As summer is ending, fall is a great time to look for the largest and the farthest. The task will be difficult so here is what you will need. First of all, a moon-free and smoke-free night sky is essential. Then a clear view into the northeast is helpful along with a pair of binoculars. For you readers in Seattle, you will never be able to see it with all the city lights washing out the subtleties of the night sky. Come over to the Methow Valley to see the stars at their best.
Look for the constellation Cassiopeia in the northeastern part of the sky. It looks like a “W” up there. A “W” has two inverted “Vs,” and use the top one as a pointer to the right. Point over about the length of the constellation. Here is where the binoculars come in handy. Use them to spot a faint blob of dim light with an oblong shape. I know, it does not look real exciting. Once you have spotted it with your binoculars see if you can see it with the naked eye. It is right at the limit it of what our eyes can see.
What is it? If you have found it, you are looking at the biggest thing you have ever seen and the farthest away thing you have ever seen. This is the Andromeda Galaxy, and the light you are seeing has been traveling a staggering two and a half million years to get to your eyes. Remember light cruises along at 186,282 miles per second so in a year it covers a lot of ground, about 5.9 trillion miles. That is a big number, and if you multiply it by two and a half million it gets even bigger.
Our own Milky Way Galaxy has about 300 billion stars, our sun being just one, and Andromeda has twice that number. More stars mean more mass, and more mass means more gravity. When you are looking up at Andromeda try to imagine that you are actually looking downhill in the biggest sense of the word. All that gravity means we are being sucked towards and are falling into Andromeda.
Try this at home
Do not worry. You do not have to rush out and buy collision insurance tomorrow. It will be about 4 billion years before we get there. I know this is all difficult to visualize, galaxies with hundreds of billions of stars careening through space and crashing into one another. Here is a little demonstration that you can do in the comfort and convenience of your own living room. Amaze your friends with your knowledge of celestial mechanics.
You will need two footballs and a measuring tape. Place the footballs 30 feet apart on the floor. Interestingly this is just about the scale of the size of the two galaxies and their distance apart. All you have to do is sit down and watch closely. In 11,111,111 years the two footballs will move 1 inch closer together! That is gravity at work, the same force that allows you to collapse into your easy chair after a hard day of working in the yard.
Astronomers say it might take a couple of billion years for the collision to unfold. Common sense tells us that stars in the two galaxies will be crashing into one another right and left. Stars are so far apart that they will rarely run into one another. The two galaxies will pass through one another like ghosts. Some stars may fall into the black holes at the center of each galaxy, and some may be ejected out into the lonely space between them.
In the end a whole new galaxy will be created. Astronomers have gotten ahead of themselves a little bit and have already named it. They are calling it “Milkomeda,” and they think it will look like the Sombrero Galaxy. Check that one out online if you want to know what the future looks like for us.
Some of the planets are visible up there and they are a lot closer than the galaxies. Look for Saturn low in the southeast just after it gets dark. Jupiter comes up a little later, and brilliant Venus is ruling the predawn sky with her magnificence.