Montana Skies: Arcturus

If you look over in the Western sky tonight, following the setting sun, you’ll find the amazingly bright star Arcturus.

It’s at the tip of the constellation Bootes, the herdsman, and if you look to the upper left, you can find the faint ring-shaped constellation Corona Borealis, the Northern Crown. Arcturus is a fascinating star, an old, cool red giant, which is burning the last of its fuel, on its way to a slow death. It’s a big star too!

Wow! Arcturus is 25 times the diameter of our Sun. But despite their differences, Arcturus and our Sun have one big thing in common: Like every other star, they are both made of about three quarters hydrogen gas and one quarter helium gas - and this is true of every star in the sky, everywhere! All stars are about three quarters hydrogen gas and one quarter helium gas, throughout the whole entire universe. Who figured that out?

Her name was Cecilia Payne. She was from England, where she studied at Cambridge University starting in 1919. But, back in those days, women weren’t allowed to receive degrees from Cambridge. So, in 1923 she sailed for America, to study at the Harvard College Observatory, where there were even special scholarships to support women studying astronomy.

Cecilia Payne used the new equations of quantum physics to analyze the complex patterns of colors that we see when we take the light from the stars, and break it up into a rainbow spectrum of colors. Cecilia Payne discovered, to everyone’s amazement, that all stars are made of three quarters hydrogen gas, one quarter helium gas, and just traces of the other elements.

That’s something to consider when you’re looking at mighty Arcturus, low in the West, in our Beautiful Montana Skies!