by Joe Rao, SPACE.com Skywatching Columnist
Stargazers looking up as darkness falls on Monday (Jan. 21) will notice an eye catching pairing-off between two of the brightest objects in the nighttime sky, weather permitting.
The moon, appearing as a waxing gibbous phase, 78 percent illuminated, will appear to stand close below a very bright, non-twinkling, silvery “star.” But it won’t be a star that will be keeping the moon company on America’s Inauguration Night, but the largest planet in our solar system: Jupiter.
Across much of the United States and southern Canada, this will be closest that the moon and Jupiter will appear relative to each other until the year 2026. On Monday night, the moon will be about of 248,700 miles (400,500 kilometers) from Earth, while Jupiter will be nearly 1,664 times farther out in space at a distance of 413.8 million miles (665.9 million km).
During Monday’s stargazing event, observers have the chance to see what astronomers call an appulse — a very close approach of the moon to Jupiter. An appulse is a phenomenon caused by perspective only. There is no close physical approach in space between the two objects involved. Astronomers insist that appulses have no direct effect on the Earth.
The moon, moving around the Earth in an easterly direction at roughly its own diameter each hour, will creep slowly toward and ultimately pass just below the giant planet. Jupiter, meanwhile, will be shining about three times brighter than the brightest star, Sirius, offering a commanding sight for stargazers despite its close proximity to the moon. [Amazing Stargazing Photos for January]
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