A search for some of the most distant stars in our Galaxy has reveled one that has already traveled halfway to the Andromeda Galaxy.
Astronomers have discovered more than 200 distant variable stars known as RR Lyrae stars in the stellar halo of the Milky Way. As per recent observations, the most distant of these stars lies more than a million light-years from Earth. This is nearly half the distance to our neighboring galaxy, Andromeda. Andromeda is the closest galaxy to the Milky Way, about 2.5 million light-years away. Astronomers believe Andromeda and the Milky Way will collide in approximately five billion years in a spectacular cosmic fusion. When this massive cosmic merger takes place, our galaxy’s spiral arms will forever vanish, as will its supermassive black hole.
A Star From the Milky Way Halfway to Andromeda
Astronomers discovered this distant “runaway star” through new observations that allowed them to trace the outer limits of the Milky Way halo. Our galactic halo is of great importance to astronomers. The stellar halo is actually much larger than the galactic disk, which is no more than 100,000 light-years across. Previous studies have shown that our galactic halo is genuinely massive, extending around one million light-years (or 300 kiloparsecs) from the galactic center. One kiloparsec equals 3,260 light-years.
The Milky Way’s Halo
Since both the Andromeda galaxy and the Milky Galaxy are so big, astronomers say there’s hardly any “space” between the two. Our solar system is located in one of the galactic arms of the Milky Way’s disk. Found in the middle of the disk is the galaxy’s central bulge. Surrounding it is the halo. This halo is home to the oldest stars in the galaxy. The stars that were found in the latest study ranged in distance from 20 to 320 kiloparsecs. “We were able to use these variable stars as reliable tracers to pin down the distances,” said Yuting Feng, a doctoral student at UCSC. “Our observations confirm the theoretical estimates of the halo size, so that’s an important result.”