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updated 9/22/2010 7:13:55 PM ET 2010-09-22T23:13:55

Check out the eastern sky just after sunset tomorrow (Sept. 22), and you'll catch a skywatching treat. The nearly full moon will be rising just above the bright planet Jupiter and a somewhat dimmer Uranus.

You'll need binoculars if you hope to spot Uranus — it appears as a tiny bluish speck, too dim for the naked eye. So the coming celestial lineup is an excellent time to find that planet with binoculars or a small telescope, using Jupiter as a helpful guidepost.

This sky map (right) shows where to spot the moon, Jupiter and Uranus this week.

Skywatching marathon
Several astronomical events happen in rapid succession this week, offering a celestial show for observers graced with clear skies. The times indicated here are for eastern North America and may vary a little if you’re elsewhere in the world:

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  • Today (Sept. 21) at 8 p.m. EDT (1200 GMT), Jupiter is in opposition. This means that Jupiter will be exactly opposite the sun in Earth’s sky. This also means that Jupiter will be visible the entire night. (Yesterday — Sept. 20 — Jupiter made its closest approach to Earth in nearly 50 years.)
  • Five hours later, at 1 a.m. tomorrow (Sept. 22), Uranus will be in opposition, taking its turn opposite the sun in the sky.
  • Later tomorrow at 3 p.m., Jupiter and Uranus will be in conjunction, less than 1 degree apart in the sky. They won’t be visible right then in North America because they will be below the horizon, but they will still be close together when they rise just after sunset. You will be able to see both planets at the same time in the field of a small telescope at low magnification.
  • The show continues tomorrow night at 11:09 p.m. EDT (0309 GMT Thursday, Sept. 23), when the sun crosses the celestial equator — a projection of Earth's equator on the sky — and enters the southern hemisphere. This is known as the equinox, meaning "equal nights." Daytime and nighttime are of equal length, about 12 hours, everywhere on Earth. (Of course, the sun won’t be visible at this time in North America, being on the other side of the planet.)
  • Finally, at 5:17 a.m. EDT  (0917 GMT) Thursday, the full moon of September will occur, since the moon will be exactly opposite the sun in the sky. This is a special full moon: It is the full moon closest to the equinox, known as the harvest moon.

So we have two planets and the moon directly opposite the sun within a two-day period. This means that all three will be grouped closely together in the sky.

When to see them
The best night to observe the moon, Jupiter and Uranus will be tomorrow, weather permitting.

The nearly full moon will rise around sunset, with Jupiter shining brightly beneath it. Uranus will be just slightly too faint to be seen with the naked eye, but will be easy to catch in binoculars or a small telescope.

This apparent close grouping of moon, Jupiter, and Uranus is actually a trick of perspective; the three objects aren’t anywhere near each other.

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The moon is very close to Earth, about 251,000 miles (404,000 km or 0.003 astronomical units) away.  One astronomical unit, or AU, is the distance between the Earth and sun, about 93 million miles (150 million km).

Jupiter is nearly 1,500 times farther from Earth than the moon, placing it about 3.95 AU away. Uranus is nearly five times farther away than Jupiter, about 19.1 astronomical units from Earth.

One way to visualize the relative distances is to imagine that the Earth is at one end of a 100-yard football field and Uranus is at the other end.

On this scale, Jupiter would be on the 20-yard line, and the moon would be about half an inch from the end zone. In the "overhead" view of the planetary alignment, the innermost circle is Earth’s orbit; the moon’s orbit is too small even to be visible.

This explains why our tiny moon appears so large in the sky while the giant planets Jupiter and Uranus are mere pinpricks of light. The moon is just tons closer. Pure and simple.

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Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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