On Display Now: Jupiter Easy to Spot

That incredibly bright star in the eastern evening sky is no star at all. It's Jupiter. The gas giant planet is closer to Earth than normal now, and it outshines all stars.

Jupiter is easy to find. Just go outside after sunset and look East. It is the brightest point of light up there. To Jupiter's left is the bright star Arcturus. Below Jupiter is Spica, another fairly bright star. [Sky map]

Astronomers measure brightness on an inverted scale. The dimmest stars visible are around magnitude 6.5, and very bright objects are magnitude 1 or so. Negative numbers are reserved for the brightest objects.

Some magnitudes to compare:

  • Jupiter: minus 2.46
  • Arcturus: minus 0.07
  • Spica: plus 0.96

Swing around toward the Southwest and you'll see Sirius, the brightest star in the sky. Yet even Sirius is much less bright, shining at magnitude minus 1.47.

Jupiter is bright enough to be visible as dusk sets in, but you'll need a clear view of the horizon to spot it early. As the night goes on, the planet rises higher into the southeastern sky.

If you are an early riser, look for Jupiter over in the western sky in the predawn, as it prepares to set. The arc it carves, from east to west overnight, is the same path followed by the Sun during the day. This ecliptic, as it is called, corresponds to the plane of our solar system inhabited by the Sun and most of the planets.

Jupiter is an obvious sight with the naked eye. A small telescope or binoculars will reveal it to be a disk rather than just a star-like point of light. With modest optical aids, you can also see up to four pinpricks of light lined up near Jupiter. Those are the Galilean moons, Jupiter's largest satellites.

A good-sized backyard telescope will reveal Jupiter's cloud bands.

Jupiter will remain a bright evening object throughout the month. On April 21 and 22 it will appear very near the Moon, making an eye-catching pair.

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