Astronomy Picture of the Day

A Galaxy is not a Comet

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#105246 by @ 03.01.2008 00:00 - nach oben -
A Galaxy is not a Comet


This gorgeous galaxy and comet portrait
was recorded on December 30th,
in the skies over Hoogeveen, The Netherlands.

The combined series of 60 x 60 second exposures finds
the lovely green coma of
Comet 8P/Tuttle
near its predicted conjunction with the

Aligning each exposure with the stars shows the comet as a
streak, slowly moving against the background stars and galaxy.

An alternative
with exposures centered on the comet, shows the background
stars and galaxy as streaks.

The alluring celestial scene would also have been a
rewarding one for the influential 18th century comet
hunter Charles Messier.

While Messier scanned French skies for comets,
he carefully cataloged positions of things which were
fuzzy and comet-like
in appearance but did not move against the background stars and
so were definitely not comets.

The Triangulum Galaxy,
also known as M33, is the 33rd object in his famous
not-a-comet catalog.

The modern
holds that the Triangulum Galaxy is a large spiral galaxy
some 3 million light-years distant.

Comet 8P/Tuttle, just bright enough to be
visible to the unaided eye in dark,
northern skies,
is about 40 million kilometers (2 light-minutes) away.

The Amateur Astronomers Association of New York Presents:
APOD Editor's Lecture: January 4th -
American Museum of Natural History

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