Greetings, stargazers.
To be consistent with my previous March columns, you will have to hear me complain about daylight saving time. Consider it done, so let’s move on.
In the early evening, near your zenith, you will find a pair of stars that are about the same moderate brightness. They are so similar in apparent magnitude that you might think them twins. At least that is what ancient astronomers thought, which is why they named Castor and Pollux the twins of Gemini.
The constellation Gemini is one of those originally labeled by Ptolemy and is one of the 12 in the zodiac. Gemini is an elongated rectangle, with Castor and Pollux being the heads at one end, and dimmer stars symmetrically filling in the rest, down to the feet at the other end.
The way I remember which is Castor and which is Pollux requires knowing two other bright stars of the winter hexagon. My column about the winter hexagon was a couple of years ago, but for Gemini, just remember that Castor, with the “C” toward the star Capella, also with a “C”, and Pollux, with a “P” toward Procyon, with the “P.”
The Milky Way goes through Gemini, so there are numerous open clusters and gas clouds, and the field is relatively rich with stars when viewed through binoculars.
The open cluster M35 near the foot on the right is interesting for a couple of reasons. First, M35 shows a sharply higher star density compared with the surrounding star field. Second, there is another, much fainter cluster that is in the same field of view. In an 8-inch telescope, M35 shows up as a typical grouping where you can easily see the individual stars. But in the more distant companion, NGC 2158, it is very challenging to make out individual stars. Instead, the combined light is more reminiscent of the faint, diffuse glow of a dim galaxy.
Castor, at magnitude 1.58, is a visual binary star. That means that through a telescope, you can easily see two stars of magnitude 1.93 and 2.97, respectively. Not readily apparent is a third, much dimmer star of magnitude 9.83 in the same system. But that’s not all. (This is where the description may sound like a television knife commercial.) Each of those three stars has also been found to be a spectroscopic binary, so there are a total of six stars in this one system.
If you were able to visit Indonesia for the total solar eclipse, then good for you, and I hope you enjoyed it. For the rest of us, there is a lunar penumbral eclipse on the morning of March 23 right before dawn. A penumbral eclipse is when the moon only goes through the edge of the Earth’s shadow, so we should only see a dimming of the moon that might not even be noticeable.
Jupiter is at its closest approach to Earth. This should provide the best views of the year, as it will be at its highest point around midnight. I have to admit that I don’t look at Jupiter as much as I should, since it is so bright and such an easy target, but I will make a special point to do so this month. If you can look at it with a small telescope, see if you can see a transit of one of the Galilean moons.
Charles Hakes is a visiting assistant professor in the physics and engineering department at Fort Lewis College and is director of the Fort Lewis Observatory. Email him at hakes_c@fortlewis.edu.
Useful links
Gemini: https://en.wikipedia.org/wiki/Gemini_(constellation)
Penumbral eclipse: http://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2016Mar23N.pdf
Astronomy picture of the day: http://apod.nasa.gov/apod/
An Astronomer’s forecast for Durango: www.cleardarksky.com/c/DrngoCOkey.html?1
Old Fort Lewis Observatory: www.fortlewis.edu/observatory
Four Corners Stargazers: http://groups.google.com/group/Four-Corners-Stargazers
