Another great year is ahead for planetary observers with at least one bright planet visible on any given evening during the year. There will be many celestial delights to behold, which include close planetary groupings with each other and the Moon, meteor showers, orbiting satellites, and possibly a few nice comets and an unexpected aurora or two. The best event for 2011 will be the rings of Saturn opening up to their best in years which will be the #1 wow-factor at public observing events.
There are no lunar or solar eclipses locally this year. The next total lunar eclipse will be on April 15, 2014 and the next solar eclipse will not occur May 20, 2012 just minutes before sunset when the Sun will hardly be 1% eclipsed at best according to the Google Earth Interactive Solar Eclipse Simulator.
Jupiter dominates the evening sky during the beginning of 2011 before handing off that honor to Saturn by March as it fades in the western twilight. Saturn will rule the evening sky well into August before Jupiter returns before midnight in the east by then. Venus will re-appear low in the southwest after sunset as the year closes. Mercury will appear briefly in the evening sky during March. Mars will finally reappear in the east before midnight as the year ends. Uranus and Neptune are never brilliant, although both are fun to locate and observe, and will be visible in the evening from August until next February. Here is the breakdown for each planet in the evening sky during 2011:
Mercury: This cratered world is always challenging to find, but will be unusually easy this year as it will be very close to Jupiter on March 16. It is easiest to see in the evening from March 8 to April 1, being highest above the horizon on March 22. Mercury grows steadily through this period from 6 to 10 arcseconds across as it approaches Earth and its magnitude will hover around 0. It will go through phases like a tiny, coppery version of the Moon, from nearly full to a thin crescent.
Venus: This torrid world will be a morning star early in the year and gradually pass behind the Sun to appear in the evening sky for a beautiful evening star by Christmas. Venus will shine around magnitude -3.8 to -4.4 throughout the year. It will be gibbous phase during the end of the year. Venus will make beautiful pairings with the crescent Moon during the year in the evenings and mornings.
Mars: This is an off-year for Mars as it remains on the far side of the Sun; distant, and very tiny. It will rise before midnight by the holidays and slowly grow larger and brighter as it heads for opposition next March.
Jupiter:This stormy world will remain at its best in years and will be a spectacular sight for all to see. Jupiter begins the year well up in the south during the early evening and will eventually become lost in the evening twilight by February as it fades to magnitude -2.0 and shrinks to 33 arcseconds across. Jupiter rises before midnight by September and is at opposition on October 29 in Pisces and will be 49.7 arcseconds across and blaze at magnitude -2.9. This hugeness will allow for highly detailed viewing of Jupiterís clouds and the Great Red Spot; its rotation should be apparent in only ten minutes. It should be possible to see the tiny discs of the larger moons, Callisto and Ganymede, and to compare their size to smaller Europa and Io. It might even be possible to detect slight color differences among them. Jupiter will become lost in the evening twilight next March as it once again fades to magnitude -2.0 and shrinks to 33 arcseconds across.
Saturn: This ringed world will remain the highlight of summer star parties as the rings continue to open and appear more visible. Saturn is at opposition on April 3 in Virgo when it will be 19.4 arcseconds across and shine at magnitude +0.4. The warmer seasons will allow for comfortable viewing and an excellent chance to study Saturnís belts and spots, and to watch the rings steadily open as the months go by. Saturn will slowly fade to magnitude +0.9 and shrink to less than 17 arcseconds across by September when it becomes lost in the evening twilight.
Uranus: This hazy world will be at opposition on September 25 in Pisces. Uranus will be 3.7 arcseconds across and shine at magnitude +5.7 to the left of the Circlet of Pisces. It can still be seen near Jupiter at the beginning of the year.
Neptune: This blustery world is at opposition on August 22 in Aquarius, close to where it was discovered in 1846. Neptune will be 2.4 arcseconds across and shine at magnitude +7.8. A finder chart for Uranus and Neptune will appear in the August issue of Telescopic Topics. Both planets will rise before midnight by August and gradually fade into the evening twilight by February 2012.
Pluto: This frozen world is now slowly emerging from the heart of the Milky Way above the spout of the Sagittarius Teapot, but will still be a challenge to find. Pluto is at opposition on June 28 among millions of stars and will shine like a faint spark at magnitude +14.0 and is only 0.1 arcseconds across. Locating Pluto will gradually become easier in the years ahead as it leaves the heart of the Milky Way by 2015, but it is slowly growing dimmer and lower in declination as it moves steadily away from Earth at each opposition.