Tonight Jupiter is at opposition and shines more brightly now than at anytime this year. Go out and get an eyeful while it’s so close to Earth. Opposition means opposite the sun, and that’s exactly where the planet will be – when the sun retires in the west this evening, Jupiter will rise 180 degrees opposite in the eastern sky. The king of the planets stays up all night long, inviting sky watchers of all kinds to marvel at his radiance.
Jupiter is located under the Square of Pegasus in the dim constellation Pisces, but you don’t really need a constellation to point you to it. The stars of Pisces and its neighbors can’t hold a candle to Jupiter’s brilliance, which is one the reasons the planet dazzles in the southeast after 9 o’clock. No competition means Jupiter rules.
When a planet’s at opposition, it lines up with Earth on the same side of the sun. All the outer planets from Jupiter to Neptune reach opposition once a year when the speedier Earth laps the slower-orbiting outer planet. Oh, and there’s Mars. Because it’s the closest outer planet and moves relatively quickly, it takes Earth a while longer to catch up and finally pass the planet; Mars oppositions occur about once every two years.
This particular Jupiter opposition is the closest since 1963 for one very good reason – Jupiter is close to perihelion. Let me explain. All the planets revolve about the sun in ellipses (ovals) rather than perfect circles. This means their distances from the sun vary over time as they curve around one end of the ellipse and then back over to the other. Earth’s elliptical orbit brings it 3 million miles closer to the sun in January than in July. Jupiter takes 12 years to orbit the sun. During that time its distance varies from 461 million miles to 507 million, a difference of 46 million miles from one end of the ellipse to the other.
When a planet is closest to the sun, it’s said to reach perihelion. Earth is at perihelion once a year in January. Jupiter reaches perihelion once every Jupiter year which is equal to 12 Earth years.
Turns out, Jupiter’s perihelion is coming up very soon – next March as a matter of fact. Tonight’s opposition happens to nearly coincide with Jupiter’s perihelion (closest approach to the sun), which means it’s especially close to the Earth. Next year, when Earth swings between Jupiter and the sun again, Jupiter will have moved past perihelion and be a smidge farther away than it is tonight.
“I Saw Her Standing There” from Please, Please Me
1963 seems like a long time ago. That was the year the Beatles released their debut album “Please, Please Me”, zip codes were first introduced in the U.S. and Martin Luther King delivered his “I Have a Dream” speech. Jupiter was in Pisces back then, too, and will when it’s close again in 2022.
A close approach like this one means the planet appears larger than usual and brighter as well. If you own a telescope, this year will be one of the best of the next 12 years to study the planet. And don’t fret if it’s cloudy tonight. Jupiter will appear nearly as bright and large well into the fall. 2022? I hope to be alive then, but just in case, I plan to scrutinize the face of the mighty planet at every opportunity this season.