Astronomy Picture of the Day |
APOD: 2002 September 22 - Two Hours Before Neptune
Explanation:
Two hours before closest approach to
Neptune in 1989, the
Voyager 2 robot spacecraft snapped
this picture.
Clearly visible for the first time were long light-colored
cirrus-type clouds floating high in
Neptune's atmosphere. Shadows of these clouds can even
be seen on lower cloud decks.
Most of
Neptune's atmosphere is made of
hydrogen and
helium, which is invisible.
Neptune's blue color therefore comes from
smaller amounts of atmospheric
methane,
which preferentially absorbs red light.
Neptune has the fastest winds in the
Solar System, with gusts reaching 2000 kilometers per hour.
Speculation holds that
diamonds may be created in the
dense hot conditions that exist under the clouds-tops of Uranus and Neptune.
APOD: 2004 June 26 - Neptune: Still Springtime After All These Years
Explanation:
In the 1960s spring came to the southern hemisphere of
Neptune,
the Solar System's outermost gas giant planet.
Of course, since Neptune orbits the Sun once every 165
earth-years,
it's still springtime for southern Neptune, where
each
season lasts over four decades.
Astronomers
have found that in recent years
Neptune has been getting brighter
as illustrated in this Hubble Space Telescope image made in 2002.
Compared
to Hubble
pictures taken as early as 1996,
the 2002 image shows a dramatic increase in reflective
white cloud bands in Neptune's southern hemisphere.
Neptune's
equator is tilted 29 degrees from the plane of its orbit,
about the same as Earth's 23.5 degree tilt, and
Neptune's weather
seems to be dramatically responding to the
similar relative seasonal increase in sunlight -- even though
sunlight is 900 times
less intense for the distant gas giant than for planet Earth.
Meanwhile, summer is really just around the
corner, coming to
Neptune's southern hemisphere in 2005.
APOD: 1998 February 21 - Neptune: Big Blue Giant
Explanation:
This picture was taken by the Voyager 2 spacecraft in 1989 - the only spacecraft
ever to visit Neptune. Neptune will be the farthest planet from the
Sun until 1999, when the
elliptical orbit of
Pluto
will cause it to once again resume this status. Neptune, like Uranus, is composed mostly of liquid water,
methane and ammonia, is surrounded by a thick gas
atmosphere of mostly hydrogen and helium,
and has many moons and rings. Neptune's moon
Triton is unlike any
other and has active volcanoes. The nature of
Triton's unusual orbit around
Neptune
is the focus of much discussion and speculation.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
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NASA Official: Jay Norris.
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EUD at
NASA /
GSFC
& Michigan Tech. U.