|Hubble telescope image courtesy NASA|
Earth-bound biologists, ecologists and climatologists have had little good news to offer us lately. But astrophysicists with their eyes on the skies continue to make new, more wondrous discoveries in exoplanetary science, assuring us that our own little solar system is not alone in the galaxy.
The older-generation Kepler and Hubble telescopes, which gave us our first glimpses of planets circling distance stars, have begun to reach their limit of usefulness. Kepler went dark last October, after almost a decade of observation from Earth orbit; Hubble remains fully functional after five in-orbit repairs but will eventually be replaced by the James Webb Space Telescope due to be launched in 2021.
NASA’s newest tool in the hunt for exoplanets is the Transiting Exoplanet Survey Satellite, or TESS, which launched last April and began observations in July, 2018. In its first four months of operation, TESS found eight confirmed new planets and 320 more as-yet unconfirmed possibilities, according to Xu Chelsea Huang of MIT.
Observations from TESS are stretching our understanding of planetary formation and what a “planet” can look like. Some of TESS’s discoveries include HD21749b, only 52 light years away, with the lowest temperature known for a planet orbiting so close to a bright, nearby star.
“If we want to study atmospheres of cool planets, this is the one to start with,” Huang said. The planet has a thick atmosphere, but Huang’s use of the term “cool” is relative: the planet is likely too hot and gassy to support life. Its orbit takes 36 Earth days, the longest known orbital period for planets transiting within 100 light-years of bright stars.
Or take the denizens of the star system Pi Mensae. Pi Mensae c orbits its star every 6.27 days and has a density similar to water; Pi Mensae b has a mass ten times that of Jupiter that orbits the star every 5.7 years in a wildly swinging ellipse—sometimes as close as that of Earth, sometimes as far as that of Jupiter.
Huang describes another planet TESS found, LHS 3844b, as “likely a lava world.” It has a radius just 1.3 times Earth’s, but it swings around its planet every 11 hours, giving it a surface temperature of about 540° C.
All of which goes to show that the universe is stranger by far than anyone could have predicted. These are only the newest planets among the thousands that have been discovered over the last decade by scientists using NASA instruments. And that can only be good news.
*Information for this post taken from “Less than a year after launch, TESS is already finding bizarre worlds,” by Lisa Grossman, Science News, January 8, 2019.