Dimitri Veras. The fates of Solar system analogues with one additional distant planet, Monthly Notices of the Royal Astronomical Society (2016). DOI: 10.1093/mnras/stw2170
The solar system could be thrown into disaster when the sun dies if the mysterious ‘Planet Nine’ exists, according to research from the University of Warwick. Dr Dimitri Veras in the Department of Physics has discovered that the presence of Planet Nine – the hypothetical planet which may exist in the outer Solar System – could cause the elimination of at least one of the giant planets after the sun dies, hurling them out into interstellar space through a sort of ‘pinball’ effect...
A star system 94 light years away is in the spotlight as a possible candidate for intelligent inhabitants, thanks to the discovery of a radio signal by a group of Russian astronomers. HD 164595, a solar system a few billion years older than the Sun but centered on a star of comparable size and brightness, is the purported source of a signal found with the RATAN-600 radio telescope in Zelenchukskaya, at the northern foot of the Caucasus Mountains. This system is known to have one planet, a Neptune-sized world in such a very tight orbit, making it unattractive for life. However, there could be other planets in this system that are still undiscovered.
Could it be a transmission from a technically proficient society? At this point, we can only ...
Credit: Harvard-Smithsonian Center for Astrophysics
The center of the Milky Way galaxy is currently a quiet place where a supermassive black hole slumbers, only occasionally slurping small sips of hydrogen gas. But it wasn’t always this way. A new study shows that 6 million years ago, when the first human ancestors known as hominins walked the Earth, our galaxy’s core blazed forth furiously. The evidence for this active phase came from a search for the galaxy’s missing mass.
Measurements show that the Milky Way galaxy weighs about 1-2 trillion times as much as our Sun. About 5/6 of that is in the form of dark matter. The remaining 1/6 of our galaxy’s heft, or 150-300 billion solar masses, is normal matter...
The dark galaxy Dragonfly 44. The image on the left is from the Sloan Digital Sky Survey. Only a faint smudge is visible. The image on the right is a long exposure with the Gemini telescope, revealing a large, elongated object. Dragonfly 44 is very faint for its mass and consists almost entirely of dark matter. Credit: Images by Pieter van Dokkum, Roberto Abraham, Gemini, Sloan Digital Sky Survey
Using the world’s most powerful telescopes, an international team of astronomers has found a massive galaxy that consists almost entirely of dark matter. The galaxy, Dragonfly 44, is located in the nearby Coma constellation and had been overlooked until last year because of its unusual composition: It is a diffuse “blob” about the size of the Milky Way, but with far fewer stars. “Very soon after its discovery, we realized this galaxy had to be more than meets the eye. It has so few stars that it would quickly be ripped apart unless something was holding it together,” said Yale University astronomer Pieter van Dokkum.
Van Dokkum’s team was able to get a good look at Dragonfly 44 thanks to the W.M. Keck Observatory and the Gemini North telescope, both in Hawaii. Astronomers used observations from Keck, taken over 6 nights, to measure the velocities of stars in the galaxy. They used the 8m Gemini North telescope to reveal a halo of spherical cluster of stars around the galaxy’s core, similar to the halo that surrounds our Milky Way galaxy.
Star velocities are an indication of the galaxy’s mass. The faster the stars move, the more mass its galaxy will have. “Amazingly, the stars move at velocities that are far greater than expected for such a dim galaxy. It means that Dragonfly 44 has a huge amount of unseen mass,” said Roberto Abraham of the University of Toronto. Scientists initially spotted Dragonfly 44 with the Dragonfly Telephoto Array, a telescope invented and built by van Dokkum and Abraham.
Dragonfly 44’s mass is estimated to be 1 trillion times the mass of the Sun, or 2 tredecillion kg (a 2 followed by 42 zeros), which is similar to the mass of the Milky Way. However, only 1/100 of 1% of that is in the form of stars and “normal” matter. The other 99.99% is in the form of dark matter, a hypothesized material that remains unseen but may make up more than 90% of the universe.
Finding a galaxy composed mainly of dark matter is not new; ultra-faint dwarf galaxies have similar compositions. But those galaxies were roughly 10,000 times less massive than Dragonfly 44. “We have no idea how galaxies like Dragonfly 44 could have formed,” said Abraham. “The Gemini data show that a relatively large fraction of the stars is in the form of very compact clusters, and that is probably an important clue. But at the moment we’re just guessing.”
Van Dokkum, Sol Goldman Family Professor of Astronomy and Physics at Yale, added: “Ultimately what we really want to learn is what dark matter is. The race is on to find massive dark galaxies that are even closer to us than Dragonfly 44, so we can look for feeble signals that may reveal a dark matter particle.” http://www.newswise.com/articles/scientists-discover-a-dark-milky-way
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