Located 2.5 million light years away, the Andromeda galaxy is our closest galactic neighbor.
The spiral galaxy is also the most distant object you can see with the naked eye from Earth, making it a good test subject for studying these massive conglomerations of gas and stars.
In a new study, NASA’s Hubble Space Telescope mapped Andromeda’s halo — the envelope of gas that surrounds the galaxy — in unprecedented detail.
The Milky Way and Andromeda are very close, on the cosmic scale, and they are getting ever-closer. Andromeda is inching towards our galaxy at an estimated rate of around 250,000 miles per hour. That’s 2,000 times faster than a fastball, according to NASA estimates.
In fact, the two galaxies are on a collision course with one another, drawn together by their gravitational force. Eventually, they will merge in around 4.5 billion years.
Andromeda’s halo helps put that time and space into perspective on the cosmic scale: These new maps reveal the halo extends some 1.3 million light-years out from the galaxy — about halfway to our Milky Way. That means that Andromeda’s halo is already ‘bumping’ into the Milky Way,according to NASA.