NASA and its partners are in the process of developing two cutting-edge technologies with the potential to significantly advance the hunt for extraterrestrial life on distant Earth-like planets. The ambitious designs currently under development could allow astronomers to cut through the intense disturbance caused by an exoplanet's parent star, allowing them to image the remote worlds directly, and make detailed observations.
The discovery of new and exotic exoplanets has began to feel almost routine at this point, largely thanks to the efforts of NASA's Kepler Space Telescope, which has been responsible for the discovery of over 1,000 alien worlds.
However, thanks to mankind's legitimate obsession with the discovery of an extraterrestrial civilization, the news that astronomers have detected a world orbiting in a star's habitable zone is still a cause for excitement. This habitable or "goldilocks" zone is essentially a region of space around a star in which an orbiting rocky planet is subjected to temperatures conducive to the presence of liquid water, and therefore life.
The problem with detecting and characterizing these worlds is that, in most instances, an exoplanet's star shines many billions of times brighter than the satellite body, leaving astronomers incapable of directly imaging the planet. Even when the world can be observed, interference from the nearby star makes it difficult for delicate instruments known as spectrographs to ascertain the properties of the planet's atmosphere.
These instruments are capable of breaking down light into its component wavelengths, and exposing the presence of life through the detection of oxygen, ozone, water, and methane, which could serve as evidence for forests and living creatures dwelling on the planet's surface.
NASA and its partners are actively working on two distinct methods of starlight suppression. The first and arguably more ambitious of the two ventures has been imaginatively designated as the starshade, seen in the following video.
Currently, Engineers and scientists working on the project at NASA's Jet Propulsion Laboratory envision a vast, 130 ft (40 m)-wide sunflower-like light-shield boasting a solid centre lined with petal-like protrusions.
"The shape of the petals, when seen from far away, creates a softer edge that causes less bending of light waves," states JPL's lead engineer on the starshade project Dr. Stuart Shaklan. "Less light bending means that the starshade shadow is very dark, so the telescope can take images of the planets without being overwhelmed by starlight."
In order to successfully utilize the starshade, a number of potent technological challenges must be overcome. Much like the highly-anticipated James Webb Space Telescope, the massive sunshade would be far too large to launch in its fully-deployed state.
Instead, the petaled light-shield would lift off folded into a cylindrical shape, designed to fit snugly within the fairing of its launch vehicle. The protective shade could either be inserted into orbit on its own, or in conjunction with a space telescope. The beauty of the concept is that the starshade could utilize onboard propulsion to reposition itself, allowing it to be compatible with any telescope in orbit at the time.
In order to be viable, NASA engineers will have to devise a method of keeping the light-shield precisely fixed in space between the target star and the telescope making use of the platform.
The second technology under development are advanced coronagraphs. The application of this technique would not require the complex tandem actions of two spacecraft working in perfect concert. Instead, the light from a distant star would be cancelled out by a mechanism housed within a next-gen orbital telescope.
A basic coronagraph places an obstruction known as a "mask" in the path of a beam of light collected by a telescope from a distant star. As the light passes through the telescope, the mask removes some of the glare from the targeted stellar body, allowing any orbiting planets to make themselves known.
The light reflected by the planets is received by the telescope's sensors at a slight angle, as they are not in the exact same position as the star. These distortions, as well as others created by miniscule vibrations in the telescope, could theoretically be accounted for with the use of a deformable mirror, which could alter its shape with the use of hundreds of tiny pistons layering its underside.
A number of coronagraphs are being designed for implementation in future NASA endeavors. One such mission, known as the Wide-Field Infrared Survey Telescope (WFIRST), will see two separate coronagraphs, known as the "hybrid Lyot", and the "shaped pupil", installed aboard an orbital telescope in the Occulating Mask Coronagraph instrument.
Should either of these ambitious technologies become a reality, the ability to block out the light from a parent star, while preserving that of the orbiting exoplanet, would undoubtedly lead to significant breakthroughs in the search for life outside of our solar system.
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