Astronomers have recently discovered three planets orbiting dangerously close to the stars approaching the end of their lives.
Of the thousands of extrasolar planets found so far, these three gaseous giant planets, first discovered by NASA’s TESS (transiting Exoplanet Survey Satellite) mission, have some of the shortest orbits around sub-giant or giant stars.
One of the planets, TOI-2337b, will be swallowed by the host star in less than a million years, before any other planet currently known.
“These discoveries are key to understanding the new frontier in the study of exoplanets: how planetary systems evolve over time,” explained lead author Samuel Grunblatt, a postdoctoral fellow at the American Museum of Natural History and the Flatiron Institute in New York City.
Grunblatt, who received his doctorate. from IfA, added that “these observations offer new windows to planets that are nearing the end of their lives, before they are swallowed by the host stars.”
The discovery and confirmation of the planet was accepted for publication in the Astronomical Journal, and was announced at a press conference of the American Astronomical Society.
Researchers estimate that planets have masses between 0.5-1.7 times larger than Jupiter’s, and sizes range from slightly smaller to more than 1.6 times larger than Jupiter’s.
They also cover a wide range of densities, from cork density to three times denser than water, implying a wide variety of origins.
These three planets are believed to be just the tip of the iceberg.
“We expect to find tens to hundreds of these evolved transit planetary systems with TESS, providing new details on how planets interact, inflate and migrate around stars, including those like our Sun,” said Nick Saunders, a graduate student at IfA and co-author of the study.
The team hopes this ‘planetary archeology’ will help us understand the past, present and future of planetary systems, moving us one step closer to answering the question, “Are we alone?”
Detailed confirmation of Maunakei
The planets were first found in NASA TESS Mission full-frame image data taken in 2018 and 2019.
Grunblatt and his collaborators identified candidate planets in TESS data and then used the WM Keck Observatory at Maunakea to confirm the existence of three planets.
“Keck’s observations of these planetary systems are critical to understanding their origins, helping to uncover the fate of solar systems like ours,” said IfA astronomer Daniel Huber, co-author of the study.
Current models of planetary dynamics suggest that planets should spiral toward their host stars as stars evolve over time, especially in the last 10% of a star’s life.
This process also warms the planets, potentially causing their atmosphere to inflate.
However, this stellar evolution will also cause the planets around the star to come together, increasing the likelihood that some of them will collide, or even destabilize the entire planetary system.
The wide variety of planetary densities found in the study suggests that these planetary systems are shaped through chaotic planet-planet interactions.
This could also have resulted in unpredictable warming rates and time intervals for these planets, giving them the wide range of densities we observe today.
Future observations of one of the systems, TOI-4329, with the recently launched James Webb Space Telescope, could reveal evidence for water or carbon dioxide in the planet’s atmosphere.
If these molecules were seen, the data would provide limitations on where these planets originated and what interactions must have occurred to produce the planetary orbits we see today.
Continuing to monitor these systems with NASA’s TESS telescope will limit the speed at which these planets twist into their host stars.
So far, no clear signal of orbital decay has been observed in any system, but a longer observation base with extended TESS missions will provide much stricter restrictions on the spiral planet than is currently possible, revealing how powerful planetary systems are influenced by stellar evolution.
Source: University of Hawaii at Manoa.