‹‹ Looking Up

The Great Square – a horse’s asterism

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great square in pegasus
Credit Pegasustheatre.org
great square in pegasus

  This is “Looking UP! in southern Colorado,” from the Colorado Springs Astronomical Society. I’m Hal Bidlack, and there are lots of reasons to look up!

This is a great time of year for astronomy. The stars of summer are still up there but we're starting to see wonderful things from the fall and getting hints of what the winter sky will look like. Rising in the southern Colorado sky, and visible until next spring, is the constellation Pegasus. This winged horse is one of the largest constellations in the sky. 

And while Pegasus is technically supposed to look somewhat equine, as a practical matter we usually talk about a subset of the entire constellation, known as the Great Square of Pegasus.

The Great Square is an asterism, a portion of a larger constellation. The Great Square of Pegasus is, as you might expect, a really big square shape in the sky. Some astronomers have called it the big square of nothing, but there’s actually something very interesting up there.

Roughly halfway between two of the stars that make up the Great Square, Scheat and Markab, is what looks like a very plain and ordinary star that is just visible to the naked eye if you’re away from a city and have dark skies. If you’re in Colorado Springs or any other urban area, you’ll need at least binoculars to find 51 Pegasi. This point of light in the sky lies roughly 50 ly from Earth. But what makes 51 Pegasi so special is what orbits around it.

In 1995, 51 Pegasi was the very first star outside of our own solar system where astronomers were able to confirm the existence of a planet orbiting another star. This was a major discovery. There were lots of theories in astronomy suggesting there ought to be other planets out there, but none have been detected. This seemingly ordinary star, located in the big square of nothing, revolutionized astronomy and our understanding of the universe.

Today astronomers have confirmed the existence of over 1000 exoplanets orbiting stars in our region of the galaxy, and thanks to massive amounts of data gathered by a remarkable spacecraft called Kepler, there are thousands and thousands more waiting to be confirmed.

If you’d like to take a closer look at Pegasus or any of the other wonderful and amazing things in the sky, please visit KRCC.org or CSASTRO.org for a link to information on our monthly meetings and our free public star parties! 

This is Hal Bidlack for the Colorado Springs Astronomical Society, telling you to keep looking up, Southern Colorado!