In a solar system filled with giants, nothing compares with mighty
Jupiter. Not the bedazzling ocher rings of Saturn, the dusky markings of
Mars, or the violent volcanoes of Io. No, only the king of planets, a
miniature solar system in itself, outweighs and outshines all other planets
in the hearts of amateur astronomers. And on January 1, 2002, as champagne
corks fill trash cans and we begin yet another year, mighty Jupiter will
reach its brightest – it will be so impressive in the evening sky that it
is sure to be mistaken for an airplane.

New Year’s Day marks Jupiter’s newest opposition, wherein it
reaches a point in the sky opposite that of the sun. It is then relatively
close to Earth – a mere 395 million miles away – which makes it appear
bright, and it is well-placed for observing throughout the night, reaching
its highest altitude at midnight. The planet will hang brilliantly among
the stars of the constellation Gemini, near the twin bright suns Castor and
Pollux, high in the southeast in the early evening sky. It will anchor the
so-called ecliptic, the arc on the sky across which the planets appear to
move, which will also host Saturn in Taurus (overhead in the evening), and
Mars in Pisces, low in the west. On January 1, Jupiter will beam with
brightness at magnitude -2.7, significantly outshining all other objects in
the sky except for the sun and moon.

As viewed through a small telescope, Jupiter delights as one of the
observational highlights of the sky. At no time is this more significant
than now. On January 1 the planet’s gaseous disk spans 45.5″, about 1/40
the size of the full moon, a testament to its great distance as the
planet’s physical diameter is slightly less than 90,000 miles. Even the
smallest telescope can replicate the view of Jupiter that Galileo marveled
at in 1610 when he became the first human to see its miniature solar
system. With a 3-inch or larger telescope you will see cloud belts and
bands crossing the salmon-colored globe, the planet’s Great Red Spot, a
sustained anti-cyclonic storm, and four bright moons aligned on opposite
sides of the disk – Io, Ganymede, Europa, and Callisto.

With these four moons regularly circling the planet – along with at
least 24 much smaller and fainter moons – an occasional shadow play occurs
across the planet’s cloud decks. When this happens, dark spots can be
glimpsed, particularly if the moon’s shadow casts into one of the planet’s
bright zones. Though the sizes of these shadows are tiny, the stark
contrast between them and the brilliant disk of Jupiter elevates them into
visibility with very small telescopes. With steady atmospheric seeing, even
a 2-inch telescope can show these shadow transits, though they are more
easily visible in a 4-inch or 6-inch scope. Spotting the disk of a moon
itself transiting across Jupiter’s face is more challenging, but possible
with scopes of 4 inches and larger. For complete details on observing
Jupiter during the current opposition and beyond, including data on
observing satellite transits, see Astronomy magazine.

Note to editors: Please see Astronomy Magazine’s website at

Contact: David J. Eicher, Astronomy Magazine

Phone: 262-796-8776 ext. 603


Caption for web photo:

Jupiter’s cloud bands and Great Red Spot as imaged with the razor-sharp
optics of the Hubble Space Telescope.

Credit: STScI