A nebula is an cloudlike mass of gases and dust particles in interstellar space.
May 23, 1999 - The Keyhole Nebula
Explanation: The dark dusty Keyhole Nebula gets its name from its unusual
shape. Officially designated NGC 3324, the Keyhole Nebula is a smaller region
superposed on the larger Eta Carina Nebula. An emission nebula that contains
much dust, the Keyhole N
August 20, 1996 - A Close-Up of the Lagoon Nebula
Explanation: Ribbons of red-glowing gas and dark dust surround massive
young stars in this close-up of the Lagoon Nebula taken by the Hubble Space
Telescope. The Lagoon Nebula is relatively close and bright - it appears larger
than the Full Moon and is v
May 4, 1998 - M57: The Ring Nebula
Now known as M57 or NGC 6720, the gas cloud became popularly known as the
Ring Nebula. As one of the brightest planetary nebula on the sky, the Ring
Nebula can be seen with a small telescope in the constellation of Lyra. Perhaps
the Ring Nebula would ap
Chandra discovers X-ray ring around
cosmic powerhouse in the Crab Nebula
28, 1999: After barely two months in space, NASA's Chandra X-ray
Observatory has taken a stunning image of the Crab Nebula, the
spectacular remains of a stellar explosion, and has revealed something
never seen before: a brilliant ring around the nebula's heart.
The Crab Nebula as seen by the Chandra X-ray Observatory. The image
links to a 533x533-pixel,
54K JPG. Credit: NASA and Chandra Science Center
Combined with observations from the Hubble Space Telescope, the image
provides important clues to the puzzle of how the cosmic
"generator," a pulsing neutron star, energizes the nebula,
which still glows brightly almost 1,000 years after the explosion.
"The inner ring is unique," said Professor Jeff Hester of
Arizona State University, Tempe, AZ. "It has never been seen
before, and it should tell us a lot about how the energy from the pulsar
gets into the nebula. It's like finding the transmission lines between
the power plant and the light bulb."
Professor Mal Ruderman of Columbia University, New York, NY, agreed.
"The X-rays Chandra sees are the best tracer of where the energy
is. With images such as these, we can directly diagnose what is going
What is going on, according to Dr. Martin Weisskopf, Chandra Project
Scientist from NASA's Marshall Space Flight Center, Huntsville, AL, is
awesome. "The Crab pulsar is accelerating particles up to the speed
of light and flinging them out into interstellar space at an incredible
The image shows tilted rings or waves of high-energy particles that
appear to have been flung outward over the distance of a light year from
the central star, and high-energy jets of particles blasting away from
the neutron star in a direction perpendicular to the spiral.
Hubble Space Telescope images have shown moving knots and wisps around
the neutron star, and previous X-ray images have shown the outer parts
of the jet and hinted at the ring structure. With Chandra's exceptional
resolution, the jet can be traced all the way in to the neutron star,
and the ring pattern clearly appears. The image was made with Chandra's
Advanced CCD Imaging Spectrometer and High Energy Transmission Grating.
The Crab Nebula, easily the most intensively studied object beyond our
solar system, is the remnant of a star that was observed to explode in
1054 A.D. Chinese astronomers in that year reported a "guest
star" that appeared suddenly and remained visible for weeks, even
during daytime. From gamma-ray telescopes to radio telescopes, the Crab
has been observed using virtually every astronomical instrument that
could see that part of the sky.
Unraveling the mysteries of the Crab has proven to be the door to
insight after insight into the workings of the universe. The Crab
convincingly tied the origin of enigmatic "pulsars" to the
stellar cataclysms known as supernovae. Observations of the expanding
cloud of filaments in the Crab were instrumental in confirming the
cosmic origin of the chemical elements from which planets (and people)
The nebula is located 6,000 light years from Earth in the constellation
Taurus. The Crab pulsar, which was discovered by radio astronomers in
1968, is a neutron star rotating 30 times per second. Neutron stars are
formed in the seconds before a supernova explosion when gravity crushes
the central core of the star to densities 50 trillion times that of lead
and a diameter of only 12 miles.
Another consequence of the dramatic collapse is that neutron stars are
rapidly rotating and highly magnetized. Like a gigantic cosmic
generator, the rotating magnet generates 10 quadrillion volts of
electricity, 30 million times that of a typical lightning bolt.
"It is an incredibly efficient generator," Ruderman explained.
"More than ninety-five percent efficient. There's nothing like it
NASA's Marshall Space Flight Center manages the Chandra program. TRW,
Inc., Redondo Beach, CA, is the prime contractor for the spacecraft. The
Smithsonian's Chandra X-ray Center controls science and flight
operations from Cambridge, MA. Chandra images are posted to the Internet
at: http://chandra.nasa.gov and http://chandra.harvard.edu
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