A 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 events for 2010 will be the return of Mars, the reappearance of Saturnís rings, and a total lunar eclipse, all of which will make for a most pleasurable year of observing.
On December 21 at 2:40 A.M. a total eclipse of the Moon begins and will last 72 minutes, ending at 3:52 A.M. If this one is clouded out, the next one will be on April 15, 2014, also during the wee hours of the morning. There are no solar eclipses locally this year and the next one will not occur until minutes before sunset on May 20, 2012 when the Sun will hardly be 1% eclipsed at best according to the Google Earth Interactive Solar Eclipse Simulator.
Mars dominates the evening sky during the beginning of 2010 as Jupiter sets in the twilight. Mars will have competition from Saturn and Venus in February and it will not be long before both dominate the evening sky well into summer as Mars slowly fades during the year. Mercury will appear briefly in the evening sky from late March into mid April. Saturn will fade into the twilight by September and Venus will quickly follow in October, but Jupiter will begin rising in the east before midnight by then and will command the evening skies for the rest of the year. 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 2010:
Mercury: This iron world is challenging to find, but well worth it. It will be surprisingly easy to see in the evening from March 25 to April 18 with it being highest above the horizon on April 8. On that evening it will be very easy to see as it will be just to the lower left of Venus and on April 15 it will be very close to a thin crescent Moon. 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 volcanic world will be a beautiful evening star from March until October. During this period Venus will start out nearly full and grow into a large, thin crescent by October. The magnitude will increase from -4.3 to -4.6 and its size will grow from 12 arcseconds to nearly one arcminute by October before moving into the morning sky for the rest of the year. Venus will make several beautiful pairings with the crescent Moon during the year in the evening and morning. The evening apparitions will be different from most in that Venus will be unusually low and among the treetops throughout.
Mars: This rusty world comes into opposition on January 29 when it reaches 14.1 arcseconds across near the Leo-Cancer border. It will shine at magnitude -1.3 and be 61.7 million miles away. It will be nowhere as large as in the past several oppositions, but it will be high enough in the sky for steadier viewing. Patience and persistence will pay off with memorable views of subtle detail. Mars will remain in good view into early spring and very slowly shrink and fade into the evening twilight by the end of the year.
Jupiter: This cloudy world will be at its best since 1999 as autumn approaches and will be stunning in telescopes with the promise to dazzle the public. Jupiter is at opposition on September 21 below the Circlet in Pisces and will be 49.9 arcseconds across and blaze at magnitude -2.9. This hugeness will allow for highly detailed viewing of Jupiterís clouds and Great Red Spot, and 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 sizes 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 February as it fades to magnitude -2.0 and shrinks to 33 arcseconds across.
Saturn: This buoyant world will be the highlight of summer star parties as the rings return! Saturn is at opposition on March 21 in western Virgo when it will be 19.5 arcseconds across and shine at magnitude +0.5. 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 toppled world will be at opposition on September 21 in Pisces. Uranus will be 3.7 arcseconds across and shine at magnitude +5.7 below the Circlet of Pisces. It will be very close to Jupiter on June 6, September 22, and next January 2 due to Jupiterís retrograde motion. Uranus and Jupiter will make a stunning color contrast through a low-power eyepiece, especially on September 22 with both near opposition.
Neptune: This chilly world will be at opposition on August 20 in Aquarius near the border with Capricornus. 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 2011.
Pluto: This dim world is all but lost this year as it remains in the heart of M24, the Small Sagittarius Star Cloud, which is part of the steam cloud of the Milky Way rising from the spout of the Sagittarius Teapot. Pluto is at opposition on June 25 among millions of stars and will shine like a faint spark at magnitude +13.9 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 will fade below magnitude +14 and grow lower in declination as it moves away from Earth in its huge orbit.