The other type is the complete destruction of the dead core of a star, known as a white dwarf. Its core collapses to form a neutron star or black hole and its outer layers fall in, then explode. One type is the destruction of a star at least 8 to 10 times as massive as the sun. Supernovae fall into two broad categories. Compared to other supernovae, it took longer to reach peak brightness, it faded more slowly, and at maximum, it was several times more powerful.
Such was the case with Supernova SN2006gy, which was discovered September 18, 2006, by an automated search program at the University of Texas’ McDonald Observatory.Īs astronomers began studying the star, they realized that it was an oddball. But some time is reserved to study targets that appear suddenly, like the exploding stars known as supernovae. Most targets for Chandra are selected months in advance. In many cases, this information can be used to determine which chemical elements are present. The primary one, called the ACIS, for Advanced CCD Imaging Spectrometer, uses a charge-coupled device detector, similar to those found in digital cameras, to record the position of each X-ray that strikes it, along with the X-ray’s energy level. The intensity of radiation at each wavelength reveals the abundance of different elements, along with the object’s density, temperature, and motion toward or away from the telescope.īeyond the gratings are the scientific instruments. The gratings contain thousands of narrow openings that segregate the X-rays by wavelength. Each mirror is most efficient at reflecting a particular range of X-ray wavelengths.Īfter bouncing off the mirrors, the X-rays travel down a 26-foot tube toward the telescope’s scientific instruments, located at the other end.ĭevices called gratings can be moved into the light path between the mirrors and the instruments. “You need two bounces to have X-rays come to a focus,” says Martin Weisskopf, Chandra project scientist at NASA’s Marshall Space Flight Center in Huntsville, Alabama, which manages the program. X-rays hit the top mirrors in each pair, then skip down to the secondary mirrors. Most of the time, this path keeps Chandra clear of the Van Allen belts, rings of radioactive particles encircling Earth, so the telescope has to shelter its instruments from the radiation for only a small portion of each orbit.Īn optical telescope uses a large, curved-glass primary mirror to gather light, but X-rays would penetrate such a mirror’s reflective coating an X-ray telescope’s mirrors must be facing almost perpendicular to the path of incoming light so that the photons graze the surface like stones skipping across a pond.Ĭhandra has four pairs of mirrors. Its highly elliptical path takes it up to 83,000 miles away. The Chandra telescope was launched by the space shuttle Columbia in 1999 and is today operated by the Chandra X-Ray Center at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.Ĭhandra completes one orbit around Earth roughly every two and a half days.
X-rays come from the hottest objects of all, such as clouds of gas between galaxies or the bands of gas spiraling into black holes.Įarth’s atmosphere absorbs X-rays, so X-ray astronomers must place their telescopes in space. Medium-hot stars like our sun peak at visible wavelengths, while the hottest stars shine brightest in the ultraviolet. Cool interstellar gas clouds, for example, emit primarily longer, infrared wavelengths. Stars, galaxies, and other astronomical objects all produce light, with a mix of wavelengths that depends on the object’s composition and temperature. The spacecraft can produce full-color images of X-ray-emitting objects while measuring the intensity at each X-ray wavelength. It sounds like a meager harvest, but those four packets of energy helped astronomers realize that the galaxy contained a type of exploding star that had never been observed before.Ĭhandra, which is named for Nobel Prize-winning astrophysicist Subrahmanyan Chandrasekhar, who first calculated the ultimate fate of stars like our sun, is the largest and most sensitive X-ray telescope ever built. In that time, one of the detectors intercepted exactly four X-ray photons. For more than eight hours last fall, the Chandra X-Ray Observatory stared at a nondescript galaxy 240 million light-years away.
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