August 17, 2004T
he Chandra X-ray Observatory, which opened up a new world of X-ray astronomy and led to a new understanding of some of the universe's most exotic and violent objects, marked its fifth year in service last week — and, astronomers say, its work may just be starting.
Launched from the space shuttle Columbia on July 23, 1999, the $1.5-billion NASA satellite has a sensitivity about 20 times greater than any previous X-ray telescope, allowing astronomers to probe the X-ray universe in as much detail as the Hubble Space Telescope allows in visible light. Chandra's 64-hour-long orbit takes it 200 times higher than Hubble, carrying it one-third of the way to the Moon on every circuit.
Scientists revealed Chandra's first results on August 26, 1999. Ever since, Chandra's performance has been "spectacular," making the craft "a super companion to Hubble," says Chandra project scientist Martin Weisskopf of NASA's Marshall Space Flight Center in Huntsville, Alabama. "I think it's every bit as exciting and interesting as Hubble has been."
X rays, like visible light, are a form of electromagnetic radiation; however, X-ray photons have much more energy than photons of visible light, and, therefore, are usually emitted by much hotter objects. So while ordinary stars emit most of their radiation at visible wavelengths, highly energetic objects like quasars and active galaxies shine like celestial beacons at X-ray wavelengths.
"It takes high energies to produce X rays, and so the physics behind the processes is usually more violent and therefore more interesting," says Weisskopf.
In the first year of operation, data from Chandra led to an astounding array of discoveries, including:
- the first clear images of X rays emitted by matter falling into the black hole at the center of the Milky Way;
- detailed images of X-ray emitting stars, including a region in the Orion Nebula containing 1,000 individual sources;
- a supernova in the Small Magellanic Cloud, a companion galaxy to the Milky Way, marked by an expanding cloud of gas and dust.