Our galactic neighbour is starting to fall apart after colliding with a nearby galaxy.
The Large and Small Magellanic Clouds are the two brightest galaxies that orbit our own, lying just 160,000 and 200,000 light years away. And the larger of the two is sucking in material from its smaller counterpart, pulling the smaller galaxy apart star by star.
and at the University of Virginia in Charlottesville, and their colleagues used the Hubble Space Telescope to track the motions of stars in the Small Magellanic Cloud relative to background quasars.
Advertisement
They didn鈥檛 see the galaxy rotating, unlike the Large Magellanic Cloud. Instead, 鈥減arts of the outer regions of the Small Magellanic Cloud are getting pulled away by the Large Magellanic Cloud,鈥� Zivick says. Stars in the southeastern and southwestern outskirts of the smaller galaxy are streaming away from its centre.
Moreover, by tracing the paths of the galaxies back in time, the astronomers reach a dramatic conclusion. 鈥淭he two galaxies smashed into each other,鈥� says team member at the University of Arizona in Tucson.
The fallout
The collision occurred just 150 million years ago. The smaller galaxy skirted only about 25,000 light years from the larger galaxy鈥檚 centre, hitting its disc.
鈥淚 find the result quite believable, and the implications are very interesting,鈥� says at the National Optical Astronomy Observatory in Tucson, Arizona.
As a result of this cosmic collision, the Small Magellanic Cloud is in distress, losing both stars and gas, and Besla predicts it will completely change its type. Right now it鈥檚 an irregular galaxy, full of gas that鈥檚 spawning the bright new stars that set it aglow. But she says the galaxy will lose its gas and eventually become a dwarf elliptical galaxy, a duller type that gives birth to no stars at all.
It鈥檚 hard to know how much of the Small Magellanic Cloud will disintegrate because of the uncertainty around the mass of both the Large Magellanic Cloud and the Milky Way. But if it is still gravitationally bound to its bigger brother, and if it has another collision, it鈥檚 probably best to avoid setting up camp anywhere nearby unless you want to end up hurtling through intergalactic space.
Despite the recent trauma, Besla says the Small Magellanic Cloud will survive, because it has plenty of dark matter whose gravitational pull will retain some of its stars.
Journal Reference:
Read more: Milky Way鈥檚 nearest galaxies may be new to the neighbourhood
