If you live in the southern hemisphere, the Magellanic Clouds are a familiar sight. These are the closest, brightest examples of dwarf galaxies we can see from the Milky Way. Radio astronomers have discovered a tenuous stream of hydrogen connecting our galaxy together with the Magellanic Clouds. This stream will help astronomers calculate the motion of the Clouds. Have they been here for a long time, or are they just passing by.
The finger of hydrogen gas, called HVC306-2+230, is piercing through the disk of the Milky Way about 70,000 light-years away from our location. The exact point of contact is near the Southern Cross (you southerners know what I’m talking about).
Astronomers used to think that the Magellanic Clouds had orbited the Milky Way many times, slowly getting dismembered. But new observations from the Hubble Space Telescope showed that they’re actually moving much more quickly than previously believed. Instead of orbiting the Milky Way, they might just be passing us once, never to return.
By detecting where this leading arm strikes the Milky Way, astronomers will have an easier time calculating the Clouds’ trajectory.
“We think the Leading Arm is a tidal feature, gas pulled out of the Magellanic Clouds by the Milky Way’s gravity,” said Dr McClure-Griffiths, the research team leader from CSIRO’s Australia Telescope National Facility. “Where this gas goes, weâ€™d expect the Clouds to follow, at least approximately.”
Their discovery actually strengthens the original theory, that the Clouds have been orbiting the Milky Way for a long time. Of course, the researchers caution that this isn’t the final word on the subject – the flyby model still hasn’t been ruled out.
But if they’re right, the Magellanic Clouds will eventually merge with the Milky Way and not zoom past.
Original Source: CSIRO News Release