The best time of 2013 to see Saturn is around now. Our planet Earth flies between the sun and Saturn today – Sunday, April 28, 2013. So Saturn is rising at sunset around now and visible all night long.
After tonight, Saturn will still be visible and in a good place to observe. Throughout May 2013, you’ll find Saturn in the eastern sky as night falls. It’ll ascend in the east during the evening hours.
Our fast movement in orbit brings us between Saturn and the sun every year. The April 28 event is called opposition by astronomers. Opposition also brings Saturn closest to Earth for all of 2013. As a result, in late April and throughout May 2013, Saturn is shining most brilliantly in our sky for the year. If you recognize it tonight or in the coming month, you’ll also enjoy it throughout the Northern Hemisphere summer, or Southern Hemisphere winter.
If you had a bird’s-eye view of the solar system today, you’d see our planet Earth passing in between the sun and Saturn. You’d see the sun, Earth, and Saturn lining up in space. But not for long. Earth moves in orbit at 18 miles per second in contrast to about 6 miles per second for Saturn. Soon, we’ll be pulling ahead of Saturn in the race of the planets.
The inner planets – Mercury and Venus – can never be at opposition, because they orbit the sun inside Earth’s orbit. Only the planets that orbit the sun beyond Earth’s orbit – Mars, Jupiter, Saturn, Uranus and Neptune – can ever reach opposition, that is, appear opposite the sun in Earth’s sky.
All the planets farther from the sun reach opposition every time our swifter-moving planet sweeps between the sun and them. That happens about once a year, since Earth takes a year to orbit the sun once, and since these outer worlds move more slowly than we do.
Saturn, the 6th planet outward from the sun, is the most distant world that’s easily visible to the unaided eye. The ringed planet returns to opposition about 2 weeks later every year. Telescopes revealed its rings in the 17th century. Spacecraft in the 20th century revealed that what we thought of as three rings around Saturn is actually thousands of thin, finely detailed rings – made of tiny chunks of ice. Saturn also has 62 moons with confirmed orbits. Only 53 of Saturn’s moons have names, and only 13 have diameters larger than 50 kilometers (about 30 miles). Saturn is truly a wondrous world of rings and moons. It’s everyone’s favorite thing to see through a small telescope, so if there’s a public astronomy night near you this month – go!
How can you find Saturn in 2013? It’s not hard to find the ringed planet this year. The planet appears to the east of the blue-white star Spica on the sky’s dome. Saturn itself is golden in color, so you should be able to tell the planet from the star. How can you find Spica? Use a phrase familiar to stargazers: follow the arc to Arcturus and drive a spike to Spica. In other words, first locate the Big Dipper in the northeast now in the evening. Follow the curve in its handle until you come to the orange star Arcturus in the constellation Bootes. Extend that line until you the star Spica. The planet Saturn will be lower in the sky, about 15o below Spica. For reference, a fist at an arm legth approximates 10o of sky.
Bottom line: Look for Saturn at opposition tonight, April 28, 2013. It will be shining in the east at nightfall, below the bright star Spica. To the eye, the ringed planet looks like a respectably bright steady star. Saturn follows Spica across the sky tonight and reaches its highest point around midnight. When Saturn climbs high in the sky, where Earth’s turbulent atmosphere thins out and settles down, Saturn is a treat for telescope users, who can view the planet’s glorious rings. Can’t see Saturn on April 28? No problem. It’ll be in an excellent place to observe throughout May 2013.