The Moon and Mars
Published on Nov 26, 2007 at 3:32 pm.
3 Comments.
Filed under skywatching.
Tonight, if you go out and look towards the east, say at about 9pm or later, you will see the Moon. Very close to the Moon will be a reddish star. That “star” is no star! It is the planet Mars. The Moon moves around the sky, taking about 27.3 days to make a complete circuit of the sky. Mars also appears to move around the sky. Both bodies follow paths in the sky similar to that of the Sun (the ecliptic). So, naturally, they will occasionally pass one another. Whenever two celestial bodies are passing closest to one another in the sky (as viewed from Earth), then you say that they are in conjunction. If one were to completely block the other one from view as it passed in front of it, then the event would be called an occultation. Tonight, the Moon will be passing very close to Mars. In fact, if you have a telescope, then you will be able to see the edge of the Moon and Mars both in the same field of view if you are using low magnification.
Mars will be easy to spot tonight, since it will be the bright “star” next to the Moon. But, the Moon is moving on, and tomorrow night, it will appear to be east of Mars (that will make it appear below Mars if you were to look in the evening, as my sky view above shows). Mars is moving, too. Usually Mars, like the rest of the bodies in the sky, moves from west to east against the background skies. West to east? Didn’t I mean east to west in the sky, you might ask? No, I did not. Yes, bodies rise in the east and set in the west. That is called diurnal motion. However, every night, the Moon is a bit farther to the east. That means that it rises a few minutes later each night. Mars typically does that, too. However, Earth orbits the Sun faster than Mars, so we pass it every now and then. Earth will be passing Mars on December 24, this year. As we pass Mars, it appears to be sliding backwards in the sky for a while. That means that it appears to be a little bit to the west each night, compared with the background stars. This westward motion is called retrograde motion. Explaining retrograde motion was a problem for astronomers who long ago believed that the Earth was the center of the universe and that things all orbited Earth.
At any rate, Mars has been in retrograde motion since November 15. It will continue retrograde motion until January 30, 2008, after which it will once again begin its eastward motion relative to the background sky (prograde motion). Interestingly, the way that the orbits work, even though we will overtake Mars on December 24, Earth and Mars will actually be closest to one another a few days earlier, on December 19. At that time, Mars will appear biggest and brightest in the sky. But, don’t get your hopes up. Even at its biggest and brightest, Mars will only appear as a bright orange/reddish star to the naked eye. The only way to see that it is biggest is with a telescope looking at it.
Mars is not too hard to find, even without the Moon nearby. For the next couple of months, it will be the bright reddish/orange star to the north of Orion. That makes it easy to find, since Orion is one of the most recognized constellations in the sky.
So, if you get clear skies tonight, to out and look at the Mars and Moon conjunction. The actually closest approach happens about midnight here in Texas (that is at about 06:00 UT on November 27). If you get a chance, then you can actually go out and look at the Moon and Mars several times tonight, and you will see the two bodies get closer together, and then start to separate as the Moon moves on past. There will be no occultation tonight, just a conjunction. But that is interesting to watch, anyway!
-Astroprof
(Image created using Stellarium)
Adam on November 27, 2007 at 12:07 am: 1
Thanks for the info. I thought it was really amazing to look up and see those two so close. I had a great view of it here in Southern California at around 10 pm pst.
Sweta on November 27, 2007 at 1:42 am: 2
When I looked at the sky today at night it was surprising to see a star next to Moon in red color, infact asked my husbad to see it too… Later in cbs news they mentioned it was planet mars and checked this website to confirm again.
Its still visible
-Northern California (bay area)
Mike F. on December 25, 2007 at 12:34 pm: 3
Thanks for satisfying my curiosity. Researching this I found a site that indicated Venus is sometimes close to the moon so I’m glad to find a better informed answer. When I was out at 9:30pm it was 24deg (in Concord - east of Cleveland) and I got chilled twice when I noticed the ’star’ next to the moon. Even got my field glasses out to get a better look. Thanks for the explanation.