Jupiter is a brilliant point of light in the south among the stars of Ophiuchus. Watch it make close encounters with the moon and an asteroid.
That bright star in the south is not a star at all, but the largest planet in our solar system, Jupiter. It has been making its way across the southern sky all summer. It continues its low slide along the southern horizon, heading west, where it will set with the sun in mid-December 2007.
Jupiter starts out in August of 2007 very close to Omega Ophiuchi, a 4.45 magnitude star. If you look at Jupiter through binoculars or a telescope you will see Omega so close that it looks like an additional moon. The actual moons of Jupiter: Io, Europa, Ganymede, Callisto, listed in order from closest to the planet to furthest, can be seen with a simple pair of binoculars. These Galilean moons are the largest of Jupiter, and Ganymede is the largest moon in the solar system. If you can't see all of them, it means one of them is currently in front of or behind the planet. Wait a couple hours and look again, you will see how the satellites have changed their positions.
If you have a telescope you can also watch as the face of Jupiter changes. Its day is 10 hours, which means that in five hours' time it will rotate halfway around and you will see an entirely new face on Jupiter. Watch the Great Red Spot rise and set on the planet.
Throughout August and September, the bright star directly below Jupiter is Antares. Antares is the brightest star in Scorpius at magnitude 1. Jupiter is close to the border with Scorpius but is in the constellation Ophiuchus. Two bright 2nd magnitude stars are above Jupiter - Eta Ophiuchi to the upper left (in late summer) and Zeta Ophiuchi to the upper right.
Two globular clusters are close to Jupiter and one can even be glimpsed the without binoculars. M4 is 5.9 magnitude and lies just over one degree to the right and a little below Antares. M80 is just under four degrees to the upper right of M4 and is magnitude 7.
In August, Jupiter will also have a brush with the fourth asteroid to be discovered, Vesta. Start looking on August 23. Jupiter is magnitude -2.27. Vesta is just above Jupiter and to its right. You will need a pair of binoculars or a telescope to spot it. (Keep in mind that if you are looking through a telescope, the image is upside down, so Vesta will be below, and not above, Jupiter.) Come out every clear night for the next two weeks and look again. Do you see the 7.09-magnitude point of light that is Vesta, slowly moving past Jupiter? On August 27, the two are only 25 arcminutes apart, with Vesta directly above Jupiter. Vesta and Jupiter will part ways, with Jupiter sliding to the west and Vesta heading to the east.
The Moon makes beautiful pairings with Jupiter each month. On August 21, the moon is just below the star Antares and six and a half degrees from Jupiter. On September 18, the moon and Jupiter are a wider nine degrees apart. On October 15, a beautiful 19 percent lit moon lies six and a half degrees below Jupiter. And on November 12, a crescent moon only eight percent lit glides five and a half below Jupiter.
Jupiter is sinking toward the southwest horizon throughout fall but because the days are getting shorter, it manages to stay up after sunset until mid-December, when it joins the sun during sunset.
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