Through the first decade of the 21st century efforts at observing what was happening at the high end of the electromagnetic spectrum in space were limited by the “seeing” power of the telescopes being used.
Here’s how energy across the electromagnetic spectrum maps out:
A significant amount of activity occurs in the x-ray and gamma ray end of the spectrum. These rays do not penetrate the earth’s atmosphere and as a result astronomers were not able to complete a detailed study of such objects as black holes, neutron and binary stars or the aftermath of super novae.
Missions by NASA and ESA such as Chandra and XMM- Newton provided some information at the lower end of the x-ray band using a technology which was limited to the lower end of the x-ray spectrum.
In June of 2012 NASA launched NuSTAR, the Nuclear Spectroscopic Telescope Array with technology designed to allow astronomers to see 100 times further into the x-ray spectrum.
NASA describes the reflecting mirrors in NuSTAR to be “refinements” to the Wolter-1 design which has formed the design basis for x-ray telescopes.
“. . . instead of a classical Wolter-I design, NuSTAR flies a conical approximation to the parabola and hyperbola, which slightly degrades the on-axis sharpness, in exchange for a more artifact free image when the source is coming in at an angle.”
Here’s how NASA describes the difference using NuSTAR:
“The NuSTAR mission has deployed the first orbiting telescopes to focus light in the high energy X-ray (6 – 79 keV) region of the electromagnetic spectrum. Our view of the universe in this spectral window has been limited because previous orbiting telescopes have not employed true focusing optics, but rather have used coded apertures that have intrinsically high backgrounds and limited sensitivity.”
By comparison, CHANDRA was limited to observations below 3 KeV.
When measuring energy an”eV” is a unit of energy equal to 10-21 joules. A”KeV” is 1,000 times that number.
NASA describes NuSTAR mission as follows:
“During a two-year primary mission phase, NuSTAR will map selected regions of the sky in order to:
- Take a census of collapsed stars and black holes of different sizes by surveying regions surrounding the center of own Milky Way Galaxy and performing deep observations of the extragalactic sky;
- Map recently-synthesized material in young supernova remnants to understand how stars explode and how elements are created; and
- Understand what powers relativistic jets of particles from the most extreme active galaxies hosting supermassive black holes.”
Now well into its mission NuSTAR has proven to be literally a new eye on activity in the universe and has provided astronomers with information about the activities around black holes, dead and dying stars and the x-ray activity of our own Sun.