A mediocre planetary alignment

SkyCaramba blog for the week ending February 19, 2011

Here’s a planetary alignment nobody’s talking about.

Planetary alignments happen all the time. Sometimes an alignment is the lining up of three or more planets in a line in the night sky. Other times, all the planets are on the same side of the sun or they’re in something sort of like a line with the sun in the middle.

Those last two have sold a lot of books and generated a lot of web site hits. About 30 years ago, an author claimed the world would end in 1983 because of how the planets would align. Now, there are people online claiming the world will end in late 2012. Some of them claim a sort of planetary alignment will be involved.

This column is about the lineups that appear in the sky, or in this case one that won’t appear. On February 22, Mercury and Neptune will be slightly more than 2.4 degrees apart. Mars will make a line with them a little more than a third of the way from Neptune to Mercury. That’s as it would be viewed from Earth if not for an interfering object.

All three planets will rise just 20 minutes before the sun! And there’s no total solar eclipse happening, so there’s no hope of seeing them. Before you get upset with me for teasing you, consider that only half the fun in astronomy is from observing. The other half is from knowing what’s happening.

This is as good an event as any for introducing you to the next best thing to seeing something with your own eyes. There are some amazing free planetarium programs you can download and use any time. My favorite is Stellarium.

In Stellarium, you can set your location and date, see the sky as it will actually look (or looked), and zoom in on deep sky objects. You can speed up and reverse time. I like using those features for seeing eclipses I’m on the wrong side of the earth for or that happened before I existed. The feature you’ll use to see the Mercury-Mars-Neptune lineup is the one that gives you the view without the atmosphere scattering light all over the place.

We can’t see nighttime stars in the daytime because light from the sun bounces off the air molecules above and around us. Starlight makes it to us in the daytime, but sunlight is so strong it gets all the credit for stimulating the rods and cones in our eyes. The light that bounces off the moon is strong enough for us to detect, so you can often see the moon in the daytime. And if you plan carefully, you can sometimes see Venus in the daytime. Otherwise, there’s just no way to see night sky objects when the sun’s up—unless simulated views count. For me, they do.

Don’t fret about not being able to see this lineup. A four-planet lineup that you can see is coming in April and May.