The Milky Way galaxy is literally eating its neighbor, according to a study conducted by a team of astronomers from the University of Virginia and the University of Massachusetts.
"Basically, the Milky Way is acting like a cannibal," said University Astronomy Prof. Steven Majewski, lead author of the study. "It is pulling this little galaxy apart, and [stars from that galaxy] are now becoming part of our galaxy."
This study, in which various University graduate and undergraduate students were directly involved, will enable scientists to learn more about the galaxy in which we live.
The debris of the Sagittarius Dwarf Elliptical galaxy -- now prominent in the Milky Way -- is not visible to the naked human eye. But by using the Two-Micron All Sky Survey, a system developed by University Astronomy Prof. Michael Skrutskie, astronomers have been able to create a survey of the entire sky at infrared wave length. They focused on M giants, stars which are rare in the outer parts of the Milky Way but which are common in the Sagittarius galaxy.
"M giants allowed us to trace out the structure of the Milky Way that we knew was there," Skrutskie said. "It was just a matter of seeing it spread across the sky in its entirety."
According to Majewski, these stars from Sagittarius wrapped around the Milky Way indicate that the Milky Way is indeed consuming the smaller galaxy.
The study, which will be published in the Dec. 20 issue of The Astrophysical Journal, shows for the first time the entrails of the Sagittarius galaxy passing through the Milky Way.
"The Milky Way looks like the pinwheel everyone is used to, plus a swirl of stars wrapping around that form this other little galaxy," Majewski said.
The realization that the Milky Way grows by consuming other, smaller galaxies discounts the oft-assumed idea that the galaxies and the Milky Way formed during the Big Bang and have remained the same since then.
According to Majewski, Sagittarius probably isn't the only galaxy the Milky Way has eaten.
"This is probably just a snack it's having right now," he said.
This new discovery will aid scientists in figuring out the exact weight of the Milky Way and in deciphering the location and distribution of dark matter within the galaxy.
Dark matter is a mysterious substance which exists in galaxies but about which very little is known. According to Skrutskie, there also are plans to study the evolution of the Sagittarius galaxy further.
"What we're working on now is to pick out individual stars which are clearly members of this galaxy and to use each as a test particle, to see how Sagittarius works and how it's evolving," he said.
The study was completed with the help of University graduate and undergraduate students.
Students participated in the theoretical modeling and worked to create online models of these galaxies, and according to Majewski, students will continue to be a part of future research.
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