Here are some of the more noteworthy sky events that will take place in 2010. Each will be covered in greater detail as the event approaches. Notes about terminology:
Magnitude: On this scale, smaller numbers represent brighter objects, with the brightest stars and planets represented by negative numbers.
Degrees: Distances in the sky, from our point of view, are measured in degrees. Your fist on an outstretched arm measures about 10 degrees of sky.
Jan. 15 – Solar Eclipse
An annular (ring) eclipse of the sun will take place over parts of Africa, India and China. Because the moon is near apogee (its farthest point from Earth in its orbit) and the Earth has just passed perihelion. So the moon appears much smaller than average, and the sun somewhat larger than average. The moon's circle is only about 92 percent as wide as the sun; so 4 percent of the sun's width shows on each side of the moon. Thus, the annular phase lasts a maximum of 11 minutes and 8 seconds. This is a very long duration indeed: nearly twice as long as some people got to watch last July's total eclipse. According to eclipse expert Fred Espenak of NASA's Goddard Space Flight Center, this is the longest annular eclipse of the 3rd Millennium – its duration will not be exceeded until the year 3043!
Jan. 29 – Mars Close Approach
Mars will be only 61.7 million miles from Earth, closer than it will be again until March 2014. Peaking at magnitude -1.3, Mars will outshine all stars and other planets except Sirius and Jupiter. Opposition to the sun occurs on the 29th. It's during January that Mars begins to become large enough to show, through telescopes, touches of dark surface detail and perhaps occasional white clouds or limb hazes in medium-sized amateur telescopes at the best moments on steady nights when it's fairly high. With time and practice you may see even more. Despite any rumors you might hear, Mars will not be "as big as the full moon" or anywhere near that large. To the naked eye, it will remain a star-like point in the sky.
Feb. 16 – Venus and Jupiter Get Together
Like two ships passing in the twilight, Venus and Jupiter come within about 0.5-degrees of each other this evening. Jupiter is heading toward the sun, while Venus is moving away from the sun. This would normally be a very striking sight, but unfortunately, this conjunction takes place with the two planets just 9 degrees east of the sun – probably too near to it to make a definite sighting. If you would still like to give it a try, then – immediately after sunset – concentrate on that part of the sky just above and to the left of where the sun has just set. Using binoculars sweep around this part of the sky; Venus (magnitude -3.8) will be sitting just below and to the left of Jupiter (magnitude -2.0).
Mar. 28 to Apr. 12: Venus and Mercury Pair Up
The two worlds make for an attractive pair in the west-northwest sky soon after sunset. Between these two dates these two planets are within 5 degrees of each other, Venus appearing to the left and slightly above the dimmer Mercury. On April 3, they will appear closest together, just a little over 3 degrees apart.
Jun. 6: Two Pairs to See
Orange-yellow Mars slides less than a degree north of the bluish star Regulus, a pretty conjunction easily seen in the middle of the evening sky. By then, Mars will have shrunk to a tiny ochre dot even in large telescopes. Also on this night, Jupiter will engage Uranus in the first of a series of three conjunction; there have been only six such triple conjunctions between 1801 and 2200. The last was in 1983 and the next will come during 2037-38.
Jun. 26: Partial Eclipse of the Moon
This eclipse favors the Hawaiian Islands, western Alaska, Australia, New Zealand, eastern portions of Malaysia and Asia. These locations will see the upper half of the moon darkened by the Earth's umbral shadow. Across parts of the eastern U.S., some evidence of the eclipse may become evident as the lighter penumbral shadow casts a "smudge" on the moon's left edge just before moonset.
Jul. 11: Total Eclipse of the Sun
Virtually the entire path of totality falls over water. It will pass within 15 miles of Tahiti (a great cruise ship opportunity) and scores a direct hit on tiny Easter Island, famous for its strange humanoid megalithic statutes. From this speck of land in the middle of the South Pacific Ocean, the sun will be totally eclipsed for 4 minutes 45 seconds. Talk about a photo-op! The only other landfall is near the very end of the totality track, over Patagonia.
Early Aug: Planetary Trio
Mars passes less than a couple of degrees south of Saturn on Aug. 1 and Venus slides just over 3 degrees to the south nine days later; on Aug. 8, the three planets will form what Jean Meeus defines as a "trio," when three planets fit within a circle with a minimum diameter smaller than 5 degrees. These three worlds are all well out (46 to 50 degrees) from the sun but, unfortunately for the Northern Hemisphere, south of it and therefore rather low to the sunset horizon.
Aug. 12: Perseid Meteor Shower
One of the best known and most reliable of the annual meteor displays reaches maximum with no moonlight to interfere. Under dark, clear skies, a single observer might see as many as 90 meteors per hour. If you aim to catch one night sky event this summer, make it this one.
Sep. 21: Jupiter, Big and High
Jupiter reaches the middle of the midnight sky, that is, at opposition (magnitude -2.9). In this part of its orbit Jupiter is nearer than its average distance, because in 2011 it will reach its perihelion on Mar. 17; so in a telescope the great banded globe appears practically as large as it can ever get; nearly 50 arc-minutes wide or 1/36 the apparent width of the full moon. Not too far away is Uranus; this is also the date of the second of the series of three Jupiter/Uranus conjunctions (See Jun. 6).
Late Oct: A Close Encounter with a Comet
Comet Hartley 2 will pass to within 11.2 million miles of the Earth on Oct. 20, just a week before it makes its closest pass by the sun. As a result, this comet should briefly become a naked eye object, perhaps becoming as bright as magnitude +4 or +5 – visible from rural locations but perhaps not from cities. The comet will be a morning object, racing rapidly southeast through the stars of Auriga and Gemini. Then, in early November the Deep Impact spacecraft, which had a rendezvous with Comet Tempel 1 in July 2005 should pass within about 600 miles of Hartley 2.
Dec. 14: Geminid Meteor Shower
Even though the moon is at a waxing gibbous phase, it will set soon after midnight, leaving the sky dark for a view of potentially up to 120 meteors per hour. For those willing to brave the cold, this event is well worth planning for.
Dec. 20-21: Total Eclipse of the Moon
North America has a ringside seat for this must-see total lunar eclipse. For the Eastern U.S. and Canada, this will be a predawn event. For the western U.S. and Canada, it comes during the middle of the night of Dec. 20-21, while for Alaska and Hawaii it occurs during the mid-to-late evening hours of the 20th. Totality will last 1 hour and 14 minutes. Western Europe will see the moon set during totality, while conversely, in Japan, the moon will rise during totality.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.