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article imageJupiter is so bright because it is so close to Earth

By Lee Labuschagne     Sep 18, 2010 in Science
If you currently look up at night, it is virtually impossible to miss noticing the planet Jupiter - the giant planet is spectacularly bright.
The reason for this is that the orbits of Jupiter and the Earth are bringing them closer together than they have been in decades. Look towards the East in the early evening and watch it throughout the night.
The night of the closest approach between Earth and Jupiter is Sept. 20-21, when Jupiter will be "only" 368 million miles (592 million kilometers) from Earth - closer to us than at any time since 1963. This is in part beause the Earth is currently between Jupiter and the sun. Astronomers call this the night of opposition" because Jupiter will be on the opposite side of the Sun to Earth.
Dr. Tony Phillips of Science@NASA says close Earth-Jupiter encounters happen every 13 months when the Earth laps Jupiter in their race around the sun. Earth takes a year to complete one orbit around the sun, while Jupiter – with its larger orbit and slower motion in orbit – needs 12 years to orbit the Sun.
But because Earth and Jupiter do not orbit the sun in perfect circles, they are not always the same distance apart during these close encounters. On Sept. 20, Jupiter will be as much as 75 million km closer than previous encounters and will not be this close again until 2022. Read more about this on the EarthSky website.
What you can see
Currently Jupiter rises at sunset and by midnight it will be almost straight above your head. Only the moon will be brighter (when it is visible) and in the early evening you will also see the bright light of the planet Venus in the West.
These two bright planets dominate the sky early in the evening, but the one that is furthest East is Jupiter and the one that sets first is Venus. Other planets visible in the early evening are Mars (close to Venus) and Saturn (difficult to see because it sets soon after the Sun - but in really dark areas with a good view of the horizon, you may be able to do so.
The view of Jupiter through even a small telescope is currently excellent. But even through a good pair of binoculars, you will be able clearly to see the planet as a yellowish disk, and also spot one or more of its large moons (more below).
Because Jupiter is so close, the planet's disk can be seen in rare detail through a telescope. Some of the things to look out for are:
* the Great Red Spot, a cyclone twice as wide as Earth, is bumping up against another storm called "Red Spot Jr."
* Jupiter's trademark South Equatorial Belt (SEB) recently "vanished", possibly submerging itself beneath high clouds. Researchers say it could reappear at any moment. The dramatic resurgence would be accompanied by a globe-straddling profusion of spots and cloudy swirls, clearly visible in backyard telescopes.
* Also look out for the four largest moons of Jupiter because they are also having a close encounter with Earth together with their planet. They are seen close to Jupiter planet in an almost straight line - but their relative positions constantly change (on either side of the planet and sometimes one or more are not visible because they are behind or in front of the planet as they orbit it).
These moons are planet-sized worlds: Ganymede is larger than Mercury and much larger than Pluto, while Callisto is only slightly smaller than Mercury. These fascinating moons have active volcanoes (Io), possible underground oceans (Europa), vast fields of craters (Callisto), and mysterious global grooves (Ganymede).
When Galileo Galilei discovered them 400 years ago, they were no more than pinpricks of light in his primitive spy glass, but some large modern amateur telescopes reveal much more - in some cases one can see actual planetary disks with colorful markings. Space missions like Pioneer II, the two Voyager and Galileo have visited Jupiter and its moons and have sent back detailed photographs of these moons.
Read more about Jupiter and its satellites here.
More about Jupiter, Venus, Red spot jupiter, Galilean moons, Ganymede
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