By Scott Levine
If you can believe it, the end of June brings us to the midway point through another trip around the sun.
This doesn’t really change anything, but it’s interesting to know that everything in space is always moving, including us. By the end of this week, we’ll have more 2020 behind us than ahead.
Earlier this year, we talked about the great pleasure of seeing brilliant Venus shine in our evening skies before it moved into the mornings a few weeks ago. Venus isn’t the only planet we can see in our skies, of course.
Tracking planets is a hobby that goes back to the ancients, who noticed some stars wandered and changed their positions among the others from one night to the next. In fact, the word planet comes from the Greek word for wanderer. They didn’t know they were seeing those other worlds moving in their orbits through space, as well as us moving in ours.
As the second half of the year starts, Jupiter and Saturn, the fifth and sixth planets from the sun, are easy to see in the evening’s southern skies. They’re the two biggest planets, but they’re also the two farthest things that most of us can see with the naked eye without leaving the solar system; about 500 million and a billion miles away.
This means that while they certainly stand out – Jupiter’s the fourth brightest object in the entire sky – they don’t always shout at you the way Venus does. If you’ve never tracked down a planet before, it’s surprisingly easy and a fun trick to share with friends.
First, get a feel for the ecliptic, the path the sun takes across the sky. All the major planets orbit around the sun’s midsection, so the ecliptic also roughly represents the plane of the solar system. Just follow the sun during the day, and then imagine that path at night. All the planets are always somewhere near that line.
Also, planets don’t twinkle the way stars do. Since planets are so close to us as these things go, we don’t just see them as one point, like the much more distant stars. Instead, we see them as many points, so their light seems much steadier. You may never have noticed, but you may even see them as small disks.
Once you’ve spotted something in the right place, with the right shape, follow it for a couple of nights. If it hops from place to place relative to other stars, congratulations! We’ll keep an eye on this pair as the year goes along, but as it happens July is a fantastic month to watch them.
On July 5, the just-past-full moon slides by and makes a gorgeous upside-down triangle with the two giant planets: Saturn to Jupiter’s left, with the moon below.
Come July 14, Jupiter will be directly opposite the sun from our point of view, an arrangement called opposition. Just a few days later, on July 20, it’ll be Saturn’s turn. Typically, opposition is when an object is at its brightest and easiest to see, so those are especially great nights to try to check them out.
Hunting down planets and imagining the constant motion of the solar system can be a great way to spend a few minutes on these short summer nights. I hope you’ll take a look.
Scott Levine (firstname.lastname@example.org) is an astronomy writer and speaker from Croton-on-Hudson. He is also a member of the Westchester Amateur Astronomers, which is dedicated to astronomy outreach in our area. For information about the club, including membership, newsletters, upcoming meetings and lectures at Pace University and star parties at Ward Pound Ridge Reservation, visit westchesterastronomers.org. Events are free and open to the public. Please note: All in-person club activities are suspended until further notice due to COVID-19.