Star Points for December 2011 by Curtis Roelle Five Planets In December Skies December offers a chance to see, at different times of the night, all five naked-eye planets. It requires patience and some effort and perhaps an alarm clock. The tour begins at dusk and ends at dawn. Each of them, except Mercury, will be visible all month, so it's not necessary to catch them all on a single night. Each will be visible to the unaided eye. A telescope will show more detail, especially with Saturn and Jupiter. May as well start with the brightest planet, Venus. Early in the month it shines low in the southwest during bright evening twilight. By 5:00 p.m. EST Venus is less than 15? above the horizon. It's the brightest "star" in the sky. This is a good place to recall that an outstretched fist is about 10? across. This works for just about everyone as long as they are using their own fist. So 15? is about 1½ fists. If your horizon is clear, Venus will be visible for at least another hour. It will be sinking, but the sky will also be compensating by getting darker, making it easer to see. Venus also gets higher each night than at the same time on the night before. By year's end, Venus is more than 30? above the horizon at 5:00 p.m., taking more than two hours to subsequently set. Next planet is the second brightest. At 6:00 p.m. in early December, Jupiter is already high in the east. Though you don't really need it, the Moon can be used for finding Jupiter this week. On Monday night (Dec. 5) Jupiter is below and to left of the Moon and, on Tuesday, to the lower right. By 9:00 p.m. Jupiter is at its highest. It rises a little earlier each night, so by year's end Jupiter reaches this high point in the southern sky a little past 7:00 p.m. The third planet up is Mars. It should be rising in the eastern sky and well above most trees by 2:00 a.m. The bright star to its upper right is the bluish Regulus, the heart of Leo the lion. Mars' ruddy color stands out in contrast with Regulus. The fourth planet is the ringed world Saturn. Prior to morning twilight at 6:00 a.m. it is fairly high, more than 25? above the southeast horizon. By year's end it will be even higher at the same time. During your observation look for two bright side-by-side stars low in the southeast. Saturn is the left one. To the right is the bright star Spica, in Virgo. Mercury, our fifth and final planet, appears low in the morning sky at mid-month and requires a clear, flat horizon without hills, trees, or buildings. For about a week starting around December 15, look for Mercury low in the southeast sky, less than 10? over the horizon. Scanning the horizon with binoculars can help. On the 22nd the Moon is to Mercury's upper right. Speaking of Mars, a couple of space missions to the Red Planet were recently launched. To conserve fuel, Mars missions are launched during periodic seasons or windows when the planets are favorably aligned. On November 8, Russia launched Phobos-Grunt, a soil-sample mission targeted for Mars' largest moon Phobos. More on that below. On November 26, the U.S. launched the Mars Science Laboratory (MSL). MSL will be carried across the Martian surface aboard the back of the latest Mars rover, named Curiosity. It is currently on an eight-month coasting journey to Mars. Now, back to Phobos-Grunt. Contact with the spacecraft was lost before it had a chance to leave Earth orbit. It has become, like UARS (see October Star*Points) before it, the latest large satellite destined for an uncontrolled re-entry back to Earth. Unlike UARS, Phobos-Grunt's fuel tanks are full and could survive re-entry and crash to the surface. Currently, Phobos-Grunt is expected to re-enter in December. For re-entry predictions, I rely on the Aerospace Corporation's re-entry predictions web page (reentrynews.aero.org/). So, get out and look at the planets this month, especially if you get a new telescope for Christmas. But first a little advice. Some telescopes come with finder scopes used to help locate objects. A finder looks like a tiny telescope mounted on the side of the main instrument. The finder is a useful tool, but only if it's aligned properly. So follow the instructions that came with your telescope so that when you center an object, such as a planet, in the finder's cross hairs, it will appear in the center field of view in the main telescope. An unaligned finder is one major source of frustration for new telescope owners.