NASA’s Transiting Exoplanets Inspection Satellite, better known as TESS, has discovered three new worlds that are among the smallest and closest exoplanets known to date . The planets in question orbit a star just 73 light-years distant from Earth and include a rocky planet slightly larger than Earth and two gaseous mini-Neptunes – planets roughly half the size of our own icy giant. .
We may have discovered thousands of exoplanets, but few have astronomers as excited as this newly discovered system.
Why is it so interesting?
Because not only could it reveal new details about the formation of planets, but it could lead to the discovery of a habitable world.
The three exoplanets orbit an unusually quiet red dwarf and appear to be linked in a resonance chain, interacting gravitationally to produce a pattern in their orbital periods.
The star has been named TOI-270 , and its planets TOI-270b (the rocky planet), TOI-270c and TOI-270d (the gaseous ones).
“TOI-270 is a true Disneyland for exoplanet science, and one of the main systems that TESS set out to discover,” commented astrophysicist Maximilian Günther of MIT’s Kavli Institute for Astrophysics and Space Research in the journal Nature Astronomy that publishes the study. “You really can do all the things you want to do in exoplanet science, with this system.”
It is quite probable that none of them are habitable; Let’s not fool ourselves. It is very complicated. TOI-270b, which is a rocky planet about 1.25 times the size of Earth , is the closest to the star, rotating in a full orbit once every 3.4 days. Although the star is much cooler than the Sun, and is only 40% its size, it is still too close to hold liquid water on the surface, one of the main metrics for determining habitability.
Of the two sub-Neptunes, one is 2.42 times the size of Earth; the other 2.13 times. The largest has an orbit of 5.7 days, which places it too close to the star for habitability.
The smallest sub-Neptune has an orbit of 11.4 days , which means that its outer atmosphere could be habitable in terms of temperature; but it is likely to have a very thick atmosphere that creates a greenhouse effect, leaving the surface too hot to survive.
The fascinating oddities of the system
Regarding the star, its sun: Most red dwarfs are turbulent with frequent solar flares, but TOI-270 is an older star. And since it’s close, it’s brilliant too. Also, because their planets pass between us and the star when they orbit, we can learn a lot about their atmospheres by studying changes in the star’s light.
This could help us learn more about how different planets form, and why some are rocky and small, and others are huge and gaseous. We cannot do this based on the planets in our own solar system, because we do not have mini Neptunes, known as the “missing link” between the rocky planets and the gas giants.
“We have found very few planets like this in the habitable zone, and much less around a quiet star, so this is rare,” clarified planetary astrophysicist Stephen Kane, from the University of California Riverside (USA).
And the moons?
According to the experts, although TOI-270d is unlikely to be habitable, it could have exomoons, so there is no doubt that it is a tremendously exciting system for future research opportunities.
“There are many small pieces of the puzzle that we can solve with this system,” Günther said. “ It is an exceptional laboratory, not for one, but for many reasons : it really ticks all the boxes.”
Referencia: A super-Earth and two sub-Neptunes transiting the nearby and quiet M dwarf TOI-270, Nature Astronomy (2019). DOI: 10.1038/s41550-019-0845-5
