Bite-Sized Milky Way: Turns Out Our Galaxy Is Smaller Than We Thought

Wanna feel small? Turns out the Milky Way — home to you and everything you love — isn’t comparatively as massive as we thought it was. In fact, compared to one of our closest neighboring galaxies, Andromeda, we are positively bite-sized.

The news comes by way of a new study published in the Monthly Notices of the Royal Astronomical Society, and that study’s findings suggest that the Andromeda spiral galaxy has twice the mass of the Milky Way. That’s a bit odd, considering that scientists for a long time have figured that our Milky Way had about the same mass as Andromeda. Not so, says the study.

Astronomers studied both the Milky Way and Andromeda, as well as their neighboring galaxies, looking at how their gravitational pulls affect each other and how the galaxies are expanding. Doing so enabled them to more accurately gauge the mass of the Milky Way and its neighbors. The method used to measure the Milky Way and the rest of the Local Group — the cluster of galaxies of which the Milky Way is a part — will help astronomers better understand the substance that makes Andromeda so much more massive: dark matter.

Dark matter is an invisible substance that makes up an incredible amount of the universe. We can’t perceive it directly, but we can measure its effects. Dark matter makes up about 90 percent of the mass of the Milky Way, according to the most recent estimates, but it appears that the Milky Way’s spiral neighbor Andromeda has more of the stuff.

If you want to feel even smaller, consider this: Scientists have discovered a “bridge” of gas that’s 20 times bigger than the Milky Way. It’s a cloud of atomic hydrogen stretching between a number of small galaxies and their larger neighbor. About 2.6 million light years separate the structures, and the mass of the connecting gas is several times more than the mass of both the Milky Way and Andromeda.

Of course, if all this learned astronomer talk of the numbers and scale of the Milky Way are making you tired and sick, you can wander off by yourself tonight into the mystical moist night-air. If you get away from the city lights, you can look up in perfect silence at the stars. Late July and early August are the perfect time to see the wisps of the immense galaxy we live in, even if it does seem just a little bit smaller now.