Looking Up: A Tunnel Runs Through It

Sep 11, 2017

M24, also known as the Sagittarius Star Cloud, crowds in just left of center along the bottom of the frame, fainter and more distant Milky Way stars seen through a narrow window in obscuring fields of interstellar dust.
Credit Terry Hancock (Down Under Observatory) / nasa.gov

This week on Looking Up Hal guides us towards the very center of the Milky Way Galaxy.

When you look at the constellation Sagittarius, now visible in the Southern Colorado sky, you are looking toward the actual center of our spinning pinwheel of a galaxy, the Milky Way. And the Milky Way is big, with at least 200 billion stars, and it is dirty – in that there are vast clouds of dust and gas that block our view inward toward the center, or core, of our galaxy.

And right there, in Sagittarius, is this star cloud, also known as M-24. It is densest concentration of stars visible in binoculars or small telescopes, with over 1000 stars visible in the eyepiece. But there is something far more special about M-24, and that is where it is.

Our galaxy has two primary arms, wrapping around the core, and a few minor arms, including the Orion Arm, where we live, along with most of the stars we can see. But M-24 is a cluster of stars, roughly three full moons in diameter, that is not in our arm at all. Rather, we can see M-24 through what might be called a tunnel, through the dust and debris, way out in a very distant and different spiral arm, known as the Norma Spiral Arm. It’s a tunnel through space 600 light years wide. How awesome is that? Very!

If you’d like to take a closer look at the Sagittarius Star Cloud or any of the wonderful and amazing things in the sky, please visit csastro.org for a link to information on our monthly meetings and our free public star parties.