is all that light coming from? It’s missing.”

The researchers are calling this giant deficit of ultraviolet light “the photon underproduction crisis.”

“In modern astrophysics, you very rarely find large mismatches like the one we are talking about here,” Kollmeier told Space.com. “When you see one, you know that there is an opportunity to learn something new about the universe, and that’s amazing.”

“The great thing about a 400 percent discrepancy is that you know something is really wrong,” study co-author David Weinberg at Ohio State University said in a statement. “We still don’t know for sure what it is, but at least one thing we thought we knew about the present day universe isn’t true.”

Strangely, this missing light only appears in the nearby, relatively well-studied cosmos. When telescopes focus on light from galaxies billions of light years away — and therefore from billions of years in the past — no problem is seen. In other words, the amount of ultraviolet light in the early universe makes sense, but the amount of ultraviolet light in the nearby universe does not.

“The authors have performed a careful and thorough analysis of the problem,” said theoretical astrophysicist Abraham Loeb, chairman of the astronomy department at Harvard University, who did not take part in this research.

The most exciting possibility these findings raise is that the missing photons are coming from some exotic new source, not galaxies or quasars at all, Kollmeier said. For example, dark matter, the invisible and intangible substance thought to make up five-sixths of all matter in the universe, might be capable of decay and generating this extra light.

“You know it’s a crisis when you start seriously talking about decaying dark matter,” study co-author Neal Katz at the University of Massachusetts at Amherst said in a statement.

There still may be a simpler explanation for this missing light, however. Astronomers could be underestimating the fraction of ultraviolet light that escapes from galaxies in the nearby universe. “All that one needs is an average escape probability on the order of 15 percent to relieve the discrepancy,” Loeb told Space.com.

Nearby, recent “low-redshift” galaxies have less gas to absorb ultraviolet rays that more distant, early “high-redshift” galaxies, Loeb noted.

“The more I think about it, the more plausible it appears that the escape fraction of ultraviolet photons is higher in local galaxies than in high-redshift galaxies,” Loeb said.

On the other hand, “the biggest problem with this possible solution is that there are measurements of local galaxies that indicate the average escape fraction is significantly lower than 15 percent — more like 5 percent,” Kollmeier said.”In principle, it is possible that these galaxies are not representative and therefore we need to do more such measurements, but we cannot just dismiss the data.”

Another potential explanation is ionization of intergalactic hydrogen by x-rays and cosmic rays, Loeb said. Although he noted this radiation does not play a major role in ionizing intergalactic hydrogen in the most distant corners and earliest times in the universe, astronomers may want to see how much of a role x-rays and cosmic rays play in the nearby universe, “where they are produced more vigorously,” he said.

The scientists detailed their findings in the July 10 issue of the Astrophysical Journal Letters.

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Space

A space object that changes the concept of the Universe is discovered: An unthinkable ancient galaxy

Photo: NRAO / AUI / NSF / S. Dagnello

Scientists at the Institute for Astronomy of the Max Planck Society in the UK announced the discovery of the oldest massive galaxy DLA0817g, which arose just 1.5 billion years after the Big Bang. It has a disk, which can change astronomers’ ideas about the mechanisms of galaxy formation. An article by astronomers is published in the journal Nature.

Researchers discovered the galaxy using the ALMA (Atacama Large Millimeter Array) radio telescope complex. This ancient object was named Wolf Disc – in honor of the astronomer Arthur Wolf. It has become the farthest spinning-disk galaxy of all detected so far, and its cosmological redshift is 4.26. 

The light from it flew 12.2 billion years, but due to the expansion of the Universe, the galaxy is currently at a distance of 24.4 billion light years. The rotation occurs at a speed of 272 kilometers per second, which is comparable to the rotation speed of the Milky Way.

According to modern models, massive galaxies are formed from the mergers of smaller mass galaxies and clusters of hot gas. These collisions prevent the formation of disks characteristic of the Universe of this age. 

Therefore, the existence of the Wolf Disc will force astronomers to reconsider the mechanisms of the appearance of such space objects. DLA0817g probably accumulated cold gas, but the question of how he managed to maintain a stable disk with such a large mass remains open.

Scientists also found that the star formation rate in the Wolf Disk is ten times higher than the star formation rate in the Milky Way. According to astronomers, he was one of the most productive galaxies in the early Universe.

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Space

Where can people live on Mars?

Life on Mars Video screenshot

Let’s imagine for a moment that scientists were able to send people to Mars. But what will they do there? Mars is not the most friendly planet for life. There is at least no oxygen, not to mention cosmic radiation, from which the atmosphere protects us on Earth, but it does not exist on the Red Planet. In fact, the question of how representatives of our species can survive in the hostile environment of distant worlds has long been of concern to scientists. 

So, researchers believe that you can survive in the harsh Martian environment deep beneath Martian soil. Since scientists recently obtained evidence that Mars is a seismically active planet, there is a network of large underground tunnels that formed as a result of thousands of years of volcanic activity.

These tunnels, or, as they are called, lava tubes, remained after the fast-flowing lava burned through the Martian soil.

