Harvard Smithsonian Center for Astrophysics | 2017 Jan 11
[img3="In this computer-generated image, a red oval marks the disk of our Milky Way galaxy and a red dot shows the location of the Sagittarius dwarf galaxy. The yellow circles represent stars that have been ripped from the Sagittarius dwarf and flung far across space. Five of the 11 farthest known stars in our galaxy were probably stolen this way. Credit: Marion Dierickx / CfA"]https://www.cfa.harvard.edu/sites/www.c ... 1/base.jpg[/img3][hr][/hr]The 11 farthest known stars in our galaxy are located about 300,000 light-years from Earth, well outside the Milky Way's spiral disk. New research by Harvard astronomers shows that half of those stars might have been ripped from another galaxy: the Sagittarius dwarf. Moreover, they are members of a lengthy stream of stars extending one million light-years across space, or 10 times the width of our galaxy.
"The star streams that have been mapped so far are like creeks compared to the giant river of stars we predict will be observed eventually," says lead author Marion Dierickx of the Harvard-Smithsonian Center for Astrophysics (CfA).
The Sagittarius dwarf is one of dozens of mini-galaxies that surround the Milky Way. Over the age of the universe it made several loops around our galaxy. On each passage, the Milky Way's gravitational tides tugged on the smaller galaxy, pulling it apart like taffy.
Dierickx and her PhD advisor, Harvard theorist Avi Loeb, used computer models to simulate the movements of the Sagittarius dwarf over the past 8 billion years. They varied its initial velocity and angle of approach to the Milky Way to determine what best matched current observations.
"The starting speed and approach angle have a big effect on the orbit, just like the speed and angle of a missile launch affects its trajectory," explains Loeb. ...
Predicted Extension of the Sagittarius Stream to the Milky Way Virial Radius - Marion Dierickx, Abraham Loeb
- arXiv.org > astro-ph > arXiv:1611.00089 > 01 Nov 2016
