Skip to main content

How did that planet get there? TESS investigates a planetary mystery

An artist’s impression of a hot-Jupiter exoplanet. C. Carreau / ESA

NASA’s planet-hunting satellite TESS, or Transiting Exoplanet Survey Satellite, has made another intriguing discovery. This time, it’s located a planet somewhere where it shouldn’t be, right in the middle of a zone in which any planet should have been annihilated by its star.

The star HD 203949 is located 257 light-years away and is a K2-type giant star, slightly cooler than our sun. Traveling around this star is a large planet, HD 203949b, which is 8.2 times the mass of Jupiter and in a 184-day circular orbit.

So far, so typical. But there’s something odd about HD 203949b because it should have been engulfed by its star long ago. The boundaries of a star, called its envelope, expand and contract over time. When the giant star HD 203949 was younger in its red giant phase, its envelope should have covered the planet and destroyed it — and yet the planet is still there.

The researchers investigated this mystery more closely using computer simulations. They came up with a theory that the planet must have started out further away from the star and been drawn closer toward it over time.

“We determined how this planet could have reached its current location, and to do so whether or not the planet had to survive engulfment within the stellar envelope of the red giant star,” co-author Dr. Dimitri Veras explained in a statement. “The work sheds new light on the survivability of planets when their parent stars begin to die, and might even reveal new aspects of tidal physics.”

This discovery of a planet shifting its orbit over time shows how complex the relationships within planetary systems can be. “This study is a perfect demonstration of how stellar and exoplanetary astrophysics are linked together,” co-author Dr. Vardan Adibekyan said in the same statement. “Stellar analysis seems to suggest that HD 203949 is too evolved to still host a planet at such a short orbital distance, while from the exoplanet analysis we know that the planet is there.”

“The solution to this scientific dilemma is hidden in the simple fact that stars and their planets not only form but also evolve together,” Dr. Adibekyan continued. “In this particular case, the planet managed to avoid engulfment.”

The findings are published in the Astrophysical Journal.

Editors' Recommendations

Georgina Torbet
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
NASA’s TESS has discovered 5,000 exoplanet candidates
nas tess satellite begins exoplanet hunt orbits planet

NASA's planet-hunting satellite TESS, or the Transiting Exoplanet Survey Satellite, has passed an impressive milestone, having identified 5,000 potential exoplanets. Launched in 2018, the hard-working telescope has been used by researchers from a variety of institutions to find tell-tale indications of planets outside our solar system.

Many of the objects TESS identifies are referred to as potential exoplanets, or TESS Objects of Interest (TOIs) because it requires multiple observations to confirm that a given signal is in fact an exoplanet. Currently, of the over 5,000 candidates discovered, 176 have been confirmed as exoplanets.

Read more
Citizen scientists help discover a Jupiter-like planet 379 light-years away
This illustration depicts a Jupiter-like exoplanet called TOI-2180 b. It was discovered in data from NASA's Transiting Exoplanet Survey Satellite.

Much of the work done in astronomy requires large groups of people co-operating and working together to make new discoveries. While most of that work is done by professional astronomers, there are some occasions where members of the public help as well. Recently, citizen scientists have helped comb through data from a NASA telescope to identify a gas giant planet located 379 light-years away.

The team of citizen scientists used data from the Transiting Exoplanet Survey Satellite, or TESS, to identity planet TOI-2180 b. It orbits a star with a similar mass to our sun, and a year there lasts 261 days, which makes it one of the further-out gas giants discovered outside the solar system. “Discovering and publishing TOI-2180 b was a great group effort demonstrating that professional astronomers and seasoned citizen scientists can successfully work together,” said Tom Jacobs, one of the citizen scientists who volunteered for the project, in a statement. “It is synergy at its best.”

Read more
Largest ever group of lonely rogue planets discovered in Milky Way
This artist’s impression shows an example of a rogue planet with the Rho Ophiuchi cloud complex visible in the background. Rogue planets have masses comparable to those of the planets in our Solar System but do not orbit a star, instead roaming freely on their own.

Deep in the cold, dark emptiness of interstellar space, you can find some lonely planets roaming freely and not orbiting a star. Known as rogue planets, these objects are elusive and are rarely discovered due to being difficult to spot -- but a new study has found the largest collection of rogue planets to date, located in a region of the Milky Way called the Upper Scorpius OB stellar association.

Finding rogue planets is hard because, unlike stars, planets are dim and give off very little light, and these tiny points have to be picked out from a background of bright stars. But an international team was able to spot this group of rogue planets by using a combination of both new observations and archival data from a large number of sources including telescopes of the European Southern Observatory, the Canada-France-Hawaii Telescope, and the Subaru Telescope. In total, the data they used added up to 80,000 wide-field images taken over 20 years of observations.

Read more