Skywatch: A bright Mars in the sky in January


To me, Mars has not been a very interesting planet to observe in the night time sky. Ok, it’s red–really red. But even through a backyard telescope, Mars is just a small red ball. Well, this month (January, 2010) Mars is much more interesting.

Mars reaches opposition on January 29th. At that time, Mars will be on the opposite side of the Earth as the Sun (or, alternatively, Earth will be exactly between Sun and Mars). This happens once every 26 months, simply because of the different orbital speeds of the two planets. Earth takes 365.25 days to orbit the Sun; Mars takes 687 days (1.88 Earth years). Mars will also be at its closest approach to Earth: 99.33 million kilometers (61.5 million miles) on the 27th. A natural result of this is that Mars is very bright in our current night time sky, at magnitude -1, brightening to -1.2 at opposition.

NOTE: to prepare you for my comments below, we measure how far apart objects in the sky appear to be from each other by using angular separation, a measurement in degrees. A simple way to visualize this measurement is to make a fist and extend your arm fully out in front of you (don’t hit anybody!). Your fist covers about 10 degrees of angular separation.

Mars, Regulus, M44 Jan. 11

Mars, Regulus, M44 Jan. 11

Mars is leaving Leo and moving into Cancer, with the bright star of Leo, Regulus, 14 degrees eastward, and the Beehive Cluster in Cancer, M44, 9 degrees westward. This week (1/11 – 1/17), Mars is due south between 2:00 and 2:30 am, MST, so it’s easy to spot rising in the east after sunset, or high in the southwest before sunrise. As Mars moves along its orbit, it is approaching the Beehive Cluster. By month’s end, Mars will be within 5 degrees of the Beehive.

Mars, Regulus, M44, Jan. 29th

Mars, Regulus, M44, Jan. 29th

The Beehive Cluster is a bright open cluster (mag. +4) that is visible to the unaided eye under clear, dark skies. The cluster of a couple hundred stars is best seen with binoculars or a telescope under low power. A waxing Moon the last week of the month will wash out the view of the Beehive, and Full Moon on the night of the 29th will only be 5 degrees away.

New Moon is on January 15th, and there is an annular solar eclipse associated with this new moon, though visible only in the eastern hemisphere. The next solar eclipse visible from Utah and the southwestern US will be on May 20th, 2012.

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2 thoughts on “Skywatch: A bright Mars in the sky in January

  1. I noticed that your entry is dated Jan. 2010. I had a question about the early morning sky Feb. 2011. There is a very bright star/planet appearing in the south east early morning about 6:00am. I wondered what this is, it is quite a beautiful sight. Thank you, Kristie

  2. Kristie,

    You’re seeing the planet Venus, which after the Sun and the Moon, is the brightest object you can see in the night sky.

    Pretty, isn’t it?

    Venus is currently moving slightly eastward each day, and will appear lower and lower against the pre-dawn southeastern horizon for the next couple of months.

    Venus will disappear behind the Sun later this summer, but will re-emerge as the “Evening Star” low in the southwest right after sunset in early December.

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