October 2 – Raise Your Hand

Today’s factismal: Contrary to armchair astronomers, Betelgeuse doesn’t mean “armpit of the giant”.

If you look into the sky early tomorrow morning, you’ll see one of the world’s most easily recognized constellations: Orion, the giant. Named by the Greeks after a son of Poseidon who liked to hunt, the constellation takes part in three different “sky stories”. In the first, he is aided by his two dogs Canis Major and Canis Minor (“Big dog” and “Little dog”) as they hunt the rabbit Lepus who hides in the grass at his feet. In the second, Orion is being cured by the great doctor Ophiuchus (“the snake”) of the venom from Scorpius (“the scorpion”) who stung him after Orion upset Gaea by trying to kill one of every animal on Earth; that’s why Ophiucus stands between Orion and Scorpius and why Scorpius is never in the sky at the same time as Orion. And, in the third story, Orion is trying to fight his way past Taurus (“the bull”) so that he can woo the Pleiades (“the seven sister”) who aren’t thrilled with the prospect of being chased by a guy who has just been hunting and is recovering from a scorpion sting.

M42 (Orion Nebula) Over Virginia (My camera)

M42 (Orion Nebula) Over Virginia (My camera)

But perhaps the most interesting story about Orion has nothing to do with the constellation; instead, it describes how the bright red star in Orion’s left arm got its name. Many armchair astronomers gleefully repeat the story that the name came from the Arabic for “armpit of the giant”. Unfortunately, that’s not true; it actually comes from the Arabic for “hand of the giant”. Either way, Betelgeuse (bay-TELL-gerz) is a fascinating star that will soon (within a million years or so) explode and become bright enough to see in the daytime.

The second-most interesting story about Orion has to do with its “sword”. Look at the fuzzy patch about halfway down the scabbard; astronomy wonks call that the Orion Nebula. See anything interesting? Now look at it through a pair of binoculars. Now what do you see? That’s right; it is a stellar nursery where hundreds of new stars are forming right now. Cool, no?

M4 (Orion) seen from Houston; the light pollution wipes out most of the fainter stars (My camera)

M42 (Orion) seen from Houston; the light pollution wipes out most of the fainter stars
(My camera)

Unfortunately, there are some places on Earth where you can’t even see Betelgeuse in the night sky! That’s because light pollution from cities has wiped out all but the very brightest stars, making it hard for us to enjoy the beauty of the night sky and for animals like sea turtles and moths and dung beetles to navigate; it is even making mother wallabies wait to give birth. Obviously, light pollution must go!

The first step in cleaning up pollution is mapping where it is. Naturally there’s a citizen science experiment for that. Called GLOBE at Night, this experiment asks you to go out once a month over the year and look at Orion. By counting the number of stars that you can see in the constellation and reporting that to the scientists, you’ll help measure light pollution. If you think you’re bright enough for this experiment, head over to:

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s