Once again next week we have a full moon lighting up the sky, making it tough to really stargaze this week, so what I want to do instead is give you my winter preview.
No, I'm not going to practice my full-time profession as a meteorologist and try to predict the weather for this coming winter. A safe long-range winter forecast is what the stars and constellations will look like.
This isn't exactly astronomical brain surgery since we see the same winter skies every year as the Earth circles around the sun. The nighttime side of the Earth faces the same direction in space each winter, so with the exception of the moon, planets, asteroids, and an occasional comet, the winter night skies are the same year after year.
If you want a sneak preview of what the early evening skies over Rochester will look like during mid-winter, in late January and early February, set your alarm. Right around 6 a.m. you'll have the same dome of stars and constellations now as you will mid-winter. That's because at 6 a.m. this time of year, our part of the Earth is pointed in the same direction in space as we are in the early evening in mid-winter.
It's a simple matter of combining the directional effects of the Earth's revolution around the sun and Earth's rotation on its axis. In fact, anytime you want to know what the evening skies will look like one season or about 100 days in advance, just look at the heavens in the pre-dawn hours.
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Best of the year
So why do you want to see the winter constellations anyway? Because in this stargazer's opinion, they're the best — worth setting that alarm for! When you're out of the sack and out in the pre-morning twilight, you'll see the prime players of winter evenings lighting up the southern half of the sky.
I call this part of the sky "Orion and his gang," since there are a lot of bright stars and constellations centered around the grand old man of the sky, Orion the Hunter. Next to the Big Dipper, Orion is probably the most familiar pattern in the sky, and most of its stars are as bright as the Big Dipper.
I know you've seen Orion before. To me it looks like a giant hourglass in the sky, but to some it looks like a giant sideways bowtie. Probably the biggest eye grabber is Orion's Belt, three bright stars lined up perfectly in a row. Nowhere else in the sky can you see such a perfect row of bright stars.
As we see now in the morning, the stars are oriented vertically. From the top down they are Mintaka, Alnilam, and Alntitak. Even though they're so nicely lined up like stellar ducks in a row, they have nothing to do with each other physically. These stars are actually separated by hundreds of light years. They just happen to fall into our line of sight that way.
Billion-mile Betelgeuse
To the upper left of the belt, at the right armpit of the hunter, is the bright reddish star Betelgeuse (pronounced "beetle-juice"), the brightest star of Orion. It's one of the biggest single stars we can see with the naked eye. Some astronomers believe its diameter at times swells out to nearly a billion miles. Our puny little sun has a waistline of less than a million miles.
The Hubble telescope has actually taken a picture of it, which is hard to do with individual stars because they're so far away. This red giant star, nearing the end of its life, is just over 600 light years away.
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To the lower right of Orion's belt is Orion's second brightest star, Rigel, at Orion's left knee. At just over 770 light years away, it's also a lot bigger and brighter than our sun. It's over 80 million miles in girth and kicks out about 60,000 times more light than our sun. If Rigel were our sun it would be 100 times larger in our sky, so to be protected from sunburn from Rigel, I would recommend a lotion of about 3000 SPF!
While you're out there early in the morning, clutching that big cup of coffee and looking at Orion, you'll also see the biggest planet of our solar system, Jupiter, and it's easy to spot. Jupiter is the brightest star-like object in the morning sky.
Look to the left of Orion's gang and you'll see Jupiter glowing brightly well above the horizon. Even with just a small telescope or a really good pair of binoculars, you can see some of the Jovian cloud bands, as well as up to four of Jupiter's largest moons. They look like little stars on either side of the planet that obediently orbit around Jupiter in periods of 2 to 17 days.
Enjoy the winter stargazing, without the windchill!
Next week in StarwatchI'll have details on a partial solar eclipse coming up on Oct. 23. It will be a good one! In the meantime, you might want to order some eclipse glasses now so you'll have them for safe viewing. You can usually find them for less than $3 online by browsing "solar eclipse glasses."
