NASA's Observatorium -- Observation of the Week

November 10, 1999

Chandra--NASA's Newest X-ray Observatory

1. Supernova remnant Cassiopeia A, or Cas A for short, as viewed by NASA's newest X-ray telescope, the Chandra X-ray Observatory. Bright yellow indicates the areas with the most intense X-ray emission. The bright, point-like object near the center of Cas A may be the long-sought neutron star that remained after the supernova explosion. Cas A is approximately 10 light-years across and lies at a distance of roughly 10,000 light-years from Earth.

2. The inner part of the Crab Nebula, another supernova remnant, imaged in X-rays by the Chandra Observatory. The image shows several rings surrounding a central object and, perpendicular to the rings, a pair of oppositely pointed jets. The bright inner ring has never been seen before. The central object is a pulsating neutron star called the Crab pulsar.

3. The Crab Nebula as seen from the ground in optical light. The arrow points to the Crab pulsar. The nebula is about 10 light-years across and lies at a distance of roughly 7,000 light-years from Earth.

4. Artist's rendition of the Chandra X-ray Observatory in Earth orbit.

Click on the images for larger views.

Image Credits: NASA, Chandra X-ray Observatory Center (CXC), and Smithsonian Astrophysical Observatory (SAO) (images 1, 2). Jay Gallagher (University of Wisconsin), WIYN Observatory, National Optical Astronomy Observatories (NOAO), and National Science Foundation (NSF) (image 3). NASA (image 4).

The first image above, of Cassiopeia A, shows X-ray emission from the expanding gas of this supernova remnant. The supernova occurred roughly 320 years ago, when a star much more massive than the Sun exploded and ejected its envelope into space.

The expanding shell of gas is plowing into surrounding gas, most of which was blown off by the star earlier in its lifetime. This collision between gas ejected by the supernova and surrounding gas creates enormously strong shockwaves and heats the matter up to 90 million degrees Fahrenheit. Gas this hot radiates predominantly in X-rays, which the instruments onboard Chandra record.

The second image above, of the Crab Nebula, shows a series of bright rings of electrically charged, high-energy particles that have been flung out by the Crab pulsar. It also shows a pair of jets of gas shooting out perpendicularly to the rings. The jets, too, originate from the pulsar.

The intense magnetic fields of the rapidly spinning Crab pulsar (it spins at a rate of 30 times per second!) accelerate electrons and other charged particles to nearly the speed of light and eject them, as seen in this X-ray image. Astronomers think this is the mechanism by which energy gets transferred from the pulsar to the rest of the Crab Nebula, making it glow brightly even today, nearly 1,000 years after the supernova explosion (image 3).

The Crab Nebula and pulsar are the result of a supernova that, according to Chinese and Japanese chronicles, exploded in 1054. Even today, the nebula is still expanding at more than 3 million miles per hour and emits radiation in all wavelengths, from gamma rays to X-rays, UV, optical, and infrared radiation, and radio waves.

The above X-ray images are two examples of a score of images and other data the Chandra Observatory has collected since it was carried into Earth orbit onboard the space shuttle Columbia on July 23, 1999. Many other stunning images are anticipated to follow during the observatory's expected five-year lifetime. They will give us a new perspective on many of the high-energy events in the universe, which include, in addition to supernovae and supernova remnants, such fascinating objects as colliding galaxies, quasars, black holes, and X-ray emission from very young and hot stars.

More Cool Stuff

For more information on the Chandra Observatory, images, press releases, and science, go to NASA's Chandra X-ray Observatory News and the Chandra X-ray Observatory Center (CXC) at the Harvard-Smithsonian Center for Astrophysics:: http://chandra.nasa.gov/chandra.html
http://chandra.harvard.edu/
After its release into space by the space shuttle Columbia at a height of 176 miles, the Chandra X-ray Observatory boosted itself into a highly elliptical operating orbit by a series of burns from its own propulsion system. During each orbit Chandra rises to a high point of roughly 86,500 miles (nearly a third of the way to the Moon) and falls to a low point of 6,000 miles. The orbital period is 63 hours and 29 minutes, with most of the time spent far from Earth. To learn more about how this operating orbit was achieved, go to the following status reports from NASA's Marshall Space Flight Center (MSFC). Click on reports dated July 23 to August 9, 1999:: http://www1.msfc.nasa.gov/NEWSROOM/news/status/chandrastatus/
We have featured the Chandra X-ray Observatory (originally know as the Advanced X-ray Astrophysics Facility, or AXAF) in our Observations of the Week before--on April 22, 1998, and July 23, 1999:: http://observe.ivv.nasa.gov/nasa/ootw/1998/ootw_980422/ob980422.html (the observatory)
http://observe.ivv.nasa.gov/nasa/ootw/1999/ootw_990723/ob990723.html (the launch)
As part of its Learning Technologies Project (LTP), NASA supports a number of educational Web sites that have excellent material on the space sciences:: http://observe.ivv.nasa.gov/nasa/education/edu/edudocs/topic_space.html

Check out other observations in the Observation of the Week Archive.