On March 4th, the planet Jupiter was in Opposition. This means that Jupiter rises at sunset and sets at sunrise; therefore Jupiter is visible all night long. Fortunately for us, Jupiter will remain in great viewing position for the rest of the Spring, rising just a bit earlier each day. Here are some facts about Jupiter:
Jupiter is
the largest planet in the solar system, measuring in at 88,700 miles across
its equator. But it has no solid surface to stand on; Jupiter is a giant
ball of gas made of 85% hydrogen. Jupiter is sometimes called a "failed
star"; if it was 10 times bigger, it would have become a star, and our
solar system would be a binary one. Jupiter may have a solid core, but
no one knows for sure. One theory states that Jupiter's core might be made
of solid diamond! Jupiter also has the shortest day of any planet in the
solar system, completing one rotation in just under 10 hours. Juipter's
year is 12 earth years long. Jupiter's weather makes it a pretty undesirable
vacation spot, with winds up to 300 miles per hour. The markings seen on
Jupiter are cloud bands. (Belts are dark, and Zones are light.)
Jupiter also has rings, like all the giant planets, but only Saturn's rings
are bright enough to be seen from Earth. The Voyager spacecraft discovered
these rings during its flyby.
Jupiter has
28 known moons (12 of these were discovered in the past few years.) Of
these, the 4 Galilean moons (shown at left) are the biggest, and can be
seen from earth with binoculars or any size telescope. Io is the
solar system's most volcanically active body, and its eruptions have been
recorded by the Galileo spacecraft.
Europa,
about the size of our own moon, is an iceball with a surface like a cracked
eggshell, and it is widely speculated that it may harbor life in a global
ocean beneath the ice. Ganymede (the largest moon in the solar system)
and Callisto both have rocky cores with jumbled surfaces of rock
and ice. Jupiter's Great Red Spot, highlighted at left, is a giant
storm that has raged for at least 300 years. It is so large that two earths
could fit inside it. In recent years the spot has paled, and looks salmon
colored to most observers. The Cassini spacecraft took this image of the
GRS on its way to Saturn in 2001. On earth, Jupiter is the second brightest
planet in the night sky next to Venus. (Mars also occasionally outshines
Jupiter, as it did last fall). On the next page, we'll explore what
can be seen on Jupiter.
The images on this page are copyright NASA, The Galileo Project, and the Cassini-Huygens Mission.