A Meeting With the Moon and Aldebaran

Hey, Sky Fans! I hope you’re having a great weekend, and are your house is festooned* with all of the traditional decorations to remember today’s 42nd anniversary of the day Gene Cernan and Jack Schmidt placed their Apollo 17 Lunar Module, Challenger, into the warm sands at Taurus-Littrow. For about three days, they drove and bunny-hopped around the Moon’s surface before turning for home. Since Cernan locked the door, rolled up the windows, and pressed what I imagine as big, brightly lit, flashing red “GO!” button, no one’s been back to the Moon. Soon, I hope.

It’s a pretty exciting week ahead for the Moon, people walking on it or not. Actually, no. As far as the Moon’s concerned, nothing unusual is going to happen at all. From Earth, though, hold onto your disappointingly expensive menorah hat:

If your skies have been like mine, you haven’t seen much lately. The weather’s been too Decembery; windy and cold. We have the first real snow of the season falling as I write this. It’s hard to complain too much; one doesn’t begrudge he zebra for having stripes, but it’d be great to se the stars again, wouldn’t it? Well, lo and behold, last night, the skies opened, and there was a healthy,  jolly gibbous Moon sitting high in the east, not far from the tiny-dipper-looking Pleiades cluster and Taurus the bull’s brightest star, Aldebaran, the night sky’s 14th brightest.

Aldebaran’s light started on its way to your eye 65 years, almost a lifetime, ago. It’s so bright that even from that distance, 65 light years (around 380 trillion miles, 615 million km), it’s one of the first stars that pop out of the deepening dark as these late fall and early winter nights… um… fall.

Keep your eye on Aldebaran and the Moon over the next couple of nights. Tonight and tomorrow, you’ll see the Moon close in on the star. Then, late in the evening Monday night, the 12th, into Tuesday the 13th, you’ll see the very-nearly-full Moon block out all that 65-year-old light. From where we see it, the Moon will pass directly between the Earth and Aldebaran, occulting it. Does this sound familiar? It might. It’s pretty much the same thing that happens during a solar eclipse, only the star being occulted by the Moon is the Sun; 8 light minutes away, not 65 light years, away. It’s the same thing, but at a much more distant scale.

December 2016 Moon-Aldebaran Occultation (screens from Stellarium)
December 2016 Moon-Aldebaran Occultation (screens from Stellarium)

As it turns out, Aldebaran is close enough to the ecliptic, the imaginary line marking the paths the Sun, Moon, and planets take across the sky, that the Moon can block it out. There are loads of stars along the ecliptic, and Aldebaran is one of the brightest the Moon can occult. We’re in the middle of a series of these occultations that will continue off into 2018. In order to see one of them, though, you need to be in a part of the world where it’s night when it happens, and the skies need to be good, you need to be wearing all purple, have a hotel on Marven Gardens, and on and on. Because of all of this, it’s not like it happens month after month for everyone. This month, it’ll be a great show for people in North America, but not so much in Australia. If you’re in a good spot, you’ll be able to see this happen with the naked eye. If you have a pair of binoculars, it’ll be a great chance to use them.

The exact timing of this matters, and is different from one place to the next. This is a little tough to read, but have a look here for some help with the timings. Just find a city near where you live, and match up the times listed in the “Disappearance” section at the top, and the “Reappearance” section toward the bottom. Times are listed in UTC. So, just subtract 5 hours for US Eastern time, 6 hours for US Central, 7 for Mountain, and 8 for Pacific. A hint for searching through, hit Ctrl+F in your browser, and then search for your two-letter state abbreviation with spaces at either side, for example ” il ” (leave off the quotation marks).

Some Sample times are:

  • White Plains, New York: Disappear 4:13 UTC / 11:13 P.M. EST Monday; Reappear 5:28 UTC / 12:28 A.M. EST Tuesday
  • Des Moines, Iowa: Disappear 3:38 UTC / 9:38 P.M. CST Monday; Reappear 4:53 UTC / 10:53 P.M. CST
  • Tucumcari, New Mexico: Disappear 3:17 UTC / 8:17 P.M. MST Monday; Reappear 4:29 UTC / 9:29 P.M. MST
  • Calexico, California: Disappear 3:01 UTC / 7:17 P.M. PST Monday; Reappear 4:08 UTC / 8:08 P.M. PDT

You’ll be able to see this with your naked eye, but if you have a pair of binoculars, they’ll certainly I hope you can give this a shot. I love things like these. Things in astronomy tend to happen so slowly in human terms that it’s great to actually see the the solar system in action. If you’re able to see it, you’ll see the Moon slowly inch toward Aldebaran until, poof! it disappears (or, maybe it’ll be “pop!” or, just maybe, “ping!”).

Thanks for spending some of your weekend here. I’ll be back tomorrow to talk full Moons with you. Clear skies, everyone!

* There are few words in English that I love more than festooned. It was used so unreachably perfectly by Carl Sagan, in his description in Cosmos of mathematician Tycho Brahe, that I almost gave up writing because of it. I definitely missed my subway stop: “Tycho himself was a flamboyant figure, festooned with a golden nose, the original having been lost in a student duel over who was a superior mathematician.”


3 thoughts on “A Meeting With the Moon and Aldebaran

  1. Yeah, we have what looks like about an inch or so down (which, as a sign of the times, I guess, is enough to delay the start of school), with plenty of cold, and lots of clouds on the schedule for the rest of the day. I don’t think I’ll be able to see any of this. I hope you can.


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