Skies to Stars: Andromeda
By Ed Downs
It was another night at the Astronomy Club of Tulsa’s observatory, just southwest of Mounds, Okla. Yes, that is in the middle of nowhere, just right for dark night observing. It was also a visitor night, with a group of kids from a scout group and many adult visitors planning to join our group of astronomy nerds as we pointed our telescopes starward. With pleasant temperatures, it looked like a great observing evening, so of course, Oklahoma weather decided not to cooperate. Altostratus and cruciform clouds covered about two thirds of the sky, but a group of diehards headed out to do what we could to entertain and educate guests.
Our local expert and guru, John Land, conducted a terrific planetarium show, using what little of the sky could be seen by using a laser pointer, all the while promoting safe use of laser pointing devices, but trying to find a good target for beginners to view proved difficult. This writer was asked to see if I could find M 31 with my 12-inch Orion reflector, sometimes called a “light bucket” due to its ability to suck in even dim objects. Sure enough, M 31 was located, and folks were invited to view this wonder of the skies. We then realized the “M 31” meant absolutely nothing to the newcomers, and finally announced, “Who wants to take a look at the Andromeda Galaxy?”
Even those not particularly interested in Astronomy recognize the name “Andromeda Galaxy.” Perhaps they remember the stories of Greek mythology, wherein Greek Hero Perseus rescues Princess Andromeda (daughter of Cassiopeia) from certain death, made famous by the stories of Homer. Maybe it was the book written by Michael Crichton, “The Andromeda Strain,” later made into a blockbuster movie of the same name in 1971. This story, about an alien virus and the hunt to find and kill it at a secret government facility named “Wildfire” would seem remarkably applicable given our current fight with Ebola. Some might even remember the TV series named “Andromeda,” about a starship lost in time, trying to rebuild a lost civilization.
But to amateur astronomers, the Andromeda Galaxy is a soft cotton ball nestled in amongst a sea of stars. Even when looked at under high power, only the most sophisticated of amateur scope can really define individual stars in this distant galaxy, but the center “bulge,” an area of intense brightness can be seen. To astronomers and astrophysicists, Andromeda is of particular interest, as it is the closest galaxy to our own Milky Way Galaxy. Andromeda is also approaching the Milky Way at a rate of 186,000 miles per second, or the speed of light. And yes, with a distance between the two galaxies of approximately 2.5 billion miles, Andromeda will overtake and consume the Milky Way in about three to five billion years.
While the Milky Way and Andromeda are both considered large galaxies, Andromeda has the edge over the Milky Way by most measures, with the exception of star “birth rates.” The fact is, new stars are being born in the Milky Way almost twice as fast as in Andromeda. But the Milky Way will never catch up in size before the collision takes place, as Andromeda has some 400 billion to 600 billion stars compared to our family of 200 to 300 billion stars. We know that the vast majority of these stars will have multiple planets, giving Si-Fi fans a lot of places to visit when we finally invent warp drive. As far a scientist can tell, our Milky Way is formed in a spiral shape (hard to tell looking from the inside out) having two prominent arms and several smaller arms, while Andromeda is more of a puffy disk. Both galaxies have massive black holes at their centers, although Andromeda’s black hole (possibly two) is nearly 25 times more massive than ours. The disk diameter of our Milky Way has a respectable radius of about 90,000 light years.
You can actually see the disk from any reasonable dark area. It will look like a silver cloud extending from the southwest to northeast horizons during the winter. You will be looking toward the outer edge of our own galaxy. The summer sky will give you an even better view, as you will be looking toward the core of our home galaxy. By comparison, the Andromeda Galaxy has a disk that is about 150,000 light years in diameter. Once the gravitational forces of this giant galaxy reaches the Milky Way, a dance will begin that will result in the complete destruction of our home in the universe, to be replaced by a new spiral galaxy that will be impressive both in density and size.
This writer mentioned the imminent collision to a visitor looking through the eyepiece of my telescope. Our guest commented, “So this is where it will all end?” Thinking for a moment, I envisioned the mating of these two giants, which is billions of years in the future, and then I imagined the new galaxy, which will be born. “No,” I answered, “perhaps this is just a new beginning.” What do you think?
