NASA’s Transiting Exoplanet Survey Satellite (TESS) is the first space-based, all-sky surveyor to search for alien worlds. The spacecraft was launched on April 18, 2018, with a SpaceX Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida. TESS will observe 400,000 stars across the whole sky to catch a glimpse of an exoplanet transiting across the face of its parent star. A team of astronomers from Cornell, Lehigh and Vanderbilt Universities has identified the most promising targets for this search. The new catalog identifies 1,822 stars for which TESS is sensitive enough to spot Earth-like exoplanets just a bit larger than our planet that receive radiation from their star equivalent to what Earth receives from our Sun.
An artists’ concept of NASA’s Transiting Exoplanet Survey Satellite against a background of stars and orbiting planets in the Milky Way. Image credit: ESA / M. Kornmesser, ESO / Aaron E. Lepsch, ADNET Systems Inc / Britt Griswold, Maslow Media Group / NASA’s Goddard Space Flight Center / Cornell University.
The 1,822 stars selected for the catalog are bright, cool dwarfs, with temperatures roughly between 2,700 and 5,000 Kelvin (2,427-4,727 degrees Celsius, or 4,400-8,541 degrees Fahrenheit).
They are selected due to their brightness; the closest are only approximately 6 light-years from Earth.
“Life could exist on all sorts of worlds, but the kind we know can support life is our own, so it makes sense to first look for Earth-like planets,” said TESS science team member Professor Lisa Kaltenegger, director of Cornell’s Carl Sagan Institute.
“This catalog is important for TESS because anyone working with the data wants to know around which stars we can find the closest Earth-analogs.”
“I have 408 new favorite stars. It is amazing that I don’t have to pick just one; I now get to search hundreds of stars,” she added.
Confirming an exoplanet has been observed and figuring out the distance between it and its star requires detecting two transits across the star.
The 1,822 stars in the new catalog are ones from which TESS could detect two planetary transits during its mission. Those orbital periods place them squarely in the habitable zone of their star.
The catalog also identifies a subset of 227 stars for which TESS can not only probe for planets that receive the same irradiation as Earth, but for which TESS can also probe out farther, covering the full extent of the habitable zone all the way to cooler Mars-like orbits.
This will allow astronomers to probe the diversity of potentially habitable worlds around hundreds of cool stars during the TESS mission’s lifetime.
“We don’t know how many planets TESS will find around the hundreds of stars in our catalog or whether they will be habitable, but the odds are in our favor,” Professor Kaltenegger said.
“Some studies indicate that there are many rocky planets in the habitable zone of cool stars, like the ones in our catalog. We’re excited to see what worlds we’ll find.”
“This is a remarkable time in human history and a huge leap for our understanding of our place in the Universe,” said TESS science team member Dr. Keivan Stassun, an astronomer at Vanderbilt University.
The new catalog was published in the Astrophysical Journal Letters.
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L. Kaltenegger et al. 2019. TESS Habitable Zone Star Catalog. ApJL 874, L8; doi: 10.3847/2041-8213/ab0e8d
