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LOST AND FOUND
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The minor planet Hermes has eluded astronomers since its close pass by Earth
in 1937. Astronomers knew that it had passed uncomfortably close to Earth,
but just after it passed by its unlit side was available. It faded from
magnitude 8 to magnitude 21, dimming by a factor of 60,000 times, in a couple
of days. After being tracked for only 5 days, with a scant 16 sightings,
of which 7 are now known to be inaccurate, the object was lost in the sun's
glare. Its orbit could not possibly be determined from that information.
For 66 years it remained the "loose cannon" of minor planet research -
a potentially hazardous asteroid that was following an unknown course through
space and occasionally approaching Earth.
Its recovery on October 15, 2003, made instant headlines in the astronomical
community, and around the world. When a bright, fast-moving object was
spotted that evening, it was almost immediately identified as Hermes.
Within days it had received extensive coverage, with optical and radar telescopes,
and had been linked to objects in pre-discovery photographs from 2001, 2002 and
2003. It is now numbered (69230).
With its orbit now very precisely known, it provides an excellent case study in
the choatic orbits of objects that pass so close to planets. Hermes frequently
passes very close to Venus, Earth, Mars, and Vesta. Its orbit is frequently
reshaped by these encounters, requiring intensive computer work to determine its
course.
It was found that Hermes passed only 741,000 km from Earth on October 30, 1937.
It passed even closer (without being spotted) on April 26, 1942, at only 634,000
km. This is just about as close as it can get in its current orbital path.
Between 1937 and 2003, it made a total of 8 close passes (< 9 million km) to either
Venus or Earth. It passed 7,157,000 km from Earth on November 4, 2003, and was
last seen on November 7, 2003.
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This animation, taken November 1, 2003, shows how quickly Hermes moved in just 5
minutes. It can be seen just up and right from center. Assembled from 4
exposures, clear filter, 30-seconds exposure time each.
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