This week, Jupiter stands at “opposition” (to the Sun), when it’s closest to us, and brightest and biggest of the entire year.
You’ve already probably noticed it. It’s that single ultrabright “star” in the east during the first part of the night, and in the south after 11 p.m. Since it is now 15 times brighter than any other starlike object, it’s pretty hard to miss.
Jupiter’s oppositions occur a month later each year, because each time our planet catches up to it in space, it has moved on a bit in its 12-year orbit. This year it’s in Leo, which is a northerly constellation and thus makes it ascend pretty high during the night.
Its 50-arcsecond diameter is enough to show a little disk through plain, steadily braced binoculars. Viewed with even the smallest telescopes, Jupiter is a worthwhile target. Its four planet-class satellites become instantly obvious – though one of them, usually Io, often darts invisibly in front of or behind the planet. The moons always appear in a straight line, since they encircle Jupiter’s Equator, which in turn moves through space horizontally. Like Mercury, this planet travels with virtually no tilt to its axis.
Its second moon, Europa, remains the likeliest place for extraterrestrial life. Its warm salty oceans get replenished with amino acids from incoming comets. If life isn’t swimming there, then it’s probably a rare phenom in the cosmos.
Alas, from our region, the night air is almost in a state of blurriness, characterized to the naked eye by twinkling stars. So if you do have a telescope, first check out whether the stars are dancing or calm before dragging it out. A night with a little haze is usually best. Even on blurry nights, when only low power must be used to minimize distortion, you’ll still see Jupiter’s disk and its moons. Using moderate magnifications of 50 to 100 power, its disk will be more than twice the width that our Moon shows to the naked eye: plenty big enough to allow its parallel dark and light bands and belts to be obvious.
Only on the rare, steadiest nights, however, and with good equipment, will you glimpse the white ovals, the famous Red Spot (which is actually now orange, and has been shrinking the past few years) and wonderful curlicues and festoons for which the giant planet is famous. There are even blue diagonal blotches where we peer deepest through breaks in the clouds, to see Jupiter’s innermost blue sky! This is the planet that shows the most detail of any in the whole universe.
But if all you have is the naked eye, fine. Look anytime this next month after around 6:30 p.m. When you’ve spotted the creamy yellow/white of the sky’s brightest star, go ahead and salute this closest approach of the largest planet.
Want to know more? To read Bob’s previous “Night Sky” columns, visit our Almanac Weekly website at HudsonValleyAlmanacWeekly.com.