Go the distance with the Andromeda Galaxy
How would you like to see the farthest thing visible to the naked eye? It’s possible, but you’ll need to bundle up and sit back on a lawn chair. Your neighbors may think you’ve cracked up sitting out there in the winter, but you’re on a mission! You’re out in the cold to find the Andromeda Galaxy, the next-door neighbor to our own Milky Way Galaxy, home to our sun and possibly another 300 billion or so stars and Lord knows how many other planets! It is possible to see the Andromeda Galaxy with the naked eye, but honestly you need to have dark countryside skies to pull that off. If you’re on a mission to spot Andromeda in areas compromised by light pollution you better have a pair of binoculars or small telescope. Maybe you received a new scope for Christmas. Here’s your chance to really go deep! Just make sure you let your new telescope and all of the eyepieces you’re going to use sit outside for a good 30-45 minutes so the glass and/or mirrors can acclimate to colder temperatures. Otherwise you can get some really blurry and funky views!
Once you settle into your lawn chair, try to give your eyes a good 15-20 minutes to adjust to the darkness and get your night vision. If you’re using any kind of star map or the diagram included with this column use a headband flashlight with a red lens so you don’t ruin your night vision. You can buy those at a hardware store or anywhere that sells camping gear. If you want you can also fire up a stargazing app on your phone or small tablet. My favorite is the one called “Sky Guide.”
The best way to find the Andromeda Galaxy is to locate the constellation Andromeda the Princess, which is attached to the constellation Pegasus the Winged Horse in the early evening Marshall western sky. Follow the left arm of the constellation Andromeda. At about the halfway point of that arc of stars is the moderately bright star Mirach. Just to the right of Mirach you’ll see two much fainter stars. Just the immediate lower right of those two stars, look for a very small, faint, patchy cloud. That’s it, the Andromeda Galaxy. Again, you may need binoculars or a small telescope to find it.
Honestly, you certainly won’t be blown away when you first spot it. All you’ll see is a ghostly patch of light and a bright nucleus. Even with my large telescopes that I bring to my stargazing parties you usually don’t see too much more than that, although through larger scopes in dark skies the galaxy will have a little more shape and definition to it. Astronomical photographs reveal more detail because that can gather and accumulate more light than our human eyes.
Nonetheless, that little ghostly patch of light is made up of the collective light of possibly a trillion stars at a distance of 2.5 million light-years away. Just one light-year equals nearly 6 trillion miles. Since a light year is defined as the distance light travels in a year’s time, the light that you’re seeing from Andromeda has been traveling to your eyes for 2.5 million years. We don’t see the light as it is now, but as what it looked like 2.5 million years ago. From what astronomers know about galaxy lifetimes it hasn’t change all that much in appearance, even over a couple of million years.
Despite that incredible distance the Andromeda Galaxy and the Milky Way are the closest neighbors to each other, but without a doubt Andromeda is a larger galaxy, possibly twice the diameter of our Milky Way. Like our home galaxy most of the mass that makes up Andromeda is invisible, what astronomers call dark matter, which still remains a big mystery.
The Andromeda Galaxy is very important to the history of astronomical discovery. Less than 100 years ago the Milky Way Galaxy was all we thought there was to the universe. What we now know as the Andromeda Galaxy was then thought to be just a big cloud of nebulosity. That all changed in the 1920s when Edwin Hubble and his assistant Henrietta Leavitt discovered that the Andromeda Galaxy was a heck of a lot farther away than it was previously believed to be. They used what is known as Cepheid variable stars to gauge just how far away Andromeda was. Cepheid variable stars vary in size and brightness over a period related to average brightness. They’re what astronomers call “standard candles.” As it turned out, through painstaking observation and photographic analysis, Cepheid variable stars were found in the Andromeda nebula. By observing their brightening and dimming cycle it was determined that the Andromeda nebulae was way, way farther away than anyone ever thought. Furthermore, it was concluded that it was a whole other galaxy of stars independent of our Milky Way. Edwin Hubble gets all the credit for this discovery but Henrietta Leavitt actually discovered the Cepheid variables in Andromeda and did most of the labor-intensive legwork.
One more thing about Andromeda, and yet one more thing you can worry about. The Andromeda Galaxy and the Milky Way Galaxy are on a collision course. They’re approaching each other at an estimated 60 to 80 miles a second! I wouldn’t let it worry you all that much because even at that speed the two galaxies won’t any time soon. Give it a little more than four billion years.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is also the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and at adventurepublications.net.