Orion’s corners are celestial feasts for the eyes

I have been accused of writing too much about the constellation Orion, but I can’t help it. It’s such a wonderful constellation, loaded with celestial treasures, especially the Orion Nebula in the sword of the hunter.

The nebula is the cosmic birthing grounds for new stars, a giant cloud of hydrogen gas more than 150 trillion miles in diameter. You can see a little of it with even the naked eye, more than 1,500 light-years away (one light year is almost six trillion miles),

In my guaranteed-to-be-last column about Orion until it comes back to the evening sky in late fall, I want to feature the four corner stars of Orion — the two bright stars above Orion’s belt and the two bright stars below it. All of them have their own special story.

The brightest star in Orion is Rigel, on the lower right corner of the hunter. It marks Orion’s left knee, and despite being the brightest star of Orion’s four corners, it’s also one of the farthest at 800 light-years away. The light we see from Rigel tonight left that star 800 years ago, before Columbus sailed to America (or at least the West Indies).

It doesn’t take a lot of brain power to conclude that if Rigel is as bright as it is, yet as far as it is, it must be a really big and luminous star.

Believe me, it is. Rigel is more than 43 million miles in diameter, 50 times the size of our sun. It also cranks out more than 60,000 times as much light and energy as our comparatively diminutive sun.

On the opposite corner of Orion is Betelgeuse, 520 light-years away and the second brightest star of the constellation. It’s one whopper of a star, a super red giant star that’s pulsating like a heart. It regularly goes from nearly 500 million miles to nearly 1 billion miles in diameter, one of the biggest single things you can see with your naked eye.

Many astronomers think that in about 200,000 years Betelgeuse will explode in a gigantic stellar explosion, a supernova. This happens to really massive stars as they run out of their nuclear fuel.

When it does happen, it will be one heck of a show as it produces and hurls out heavy elements that will be the building blocks for new stars and planets in the Milky Way Galaxy. What’s left of Betelgeuse after the blast will probably be a collapsed black hole that has so much gravitational pull that not even light can escape.

Again, Betelgeuse is expected to explode within a couple hundred thousand years, which is a very small amount of astronomical time.

The third brightest and smallest star in the four corners of Orion is Bellatrix, Orion’s right shoulder. Bellatrix is the closest of the quartet of stars at just 240 light-years away. It’s only six times the size of our sun.

Ever get the idea that our sun is a small star? You’re right!

Anyway, the light we see tonight from Bellatrix left that star in 1768, a few years before the U.S. Declaration of Independence was signed by Ben Franklin, John Adams and that whole crowd. Bellatrix is a star about to expand into a red giant star, and it will be nearly as big as Betelgeuse. It’s also one of the hottest established stars known, at 40,000 degrees, four times hotter than our sun.

The dimmest of Orion’s four corners is Saiph, but by no means is it a wimpy star. Its diameter beats out our sun’s 38 times over, and it kicks out more than 10,000 times as much light as our little home star. It’s the dimmest of Orion’s four corners because of its distance, 820 light-years.

That’s it. I’m done writing about my favorite constellation for this season. As the weather gets warmer and the night gets shorter this spring, Orion and his gang will start out the evening lower and lower in the southwestern sky, and by early May it will be out of the evening sky until November. Say goodbye to the big guy for now.

As you’re watching Orion this week, there’s a very nice conjunction Tuesday night. The thin crescent moon will be among the stars in the bright Pleiades star cluster. It’s a must see with binoculars or a telescope.

Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO radio in Minneapolis and is author of the book, “Washington Starwatch,” available at bookstores and at his Web site www.lynchandthestars.com.

The Everett Astronomical Society welcomes new members and puts on public star parties. The Web site is members.tripod.com/everett_astronomy.