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Mars in the Middle

June 12, 2001

[Note added June 12, 2001, after this page was originally written: I just learned that the CNN article quoted below has been fixed. The quotation I give below was accurate earlier in the day (I received three emails about the CNN error before I wrote my page) but evidently CNN edited the page to correct their error. I think that's great. Fixing errors and increased accuracy is what science (and science reporting) is all about. I abashedly admit I did not write CNN about the error; it has been my experience letters to big companies about errors of this sort get ignored. It appears I was wrong, and in the future I will send email first before writing up a citation. ;-)]

Hubble image of Mars Have you noticed that phenomenally bright red "star" high in the south around 11 o'clock at night? That's no star, it's the planet Mars, and right now it's about as close to the Earth as it ever can get. As both Mars and Earth orbit the Sun, the distance between the two planets changes a lot. When we are close, Mars is bright, and it dims as the distance increases.

diagram of orbits of Earth and Mars Earth is closer to the Sun than Mars, so we go around the Sun faster than Mars does. As we pass it on the inside track, Mars is closest to us when it appears opposite the Sun in the sky. The technical term for this is to say that Mars is at opposition. You can see a diagram of this for today's date (as I write this) at NASA's Solar System Simulator. Note how from the Earth, the Sun would be on one side of the sky and Mars on the other.

Of course, this isn't the way that CNN sees it! In yet another website goof, CNN has an article about Mars at opposition with an odd error in it. The article says: "On June 13, the red planet reaches 'opposition,' the moment when the Sun, Earth, and Mars form a straight line with the Sun in the middle." Actually, the Sun is not in the middle, the Earth is. If the Sun were between the Earth and Mars, then Mars would appear to be very near the Sun and quite invisible against the glare (the technical term for this is "superior conjunction").

Anyway, to find out more about seeing the Red Planet now, try Astronomy Magazine's website or the website for Sky and Telescope magazine. To get info about Mars in general, go to Bill Arnett's Nine Planets website.

©2008 Phil Plait. All Rights Reserved.

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