Lava tubes – cavities in lava flows, elongated like corridors. Such channels are obtained by uneven cooling of the lava flowing from the slopes of the volcano.

What threatens future Martians?

Space, as you know, is not a suitable place for life forms such as Homo Sapiens. The harsh space environment, penetrated by radiation, in the literal sense of the word destroys all living things. Even tardigrades are microscopic animals that can survive in the most extreme conditions. Back in 2007, researchers found that these “water bears” withstand the short-term effects of extremely low temperatures, cosmic radiation and an almost complete vacuum. Agree, this is amazing. But even they cannot be in outer space for a long time. What can we say about you and me.

And yet, we have created technologies with which you can go into the Earth’s orbit and even its moon. In theory, we are close to interplanetary flights, and I think it is no secret that the governments of many countries plan to send a man to Mars. But what do we have in practice?

Such colonies can only be built after we solve the problem of cosmic radiation

Our regular readers are probably aware that the biggest problem for future space travelers is space radiation. In a previous article, I said that the results of scientific research have shown that prolonged exposure to space has a devastating effect on the brain.

It turns out that if the flight to the Red Planet takes about 7 months, then people with severe brain damage can land on Mars and, most likely, they will not even understand where they are. We note that today there is no solution to this problem. 

Lava tubes on Earth look like this

Life on Mars

So, given all the available knowledge about Mars, the only more or less safe habitat for humans are underground tunnels or lava tubes. According to astrophysicist Antonio Paris and his team, which has been researching and assessing the safety of Martian lava pipes, sheltering future colonists in deep underground tunnels can significantly reduce exposure to hazardous cosmic radiation. Moreover, the researchers are convinced that the “Greek plain” of Hellas Planitius is the best place to land.

The fact is that less cosmic and solar radiation falls on this part of Mars than on most of the rest of the planet’s surface. According to Antonio Paris, sheltering astronauts in deep lava tubes can reduce its impact even more, thereby ensuring the colonists survival. But how to measure the level of radiation in the lava tubes on Mars?

It is hoped that no one lives under Martian soil

This is where knowledge of lava tubes on Earth comes in handy – by measuring their external and internal radiation levels, Paris got a general idea of ​​whether the structure of lava tubes can reduce the effects of cosmic radiation. The results of the study are published in the journal of the Washington Academy of Sciences.

“Lava tubes can help in the study of Martian geology and geomorphology, and also potentially help to find any evidence of the development of microbial life in the early stages of the natural history of Mars,” Paris writes in his twitter.

So, lava tubes may very well become our new home on another planet. Agree, the prospect sounds so-so. Surely everyone remembers horror films about cave dwellers and other troubles that can happen there (for example, in the movie “Descent” or the TV series “LOST”), but given the fact that we may not have another option – life in lava tubes – this is far from the worst that awaits a person on other planets.

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Signs of ongoing tectonic activity found on the moon

LROC Team / Arizona State University

Astronomers have found new evidence that the moon can still be tectonically active. This is a network of young ridges on the visible side of the Moon, which, according to scientists, is a kind of echo of the cataclysm that spawned the South Pole-Aitken basin several billion years ago. The article was published in the journal Geology.

It is known that the Moon was geologically active several billion years ago, but there is evidence of continued to this day small tectonic activity on the Earth’s natural satellite, which is caused by global compression of the bowels due to the cooling of the Moon and tidal forces from the Earth. 

Seismographs of US Apollo manned missions from 1969 to 1977 recorded 28 seismic oscillation events, eight of which could actually be  generated by fault movements as mechanical stress in the lunar crust increased. In other studies, based on images obtained by lunar orbiting vehicles, it is shown that narrow ridges observed on the moon in many places and ledges crossing small craters speak of tectonic processes that took place less than a hundred million years ago. 

Adomas Valantinas from the University of Bern and Peter Schultz from Brown University searched the region for regolith-free areas on the Moon using images taken with the NAC camera of the Lunar Reconnaissance Orbiter, as well as data on satellite surface temperature obtained by the on-board radiometer Diviner. They found more than five hundred areas with open bedrock on the ridges, as well as narrow (about thirty meters) ledges and grabens . 

The absence of small craters in these areas indicates geologically young areas (less than ten million years), which form faster than collapse as a result of meteorite bombardment. Many of these ridge systems are far beyond the masonry in the lunar seas and are not associated with any global tectonic pattern. 

Scientists suggest that the discovered systems of ridges are still being formed, and the process itself was launched during the collision of the Moon with a large body several billion years ago, which led to the formation of the South Pole – Aitken basin , considered one of the largest impact craters in the Solar System. 

The data from GRAIL probes speak in favor of this  – in 2014, it discovered a network of cracks in the Moon’s crust, through which in the past magma flowed to the surface of the Moon. The ridge network spatially correlates with these ancient deep dykes. Perhaps the “moonquakes” recorded by the Apollon seismographs are also associated with the consequences of the cataclysm that generated the South Pole – Aitken basin. 

Astronomers believe that in order to fully understand the current seismic activity of the Moon and the processes occurring in its interior, it is necessary to deploy a global geophysical network of sensors on the surface of the Earth’s satellite .

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