ON THE HUNT FOR BLACK HOLES

ON THE HUNT FOR BLACK HOLES  Bayu7key.

A new X-ray telescope being prepared for launch will be able to ferret out hiding places of black holes by peering into the dusty centers of distant galaxies.

The Nuclear Spectroscopic Telescope Array, or NuSTAR, is the first space observatory to focus on what is known as "hard X-rays" -- the type used in dental X-rays to see inside teeth.

Objects that give off this type of radiation are among the most active and violent in the universe, including galaxy clusters, supernova explosions, high-temperature gas and regions where particles are being accelerated close to the speed of light.

"There's a whole variety of phenomenon from very extreme neutron stars to remnants of old stellar explosions we haven't discovered yet," lead scientist Fiona Harrison, with the California Institute of Technology, told Discovery News.

One of the telescope's first jobs will be to conduct a sky survey, which will give astronomers an idea about how galaxies formed. They are also eager to study supernova -- the exploded remains of giant stars -- to look for the telltale chemical fingerprints of radioactive titanium.

"Different models of how a supernova explosion happens imply very different observables of how the titanium would be distributed, both spatially and in velocity. With these observations we'll get a better idea of the physics of supernova explosions," NuSTAR project scientist Daniel Stern, with NASA's Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News.

Supernovas are an important measuring stick for determining the universe's rate of expansion. Because astronomers believe they give off basically the same amount of light, measuring their brightness has been used to determine how distant they are, much like how a standard 100-watt light bulb appears dimmer if it is farther away.

"Cosmologically, we'd like to understand supernova a little bit better since we're giving Nobel Prizes using them as cosmologically probes," Stern said.

Studying high-energy X rays, which can pass through obscuring gas and dust, also should reveal the locations of black holes.

"We're pretty sure that every big galaxy has a super-massive black hole in its center and the models predict that most of the ones that are actively accreting material and get very bright are being hidden by gas and dust around them," Stern said.

NuSTAR will be able to pin down how many black holes are hidden, how big they are and where they are located.

Another target of study is the sun. Hard X-rays coming from micro-flares could help resolve a long-standing mystery of how the sun's corona gets heated to 1 million degrees.

NuSTAR complements NASA's Chandra X-ray observatory and Europe's XMM-Newton telescope, both of which image the X-ray sky in lower energy wavelengths.

"There won't be these beautiful pictures like what Hubble takes, but for an X-ray astronomers they will be because they'll be much sharper than anyone has ever done before," Stern said.

NuSTAR will be put into a low-Earth, near-equatorial orbit by an air-launched Pegasus rocket flying from the Kwajalein Atoll in the Marshall Islands. Launch is targeted for March 14.

The telescope consists of two sets of 133 concentric shells of mirrors, made from flexible glass, such as what is used in laptop computer screens. Because X-rays need a large area to focus, NuSTAR has a 33-foot mast that will unfold after launch.

The mission is expected to last at least two years.

discovery.com

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