Tag: galaxies

The Milky Way’s council of galaxies.

8:02 am

The Milky Way’s council of galaxies.

“All bright galaxies within 20 million light years, including us, are organized in a ‘Local Sheet’ 34-million light years across and only 1.5-million light years thick,” says McCall. “The Milky Way and Andromeda are encircled by twelve large galaxies arranged in a ring about 24-million light years across – this ‘Council of Giants’ stands in gravitational judgment of the Local Group by restricting its range of influence.”

McCall says twelve of the fourteen giants in the Local Sheet, including the Milky Way and Andromeda, are “spiral galaxies” which have highly flattened disks in which stars are forming. The remaining two are more puffy “elliptical galaxies”, whose stellar bulks were laid down long ago. Intriguingly, the two ellipticals sit on opposite sides of the Council. Winds expelled in the earliest phases of their development might have shepherded gas towards the Local Group, thereby helping to build the disks of the Milky Way and Andromeda.

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Astronomers watch the central supermassive black hole of a galaxy eat something, either a planet or a brown dwarf.

9:24 am

Astronomers watch the central supermassive black hole of a galaxy eat something, either a planet or a brown dwarf.

Astronomers were using Integral to study a different galaxy when they noticed a bright X-ray flare coming from another location in the same wide field-of-view. Using XMM-Newton, the origin was confirmed as NGC 4845, a galaxy never before detected at high energies. Along with Swift and MAXI, the emission was traced from its maximum in January 2011, when the galaxy brightened by a factor of a thousand, and then as it subsided over the course of the year. “The observation was completely unexpected, from a galaxy that has been quiet for at least 20–30 years,” says Marek Nikolajuk of the University of Bialystok, Poland, lead author of the paper in Astronomy & Astrophysics.

By analysing the characteristics of the flare, the astronomers could determine that the emission came from a halo of material around the galaxy’s central black hole as it tore apart and fed on an object of 14–30 Jupiter masses. This size range corresponds to brown dwarfs, substellar objects that are not massive enough to fuse hydrogen in their core and ignite as stars. However, the authors note that it could have had an even lower mass, just a few times that of Jupiter, placing it in the range of gas-giant planets.

All the instruments listed above are orbiting space telescopes. You can read the science paper here.

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Astronomers have discovered that a large number of dwarf galaxies are orbiting Andromedea in a flat plane, like our solar system, contrary to all predictions.

10:40 am

The uncertainty of science: Astronomers have discovered that a large number of dwarf galaxies are orbiting Andromedea in a flat plane, like our solar system, contrary to all predictions.

The study reveals almost 30 dwarf galaxies orbiting the larger Andromeda galaxy in this regular, solar system-like plane. The astronomers’ expectations were that these smaller galaxies should be buzzing around randomly, like bees around a hive. “This was completely unexpected,” said Geraint Lewis, one of the lead authors on the Nature publication. “The chance of this happening randomly is next to nothing.” The fact that astronomers now see that a majority of these little systems in fact contrive to map out an immensely large – approximately one million light years across – but extremely flattened structure, implies that this understanding is grossly incorrect. Either something about how these galaxies formed, or subsequently evolved, must have led them to trace out this peculiar, coherent, structure.

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Some spectacular images of galaxies from the new Discovery Channel Telescope.

9:26 am

Some spectacular images of galaxies from the new Discovery Channel Telescope (DCT).

Funded privately by the Discovery channel, the DCT has a primary mirror 4.3 meters wide, or about 170 inches, almost as large as the Hale Telescope on Palomar Mountain. This is a world class telescope which will do real research, and it was built the old-fashioned way, with private money donated to a private observatory in exchange for publicity and good will.

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Astronomers think they have discovered a distant supermassive black hole that is being ejected from its galaxy at a speed of several million miles per hour.

4:48 pm

Astronomers think they have discovered a distant supermassive black hole that is being ejected from its galaxy at a speed of several million miles per hour.

Although the ejection of a supermassive black hole from a galaxy by recoil because more gravitational waves are being emitted in one direction than another is likely to be rare, it nevertheless could mean that there are many giant black holes roaming undetected out in the vast spaces between galaxies. “These black holes would be invisible to us,” said co-author Laura Blecha, also of CfA, “because they have consumed all of the gas surrounding them after being thrown out of their home galaxy.”

This conclusion however is not final. The data could also be explained by the spiraling in of two supermassive black holes.

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Mature galaxy cluster found in young universe

4:42 pm

A mature galaxy cluster has been found by astronomers at a time when the universe is thought to be only a quarter of its present age.

This discovery could be very significant, since astronomers think mature galaxy clusters need time to form, and shouldn’t exist in the early universe. “If further observations find many more [of these clusters] then this may mean that our understanding of the early Universe needs to be revised.”

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Hubble marches on: Pinwheel of star formation

3:27 pm

Despite its age (20 plus years), the Hubble Space Telescope continues to produce amazing images. The mosiac below shows the beautiful pinwheel galaxy NGC 3982. From the caption:

NGC 3982 is located about 68 million light-years away in the constellation Ursa Major. The galaxy spans about 30,000 light-years, one-third of the size of our Milky Way galaxy. . . .The arms are lined with pink star-forming regions of glowing hydrogen, newborn blue star clusters, and obscuring dust lanes that provide the raw material for future generations of stars. The bright nucleus is home to an older population of stars, which grow ever more densely packed toward the center.

Pinwheel galaxy

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