TESS Finds Related Stars Have Young Exoplanets

Thanks to data from NASA’s Transiting Exoplanet Survey Satellite (TESS), an international collaboration of astronomers has identified four exoplanets, worlds beyond our solar system, orbiting a pair of related young stars called TOI 2076 and TOI 1807.

These worlds may provide scientists with a glimpse of a little-understood stage of planetary evolution.

TOI 2076 and TOI 1807 reside over 130 light-years away with some 30 light-years between them, which places the stars in the northern constellations of Boötes and Canes Venatici, respectively. Both are K-type stars, or dwarf stars more orange than our Sun, and around 200 million years old, or less than 5% the Sun’s age. In 2017, using data from ESA’s (the European Space Agency’s) Gaia satellite, scientists showed that the stars are traveling through space in the same direction.

Astronomers think the stars are too far apart to be orbiting each other, but their shared motion suggest they are related, born from the same cloud of gas.

Both TOI 2076 and TOI 1807 experience stellar flares that create strong bursts of X-ray and UV light.

Scientists discovered three mini-Neptunes, worlds between the diameters of Earth and Neptune, orbiting the star. Innermost planet TOI 2076 b is about three times Earth’s size and circles its star every 10 days. Outer worlds TOI 2076 c and d are both a little over four times larger than Earth, with orbits exceeding 17 days.

TOI 1807 hosts only one known planet, TOI 1807 b, which is about twice Earth’s size and orbits the star in just 13 hours. Short-period planets are rare, and TOI 1807 b is the youngest example yet discovered.

According to theoretical models, planets initially have thick atmospheres left over from their formation in disks of gas and dust around infant stars. Where they form in a disk helps determine the composition of their atmospheres. In some cases, planets lose their initial atmospheres due to stellar radiation, leaving behind rocky cores. Some of those worlds go on to develop secondary atmospheres through planetary processes like volcanic activity.

The ages of the TOI 2076 and TOI 1807 systems suggest that their planets are somewhere in the middle of this atmospheric evolution. 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.

Studying them further with ground-based observatories may eventually yield mass measurements. If they have low masses, missions like NASA’s Hubble and the upcoming James Webb space telescopes may be able to observe their atmospheres, if they have them, and tell us more about their compositions, providing further clues about the planets’ evolutionary stages.

Music Credit: "Building Ideas" from Universal Production Music

Video credit: NASA's Goddard Space Flight Center
Chris Smith (KBRwyle): Lead Producer
Chris Smith (KBRwyle): Lead Animator
Jeanette Kazmierczak (University of Maryland College Park): Lead Science Writer
Christina Hedges (BAERI/Ames): Lead Scientist

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