Super-thin X-ray Mirrors Will Make X-Ray Space Telescope 100 Times Better

Super-thin, lightweight X-ray mirrors made of silicon can make next-generation X-ray space telescopes.

Above – Goddard scientist Will Zhang holds mirror segments made of silicon. These X-ray optics have been baselined for the proposed Lynx X-ray Observatory.
Credits: Chris Gunn/NASA

X-ray mirror technology being developed at NASA’s Goddard Space Flight Center has been baselined for the conceptual Lynx X-ray Observatory. Lynx is one of four potential missions that scientists have vetted as worthy pursuits under the 2020 Decadal Survey for Astrophysics.

In the 2030s, Lynx could literally carry tens of thousands of Zhang’s mirror segments, which would offer a two orders-of-magnitude leap in sensitivity over NASA’s flagship Chandra X-ray Observatory and the European Space Agency’s Advanced Telescope for High-Energy Astrophysics, or Athena. Chandra itself offered a significant leap in capability when it launched in 1999. It can observe X-ray sources — exploded stars, clusters of galaxies, and matter around black holes —100 times fainter than those observed by previous X-ray telescopes.

In another development, Zhang and his team have secured a nearer-term flight opportunity aboard a sounding rocket mission scheduled for 2021. This would represent the technology’s first demonstration in space.

Seven-Year Development Effort

The effort to develop the new optic began seven years ago when Zhang began experimenting with mono-crystalline — a single-crystal silicon that had never before been used to create X-ray mirrors. These specially fabricated optics must be curved and nested inside a cylindrically shaped container so that highly energetic X-ray photons graze their surfaces and deflect into an observatory’s instruments rather than passing through them.

This particle beam polishes the surface of a new X-ray optic made of silicon.
Credits: Chris Gunn/NASA

The goal was to develop easily reproducible, lightweight, super-thin mirrors, without sacrificing quality.

“What we’ve done is shown from a scientific perspective and empirically that these optics can be built” using an inexpensive, abundantly available material that is immune from the internal stresses that can change the shape of X-ray mirrors made of glass, the more traditional mirror-making material, Zhang said.

NASA’s review panel deemed two other technologies – full-shell mirrors and adjustable optics – will be able to fulfill the requirements of the conceptual Lynx Observatory.

Zhang’s mirrors provide 0.5 arc-second resolution — comparable to the image quality afforded by ultra-high-definition television — they also met Zhang’s low-mass requirements. They are 50 times lighter and thinner than Chandra’s, Zhang said. Future observatories could carry far more mirrors, creating a larger collection area for snagging X-rays emanating from high-energy phenomena in the universe.

Written By Brian Wang,