Our galactic home in the cosmos — the Milky Way — is only one of two trillion galaxies in the observable Universe.
Our galactic home in the cosmos — the Milky Way — is merely one among the observable Universe’s two trillion.
From our own perspective on Earth, we’ve identified the presence of spiral arms.
However, being stuck within the Milky Way itself, we exclusively view it edge-on.
Even our best spaceborne views leave much ambiguity in our galaxy’s overall structure.
We’re not a grand spiral galaxy, as we’re lacking extended outer arms.
Nor are we similar to Andromeda, our nearest large neighbor, which lacks a central bar.
While one-third of spiral galaxies have bars, ours is smaller than many, like NGC 1300’s.
The outer arms are neither irregular nor tightly wound; we’re not “flocculent.”
Additionally, the Milky Way possesses a small but significant central bulge.
We also exhibit major arms, minor arms, and spurs, with the Orion spur home to our Sun.
While many galaxies copiously form stars, the Milky Way is relatively quiet.
Only within the arms themselves are new stars primarily formed.
It’s as though the Milky Way is a large, barred spiral galaxy with a small, elliptical center.
Many similar galaxies are known, but nobody knows exactly which one is most like our Milky Way.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.