Tonight – October 16, 2014 – stay up later than you usually do and watch for the moon and Jupiter to rise over the eastern horizon in the wee hours after midnight. The moon will rise first, followed by the dazzling planet Jupiter about one-half hour later. Once the moon and Jupiter climb over the east-northeast horizon, they’ll be out until dawn. By tomorrow before dawn (October 17), you’ll be looking high in the east for the waning crescent moon and Jupiter.
At present, Jupiter shines near the border of the zodiacal constellations Cancer and Leo. If you’re up before the sun, you can also see Leo’s brightest star, Regulus, beneath the moon and Jupiter.
As seen from Earth, the moon looks much larger than Jupiter. But Jupiter is actually much larger than our moon. The moon only appears bigger, because it’s so much closer to us. Astronomers often list distances of solar system objects in astronomical units. The astronomical unit equals the sun-Earth distance, a measure of about 150,000,000 kilometers (93,000,000 miles) or 8.3 light-minutes. This evening, the moon is about 1/400 of an astronomical unit away. Meanwhile, Jupiter resides more than 5.6 astronomical units from Earth. That places Jupiter over 2,000 times farther away than tonight’s moon.
Jupiter’s diameter is about 40 times greater than our moon’s diameter. To gauge the size of our moon relative to Jupiter, look at Jupiter though a backyard telescope sometime. Jupiter’s four major moons – called the Galilean moons – are pretty easy to see. You might miss a moon or two on occasion, because these moons routinely swing in front and in back of Jupiter. In their outward order from Jupiter, these moons are Io, Europa, Ganymede and Callisto. Io and Europa are about the same size as our moon, whereas Ganymede and Callisto have diameters of about 1.5 times that of our moon.
It’s best to view Jupiter’s moons with the telescope, though it’s possible to glance at them through binoculars. It’s often difficult to get a crisp focus on sky objects near the horizon because of the greater thickness of the Earth’s atmosphere. If you’re not an early morning person, wait till January 2015 or February 2015 to see Jupiter in the early evening sky. On February 6, 2015, Jupiter will be at opposition – opposite the sun in Earth’s sky – so the king planet will be out all night long and conveniently placed for evening viewing.
Bottom line: The bright object near the moon – from the wee hours after midnight on October 17, 2014 until the hours before dawn – is the giant planet Jupiter.