The Star Arcturus

September 07, 2018

We can thank Tropical Depression Gordon for the cloudy, rainy weather this weekend… but if we COULD see the stars, we wouldn’t have any trouble finding this weekend’s target. It’s one of the brightest stars in the sky.

I’m Matt Pelsor, and this is your weekend sky report.

Arcturus has been observed as long as humans have looked up. Ancient Polynesians used it to navigate to Hawaii… Mesopotamians linked it to the god Enlil (EN-lil). Ancient Romans thought the star warned of stormy weather… hmph. It’s even mentioned in some translations of the Bible. Job chapter 38, verse 32 of the King James reads “Canst thou guide Arcturus with his sons?”

If it were clear, you’d find it by looking high to the west around 9pm. Arcturus is a bright orange-white star.

In fact, it’s so bright, it can be observed in the daytime! The French astronomer and mathematician Jean-Baptiste Morin located it with a telescope one afternoon in 1635.
Arcturus is bright for a number of reasons. For one, it’s big. It’s just slightly more massive than our sun, but it’s in a different stage of life… it’s a red giant, which means it’s burned through all of the hydrogen at its core, so it’s 25 times larger than the sun, and 170 times brighter.

It’s also pretty close… less than 37 light years away. This also makes it a popular setting for science fiction. It’s been mentioned in Buck Rogers, Superman, Hitchhiker’s Guide to The Galaxy, and many other stories.

So even if we can’t SEE it this weekend, maybe just knowing it’s there might inspire you to write a little stellar fan fiction.

I’m Matt Pelsor… happy skywatching.