Looking Up: Star Hunt

Sep 2, 2019

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Credit Online Star Register / https://osr.org/blog/astronomy/alpha-gruis/

This week on Looking Up Hal takes us on a star safari to search for possibly the southern most star visible from the Colorado sky.

Do you feel like going on a bit of a star hunt? If so, pay attention as I tell you about the elusive star Al Nair, currently low in the SW sky.

This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
Credit Till Credner / AlltheSky.com / wikimedia.org

Al Nair is fun to hunt for, because it is just about the southern most star you can see from Colorado. It’s the brightest star in the constellation Grus, the Crane, and is the 31st brightest star in our sky. Al Nair is the southwest foot of Grus the Crane, and oddly is also known as “the Bright One of the Tail of the southern Whale” in Arabic.

To spot Al Nair you’ll need a fairly flat southern horizon, as this star never gets too high above the horizon at our latitude. It’s directly south of the Southern Fish constellation, and it is a hot blue star. It’s about 100 LY away, and is about 3 ½ times bigger than our Sun. It is also spinning very quickly. While our Sun moves at about 4500 mph at the equator, and takes about 28 days to rotate once, Al Nair rotates at over 500,000 mph, and even though it’s much larger, a day on Al Nair is less than 24 hours.

Al Nair is very handy for astronomers to use as a yardstick, so to speak, because it is a very good “normal” example of a class B subgiant star, and its characteristics can be used to compare other stars to for scientific evaluation.  So, find a spot with a good view to the south, and see if you can spot our visitor from way down there, Al Nair. 

This file is licensed under the Creative Commons Attribution 3.0 Unported license.
Credit IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg) / wikimedia commons

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