Astronomy Picture of the Day 10-01-04

Explanation: On Wednesday, September 29, the Earth came within one million miles of the asteroid Toutatis -- the closest predicted aproach of our fair planet to a sizable asteroid or comet in this century. Coming within one million miles or about 4 times the Earth-Moon distance, Earth would appear to be nearly the size of the full moon in the asteroid's sky, as suggested in this illustration. In Earth's sky, Toutatis appeared only as a faint object rapidly moving against a background of stars. Also known as Earth-crossing asteroid 4179, Toutatis is in an eccentric 4 year orbit which moves it from the asteroid belt between Mars and Jupiter to just inside Earth's orbit. When the Earth passed near it in 1992 Toutatis was imaged by radar and seen to be two irregularly shaped lumps, perhaps joined by a narrow neck. This bizarre object is up to 1.5 miles wide, 3 miles long, and is tumbling through space. Studies of Toutatis and other Earth-crossing asteroids help reveal connections between the Solar System's meteorites, main-belt asteroids and comets. These asteroids also offer tantalizing targets for robotic exploration and, over time, represent potential collision hazards for planet Earth!

Music rings of Saturn
CASSINI PHOTO RELEASE
Posted: September 29, 2004

Looking something like the fibrous bow of a violin, Saturn's colorful rings sweep through this spectacular natural color view while two small moons look on.

Credit: NASA/JPL/Space Science Institute
Download larger image version here

From left, the moons visible here are Janus (181 kilometers, or 112 miles across) and Mimas (398 kilometers, or 247 miles across). Cassini's view in this image is from beneath the ring plane; the moons are on the far side of Saturn. Janus leads Mimas as the two moons orbit the planet.

Nearly the entire ring system can be seen in this view. The diaphanous C ring appears at the upper right, followed by the multi-hued B ring. Next, the famous Cassini division (4,800 kilometers, or 2,980 miles wide) separates the A and B rings. The outer edge of the B ring which forms the inner boundary of the Cassini division is maintained by a gravitational resonance with Mimas. Near the outer edge of the A ring are the Encke Gap (325 kilometers, or 202 miles wide) and the barely visible Keeler Gap (35 kilometers, or 22 miles wide). The faint, thread-like F ring is discernible just beyond the main rings.

The image was obtained with the Cassini spacecraft narrow angle camera on August 27, 2004, at a distance of 9.1 million kilometers (5.6 million miles) from Saturn. Images taken with red, green and blue filters were combined to create this color view. The moons have been enhanced in brightness to increase their visibility. The image scale is 54 kilometers (34 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras, were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

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