Moon, Jupiter to shine near each other tonight
Moon meet Jupiter, Jupiter meet moon. The two most brilliant objects in our current night sky will make for an eye-catching duo tonight, weather permitting.
The two most brilliant objects in our current night sky will make for an eye-catching duo tonight (Oct. 13), weather permitting.Skip to next paragraph
In Pictures Awesome photos of Jupiter
In Pictures We love the moon
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Looking low to the east-northeast around 7:30 p.m. local daylight time, you’ll see a nearly full waning gibbous moon. Sitting just to the right of the moon will be the lordly light belonging to the largest planet in our solar system: Jupiter.
Jupiter will hover about 5 degrees from the moon's right. Your clenched fist held at arm's length covers about 10 degrees, so moon and Jupiter will be separated by about half a fist.
The sky map of the moon and Jupiter here shows how they will appear together tonight.
IN PICTURES: Awesome photos of Jupiter
Cosmic dance of Jupiter and moon
If you stay up through the night, you may notice the moon slowly pulling away from Jupiter at a rate of one lunar diameter per hour, and the orientation between the two bright objects will change as well. [Photos of Jupiter: Solar System's Largest Planet]
By around 1 a.m. local daylight time (early Friday morning), the moon will seem to hover high above and to Jupiter's left. By 6:30 a.m. — with morning twilight rapidly brightening the sky in the east — the moon will seem to hang high and almost directly above Jupiter.
In the days that follow, the moon will pull away to the east and diminish in illumination, leaving glorious Jupiter to rule the October night.
On Oct. 28, Jupiter will arrive at opposition against the sparse background stars of the constellation Aries, the Ram. Since it is then opposite to the sun, the planet rises at sunset, crosses the sky from east to west during the night and sets at sunrise.
Beginning in November, Jupiter will already be up in the eastern sky when the sun goes down. This will continue for the rest of the fall season in the Northern Hemisphere.
Jupiter shining bright
Opposition generally brings a "superior" planet (an outer planet as compared with Earth) closest to the Earth, and this is why Jupiter now shines more brilliantly than it has all year.
Astronomers use a reverse number scale to measure the brightness of objects in the sky, with smaller numbers corresponding to brighter objects. A negative number, for example, represents an extremely bright object. At an eye-popping magnitude of - 2.9 — fully four times brighter than Sirius, the brightest star — Jupiter is far brighter than any nighttime star.
But this year's apparition of Jupiter is an exceptionally good one. Although "Big Jupe" comes to opposition every 13 months (every time the Earth sweeps between it and the sun), 2011 is also Jupiter's year of perihelion. This is when it is closest to the sun in its 12-year orbit, so it's also particularly close to the Earth.