Jupiter to dance with moon on January 21
Jupiter, the second-brightest planet, will be appearing less than a finger-width from the Moon throughout North America on January 21, 2013.
Additionally, in much of South America, the Moon will actually pass right in front of Jupiter, hiding it from view.
The pair is already very close together at sunset. The time of their closest approach on the evening of January 21st depends on your location; it's around 7 p.m. in the Pacific time zone, 8:30 p.m. Mountain, 10 p.m. Central, and 11:30 p.m. Eastern time.
Although the Moon and Jupiter look close together, they're definitely not. The Moon is 1.3 light-seconds (250,000 miles) distant from Earth. Jupiter is 1,700 times farther away in the background, at a distance of 37 light-minutes.
Nevertheless, the pair makes for an amazing sight to the unaided eye, through binoculars, or through a small, wide-field telescope at magnification of 40x or lower.
"You'll also get an opportunity to attempt an unusual feat: spotting Jupiter in the late afternoon, before the Sun sets," Tony Flanders, associate editor at Sky and Telescope magazine, said.
"First locate the Moon medium-high in the east; then look a few Moon-widths left or lower left of the Moon for Jupiter. It should be easy to spot with binoculars if the air is clear," Flanders said.
Telescope owners have a couple of additional treats. Jupiter's Great Red Spot is visible roughly from 9:00 to 10:40 p.m. EST (6:00 to 7:40 PST). And Jupiter's moon Europa crosses in front of the planet from 8:13 to 10:37 p.m. EST (5:13 to 7:37 p.m. PST).
Europa is well camouflaged against Jupiter's bright disk, but it should be easier to spot Europa's tiny black shadow crossing Jupiter from 10:22 p.m. to 12:46 a.m. EST (7:22 to 9:46 p.m. PST).
As icing on the cake, the bright orange star Aldebaran shines to the lower left of Jupiter and the Moon. "Binoculars show that the entire event takes place on the outskirts of the Hyades, the closest true star cluster to Earth," says Sky and Telescope senior editor Alan MacRobert.
"The lovely Pleiades cluster lies nearby," he added.