Scientists have discovered the edge of our galaxy
By: Charles Xue
The Milky Way stretches 1.9 million light years in diameter, and its core is 950,000 light years away from it’s edge. How do we know this? We can thank Alis Deason and her colleagues at Durham University in England for that.
Astronomers have known for a long time that the brightest part of our galaxy is a round, flat disk of stars that hosts our sun. Beyond this disk is another disk made of gasses. Furthermore, a vast halo of dark matter encircles both of these disks. However, astronomers have never been able to figure out how big our galaxy is.
To find the Milky Way’s edge, Deason’s team used computer simulations to find out how giant galaxies form. In this case, they were looking for two galaxies that formed side by side because each galaxy’s gravity pulls on the other. These simulations showed that the smaller galaxies beyond the Milky Way have much smaller velocities. After that, Deason’s team used existing telescope observations to find a similar plunge in velocities about 950,000 light years away from the Milky Way’s core.
Using their findings, Deason’s team figured out that the flat, round disk of stars that hosts our sun is about 120,000 light years in diameter, while the diameter of the entire Milky Way is about 15 times longer than the diameter of the disk that hosts our sun.
In fact, the New York Times states: “To put that size into perspective, imagine a map in which the distance between the sun and the Earth is just one inch. If the Milky Way’s heart were at the center of the Earth, the galaxy’s edge would be four times farther away than the moon actually is.”
Although these findings are accurate, they are not perfect. Luckily, future astronomers should be able to pinpoint the exact location of the edge of the Milky Way by discovering additional small galaxies nearby.