Andromeda Galaxy and Companions
Andromeda, like all large galaxies, travels through space with an escort of smaller galaxies known as companion or satellite galaxies. An analogy might be how an aircraft carrier is flanked by cruisers, destroyers, frigates, and an unconfirmed submarine or two. Andromeda is the largest such fleet in our section of Universe, having at least 13 such "satellite" galaxies. While two are obvious in this image, most orbit much farther away from Andromeda's core, and thus are out of frame. More like those submarines, are probably there too, just extremely difficult to detect.
Our own Milky Way has somewhere between 18 and 60 satellite galaxies depending on whether you still count those that are already mostly digested like food in so many vacuoles of a giant amoeba that is our Milky Way Galaxy. It appears that galaxies grow as they engulf their satellite galaxies or merge with full-sized galaxies. The Andromeda Galaxy is the closest full-sized and independent galaxy to the Milky Way at only 2.5 million light years away.
In a BIG telescope with a wide field of view, you can see those two brightest satellite galaxies of Andromeda plainly. Also look for how the its core is surrounded with two ringlets of galactic arms, recognizable by their central black ribbons of lumpy darkness. Normally, galactic arms take on a spiral pattern as they extend into the core. It’s assumed that Andromeda lost her figure-skater figure after having adsorbed another large galaxy or two. What’s known for certain, and nobody can do anything about it, is that she is coming for us next.
She is even bigger than our galaxy and we are on a convergent course with a closing velocity of ~180,000 miles per hour. Don't worry, Andromeda will never in your lifetime appear as big in the sky as it will in this art hanging on your wall. That's because even at that phenomenal speed, it will be 4 billion years before our galaxies start to merge -- plenty of time to amass a collection of Dark Ranger Telescope Astro Art.
