Cosmic Bar Codes
Jelle Kaastra of the Space Research Organization Netherlands in Utrecht and colleagues used Chandra's the Low Energy Transmission Grating in conjunction with the High Resolution Camera to measure the number of X rays present over a range of energies. With this information they constructed an X-ray spectrum of the source.
Right: This figure is the X-ray spectrum of the central region of the galaxy, NGC 5548. The spectrum shows the number of X rays present at each energy or wavelength, and amounts to a cosmic bar code. It allows scientists to take an inventory of the gas around the giant black hole in the center of the galaxy. The deep valleys in the spectrum are produced when a blanket of warm (few million degree) gas absorbs X rays of specific energies from hotter gas close to the central black hole.
Astronomers have used optical, ultraviolet, and X-ray telescopes in an effort to disentangle the complex nature of inflowing and outflowing gas at different distances from the black hole in NGC 5548. X-ray observations provide a ringside seat to the action around the black hole. By using the Low Energy Transmission Grating, the Dutch-US-German team concentrated on gas that forms a warm blanket that partially covers the innermost region where the highest energy X-rays are produced.
Below: This might resemble a fried egg you've had for breakfast, but it's actually much larger. In fact, ringed by blue-tinted star forming regions and faintly visible spiral arms, the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. Like NGC 5548, this galaxy is a Seyfert galaxy - a type of active spiral galaxy with a center or nucleus that is very bright at visible wavelengths. Galaxies like NGC 7742 and 5548 are thought to harbor massive black holes at their cores.
Sign up for our EXPRESS SCIENCE NEWS delivery
The Low Energy Transmission Grating was built by the Space Research Institute of Netherlands and the Max Planck Institute under the direction of Albert Brinkman. The High Resolution Camera was built by the Smithsonian Astrophysical Observatory in Cambridge, Mass., under the direction of Stephen Murray.Web Links
Chandra home page -from Harvard
Chandra News -from NASA
Black Holes -a tutorial about black holes and accretion disks
X-Rays - Another Form of Light - the basics of X-rays from the Chandra home page at Harvard