Astronomers find the edge of our galaxy

Astronomers find the edge of our galaxy

Astronomers find the edge of our galaxy

The Andromeda Galaxy captured by the NASA Galaxy Evolution Mapper in 2012.

The Andromeda Galaxy captured by the NASA Galaxy Evolution Mapper in 2012.
Image: NASA/JPL-Caltech

In their search for the outer limits of our galaxy, astronomers have discovered more than 200 stars that form the edge of the Milky Way, the most distant of which is more than a million rays of light.years away – almost half way through the Andromeda galaxy.

The 208 stars the researchers identified are known as RR Lyre stars, these are stars with a brightness that can change from Earth. These stars are typically old and get brighter and fainter at regular intervals, which is a mechanism that allows scientists to calculate how far away they are. By calculating the distance to these RR Lyrae stars, the team found that the farthest of the bunch was about halfway between the Milky Way and the Andromeda galaxy, one of our cosmic next-door neighbours.

“This study redefines what constitutes the outer boundaries of our galaxy,” Raja GuhaThakurta said in a press release. GuhaThakurta is a professor and chair of astronomy and astrophysics at the University of California at Santa Cruz. “Our galaxy and Andromeda are both so big that there’s hardly any space between the two galaxies.”

Image for article titled Astronomers find the edge of our galaxy

Illustration: NASA, ESA AND A. FEILD (STSCI)

The Milky Way galaxy is made up of a few distinct parts, the primary of which is a thin spiral disc about 100,000 light-year left. Oyou are at home solar system sits on one of the arms of this disk. An inner and outer halo surround the disk, and these halos contain some of the oldest stars in our galaxy.

Previous studies have placed the edge of the outer halo at 1 million light-years from the Milky Way’s center, but based on the new work, the edge of this halo should be about 1.04 million light-years from the galactic center. Yuting Feng, a doctoral student at the university working with GuhaThakurta, led the study and is presentation of findings this week at the meeting of the American Astronomical Society in Seattle.

“We were able to use these variable stars as reliable tracers to determine the distances,” said Yuting Feng, a doctoral student at the university who is collaborating with GuhaThakurta. “Our observations confirm the theoretical estimates of the halo’s size, so that’s an important result.”

Space is vast and lonely-but we can feel a little more cozy knowing that our galactic neighbor is closer than we thought.



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