Sibling Stars Found with Teenage Exoplanets

Beth Johnson
3 min readJul 22, 2021

Four new teenage planets were found orbiting two separate but related stars in data collected by the TESS spacecraft, adding to the theory of planetary formation.

IMAGE: Short-period planets, or those with orbits shorter than one day, are rare. Potential lava world TOI 1807 b, illustrated here, is the youngest example yet discovered. CREDIT: NASA’s Goddard Space Flight Center/Chris Smith (KBRwyle)

At first glance, this story was interesting because more exoplanets were found, but we’ve been announcing new exoplanets almost steadily for the last decade-plus. Digging a little deeper, this story involves a new paper published in The Astronomical Journal about four new exoplanets that were found orbiting a pair of stars. These stars are related, the planets are teenagers, and they are all giving us more information about a stage of planetary formation we don’t yet understand.

I know. I say all the time that we’re never going to completely understand planetary formation. But with every story that comes out with new information, I’m beginning to think I will be proven wrong. And that’s wonderful.

What makes these stars and their planets so special? According to lead author Christina Hedges: The planets in both systems are in a transitional, or teenage, phase of their life cycle. They’re not newborns, but they’re also not settled down. Learning more about planets in this teen stage will ultimately help us understand older planets in other systems.

The two stars are TOI 2076 and TOI 1807, they are K-type stars or dwarf stars oranger than the Sun, they are 130 light-years away and 30 light-years apart from each other. They are relatively young stars as well, only about 200 million years old. By comparison, that is less than 5% the age of the Sun. And thanks to data from the amazing Gaia satellite, we know they are moving in the same direction, which is how we know they’re related.

As for the planets, TOI 2076 has three mini-Neptunes with the innermost orbiting every ten days. The outer two, per the press release, have “orbits exceeding 17 days”. TOI 1807 has one planet, about twice the size of Earth, and orbiting in 13 hours. So these are incredibly close to their stars. Both stars likely experience flares that give off far more energy than the ones our Sun produces, and they likely produce those flares frequently, so neither system sounds very good for life.

But life isn’t the purpose of studying this system. Again, these planets seem to be at a point in their…

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Beth Johnson

Planetary scientist, podcast host. Communication specialist for SETI Institute and Planetary Science Institute. Buy me a coffee: https://ko-fi.com/planetarypan