Close encounters of the Jovian kind

At midnight on February 2, Jupiter will stand high in the sky as Earth, Sun and this distant gaseous world align. The exact alignment will occur at 3 a.m. EST (9 GMT). To the naked eye, however, Jupiter will appear to cross the celestial meridian - the line that divides the sky in half from north to south - at midnight the world over.

As Earth and other planets orbit the Sun, they periodically align. An alignment with Earth between the Sun and another planet is called an opposition. Geometrically, the Sun, and in this case Jupiter, are on opposite sides of Earth, with the Sun being directly below someone's feet at midnight, while the planet is directly overhead.

This year, the unique geometry of the sky will cause Jupiter to be straight overhead for people living at 18 degrees North latitude. For these residents of Central America and Africa, the view of Jupiter will be truly superb. The closer to straight overhead, or zenith, that an object is located, the less the atmosphere will cause its light to dance around and twinkle.

The day of opposition is not only a day of special alignments, it is also the day that Earth and Jupiter are closest. This year, Earth and Jupiter will be separated by a mere 4.3 astronomical units (AU) or 4.3 times the distance between Earth and the Sun. On average, Jupiter and Earth are separated by more than 5 AU. During this closest approach, Jupiter will appear 45 arcseconds in diameter, which is the largest it will be until next year's opposition.

On February 2, Jupiter's moons Io and Callisto should be clearly visible, with Europa and Ganymede appearing in the morning and evening. With a pair of everyday binoculars, Jupiter should appear as a disk with a line of small orbs strung out to its sides.

For more information on observing Jupiter, including finding charts and a list of other objects that may interest you, see the February issue of Astronomy magazine, available at Barnes and Noble bookstores and other newsstands everywhere. Let Jupiter's opposition be your excuse to spend an evening looking up.

For additional materials and images, please see: http://www.astronomy.com/content/static/PressRoom/default.asp For more information, please contact Astronomy magazine's astronomer Pamela Gay at 262-796-8776 or pgay@astronomy.com.

Thursday, January 23, 2003
Source: CCTV