From nanometers to gigaparsecs: The role of nanostructures in unraveling the mysteries of the cosmos

High launch costs and the extreme distance to astrophysical objects place a premium on astrophysical instrumentation with the highest attainable sensitivity and resolution at the lowest possible weight and cost. Many interesting and useful optical phenomena occur when the size and placement accuracy of features are comparable to, or smaller than, the wavelength of light. These considerations have compelled us to develop a variety of nanotechnoligies that have now been utilized in space physics instrumentation on nine missions. These include 200- and 400-nm-period membrane-supported transmission gratings for high-resolution spectroscopy of astrophysical x-ray sources, mesh-supported transmission gratings for solar extreme ultraviolet (EUV) monitoring, and UV nanofilters with 45 nm slots that are key components of atom cameras observing Earth’s magnetosphere. This article will describe instruments on space missions where we have applied nanotechnology. One application is the NASA Chandra Observatory x-ray telescope, for which we manufactured a large quantity of transmission gratings for high-resolution spectroscopy. Chandra is now returning a torrent of high-quality x-ray images and spectra from such interesting objects as supernova remnants, the accretion disks around black holes and neutron stars, stellar coronae, galaxy cluster cooling flows, and other x-ray-emitting objects up to gigaparsecs distant. [A short astronomy lesson: As Earth orbits Sol, nearby stars in the sky appear to wobble due to parallax. At a distance of one parsec (a “parallax-second”), the diameter of Earth’s orbit $(∼1.5×1011$ m) subtends one arcsecond, so a parsec is around 3.3 light years, or $3.1×1016$ m. For reference, the nearest star is around a parsec away, our Milky Way galaxy is a few kiloparsecs across, nearby galaxies are megaparsecs away, and the known universe is measured in gigaparsecs $(1025$ m).] Another application is the atom “camera” on the NASA Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft that studies Earth’s magnetosphere, the belt of plasma around the Earth formed by swept-up ions from the Solar wind trapped in the bottle of Earth’s magnetic field. The camera images the magnetosphere in the “light” of neutral atoms, rather than photons, emitted from the plasma due to charge exchange processes. We developed nanofilters, consisting of 500-nm-thick gold foils with 45-nm-wide slots, that are designed to block unwanted deep-UV and EUV photons which would otherwise overwhelm the detector with a million-to-one noise-to-signal ratio, thus allowing the camera to detect the weak atom fluxes. IMAGE is now sending back spectacular atom movies of the magnetosphere revealing a wealth of new information about this complex and dynamic environment. Finally, I describe work in our laboratory aimed at developing microtechnology for the shaping and assembly of glass microsheet optics to few-nanometer accuracy. We believe these new x-ray optics will spawn a new generation of diffraction-limited x-ray telescopes with massive collecting areas and resolution approaching 0.1 microarcsecond (∼1 picoradian). These new telescopes may enable the direct imaging of the massive black holes believed to lurk at the center of most galaxies.