Starwatch: See our neighboring galaxy with your own eyes
This time of year you have the best chance to see the farthest thing away that you can see with the unaided human eye. It's the Andromeda Galaxy, the next door neighbor to our home Milky Way Galaxy, and if you look in a dark-enough sky, you can see it with the naked eye!
Last week in this column, I told you as much as I could about the constellations Pegasus the Winged Horse and Andromeda the Princess, that are literally linked together in the night sky, and also how their story is a great celestial saga involving many constellations in that same part of the night sky.
The main part of Pegasus is called the "Square of Pegasus." Look for the square orientated diagonally in the eastern sky. They're the brightest stars in that part of the sky. Next look for two curved lines of stars that arc off to the left of the star Alpheratz (pronounced Al-fee-rats), on the left corner of the Square of Pegasus. The lower arc of stars is much brighter than the upper arc. The lower arc outlines the wings of Pegasus the Winged Horse. The fainter upper arc outlines Princess Andromeda.
A little, faint cloud
The best way to find the Andromeda Galaxy is to follow the lower line, or wing, of the horse two stars to the left of Alpheratz. The second star to the left of Alpheratz is Mirach. Then look above Mirach for two fainter stars. Just above the upper star there will be a very small, faint, patchy cloud. That's it, the Andromeda Galaxy. If you can't see it with the naked eye, try to see it with a small telescope or a pair of binoculars and scan that part of sky.
Now I guarantee it's not going to wow you all that much. Even with my large telescopes, you're not going to see a whole lot more. The image has a little more shape to it and you can see a brighter nucleus, but that's about it. While it's not one of the prime telescope targets in the sky, it is very significant
The Andromeda Galaxy is about 2.5 million light-years away, or about 15 trillion miles. By comparison, the Hubble Telescope has detected galaxies over 12 billion light-years away. It's no small universe!
Galaxies are vast islands of billions of stars. They come in all shapes and sizes. Our home galaxy, the Milky Way, is thought to have some 200 billion stars arranged in a giant spiral over 100,000 light-years in diameter. All the stars we see in our sky are members of the Milky Way galaxy.
The Andromeda Galaxy is a larger spiral galaxy with maybe a trillion stars with a diameter of over 200,000 light-years. Just as it is with our Milky Way, all the stars in the Andromeda Galaxy are orbiting around a super massive black hole at Andromeda's center. It's the glue that gravitationally holds Andromeda together and may be a 100 million times more massive than our sun! In our own galaxy, the central black hole is believed to be about 4 million times more massive than our sun.
In our Milky Way Galaxy, the Andromeda Galaxy, and other galaxies it's now believed that there are more planets than there are stars. Could any be like Earth? Could any have life? Intelligent life? Stay tuned.
Here's one more thing to think about when you gaze upon Andromeda. Every second we get 50 miles closer to Andromeda. The Milky Way and the Andromeda Galaxies are on a collision course. Starting around 4 billion years from now, the Milky Way and Andromeda galaxies will merge. Because of the vast distances between stars, the two galaxies may just slip through each other. I wish corporate mergers on Earth could be that smooth!
Celestial hugging this week
In the early morning eastern pre-twilight skies this week, there's an fabulous three way conjunction between the planets Venus, Jupiter and Mars. Venus is the brightest of trio. With a pair of binoculars or a small telescope, Venus will sport the appearance of a half moon and you'll see tiny "stars" surrounding Jupiter that are actually Jupiter's largest moons. Even though the planets are nearly in the same line of sight, they're nowhere near each other. Jupiter's over 550 million miles away. Mars is over 200 miles distant. Venus is the closest, at just under 60 million miles from your backyard.