THE SOLAR SYSTEM
Hale and Thomas Bopp. It was by no means a faint tele-
scopic object, but was 900 million kilometres (560 million
miles) from the Sun, beyond the orbit of Jupiter. It bright-
ened steadily; by the autumn of 1996 it had reached
naked-eye visibility, and became brilliant in March and
April 1997, with a magnitude exceeding 1. It passed
Earth on 22 March 1997, at over 190 million kilometres
(120 million miles); had it come as close as Hyakutake had
done, it would have cast shadows. Perihelion was reached
on 1 April, at over 125 million kilometres (over 80 million
miles) from the Sun. It will return in about 3500 years.
Hale–Bopp was a very active comet, throwing off
shells from its rotating nucleus; there was a curved
reddish-brown dust tail and a very long, blue gas or ion
tail. Unquestionably, it was the most striking comet of
recent times, and possibly the best since the Daylight
Comet of 1910. Astronomers everywhere were sorry to
bid it farewell!
On 22 September 2001, the spacecraft Deep Space 1
flew past Borrelly’s periodical comet, and sent back close-
range images of the nucleus. This is a typical, short-period
comet; it was discovered in 1904, and returns every 6.9
years. It is an easy telescopic object, but never becomes
visible with the naked eye.Comet Hale–Bopp,
photographed by the author
on 1 April 1997, at Selsey,
West Sussex (Nikon F3,
50 mm, exposure 40
seconds, Fuji ISO 800). Comet Borrelly’s nucleus,
from Deep Space 1. Dust jets
can be seen; the main one is
directed towards lower left,
and a smaller one appears to
emerge from the tip. Comet Wild 2,taken from
the NASA spacecraft
Stardust on 2 January 2004.
It has a variety of surface
features, including pinnacles
and craters. This image was
taken from a distance of
236 km (147 miles) and is
the closest short exposure
of the comet. Deep Space 1, in an artist’s
impression. Launched in
1998, Deep Space 1’s main
purpose was to rendezvous
with the asteroid 9969 Braille,which it accomplished in- The close encounter
with Borrelly’s Comet was a
very successful addition to
DS 1’s mission.
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