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Detection Of Light From First Stars Might Be Used To Study Dark Matter

Scientists have reported important observations from the indirect light of the first stars in the universe that they suggest could hint at an important piece of the puzzle that is dark matter. Dark matter was proposed in the 60s to explain certain features seen in galaxies, and it became key to our understanding of the universe. However, it has so far eluded all our attempts at detecting it. Researchers used the EDGES experiment to detect a particular radio signal emitted by the hydrogen gas that surrounded and absorbed the light of the first stars. The signal was almost twice as strong as the theoretical expectations and, in a paper published in Nature, Professor Rennan Barkana points the finger at dark matter. The strength of the signal suggests that the hydrogen gas was cooler than expected. Using standard thermodynamics, Barkana argues that to cool down the hydrogen, you need something cooler to take away the energy. And that thing could be dark matter.  “I realized that this surprising signal indicates the presence of two actors: the first stars, and dark matter,” Professor Barkana, who works at Tel Aviv University, said in a statement. “The first stars in the universe turned on the radio signal, while the dark matter collided with the ordinary matter and cooled it down. Extra-cold material naturally explains the strong radio signal.” Assuming that the cause of the cooling is truly dark matter, it is possible to work out some of its properties. Dark matter particles cannot move at relativistic speed and they have to be light – about several times the mass of the protons.

This latter prediction goes against the current consensus, which expects dark matter particles to be significantly heavier. This is an exciting consequence of an already exciting series of observations, but it shouldn’t be interpreted as a conclusive statement on the nature (or even existence) of dark matter. It’s a start, a potential new avenue to uncover its true nature. Barkana believes that dark matter could create a specific pattern in the primordial hydrogen gas observations and that a next-generation radio observatory like the Square Kilometer Array (SKA) could see it. “Such an observation with the SKA would confirm that the first stars indeed revealed dark matter,” added Barkana. Dark matter is believed to be six times more abundant than the regular matter that makes stars, planets, us, and possums. Together with dark energy (another mysterious component), they make up the standard model of cosmology, which has been used to successfully explain many features observed in the Universe.
Astronomers have been planning to use star S0-2 to test Einstein’s theory of general relativity because the star is in a truly unique position. It orbits Sagittarius A*, the supermassive black hole at the center of the Milky Way and it will make its closest approach this spring. While the possibility of this test was exciting, researchers were concerned that S0-2 was a binary system. This would have made the analysis a lot more complex. However, the star is most likely single and, as reported in The Astrophysical Journal, the researchers have the go-ahead to continue with the test. A team led by scientists at UCLA have used the Keck Observatory on Mauna Kea to look at the light spectrum of the stars. Their goal was to work out the influence that a potential second star might have on S0-2’s light. They didn’t find any, so even if it has a companion, it’s not massive enough to matter. “This is the first study to investigate S0-2 as a spectroscopic binary,” lead author Devin Chu of Hilo, from UCLA, said in a statement. “It’s incredibly rewarding. This study gives us confidence that an S0-2 binary system will not significantly affect our ability to measure gravitational redshift.”
The gravitational redshift is what the team, known as the Galactic Center Group, is going to measure to test relativity. As the star approaches the supermassive black hole, the wavelength of the emitted light will be stretched due to the incredible gravitational force present at the center of our galaxy. If there is a deviation between the theory and reality, it will be more obvious where gravity is strongest. “It will be the first measurement of its kind,” said co-author Tuan Do, deputy director of the Galactic Center Group. “Gravity is the least well-tested of the forces of nature. Einstein’s theory has passed all other tests with flying colors so far, so if there are deviations measured, it would certainly raise lots of questions about the nature of gravity!” Astronomers have been studying the stars at the center of the Milky Way for a long time. There are two decades of repeated observations that have already served to test relativity, but to finally see S0-2 getting to its closest approach is important. Researchers also hope to better understand this star and other similar objects around Sagittarius A*. “S0-2 is a very special and puzzling star,” added Chu. “We don’t typically see young, hot stars like S0-2 form so close to a supermassive black hole. This means that S0-2 must have formed a different way.” Various hypotheses and general relativity will be put to the test with the next round of observations for the object. When you think of must-have equipment for an information and communication technology (ICT) class, computers are at the very top of the list. But, this week, pictures of a Ghanaian teacher using much more creative methods have gone viral. Meet Richard Appiah Akoto. Akoto, 33, is an ICT teacher at Betenase M/A Junior High School in Sekyedomase, a town in the Ashanti Region of Ghana and a two hours’ drive from Ghana’s second city, Kumasi. Instead of desktops and tablets, Akoto uses blackboards and chalk. He teaches his students how to use computers by drawing meticulously detailed pictures. This one of a word processing window took the Internet by storm after he posted it on Facebook two weeks ago. Like many teachers, Akoto goes by a different name on the social media platform.
An asteroid is going to fly past Earth tomorrow and, while it won’t hit us, it’s actually going to fly pretty close.0 The bus-sized steroid 2018 DV1, classified as a near-Earth asteroid, will pass about 105,000 kilometers (65,000 miles) from our planet at about noon EDT tomorrow, March 2.  For comparison, the Moon orbits at 385,000 kilometers (240,000 miles), meaning 2018 DV1 will come more than three times closer. It will be the sixth closest asteroid to pass Earth in 2018, and the 18th to fly within the orbit of the Moon. This asteroid is in an orbit around the Sun that takes about 358 Earth days. The furthest distance from the Sun it reaches, its aphelion, is 1.15 AU (1 AU, astronomical unit, is the Earth-Sun distance). Its closest point, its perihelion, is 0.82 AU. Looking back at its previous passes, we can see this is the closest it has ever come to our planet. Its previous closest approach was also March 2, way back in 1906. Back then, it reached a distance of 442,000 kilometers (275,000 miles). Our predictions for its orbit up to 2067 (there’s no available data beyond that) don’t show it making any approaches as close as the one tomorrow. And fortunately, there are no known asteroids on a collision course with Earth. Hooray! We’ve had quite a few asteroids make close passes to Earth already this year, though. Back on February 4, we had 2002 AJ129, which flew past at a relatively large distance of 4.2 million kilometers (2.6 million miles). But its size, comparable to a skyscraper, drew some attention. Then on February 9, an asteroid called 2018 CB flew past at a distance of 64,000 kilometers (39,000 miles). Both of those were close enough to earn them the moniker of a “potentially hazardous asteroid” (PHA), although don’t worry too much. NASA classifies anything as a PHA that exceeds 500 feet (140 meters) in size and comes closer than 7.5 million kilometers (4.6 million miles) to Earth. So 2018 DV1 is yet another space rock heading our way, but as usual there’s nothing to worry about. Still, if you’re interested, you’ll be able to watch it online at the Virtual Telescope Project. And there’s another asteroid to look forward to on March 7, called 2017 VR12, which will pass 1.4 million kilometers (870,000 miles) from our planet. Also, it might be worth thinking about asteroids a bit more seriously at some point, if we want to avoid the fate of the dinosaurs in the future. Just saying.

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