Hubble's New Eye Espies Black-Hole Havoc

Science News Staff
1997-05-12 (All day)
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WASHINGTON, D.C.--NASA today offered a look at the first fruits of two new instruments installed aboard the Hubble Space Telescope (HST) during February's servicing mission. Among the early results of one instrument: the clearest picture yet of the maelstrom created by a supermassive black hole at the heart of a distant galaxy. Tempering the good news, however, NASA scientists reported this morning that glitches in a second new instrument could cut its lifetime almost in half.

The Space Telescope Imaging Spectrograph (STIS) revealed the signature of a black hole when HST scientists aimed it at the center of M84, a galaxy 50 million light-years away. By tracking shifts in the spectrum of the light, the STIS can precisely record the movement of gas, dust, and stars toward or away from Earth. The resulting image--"the best spectrum ever of a black hole," says Hubble project scientist Ed Weiler--shows that light from gas and stars above the galaxy's center is shifted far to the blue end of the spectrum, while just below the center the light is shifted far to the red. The extreme spectral shift indicates that the gas is whirling around the galactic center at 400 kilometers per second. NASA scientists estimate that it would take a black hole with a mass of 300 million suns to whip the stars and gas around so fast.

By taking the spectrum of many points across the galaxy at once, STIS can record such movements in about 20 minutes, says Weiler--40 times faster than the best instrument previously available. Such speed, he says, will allow researchers to survey hundreds of black holes over the next several years. "You don't really learn a lot about humans by studying one here and one there," Weiler says. "You really have to study a whole population. We've now got a census taker in the STIS. The next few years are really going to teach us a lot about the demographics of supermassive black holes."

Less certain, however, is the status of the other new Hubble instrument, the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Two of its cameras are working fine, as images released this morning--of an exploding star and a star-forming region in the Orion nebula--demonstrate. But engineers discovered in March that the solid nitrogen that was supposed to keep the instrument cool had expanded more than expected. The expansion appears to have pushed a third camera out of focus and has allowed the nitrogen to come in contact with part of its container. That contact is warming the coolant and causing it to escape into space more quickly than planned. According to Hubble project scientist David Leckrone, the coolant loss could bleed off as much as 2 years from NICMOS's planned 4-year lifetime. To compensate, he says, as much as 50% of Hubble's observing time will be dedicated to NICMOS over the next 18 months--twice as much as originally planned.

The colorful "zigzag" on the left is not the work of a flamboyant artist but the signature of a supermassive black hole in the center of galaxy M84, discovered by the Hubble Space Telescope's Space Telescope Imaging Spectrograph (STIS).

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