69230 Hermes
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69230 Hermes is an Apollo, Mars- and Venus-crosser asteroid that passed within 0.005 AU of the Earth (approximately 1.5 the distance of the Moon) on October 30, 1937.
At the time, this was the closest known approach of an asteroid to the Earth. Not until 1989 was a closer approach observed (by 4581 Asclepius). At closest approach, Hermes was moving 5° per hour across the sky and reached 8th magnitude.
It was discovered by Karl Reinmuth in images taken on October 28, 1937. Only five days of observations could be made before Hermes became too faint to be seen in the telescopes of the day. This was not enough to calculate an orbit, and Hermes was "lost". It thus did not receive a number, but Reinmuth nevertheless named it after the greek god Hermes. It was the only unnumbered but named asteroid, having only the provisional designation 1937 UB.
In October 2003, Brian A. Skiff of the LONEOS project made an asteroid observation that, when the orbit was calculated backwards in time, turned out to be a rediscovery of Hermes. The orbit is now well known, and Hermes has been assigned sequential number 69230. In retrospect it turned out that Hermes came very close to Earth a second time in 1942 with 1.6 moon distances without being observed.
Hermes is an S-type asteroid, and radar observations showed it to be a binary asteroid with two equal-sized components almost in contact with one another. Each component is about 300–450 metres in diameter.
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