Tonight – June 2, 2016 – according to clocks in North America, our planet Earth will fly between the ringed planet Saturn and the sun, bringing Saturn to what astronomers call opposition. In other words, Saturn is opposite the sun now. This is a big milestone for our year of observing the ringed planet! We go between Saturn and the sun on June 3 at 0700 UTC. For the Americas, that places Saturn’s opposition on June 3 at 3 a.m. EDT, 2 a.m. CDT, 1 a.m. MDT and midnight PDT.
So this is Saturn’s special day, its yearly opposition, when Saturn is opposite the sun in Earth’s sky. As a consequence, Saturn rises in the east at sunset, climbs highest up for the night at midnight and sets in the west at sunrise. It is visible all night, closest and brightest for this year.
Although Saturn comes closest to Earth for the year on the same date that it reaches opposition, the ringed comes nowhere as close to Earth as the above diagram might lead you to believe. At present, Saturn lies some 10 times the Earth’s distance from the sun, or 9 times the Earth-sun distance from Earth. (Astronomers refer to the Earth-sun distance as the astronomical unit.) For a realistic depiction of Saturn’s size relative to that of our planet Earth, take a good look at the illustration below.
Top 3 tips for recognizing Saturn. Don’t assume this is a one-night-only event. Saturn’s opposition guarantees the ringed planet will be in good view throughout June and July 2016. Here are three tips for recognizing it:
1. Saturn near the planet Mars, which was closest to Earth on May 30 and is now extremely bright, brighter than any other object in the eastern half of the sky each evening. Find Mars, and you can find Saturn nearby.
2. Saturn is also near the star Antares in the constellation Scorpius the Scorpion. Antares is not as bright as Mars, but it is a reddish star, bright and a great twinkler.
3. Saturn, Mars and Antares make a triangle on the sky’s dome. Very noticeable. If you have a dark sky, you’ll see that this triangle places Mars and Saturn on opposite sides of the arc of three stars close to Antares in the night sky, called the Crown of the Scorpion. See the chart above.
Saturn will remain a fixture of the evening sky until October 2016. All the while, golden Saturn shines in close vicinity of ruddy Antares, the brightest star in the constellation Scorpius the Scorpion, and to very bright Mars.
What is opposition? Our fast movement in orbit brings Earth between Saturn and the sun every year – or, more precisely, about two weeks later every year. Two years ago, for instance, Saturn’s opposition happened on May 10, 2014. Last year, in 2015, it was May 23. This year, opposition happens on June 3, 2016. Next year, in 2017, Saturn’s opposition will come on June 15. If you recognize this golden world tonight or later this 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 these superior planets – planets that orbit the sun outside of Earth’s orbit. Mars returns to opposition every other year. Jupiter’s opposition happens about one month later each year, whereas Saturn’s opposition occurs about two weeks later yearly. The farther that a planet resides from the sun, the shorter the period of time between successive oppositions.
Saturn, the 6th planet outward from the sun, is the most distant world that’s easily visible to the unaided eye. Telescopes revealed its rings in the 17th century. Spacecraft in the 20th century revealed that what we thought of as three rings around Saturn to be 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 celestial object to gaze at through a small telescope, so if there’s a public astronomy night near you this month – go!
Bottom line: Look for Saturn at opposition tonight – June 2-3, 2016. It will be shining in the east this evening, above the bright star Antares. Can’t see Saturn tonight? No problem. It’ll be in an excellent place to observe throughout June and July 2016.