Look to southeast skies for the winged horse

Published 9:32 am Thursday, November 21, 2013

Last month in Starwatch I featured the constellations Pegasus the Winged Horse and Andromeda the Princess.

The heart of the winged horse is called the “Square of Pegasus.” Look for the square orientated diagonally in the southeastern sky. It’s easy to see because the stars that make it up are some of the brightest shiners in that part of the night sky right now.

Alpheratz (al-fee-rats) is the star left of the diamond. To the upper left of the “rats” star you can easily see a longed curved line of stars that outlines the wingspan.

If it’s dark enough where you’re stargazing from look for a fainter arc of stars also originating from Alpheratz and extending to the upper left above and nearly parallel to the wing.

There’s a whole long Greek tale that describes how the hero Perseus used Pegasus the winged horse to rescue Princess Andromeda from a sea monster.

Just above the horse drawn princess is where you can really go deep. Even if you’re watching from a place plagued with moderate light pollution it’s reachable with a decent pair of binoculars: It’s the Andromeda Galaxy.

It looks like a very tiny diffuse cloud. You really need to be in the countryside with a pitch-black sky on a moonless night to spot it.

The second star to the left of Alpheratz on the wing of Pegasus is Mirach. The Andromeda Galaxy will be a little over half of the width of your outstretched fist above and a little to the left of Mirach.

If you have any light pollution you won’t see the Andromeda Galaxy with the naked eye, but you have a good chance of finding it with a small telescope or even a pair of binoculars.

It’s an underwhelming oblong fuzz ball with a brighter nucleus unless you have a really powerful scope and super dark skies. The big deal is that it’s a whole other galaxy of stars, planets and more.

It’s also our galactic next-door neighbor, about 2½ million light-years away, with just one light-year equaling 6 trillion miles. Also, 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 more than 2 million years.

The Andromeda Galaxy, like our Milky Way, is a spiral type galaxy with most of the stars in the central nucleus and the rest of the stars arranged in spiral arms.

The Andromeda Galaxy is also historical. As late as the early 1900s astronomers thought the Milky Way Galaxy was all there was to the universe. 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 previously believed.

They used what is known as Cepheid variable stars to gauge just how far away it is. Cepheid variable stars vary in size and brightness over a period related to average brightness. They’re what astronomers call “standard candles.”

Through laborious observation over photo plates, Cepheid variable stars were found in the Andromeda nebula. Observing their brightening and dimming cycles it was determined that the Andromeda nebulae was way, way farther away than anyone ever imagined,

Hubble and colleagues realized what they were observing was a whole separate galaxy independent of our Milky Way. Since then other galaxies have been discovered in the heavens above us.

Mike Lynch is author of “Stars, a Month by Month Tour of the Constellations.”