Image: Jupiter
Anthony Wesley via The Planetary Society
This photo of Jupiter, taken May 9, 2010, shows it without the large band of reddish clouds that makes up its Southern Equatorial Belt. 
updated 9/17/2010 12:05:45 PM ET 2010-09-17T16:05:45

Stargazers can get a great look at Jupiter on any clear night for the rest of September. The giant planet, always bright, will be especially hard to miss as it approaches closer to Earth than it will at any time until 2022.

In North America this month, Jupiter will be low in the east shortly after twilight, moving higher up toward the southeast as the evening grows late, according to NASA and Sky & Telescope magazine.

Jupiter will be nearest to Earth on Monday night, when it passes 368 million miles away. For comparison, the sun is about 93 million miles from us. But viewers shouldn't despair if they miss the show on the 20th: Jupiter will be nearly as close and bright all month.

Earth orbits the sun in about 365 days. But Jupiter, farther out there, takes 4,332 Earth-days to make the same trip. Therefore, Earth laps Jupiter periodically, on the inside track. As that pass occurs, the two worlds come much closer than when they are on opposite sides of the sun. Because the planets' orbits are not perfect circles, some passes are tighter than others.

This Jupiter sky map shows where to look to see the bright planet on the night of Sept. 20.

This year's close pass should beat out other years to give a spectacular show, with Jupiter coming nearer to Earth than at any time between 1963 and 2022, according to a Sky & Telescope announcement. At the closest point of its previous swing-by in August 2009, for example, Jupiter was more than 7 million miles farther away. That translated into the planet appearing 8 percent dimmer, all things considered.

Jupiter is also an extra 4 percent brighter than usual because one of its brown cloud belts has gone missing.

For nearly a year, the giant planet's South Equatorial Belt, usually easy to see in a small telescope, has been hidden under a layer of bright white ammonia clouds. This lets more sunlight reflect off the planet, giving it an overall brightness boost.

Uranus makes an appearance
There's more to see in the heavens right now than just Jupiter. The giant planet is lined up almost perfectly with Uranus at the moment.

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Uranus is five times farther away and almost 3,000 times dimmer than Jupiter, so it's invisible to the unaided eye. But binoculars or a telescope — as well as access to a detailed chart — will show Uranus less than 1 degree from Jupiter now through Sept. 24, Sky and Telescope said. (A fist held at arm's length covers about 10 degrees of the sky.)

On the other end of the brightness scale, the full moon joins this celestial scene around the same time, shining above Jupiter on the evening of Sept. 22 and to the left of it on Sept. 23.

Special view of Mercury
Also, this week is one of the few occasions when stargazers will be able to get a good look at Mercury. Though Mercury is very bright, its orbit's extreme closeness to the sun dictates that the sun's glare usually overpowers the small, rocky planet.

But twice each year, once in the evening and once in the morning, Mercury stands highest in the sky, giving skywatchers the best opportunity to spot it. This week offers its best morning appearance of the year.

To see Mercury, skywatchers should go out any morning this week about 30 minutes before sunrise. A low, cloudless sky and an unobstructed view of the eastern horizon are necessary. Mercury should be visible just above where the sun will rise, about 10 degrees above the horizon.

Stargazers may need binoculars or a small telescope to see Mercury at first, but once spotted it should be visible to the unaided eye.

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Photos: Jewels from Jupiter

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  1. Jupiter loses a stripe

    The weather on Jupiter is changeable, as these before-and-after pictures show. The photograph on the left shows Jupiter as seen in June 2009. The photo on the right, taken on May 9, 2010, reveals that one of the planet's prominent dark cloud belts has faded away. The lightening of the South Equatorial Belt is due to atmospheric changes. Both pictures were taken by Anthony Wesley, an amateur astronomer in Australia. (Anthony Wesley via The Planetary Society) Back to slideshow navigation
  2. Family portrait

    Launched in 1989, the Galileo spacecraft has photographed Jupiter as well as several of the giant planet's satellites. Here's a montage that shows Jupiter's Great Red Spot and the four largest moons. From top, they are Io, Europa, Ganymede and Callisto. (NASA) Back to slideshow navigation
  3. Cratered Callisto

    Callisto is considered the most cratered celestial body in the solar system. The false-color overlay at right exaggerates the moon's surface features, including the Valhalla impact structure near the center of the disk. (NASA) Back to slideshow navigation
  4. Dark face

    Colors are enhanced in this view of Ganymede's trailing hemisphere, highlighting the moon's polar caps. The violet color indicates where small particles of frost may be scattering light on the blue end of the spectrum. (NASA) Back to slideshow navigation
  5. Cloudy weather

    The mosaic at left shows the true colors of the cloud patterns in Jupiter's northern hemisphere. The rendition at right uses false colors to represent the height and thickness of the cloud cover. (NASA) Back to slideshow navigation
  6. This is the Spot

    A true-color picture captures the subtle shadings of Jupiter's Great Red Spot, a massive, long-lived storm system in the planet's thick atmosphere. (NASA) Back to slideshow navigation
  7. A big splash on Europa

    A computer-generated perspective view shows the Pwyll impact crater on Europa, an ice-covered moon of Jupiter. The heights are exaggerated, but the central peak indicates that the crater may have been modified shortly after its formation by the flow of underlying warm ice. (NASA) Back to slideshow navigation
  8. A blast at Io

    This image of Io, thought to be the solar system's most volcanically active world, shows the plumes of two eruptions. One plume can be seen at the very edge of the disk, the other is puffing up from the dark volcanic ring near the center of the disk. (NASA) Back to slideshow navigation
  9. Lava light

    An active volcanic eruption on Jupiter's moon Io flares in an image taken in February 2000 by the Galileo spacecraft. The dark L-shaped lava flow to the left of center marks the site of energetic eruptions in November 1999 at Tvashtar Catena, which is a chain of giant volcanic calderas. The two small bright spots at left side of image are sites where molten rock is exposed to the surface at the toes of lava flows. (NASA) Back to slideshow navigation
  10. Crazy quilt

    The thin crust of Europa's Conamara region is criss-crossed by craters, cracks and lines - indicating that the surface ice was repeatedly disrupted. The colors, which are enhanced in this view, show where light ice crystals and dark contaminants have settled onto the surface. (NASA) Back to slideshow navigation
  11. A moving moon

    In a picture taken in April 2001 by NASA's Cassini spacecraft, the moon Io looks like a marble set against the background of Jupiter. Io is the giant planet's third-largest satellite. (NASA) Back to slideshow navigation
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