NuSTAR: NASA’s New Space Telescope

High Energy, Low Cost

 

At the recent Caltech alumni conference, Caltech Professor Fiona Harrison presented NuSTAR, NASA’s newest space telescope. Harrison is the Principal Investigator and creator of NuSTAR.

 

NuSTAR focuses high-energy X-rays (6 to 79 keV) as never before possible. Each time astronomers have been able to observe the universe in a new way, they have made remarkable and unanticipated discoveries. We expect NuSTAR to be equally amazing. And costing only $160 million, it is bargain-basement by NASA standards.

 

Because of its focusing lens and advanced detector, NuSTAR is hundreds to thousands of times more sensitive than any previous instrument in this energy range.

 

During its two-year primary mission, NuSTAR will apply its unique capabilities to:

(1) taking a census of neutrons stars and black holes, both in our galaxy and beyond
(2) examining explosion processes in supernovae
(3) analyzing relativistic jets in active galactic nuclei
(4) studying our Sun’s corona.

 

For 400 years, astronomers have built telescopes that focused visible light with mirrors and lenses. But high-energy X-rays are a problem because their “size” (wavelength) is smaller than an atom. This means that instead of “seeing” the smooth surface of a mirror they instead “see” the mirror’s individual atoms as large boulders, so they crash instead of bounce.

 

Fiona Harrison developed a mirror surface coating that reflects high-energy X-rays that hit the mirror at a small grazing angle. The reflection slightly changes the X-ray’s direction, focusing it onto a detector. Since only a few X-rays will hit the mirror just right, Harrison’s team built an array of 130 concentric cylinders, each coated with 400 layers of different materials - the layers are only a few atoms thick. The long axis of the cylindrical array is pointed at the X-ray source. The X-rays enter the array at one end and exit the other end after being slightly focused.

 

The mirror system is made of glass sheets that must be as thin, strong, and flexible as possible. The best glass turns out to be the glass used in iPhones and iPads.

 

Asked how she managed to construct such as elaborate mirror system, Fiona replied: “We burned through a lot of graduate students.”

 

One of NuSTAR’s pair of cylindrical mirror systems is 1.5 feet long by 15 inches across.

 

Because the X-rays are only slightly deflected by the mirror system, the detector must be 33 feet away. Since that’s too long to be launched in the rocket, an expandable mast had to be developed. The mast is only 6 feet long when launched and then unwinds as it spools out to the full 33-foot length.

 

The entire NuSTAR telescope was loaded into a modest rocket (Orbital Science’s Pegasus XL) and strapped to the belly of an L-1011 aircraft. On June 13, 2012, the plane took off from Kwajalein (the world’s largest coral atoll,  midway between Hawaii and Australia) and flew up to 40,000 feet, where the rocket was released. The rocket subsequently fired and carried NuSTAR to an altitude of 380 miles.

 

Observations have just begun. Shown below is NuSTAR’s first image, taken of Cygnus X-1, one of the first black holes ever found. To the right of the sky diagram are two inset images of Cygnus X-1’s accretion disk; the upper image was taken by the best prior high-energy X-ray telescope, and the lower by NuSTAR. What a difference!

 

 

With its ability to pinpoint high-energy X-ray sources, NuSTAR will count and catalog our galaxy’s population of neutron stars and black holes. It will also be used to study the outflow of heavy elements in supernovae explosions, hopefully shedding light on the collapse and explosion processes in these cosmic cataclysms.

 

NuSTAR’s superior resolution will allow astronomers to image X-ray emissions from supermassive black holes in distant galaxies in order to better understand their accretion processes and impact on their host galaxies.

 

NuSTAR is also expected to help us better understand our Sun’s corona, its wispy outer atmosphere that reaches temperatures over a million degrees and reaches million of miles above the Sun’s surface. We wish to better understand how this most distant part of the Sun can be vastly hotter than its surface.

 

Fiona Harrison explained that NuSTAR is the realization of a dream she has nurtured for over a decade. Congratulations to her and her team!

 

Best Regards,

Robert

 

September 26, 2012

 

Note: Previous newsletters can be found on my website.

 

 

Artist’s view of NuSTAR in space seen below:

 

 

Dr. Robert Piccioni

www.guidetothecosmos.com
Author of "Everyone's Guide to Atoms, Einstein, and the Universe",
"Can Life Be Merely An Accident?"
& "A World Without Einstein"

 

 

 



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