Jupiter takes the high arc
Jupiter is named after the king of the gods, according to old Roman mythology. It's not only visible all night long right now, but it's also about as close to Earth as it’ll be in 2011.
This week, it’s about 372 million miles away. It is the brightest star-like object in the night sky. You can easily see it in the low eastern sky as evening begins; through the rest of the night, it’ll take a high arc westward across the southern half of the sky.
For early risers, Jupiter can still be seen in the western sky as it prepares to set around sunrise.
Just a few weeks ago Jupiter reached what astronomers call opposition. It’s called that because just like a full moon, Jupiter and the sun are at opposite ends of the sky.
This happens because Earth lies between the sun and Jupiter. Because they’re at opposite ends of our celestial dome, as soon as the sun sets in the west, Jupiter rises in the east, and vice versa.
You can also see that geometrically, Jupiter and the Earth are at their minimum distance from each other. Earth and Jupiter get into the opposition position every 399 days. That’s because it takes Earth a little more than 365 days to make one complete orbit around the sun, while it takes Jupiter 12 years to make its much larger solar circuit.
So in the year’s time that Earth takes to circle the sun, Jupiter’s only 1/12 of the way around it. It takes Earth about another month to catch up to where it’s once again in line between the sun and Jupiter.
Bands of Jupiter
With even a small telescope, not only can you easily see Jupiter’s moons, but you can also clearly resolve the disk of the planet and maybe some of its cloud bands and zones that stripe it.
Jupiter is mostly a big ball of hydrogen and helium gas, but in its outer atmosphere there’s methane, ammonia, sulfur and other gases that create the multi-color cloud bands. There are two darker bands of clouds on either side of Jupiter’s equator that are the easiest to spot.
There are also storms circulating in Jupiter’s upper atmosphere, with the biggest one known as the Great Red Spot, which is three times the diameter of Earth. This giant hurricane-like storm has been raging on Jupiter for hundreds of years.
Despite its moniker, the Great Red Spot isn’t all that red, but instead more of a pale pink. Unless you have a moderate to large telescope and clear conditions, it’s hard to spot it in Jupiter’s southern horizon.
What also make it tough to see is that it’s not always facing Earth. That’s because Jupiter rapidly rotates on its axis once every 10 hours, so half of the time the Red Spot is facing away from us.
In general, viewing Jupiter through a telescope requires patience. First, wait until Jupiter is at least 30 degrees above the horizon so you don’t have to look through as much of Earth’s blurring atmosphere to see it. This week it should be high enough for decent viewing after about 7 p.m.
Also it’s a good practice whenever you have your telescope trained on any of the planets to take long continual views through the eyepiece. That’ll not only give your eyes a chance to get used to the light level within the eyepiece, but you’ll also have a better chance of catching clearer views of Jupiter.
Get used to seeing Jupiter in our night sky as it’ll be visible through late March.