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Icarus

Sky & Telescope, 50 & 25 years ago, September 1999, p. 12:

September 1949: On the evening of June 26, 1949, Dr. Walter Baade had
taken a 60-minute exposure near Antares with the new 48-inch Schmidt
telescope on Palomar Mountain. Upon examining the plate next day he came
across an asteroid trail so long that it would have covered a distance
equal to the apparent angular diameter of the full moon in 11 hours ...
"Two [crucial] positions of July 12th and 13th enabled the true
character of the orbit to be fixed without much further doubt. The mean
distance [from the Sun] barely exceeds one astronomical unit, which is
much smaller than that of any known asteroid or comet. At perihelion the
asteroid passes inside the orbit of Mercury to within 21 million miles
of the sun; while at aphelion it recedes beyond the orbit of Mars to a
distance of 177 million miles. The closest approach of the orbit of the
asteroid to the orbit of the earth occurs near the descending node, at a
distance of about 4,600,000 miles....
"[Baade] has the distinction of discovering the asteroid with the
smallest perihelion distance, and the first body aside from comets and
meteors [sic] to pass within the orbit of Mercury."

This asteroid became known as 1566 Icarus, a member of the so-called
Apollo group. Its namesake was first observed in 1932 but was lost and
not rediscovered until 1973. These small bodies have spectra resembling
chondritic meteorites. Modern values for Icarus's perihelion and
aphelion distances are 17 and 183 million miles, respectively.


Best wishes,

Bernd

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