If you have a new telescope, now's a great time to give it the acid test because Saturn's on the rise in the early evening sky. It's the brightest star-like object you see in that part of the celestial dome. The next brightest is Antares, a star with a ruddy glow that serves as the brightest star in the constellation Scorpius the Scorpion.
Without a doubt Saturn is my favorite telescope target. It's so beautiful. I know that I've won over many people at my stargazing parties when they've seen Saturn through my telescope for the first time. I love hearing the oohs and aahs.
The sixth planet out from the sun in our solar system is basically a ball of hydrogen and helium gas about 75,000-miles in diameter. This makes it the second largest planet in our solar system. Believe it or not, this planet's density is less than that of water, so if you could get a swimming pool big enough, Saturn would float on it like a colossal beach ball. Saturn's hallmark, though, is its wonderful, intricate ring system that spans a diameter more than 175,000 miles, more than half 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 of 24 degrees to our line of sight, making it really visible to us. Keep in mind that 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.
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, more than 3,200 miles in diameter. That's larger than the planet Mercury. Observations of Titan, including those of the Cassini spacecraft and Huygens probe, which actually landed on Titan some years back shows that it's a bizarre world with a heavy methane atmosphere and lakes and streams of liquid methane and other chemicals.
This month, Saturn is just about at it closest approach to the Earth for 2015 at about 837 million miles way. It was actually a little closer to the Earth last month, but I waited to write about viewing Saturn until now because at the end of evening twilight it's a lot higher above the horizon and there isn't so much of Earth blurring atmosphere between you and Saturn.
Why Saturn and Earth are so close together right now has to do with fairly simple orbital mechanics. Since Earth is a lot closer to the sun, it only takes one year to circle our home star, while Saturn takes almost 30 years to make its much longer circuit. As a result, once a year plus 23 days, Earth and Saturn make their closest pass to each other, something astronomers call opposition.
There's also a bonus to opposition time. Since Earth lies in a line between the sun and Saturn, the sun and the ringed wonder are at opposite ends of the sky, hence the term opposition. When the sun sets in the west, Saturn comes up in the east, and when the sun rises in the east, Saturn sets in the west. The bottom line here is that Saturn is visible all night long.
Unfortunately, even though we'll have Saturn in our evening skies through the rest of summer, it won't get all that high up in the heavens because where it is among the backdrop of stars this year. Since all the planets in our solar system orbit around the sun in nearly the same mathematical plane, they're all found in what's called the zodiac band which runs along either side of the ecliptic, the apparent path the sun seems to take among the stars as Earth orbits our home star.
Because of the tilt of Earth's axis, the zodiac band has its high points and low points in our celestial sphere. Unfortunately, this year Saturn's taken up residence in the lower reaches. So, even at its highest point Saturn's climbs into our sky isn't all that high. In fact, it'll only rise about a third of the way between the horizon and the overhead zenith in the southern sky. Saturn will be much more subject to the blurring effects of Earth's atmosphere than we would be if Saturn reached high into the celestial dome. This is what stargazers call "bad seeing".
Nonetheless, Saturn is ripe for the celestial picking all night long with your telescope but be patient. As it is with all planets, it's very important to take long uninterrupted views of it. You need to get your eye used to the light level in the eyepiece field. This also helps because the clarity of Saturn can vary from minute to minute and even second by second due to high winds in the Earth's atmosphere. Some nights will be better for viewing Saturn than others, even if the skies are still.
Enjoy the Lord of the Rings.
Celestial hugging
Jupiter and Venus, the brightest star-like objects in the early evening sky, continue to draw closer and closer to each other in the western sky. At the end of June and the beginning of July, they'll appear to be practically touching. Stay tuned.
(Lynch is an amateur astronomer and is author of the book, "Stars, a Month by Month Tour of the Constellations. Contact him at mikewlynch@comcast.net.)