Astronomy Picture of the Day |
APOD: 1999 May 19 - M31: The Horsehead Nebula
Explanation:
One of the most identifiable nebulae in the sky,
the Horsehead Nebula in Orion, is part of a large, dark,
molecular cloud.
Also known as Barnard 33, the unusual shape was first
discovered on a photographic plate in the late 1800s.
The red glow originates from
hydrogen gas predominantly behind the nebula,
ionized by the nearby bright star Sigma Orionis.
The darkness of the
Horsehead is caused mostly by thick
dust,
although the lower part of the
Horsehead's neck casts a shadow to the left.
Streams of gas leaving the nebula are funneled by a strong
magnetic field.
Bright spots in the
Horsehead Nebula's base are
young stars just in the
process of forming.
Light takes about 1500 years to reach us from the
Horsehead Nebula. The
above image was taken with the
0.9-meter telescope at
Kitt Peak National Observatory.
APOD: 1999 May 5 - Molecular Cloud Barnard 68
Explanation:
Where did all the stars go?
What used to be considered a hole in the sky
is now known to astronomers as a dark molecular cloud.
Here, a high concentration of
dust and
molecular gas
absorb practically all the visible light
emitted from background stars.
The eerily dark surroundings help make the interiors of
molecular clouds some of the coldest
and most isolated places in the universe.
One of the most notable of these
dark absorption nebulae
is a cloud toward the constellation
Ophiuchus known as Barnard 68,
pictured above.
That no stars are visible in the center indicates that
Barnard 68 is relatively nearby,
with measurements placing it about
500 light-years away and half a light-year across.
It is not known exactly how
molecular clouds
like Barnard 68 form, but it is known that
these clouds are themselves
likely places
for new stars to form.
APOD: 1997 June 21 - The Pipe Dark Nebula
Explanation:
The dark nebula predominant at the lower left of the above photograph
is known as the
Pipe
Nebula.
The dark clouds, suggestively shaped like smoke rising from a pipe,
are caused by absorption of background starlight
by dust. These dust clouds
can be traced all the way to the
Rho Ophiuchi nebular clouds on
the right. The brightest star in the field is
Antares.
Many types of nebula are highlighted here: the red are
emission nebula, the
blue are
reflection nebula,
and the dark are
absorption nebula.
This picture has been
digitally
enhanced.
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.