Starwatch: Buckle up for the end of winter star-watching
It's a joy for me to get folks at any age turned on to stargazing and astronomy. Usually what does the trick is to have them look through one of my larger telescopes at my star parties.
Another way is to point out what's known astronomically as conjunctions. I call them "celestial huggings," and what they are is a close temporary approach between two, three or more bright celestial objects in the night sky, such as stars, planets and the moon. Now, the participants in these celestial huggings aren't actually physically close together, but they are nearly in the same line of sight from our Earthly home. They can be truly beautiful.
A great conjunction is going on Sunday night over Rochester, and hopefully, it will add to your St. Patrick's Day celebration. It's a really tight tango tonight between Jupiter and the new crescent moon. Jupiter will be less than three degrees to the upper left of the moon in the high southwestern evening sky.
Both objects are wonderful telescope targets. The moon, with all its craters, mountains and dark plains, is something I never get tired of aiming my telescopes at. Even with a small telescope, you can resolve the disk of 88,000 mile-wide Jupiter, now more than 490 million miles away. You may also see parallel bands striping the planet. Those are Jupiter's clouds, made of methane, ammonia and other gases.
For sure, you can see at least some of Jupiter's brightest moons, which resemble tiny stars on either side of Jupiter. Tonight you can see all four of them; Europa and Ganymede to the lower right, Io and Callisto on the upper left.
The only trouble with conjunctions like Jupiter and the moon is that they usually only last one or two nights. There is a one celestial conjunction that you can see every clear winter evening and even into the spring, however. It's the fabulous belt of Orion, made up of three bright stars tightly and evenly spaced in a perfect row.
Orion's belt lies right in the middle of the constellation Orion the Hunter. Even if you're not turned on to stargazing yet, I know you've seen it before. As soon as it's dark enough, look for a bright star formation that at first glance looks like either an hourglass or a sideways bowtie in the southern sky. It doesn't take too much imagination when you look at it to see the outline of a broad-shouldered man.
All of Orion's stars are bright, but the very brightest are Rigel, which marks the hunter's left knee; and Betelgeuse, a bright star tinted orange-red even to the naked eye, that marks Orion's right armpit. In fact, Betelgeuse is an Arabic name that roughly translates to "armpit of the great one."
Betelgeuse is simply the biggest thing you've ever seen, except for the latest figure for our national debt. It's a dying pulsating star that occasionally bloats out to a diameter of nearly a billion miles! Our own sun is no match in size, at less than a million miles across. Keep an eye on Betelgeuse, because sometime between tonight and the next million years Betelgeuse will blow itself to smithereens. I wouldn't wait up for it, though.
Orion's belt, though, is definitely the hunter's calling card. Nowhere else in the sky anywhere in the world will you see a more perfect alignment of stars this bright. From the lower left to the upper right are Alnitak, Alnilam, and Mintaka. You would think that these stars are physically related to each other but that's just not the case, not even close. They have nothing to do with each other astronomically. They are actually hundreds of light years apart. Their arrangement in our sky from our vantage on planet Earth is purely accidental, although sometimes I wonder.
All three stars are much larger than our sun, and each is unique in its own way. The largest of the trio is Alnilam, an Arabic name that roughly translates to English as "string of pearls." Alnilam, the 30th brightest star in the heavens, has a diameter of more than 4 billion miles, more than 44 times larger than our sun. It would be a whole lot brighter in the night sky if it weren't so far away. It shines from a distance of 1,359 light years, or nearly 8,000 trillion miles away. The light that we see from Alnilam tonight left that star in 654 A.D.
Alnitak, on the lower left side of Orion's belt, is an Arabic name that means "girdle," and it's the second-largest of the three stars. This giant nuclear fusion gas ball is over 21 million miles in girth and is a little over 800 light years away. Mintaka, which translates to "belt" from Arabic, is on the upper right hand side of the belt. Mintaka is about the same size as Alnitak and is about 900 light years away.
We're into our last few nights of enjoying Orion's belt this winter because Wednesday will be the first day of spring, the Vernal Equinox. That's when both the Northern and Southern hemispheres receive the same amount of radiation from the sun. No, you can't balance an egg on its end any easier on the equinox than any other time of the year, but you'll still see folks try it this Wednesday on the TV news.
Also, as of today, St. Patrick's Day, days are now longer than night. We don't have to wait until the Vernal Equinox for that to happen. I'll explain why in next week's Starwatch column.