Deep in the cosmos, NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered four new worlds orbiting a pair of young stars. These planets are providing scientists with a glimpse into a little-understood stage of planetary evolution - the time when atmospheres are being formed.
The stars TESS looked at are TOI 2076 and TOI 1807 and reside over 130 light-years away with some 30 light-years between them and are located in the northern constellations of Boötes and Canes Venatici. Both are K-type stars, dwarf stars more orange than our Sun, and around 200 million years old, or less than 5% of the Sun’s age.
In 2017, using data from ESA’s Gaia satellite, scientists showed that the stars are traveling through space in the same direction leading them to think they are related, born from the same cloud of gas..
These stars are hyperactive, experiencing stellar flares much more energetic and frequent than those produced by our own Sun.
Around TOI 2076, astronomers discovered three mini-Neptunes, worlds between the diameters of Earth and Neptune
The innermost planet, TOI 2076 b, circles its star once in only 10 days. The outer planets, c and d, have orbits exceeding 17 days.
TOI 1807 hosts only one known planet, TOI 1807 b and is the most extreme of the bunch. It orbits its star in an astonishingly fast 13 hours, making it one of the youngest ultra-short period planets ever discovered.
Theories suggest that planets initially have thick atmospheres left over from their formation. But stellar radiation can erode these atmospheres, leaving behind rocky cores. Some planets may then develop secondary atmospheres through planetary processes like volcanic activity.
The ages of the TOI 2076 and TOI 1807 systems suggest that their planets may be somewhere in the middle of this atmospheric evolution.
All of these planets are bombarded with UV radiation, making life here unlikely at this stage in their development. TOI 2076 b receives 400 times more UV light from its star than Earth does from the Sun – and TOI 1807 b gets around 22,000 times more.
Scientists are currently working to measure the planets’ masses, but the interference from their hyperactive stars could make this challenging.
If scientists can discover the planets’ masses, that will help NASA’s James Webb space telescope determine if they have atmospheres and study them.
This discovery is a tantalizing glimpse into the early stages of planetary evolution. By studying these worlds, scientists can learn more about how planets form and how their atmospheres develop.