An artist's view of Sedna
In March, 2004 astronomers announced the discovery of the coldest,
most distant object known to orbit the Sun. The object was found at a
distance 90 times greater than that from the Sun to the Earth -- about 3
times further than Pluto. Astronomers
have given it the name of Sedna.
To find objects, they take three pictures of a small region of the
night sky over three hours and look for something that moves. The many
billions of stars and galaxies visible in the sky appear stationary, while
satellites, planets, asteroids, and comets appear to move. Objects in the
inner Oort cloud are extremely distant and so move extremely slowly.
At right is an animatation that shows the three discovery images. The total
area of sky shown in the bottom image is equivalent in size to the head of a
pin held at arm's length. Incidentally, that is how big the Sun would appear
from Sedna.
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