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PLANETS Telescope to Explore Solar System Atmospheres, Exoplanets

Model of PLANETS telescope

Model of the PLANETS telescope structure

A big telescope is not necessarily the best possible instrument for all purposes. “Sometimes we don't need a bigger telescope, we just need a better telescope,” explains Jeff Kuhn, the IfA scientist spearheading the development of the 2-meter PLANETS (Polarized Light from Atmospheres of Nearby ExtraTerrestrial Systems) telescope on Haleakalā.

One of the primary goals of this telescope will be detecting the light from exoplanets and from the outer atmospheres of planets in our solar system. Achieving this goal requires minimizing scattered light from the host star (or planet) and maximizing the ability of the telescope’s detectors to see faint objects near a very bright one. To achieve this goal, PLANETS will be different from most telescopes in that it is designed for what scientists call “high photometric dynamic range.” Until the Daniel K. Inouye Solar Telescope comes online a few years later, PLANETS will be the world's largest off-axis optical telescope, which means there will be no obstructions to the incoming beam of light due to the secondary mirror and its supports. To minimize its cost, the telescope will also use innovative technology to achieve the thinnest primary mirror of any comparable astronomical telescope. All of its design features greatly reduce  the amount of diffraction—the unwanted “glare” from light that is spread out as a result of passing through a narrow aperture or across an edge. PLANETS’ mirror will also be polished to be very smooth to minimize diffuse scattered light from mirror roughness, a major source of light scattering.

PLANETS will also have a stellar coronagraph to block out the blinding glare from the star. While most coronagraphs have been used to create an artificial solar eclipse to see the corona of our Sun, the PLANETS’ stellar coronagraph can be used to see planets around other stars, the disks that form them, or the tenuous outer atmospheres of solar system planets like Mercury. These exoplanets, outer atmospheres, and disks can be millions to billions times fainter than the glare around them. Making a telescope capable of containing and removing the glare allows for the detection and study of the light from the faint source. In this way, PLANETS can also be used to see a variety of what would otherwise be hidden objects.

The State of Hawai‘i DLNR permit process that would allow PLANETS to be installed at Haleakalā Observatories in a “re-tasked” structure that houses the University of Chicago Neutron Monitor observatory has been initiated. The major scientific and funding partners for this project include Tohoku University in Sendai, Japan, the Kiepenheuer Institute for Solar Physics in Freiberg, Germany, and the IfA. If the project receives final DLNR approval, it will take about two years to complete.