Saturn shines big and bright
The ringed planet reaches its closest point to Earth.
January 11, 2005
Saturn's high-altitude clouds are made of colorless ammonia ice. Above these clouds is a layer of haze or smog, produced when ultraviolet light from the sun shines on methane gas. The smog contributes to the planet's subtle color variations. One of Saturn's moons, Enceladus, is seen casting a shadow on the giant planet as it passes just above the ring system.
Photo by AURA / STScI / NASA
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January 11, 2005
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|IN THIS RELEASE: CLOSE TO THE RINGMASTER — RINGS TILT TOWARD US — ALL EYES ON SATURN — SATURN FACTS — SATURN'S RINGS FACTS — SUPPLEMENTAL INFORMATION — ASTRONOMY MAGAZINE'S EXTENSIVE CASSINI COVERAGE|
WAUKESHA, WI — On January 13, Saturn reaches its closest point to Earth and shines at its brightest. Using telescopes, binoculars, even just the naked-eye, people can enjoy a view of Saturn. Through a telescope, Saturn is one of the most striking objects visible in the night sky with its pale sphere set within the bright, broad set of rings.
The ringed planet reaches its closest point just 1 day before the European Space Agency's Huygens probe plunges into the atmosphere of Saturn's largest moon, Titan. So while people are looking at the bright planet, Huygens prepares for its historic, fateful trip to the surface of Titan.
Saturn is easy to find near the brightest stars of Gemini — Castor and Pollux — as darkness falls. On January 13, Saturn rises in the east at sunset, reaches its highest point in the sky at midnight, and sets in the west at dawn. Because Saturn is opposite the Sun as seen from Earth then, astronomers term this event "opposition." Oppositions occur each time faster-moving Earth laps farther planets as they orbit around the Sun.
Close to the ringmaster
Saturn follows a slightly stretched-out orbit that brings it closest to the Sun every 29.5 years. It reached that point in 2003 and has been moving farther from the Sun ever since. So, during the next few weeks, the ringed planet offers observers their best views for decades to come.
At opposition, Saturn lies 750 million miles (1.2 billion kilometers) from Earth. Even at its closest, Saturn is so far away that the light we see — and data sent from the orbiting Cassini spacecraft and Huygens probe — takes 1 hour, 7 minutes to reach us.
Rings tilt toward us
At each opposition, we see Saturn's beautiful ring system at slightly different angles because Saturn itself is moving around the Sun. Right now, the tilt is 23° and near its maximum, but the rings will appear less distinct at coming oppositions until 2009. At that point, Earth passes through the rings' plane and the rings will all but disappear. They continue to open each successive year until 2016, when then the process reverses.
All eyes on Saturn
Amateur astronomers aren't the only ones excited about Saturn's opposition. The alignment between Earth, Sun, and Saturn is so good that, seen from Saturn, Earth would appear in silhouette crossing the Sun's disk.
Astronomers plan to monitor the ringed planet from 10 observatories around the world — and with the Hubble Space Telescope — to record how the ringed planet's icy moons brighten as sunlight strikes them face-on. Called the "opposition effect," the moons can shine up to 20 percent brighter when Saturn, Earth, and the Sun align. Such an alignment won't occur again until 2020.
For more information on the Saturn opposition observing campaign including the 10 observatories and Hubble, visit
Saturn viewing conditions — brightness, ring orientation, and closeness to Earth — will not be as favorable as this year's until the opposition of 2029. Saturn would hold 9.5 Earths spread across its face. It is the second-largest planet in the solar system and has a diameter of 74,900 miles (120,500 kilometers). Saturn takes 29.5 Earth-years to orbit the Sun. Saturn will reach its next farthest point from the Sun in 2018 and its next closest pass to the Sun in 2032.
Saturn's rings facts
Earth crosses the plane of Saturn's rings in September 2009, when they will appear edge-on. The main rings cover an area of just over 15 billion square miles (40 billion square kilometers), or 80 times Earth's total surface area. The rings span 174,000 miles (280,000 km), or about 73 percent of the distance separating Earth and the Moon. It's little wonder the rings vanish when they're seen edge-on to Earth — they are less than 100 feet (30 meters) thick. The total amount of material in the rings is surprisingly small, about the same mass as Saturn's moon Mimas (120 miles, or 195 km across). In 1676, Giovanni Domenico Cassini (1625-1712) observed a gap in the rings known today as the Cassini Division. It's caused by the gravity of the saturnian moon Mimas. Other, smaller gaps are associated with different saturnian moons. The Cassini spacecraft flew through the Cassini Division when it entered orbit around Saturn June 30, 2004. In 1858, physicist James Clerk Maxwell (1831-1879) proved the rings are made of billions of particles orbiting independently.
More information on Saturn from Astronomy magazine:
Astronomy magazine's extensive Cassini coverage
In-depth information on this landmark mission can be found in "Journey to Saturn," an 8-page feature in the January 2004 Astronomy magazine.
The article includes a graphical summary of Cassini's long journey; images of Saturn's atmosphere; top 10 (projected) Cassini mission highlights; information on the spacecraft namesakes: Giovanni Cassini and Christiaan Huygens; a summary of Huygens' instruments — with a full-color illustration of Huygens' descent; and, an overview of Saturn's medium-size moons.
For a copy of this issue, please contact Matt Quandt: firstname.lastname@example.org or 262.796.8776 x419.
Astronomy magazine and Astronomy.com will keep you abreast of the latest findings from both Cassini and the Huygens probe.
Saturn is at its closest and brightest January 13, 2005.
Saturn and its moons as seen through a telescope on January 14, 2005, the day Huygens arrives at Titan.
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