Asteroid 243: a moon of its own?ASTEROID 243 Ida: A moon of its own?
Ida appears to have a friend.
An image of the asteroid 243 Ida, being radioed piecemeal to Earth by the Galileo spacecraft, indicates that the rocky body has a tiny moon orbiting it. If confirmed when Galileo finishes transmitting the image late this month, this would be the first moon of an asteroid ever detected.
During a brief photo session with Galileo last August, Ida became the second asteroid ever to be imaged from space (SN: 11/6/93, p.300). But because the craft's main antenna never fully opened, Galileo couldn't radio the pictures immediately Instead, it stored them on a tape recorder tape recorder, device for recording information on strips of plastic tape (usually polyester) that are coated with fine particles of a magnetic substance, usually an oxide of iron, cobalt, or chromium. The coating is normally held on the tape with a special binder. for transmission later at a much slower rate by a less powerful antenna.
One complete image, a high-resolution portrait of the 56-kilometer-long asteroid received in September, gave no hint of a moon. But parts of a second, lower-resolution image reveal an intriguing feature.
Galileo began sending this image 3 weeks ago. The trickle of data received so far - thin, widely spaced strips of the full picture - shows a bright area distinct from the asteroid. This bright patch appears to be sunlight reflecting off a neighboring neigh·bor
1. One who lives near or next to another.
2. A person, place, or thing adjacent to or located near another.
3. A fellow human.
4. Used as a form of familiar address.
v. body, probably a moon of the asteroid, says Galileo project manager William O'Neil
Jet Propulsion Laboratory (JPL) is a NASA research center located in the cities of Pasadena and La Cañada Flintridge, near Los Angeles, California, USA. in Pasadena, Calif.
He says it's less likely, though possible, that the body, instead of orbiting Ida, simply happened to pass near the asteroid during Galileo's flyby fly·by also fly-by
n. pl. fly·bys
A flight passing close to a specified target or position, especially a maneuver in which a spacecraft or satellite passes sufficiently close to a body to make detailed observations without , The size and proximity of the body to Ida remain unknown.
O'Neil notes that researchers think the patch is real because two instruments aboard Galileo, the solid-state imaging camera and the near-infrared mapping spectrometer spectrometer
Device for detecting and analyzing wavelengths of electromagnetic radiation, commonly used for molecular spectroscopy; more broadly, any of various instruments in which an emission (as of electromagnetic radiation or particles) is spread out according to some , both indicate the same feature. "It's not a surprise," he says, to find that an asteroid has a moon. But until the Galileo encounter, O'Neil adds, astronomers Famous astronomers and astrophysicists include:
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