Jimmy Westlake: Jupiter rules the night
November 14, 2012
Have you noticed the really bright "star" rising over the eastern mountains shortly after darkness falls? It's not really a star at all — it's the giant planet Jupiter, the largest planet in our solar system.
Jupiter really wears the crown when it comes to ruling the midnight sky. The gap between Earth and Jupiter has been shrinking during the past few months, and the two planets will be as close together as possible on the night of Dec. 2, when Jupiter reaches opposition. For a few weeks around that date, Jupiter will be opposite the sun in the sky, rising in the east as the sun sets in the west. It will gleam brilliantly as the brightest object in our midnight sky.
On the night of opposition, Jupiter will be about 380 million miles from Earth. After Dec. 2, that distance will grow a little each day, but the king of the planets will remain a constant companion in our evening sky throughout the winter and spring of 2013.
Jupiter is a totally different kind of planet than Earth. It is a colossal ball of hydrogen and helium held together by its enormous gravity. Jupiter has no solid surface to stand on. If you tried to land on it, you would just sink down into its deep atmosphere and eventually splash into an ocean of liquid hydrogen thousands of miles deep. NASA's Juno spacecraft is on its way to Jupiter and will arrive in 2016 to study Jupiter's internal structure and composition.
Steady binoculars or any small telescope will reveal Jupiter's four traveling companions, discovered by Galileo in 1610. They are the moons Io, Europa, Ganymede and Callisto — the four largest of Jupiter's 66 known moons. Watch from night to night as the moons change their positions around Jupiter. The nights of Nov. 16, 23 and 30 will be particularly good nights to observe the moons, when all four will be near their greatest elongations from the planet and easiest to spot. With a medium-sized telescope, you also should see the two main cloud stripes straddling Jupiter's equator and maybe even the famous Great Red Spot.
This year, Jupiter shines down on us from one of the most magnificent constellations, Taurus the Bull. That places it very close to the bright orange star Aldebaran and not far from the glittering Seven Sisters, or Pleiades, star cluster.
As a prelude to the Dec. 2 opposition, don't miss dazzling Jupiter rising only 1 degree from the full "Long Night Moon" at dusk Nov. 28.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. Check out Westlake's astrophotography website at http://www.jwestlake.com.