via Universe Today.
In 2003 a new class of stars was announced – ultracool subdwarfs – so called because they are very cold, very low in elements other than hydrogen and helium and very small, some only just outside the range of brown dwarfs, the stage between star and gas giant planet. Because of their low temperatures and masses, these objects are pretty faint and so hard to detect amidst the brighter members of the stellar population of the galaxy, but several have been found and their orbits calculated. The results have been a bit of a surprise.
If stars are like planets, orbiting the centre of the Milky Way as Earth or Mars orbits the Sun, these cold stars are rather more like comets, with highly eccentric orbits taking them close into the centre and then far out from it again. In addition to this one has taken the appearance of a long period comet, stretching out 200,000 light years from the centre of the galaxy, ten times the distance we are from it and even farther out than some of the Milky Way’s closer neighbours.
2MASS 1227-0447 as the thing is romantically named presently lies in the constellation of Virgo. Adam Burgasser and colleagues of the Massachusetts Institute of Technology studied its motion and calculated its orbital parameters. Its highly eccentric billion year long orbit suggests that it might not be a local boy. The star may well have come in from another galaxy that either interacted with the Milky Way and had some of its matter torn off it as a result, or maybe the galaxy itself has merged with the Milky Way, leaving 2MASS 1227-0447 orphaned and adopted by our galaxy. Alternatively, 2MASS 1227-0447 may well have originated here and survived being torn away during a previous interaction. Either way, as these objects cut a dash through the galactic halo, learning more about them may teach us more about how the galaxy acquired that mysterious shell of Dark Matter.
Where the Sun hits the sky 