Uranus reaches its 2012 peak
Late September nights will be the best time to observe the blue-green planet.
September 19, 2012
Now’s the time to seek out Uranus, the oddball planet that rolls around the Sun seemingly on its side. On September 29, the ice giant world reaches opposition, meaning it lies opposite the Sun in our sky and remains visible from sunset to sunrise. Uranus also glows brighter and appears larger through a telescope than at any other time this year.
Distant Uranus lies near the border between Pisces and Cetus at opposition September 29. The 6th-magnitude world outshines most of the stars in its immediate vicinity. Astronomy: Roen Kelly
“Uranus peaks at magnitude 5.7, which makes it just bright enough to see with naked eyes if you observe under a dark sky,” says Senior Editor Richard Talcott. “Even from the suburbs, though, a small telescope will make the planet’s disk stand out.”
Start looking for Uranus a week before opposition on the border between the constellations Pisces the Fish and Cetus the Whale. The 6th-magnitude world outshines most nearby stars except 44 Piscium. On September 22, the ice giant appears 1.4' due east of this sun. View the double-star-like pair through your telescope at medium power. Uranus’ blue-green color and 3.7"-diameter disk creates a nice contrast with the pinpoint star.
By opposition, the planet and its stellar companion lie some 15' apart. That night, you can use the night sky’s brightest object to spot the pair: On the evening of September 29/30, the Full Moon passes 5° north of the duo. Although the glare of our satellite washes out a lot of the sky, binoculars should still reveal Uranus and its “companion.”
“You won’t see any detail on Uranus’ disk, even through a telescope,” Talcott says, “but it’s still exciting to spot the first planet discovered since antiquity, knowing it eluded observers for centuries.”
- Uranus was the first planet discovered with telescopic aid, first spotted by British astronomer William Herschel on March 13, 1781.
- Uranus’ blue-green color is a result of the planet’s methane, which absorbs red wavelengths and reflects blue.
- Uranus has a ring system that earthbound observers see edge-on every 42 years due to the distant planet’s changing seasons.
- Planetary scientists have discovered 27 satellites orbiting Uranus and have named them all after characters in works by William Shakespeare and Alexander Pope.
- Scientists think a huge collision early in Uranus’ history knocked the planet on its side; its rotation axis is now nearly parallel to its orbit.
- Uranus completes one orbit in 84.01 Earth years, and it rotates once every 17.24 Earth hours.