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Astronomy Picture of the Day |
APOD: 1996 December 10 - Comet Halley's Nucleus
Explanation:
Here is what a comet nucleus really looks
like. For all active comets except Halley,
it was only possible to see the surrounding opaque gas cloud called
the coma. During Comet Halley's
most recent pass through the inner Solar System
in 1986, however, spacecraft Giotto
was able to go right up to the comet and photograph its nucleus.
The above image is a composite of hundreds of these photographs.
Although the most famous comet, Halley
achieved in 1986 only 1/10th the brightness that Comet Hyakutake
did last year, and a similar comparison is likely with next year's
pass of Comet Hale-Bopp. Every 76
years Comet Halley comes around again,
and each time the nucleus sheds about 6 meters of ice and rock
into space. This debris composes Halley's tails
and leaves an orbiting trail that, when falling to Earth,
are called the Orionids Meteor Shower.
APOD: 1997 October 3 - Comet Halley and the Milky Way
Explanation:
Comet Halley was photographed superposed in front of the disk of our
Milky Way Galaxy in 1986 by the
Kuiper
Airborne Observatory. Comet Halley is the bright white streak near this photograph's center.
Comet Halley is the most
famous comet in history, and returns to the inner
Solar System every 76 years.
Stars visible in our
Milky Way Galaxy typically lie
millions of times further in the distance and
orbit the
Galactic center every 250 million years.
Billions of
comets are thought to orbit our
Sun
but most do not get close enough for us to see.
Similarly, billions of stars orbit our Milky Way's center but do not get close enough for us to see.
APOD: 1996 July 6 - Edmond Halley's Greatest Discoveries
Explanation:
Sir Edmond Halley was quite a discoverer. Born in 1656, he computed in
1705 that a bright comet was periodic and would make another appearance in
1758. The comet appeared as predicted and is now known as
Comet Halley.
Unfortunately, Halley died in 1742 and never saw his prediction come true.
In 1716
Halley proposed two types of diving bells that would enable people
to explore the deep sea.
Halley pioneered our understanding of trade winds,
tides, cartography, naval navigation, mortality tables, and stellar proper
motions.
Halley (incorrectly)
proposed that the Earth was made of
concentric spheres the size of the inner planets each of which might
contain life. Perhaps Halley's greatest discovery, however, was that his
contemporary
Isaac Newton
had discovered a powerful mathematical formulation of gravity.
Authors & editors:
Robert
Nemiroff
(MTU)
& Jerry Bonnell (USRA)
NASA Technical Rep.:
Jay Norris.
Specific rights apply.
A service of:
LHEA at
NASA/
GSFC
&
Michigan Tech. U.