Magazine article Science News

An Asteroid Hunt Finds Mysterious Object

Magazine article Science News

An Asteroid Hunt Finds Mysterious Object

Article excerpt

It took astronomer James V. Scotti several nights before he detected a puzzling pattern in a series of images taken three weeks ago with a telescope atop Arizona's Kitt Peak. These images reveal the motion of a mysterious object that in astronomical terms will come a hair's breadth from Earth on Dec. 5 -- passing within 468,000 kilometers, or a little more than the distance between the Earth and the moon.

Could the object, no more than 10 meters across, represent a nearby asteroid? Leftover debris from a space mission? An alien spacecraft? As recently as last week, researchers had ruled out only the last possibility. This week, some say the mystery appears solved.

Brian G. Marsden of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., traced back in time the apparent orbit of the unknown object -- dubbed 1991 VG. His calculations indicate that this body probably constitutes a remnant of the rocket that in December 1974 launched Helios-A, a spacecraft that studied the sun.

Scotti calls the conjecture "circumstantial evidence" that will likely remain incoclusive unless researchers can analyze how the body reflects sunlight--no mean feat since the tiny object, though nearby, appears as only a faint speck of light. Irregularly shaped spacecraft debris should tumble faster than an asteroid, he notes, thus exhibiting greater variations in the amount of sunlight it reflects. A natural body would also absorb specific wavelengths of light and thus be distinguishable from metallic debris when viewed through colored filters.

Such analyses may require a larger telescope than the 0.9-meter Kitt Peak instrument called Spacewatch, used since 1990 by Scotti, Tom Gehrels, David Rabinowitz and their colleagues at the University of Arizona in Tucson to automatically scan the sky for fast-moving objects. Indeed, Marsden notes, the European Southern Observatory in Garching, Germany, and several other research groups with large telescopes plan to monitor the body in coming weeks. …

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