THE SOLAR SYSTEM
Asteroid 4015. This was
discovered by Eleanor Helin
in 1979. It was subsequently
found to be identical with
Comet Wilson–Harrington,- The picture at left
shows it in 1949, with a
cometary tail; at right it
is seen in its 1979 guise,
when in appearance it was
purely asteroidal. This seems
to support the suggestion
that at least some close-
approach asteroids are
extinct comets.
Eros, from orbit.
Images were obtained on
12 February 2000 by the
camera aboard the NEAR
spacecraft. At left is a single
image; at right is a
composite of 20 images.
Computer processing has
been used to bring out
details.The Trojan asteroids.
The Trojans move in the
same orbit as Jupiter,
but keep prudently either
60 degrees ahead of or
60 degrees behind the Giant
Planet, so that they are in nodanger of collision – though
naturally they oscillate to
some extent round their
mean points. Several Mars
Trojans are known, and in
2003 one Neptune Trojan
was discovered.OrbitofJupiterSunJupiterTrojan asteroid Trojan asteroidAsteroid 4179 Toutatis.
The four images at top were
constructed using radar
information from NASA’s
Goldstone and Arecibo radar
telescopes. The asteroid
appears to consist of two
irregularly shaped, cratered
objects, a few kilometres
wide, which are probably in
contact with each other.
Below is a composite of five
exposures, obtained with the
3.5-m ESO New Technology
Telescope on 21 December- At this time, Toutatis
was about 13 million km
(8 million miles) from Earth.
The unusually rapid motion
of Toutatis is well illustrated
on the photo. The first
exposure (at the arrow) was
obtained at 8:05 UT; the next
(moving towards the upper
right) at 8:10; the next at
8:15, and the last two (near
the right edge of the photo)
at 8:59 and 9:01. During this
one-hour interval, Toutatis
moved a distance of more
than 3 arc minutes in the sky.
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