Starwatch: Saturn is the late-night telescope king

June 24, 2017 GMT

Since 1989, there have been nearly 3,500 confirmed extrasolar planets orbiting other stars, just in our immediate vicinity — our vast home galaxy, the Milky Way.

There are also nearly 5,000 possible planets discovered that haven’t been officially confirmed. On top of all that, since 2010 nearly 600 other solar systems have been confirmed.

We certainly haven’t been able to see any of these planets with much detail because of the vast distances, but that day may come. In the meantime, it’s hard to imagine a planet much more beautiful than our Earth. Second place, in my opinion, is Saturn, which is now joining Jupiter in our early evening skies. Unfortunately, early evening this time of year is a bit of an oxymoron for stargazing because of the late sunsets and twilights of the year.

Without a doubt, my absolute favorite telescope target since I was a kid has been Saturn. Even through a small telescope that gives you a really tiny image of Saturn you can see its ring system. That was a real thrill for me way back when, and now that that I’m blessed to own much larger telescopes, Saturn is over the top!

Even more fun for me is being able to show Saturn off over many years to hundreds and hundreds of folks at my astronomy programs, especially the kids. I never ever get tired of hearing excited reactions.

Close call

If you’ve never seen Saturn through any telescope, now is the time. This month, Earth and Saturn are at what astronomers call opposition, their closest approach to each other for 2017. This year Earth and Saturn are separated by just under 840 million miles.

Opposition occurs when the Earth, in its orbit around the sun, finds itself in a line between the sun and Saturn. This happens every 378 days or so, just over a year. As you can see in the diagram, it takes just over a year for this alignment to happen because in the year it takes our Earth to orbit the sun Saturn only moves about 1/29th of its orbital distance around the sun because of its much larger and slower orbit. It takes the Earth about two more weeks to once again be between Saturn and the sun.

Another great thing about viewing Saturn at opposition is that it’s available all night long, rising at sunset and setting at sunrise, just like a full moon.

So just as evening twilight is ending, look for the brightest “star” you can see in the very low south-southeastern Rochester sky. That’s Saturn! You can try to get a close look at it with your telescope then, but you’ll probably be disappointed because it’ll look really fuzzy. That’s because when you observe any celestial object when it’s low in the sky you have to look though more of Earth’s blurring atmospheric shell than you do when the target is higher, so my advice is to make a late-night viewing party for Saturn, and I mean really late, like after midnight.

What’s also a real bummer this summer is that even after midnight Saturn will still probably be a little blurry depending on humidity, wind, and other atmospheric conditions. Because of where it is among the background stars this year, Saturn is not going to get all that high, not much more than 20 degrees above the southern horizon at best. Unfortunately that’s the celestial card dealt to us this year.

Big rings

But Saturn still worth losing some sleep to check out. Like all the planets beyond Mars in our solar system, it’s basically a ball of hydrogen and helium gas about 75,000 miles in diameter. It’s the second-largest planet in our solar system.

Saturn’s hallmark, though, is its wonderful, intricate ring system that spans a diameter over 175,000 miles, more than half of the distance between Earth and its moon. Amazingly, the ring system is only about 50 feet thick!

The rings are made up of billions and billions of ice covered rocks, from the size of dust grains to more than the size of your house. Most likely these rocks are the pulverized remains of one or two of Saturn’s moons that were ripped apart by the planet’s tremendous tidal forces. As you gaze upon the rings, see if you can spot a black band right in the middle of the system. That gap in the rings is called Cassini’s division, and it is nearly 3,000 miles wide.

What’s really good about observing Saturn this year is that the tilt of Saturn’s ring system is nearly at its maximum to our line of sight, making it really visible to us. In fact, when you glance at Saturn with the naked eye, most of the light you see is sunlight reflecting off all the ice in Saturn’s rings.

Saturn’s moons

Along with Saturn’s rings, it’s also possible even with a small telescope to see some of Saturn’s larger moons, which look like tiny little stars surrounding the planet. The brightest and biggest is Titan, over 3,200 miles in diameter. That’s larger than the planet Mercury!

Enseladus, one of Saturn’s much smaller moons, is a strong candidate for possible life under its surface. The Cassini spacecraft that’s now plunging toward Saturn after an extremely successful 13-year-plus mission exploring around Saturn, has detected geysers of water shooting out of Enseladus.

When you’re viewing Saturn or any other planet with a telescope, it’s important to discipline yourself to take long continuous views through your ‘scope. Your eye needs to adjust to the level of light coming into your ’scope.

Also, because Saturn is such a “low rider” in the night sky this summer, you want to hang in there and keep your eye over that eyepiece long enough to catch at least brief better views of Saturn. If there’s pockets of calmer and clearer air between you and Saturn, you’ll be rewarded persistence for your telescope.

Enjoy Saturn. It’s the best!