NASA’s planet-hunting TESS Mission keeps giving astronomers new realities to examine and explain and now the NASA’s TESS helps astronomers study the red giant stars and explore them close to the planet.

Astronomers using the tools of asteroseismology the observations and measurements of a star’s oscillations, or starquakes, that appear as changes in brightness have learned more about two stars bright enough to be visible in a dark sky to the naked eye.

These red giant stars older, retired stars no longer burning hydrogen in their cores known as HD 212771 and HD 203949.

Both stars are known to host their planets. And the TESS data say one of those exoplanets (the general term for planets that orbit stars other than our sun) is so close to its host star it shouldn’t have survived the star’s expansion as a red giant if, that is, the star is old enough to have expanded and retreated.

Researchers used that data to determine actual values mass, radius and evolutionary stage for these stars.

Asteroseismology can tell us all these things and more about stars that are difficult to with other tools.

The new work, the authors wrote, is a way of further showcasing the mission’s potential to conduct asteroseismology of red-giant stars. The study indicated star HD 203949 was less massive than before thought.

That meant for its planet to be moving as fast as the astronomers determined, it had to be much closer to the star than expected. So close, it would be engulfed by the star’s expansion as a red giant.

The host star is early in its red giant expansion and has yet to engulf and destroy the planet. Or computer simulations of star-planet tides say the planet could have dragged from a wider orbit, where it avoided destruction by the star, and then settled into a closer orbit once the star retreated.

As astronomers continue to analyze data for clues about how planets and stars evolve with each other.

TESS the Transiting Exoplanet Survey Satellite, led by astrophysicists from the Massachusetts Institute of Technology launched in April 2018.

The spacecraft and its four cameras are on a two-year mission to survey 85 percent of the sky, looking for planets by detecting tiny dips of light as they pass in front of their host stars.

Those cameras also collect star data that are useful for planetary studies, too.

Characterization of host stars is a critical component of understanding their planets, the authors wrote. The asteroseismology techniques described here are thus an important component of planetary system characterization.