Mars Shines - A Bright Christmas Beacon
Mars Shines as a Bright Christmas Beacon, lighting up our Christmas evening 2007 like a big red Christmas tree decoration in the celestial sphere.
Beginning in the month of November, from roughly the 7th, Mars started moving retrograde through the skies, at least relative to Earth. These retrograde motions are an illusion based on the different orbital positions of Mars relative to Earth, and show an apparent complexity that baffled astronomers for thousands of years, because of a reference frame shift.
What you'll see is that Mars has apparently reversed direction in the sky for a bit, moving to the east instead of to the west for 7 weeks, as it grows gradually brighter, and its visible disk increases by a factor of 8.
The Orbit of Mars
What's actually happening here is Mars' orbit is roughly 50% larger than Earth's, and it moves slightly slower in its orbit, taking 24.5 months to complete one orbit, versus 12. Imagine a clock face that has two circles printed on it, one marked 1 through 12, and one marked 1 through 24, with a half tick. In the time it takes Mars to make one circumference, the Earth makes two. This means that like a second hand sweeping past the minute and hour hand, it catches up to the direction Mars is away from the Sun, and then passes it by. This "catch up and pass" mechanism is what makes Mars appear to stop and suddenly move retrograde in the sky, from the frame of reference of the moving Earth, that's what's happening.
This period, where Earth passes by Mars is the closest approach to Mars, and is called the opposition (because the Sun and Mars are on the opposite sides of the Earth.) During this period, the distance to Mars can be as low as 0.6 AU, or about 300 light seconds, or 90 million kilometers.
For amateur astronomers, what this means is that Mars' visual diameter will be as large as it's going to get for the next nine years.This is due to the elliptical orbit of Mars, and how close we are to Mars at opposition is dependant on where we catch up to the red planet in its orbit. Right now, Mars is slated to get to almost 16 arc seconds (Saturn gets to about 18 arc seconds). Mars will be at magnitude 1.8, making it brighter than any star in the heavens, and only a little dimmer than Jupiter.
What you will see
You will be able to see the bright orange-red color with the naked eye, and with a decent telescope (3 inches or more), you should be able to make out some surface details. In Mars Northern Hemisphere, you'll be able to make out some dark smudges for Syrtis Major, and in the Southern Hemisphere, you'll find Solis Lacus if you have very sharp eyes.
10" or greater telescopes may be able to see some of the effects of the Martian atmosphere at the "edge" of the globe. In general, you'll want to limit magnification to about 35x per inch (25 mm) of telescope diameter, to avoid optical illusions. If you use filters, a blue filter will be good for pulling out the cloud features, and a red or orange filter will improve contrast for surface features.
The brightest viewing day for Mars will be December 23/24/25th, when it's at Opposition. It will be at its closest point on the 18/19th when it will be both slightly Larger yet fractionally dimmer than on Christmas day.
You'll be able to see it in the mid-to late evening, in the constellation Taurus, at about 20 degrees north of the celestial equator.
For a detailed chart showing the position of Mars and to discover heaps more hints, tips and little known secrets, showing the fun and easy way to discover all the delights of the universe around us, go to http://www.nightskysecrets.com
From there you will be able to download a f r e e copy of my audio "Night sky secrets revealed" and get Access to my blog page with maps of Mars and its position in the evening sky updated weekly.
Happy Mars hunting.
Ian Maclean - Author, Presenter and Radio Show host of "The Science Hour" Homepage: http://www.nightskysecrets.com
Recommend Website : Thai Song , Promote Website , Online News , Bookmark Site
