Hot Gas in the Milky Way Halo Appears to be Rotating Almost as Fast as the Disk
Astronomers at the University of Michigan have discovered that the hot gas in the halo of the Milky Way galaxy is spinning in the same direction and at a comparable speed as the galaxy's spiral-shaped disk, which contains our stars, planets, gas, and dust. This new knowledge sheds light on how individual atoms have assembled into stars, planets, and galaxies, and what the future holds for these galaxies.
"This flies in the face of expectations," says Edmund Hodges-Kluck, assistant research scientist. "People just assumed that the disk of the Milky Way spins while this enormous reservoir of hot gas is stationary. But that is wrong. This hot gas reservoir is rotating as well, just not quite as fast as the disk."
The new NASA funded research using archival data obtained by XMM-Newton, a European Space Agency (ESA) telescope, focused on our galaxy's hot gaseous halo, which is several times larger than the Milky Way disk and is composed of ionized plasma.
Because motion produces a shift in the wavelength of light, the University of Michigan researchers measured these shifts around the sky using lines of very hot oxygen. What they found was groundbreaking -- The line shifts measured by the researchers show that the galaxy's halo spins in the same direction as the disk of the Milky Way and at a similar speed -- about 400,000 mph for the halo versus 540,000 mph for the disk.
"The rotation of the hot halo is an incredible clue to how the Milky Way formed," said Hodges-Kluck. "It tells us that this hot atmosphere is the original source of a lot of the matter in the disk."
Scientists have long puzzled over why almost all galaxies, including the Milky Way, seem to lack most of the matter that they otherwise would expect to find. Astronomers believe that about 80 percent of the matter in the universe is the mysterious "dark matter" that, so far, can only be detected by its gravitational pull. But even most of the remaining 20 percent of "normal" matter is missing from galaxy disks. More recently, some of this missing matter has been discovered in the halo. The University of Michigan researchers say that learning about the direction and speed of the spinning halo can help us learn both how the material got there in the first place, and the rate at which we expect the matter to settle into the galaxy.
"Now that we know about the rotation, theorists will begin to use this to learn how our Milky Way galaxy formed... and its eventual destiny," says Joel Bregman, a University of Michigan Professor of Astronomy.
"We can use this discovery to learn so much more. The rotation of this hot halo will be a big topic of future X-ray spectrographs," Bregman says.
For more information:
http://www.nasa.gov/feature/goddard/2016/astronomers-discover-dizzying-spin-of-the-milky-way-galaxy-s-halo
http://www.astromart.com/news/news.asp?news_id=1506
http://www.astromart.com/news/news.asp?news_id=1473
http://www.astromart.com/news/news.asp?news_id=626
http://www.astromart.com/news/news.asp?news_id=437
AstroMart News Archive:
http://www.astromart.com/news/search.asp?search=.+
"This flies in the face of expectations," says Edmund Hodges-Kluck, assistant research scientist. "People just assumed that the disk of the Milky Way spins while this enormous reservoir of hot gas is stationary. But that is wrong. This hot gas reservoir is rotating as well, just not quite as fast as the disk."
The new NASA funded research using archival data obtained by XMM-Newton, a European Space Agency (ESA) telescope, focused on our galaxy's hot gaseous halo, which is several times larger than the Milky Way disk and is composed of ionized plasma.
Because motion produces a shift in the wavelength of light, the University of Michigan researchers measured these shifts around the sky using lines of very hot oxygen. What they found was groundbreaking -- The line shifts measured by the researchers show that the galaxy's halo spins in the same direction as the disk of the Milky Way and at a similar speed -- about 400,000 mph for the halo versus 540,000 mph for the disk.
"The rotation of the hot halo is an incredible clue to how the Milky Way formed," said Hodges-Kluck. "It tells us that this hot atmosphere is the original source of a lot of the matter in the disk."
Scientists have long puzzled over why almost all galaxies, including the Milky Way, seem to lack most of the matter that they otherwise would expect to find. Astronomers believe that about 80 percent of the matter in the universe is the mysterious "dark matter" that, so far, can only be detected by its gravitational pull. But even most of the remaining 20 percent of "normal" matter is missing from galaxy disks. More recently, some of this missing matter has been discovered in the halo. The University of Michigan researchers say that learning about the direction and speed of the spinning halo can help us learn both how the material got there in the first place, and the rate at which we expect the matter to settle into the galaxy.
"Now that we know about the rotation, theorists will begin to use this to learn how our Milky Way galaxy formed... and its eventual destiny," says Joel Bregman, a University of Michigan Professor of Astronomy.
"We can use this discovery to learn so much more. The rotation of this hot halo will be a big topic of future X-ray spectrographs," Bregman says.
For more information:
http://www.nasa.gov/feature/goddard/2016/astronomers-discover-dizzying-spin-of-the-milky-way-galaxy-s-halo
http://www.astromart.com/news/news.asp?news_id=1506
http://www.astromart.com/news/news.asp?news_id=1473
http://www.astromart.com/news/news.asp?news_id=626
http://www.astromart.com/news/news.asp?news_id=437
AstroMart News Archive:
http://www.astromart.com/news/search.asp?search=.+
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