🌍 Discovery of a super-Earth with intermittent habitability

A super-Earth with extreme climatic conditions has been identified 2,472 light-years from our planet. This world, named Kepler-735c, has the unique characteristic of being habitable only during part of its orbit around its star.

The detection of this exoplanet was made possible through transit timing variations (TTV), an indirect method that does not require directly observing the planet. This technique relies on analyzing the gravitational perturbations that an invisible planet induces on the orbit of another planet in the same system.


Kepler-735c orbits a Sun-like star alongside a gas giant, Kepler-725b. The observed TTVs of the latter allowed scientists to deduce the presence and characteristics of the super-Earth. With a mass ten times that of Earth, Kepler-735c intrigues researchers due to its still poorly understood properties.

The highly elliptical orbit of Kepler-735c periodically takes it through its star's habitable zone. This peculiarity raises questions about the possibility of life adapted to these changing conditions. Unfortunately, the absence of direct transits prevents the study of its atmosphere with instruments like the James Webb Space Telescope.

Future missions, such as the European Space Agency's PLATO, could discover other similar planets using TTVs. This method expands our horizons by revealing worlds on wider orbits, less accessible through traditional techniques. The case of Kepler-735c illustrates the potential of TTVs in the search for habitable planets.

This discovery, published in Nature Astronomy, opens new avenues for understanding the diversity of planetary systems. It shows that habitability can be a temporary condition, dependent on the orbital dynamics of planets.

How do transit timing variations reveal invisible planets?

Transit timing variations (TTVs) are a clever method for detecting planets that do not pass directly in front of their star from our vantage point. They exploit the gravitational perturbations one planet exerts on another, slightly altering the regularity of its transits.

This technique allows scientists to infer the presence, mass, and orbit of otherwise undetectable planets. It is particularly useful for planets on wide orbits, where transits are rare or nonexistent.

TTVs have already helped complete several planetary systems. They complement traditional methods, such as radial velocity measurements or direct transit observations.

With the advent of more sensitive telescopes, TTVs could become a key tool in discovering new exoplanets, especially those located in their stars' habitable zones.

What makes a super-Earth potentially habitable?

A super-Earth is a planet with a mass between that of Earth and a gas giant like Neptune. Their habitability depends on several factors, including their distance from their star, the presence of an atmosphere, and the composition of their surface.

The planet's orbit also plays a crucial role. A highly elliptical orbit, like that of Kepler-735c, can lead to extreme climatic variations.

The presence of liquid water is another essential criterion. However, on a super-Earth, strong gravity could affect the atmosphere and the stability of oceans.

Finally, geological activity, such as volcanism or plate tectonics, could influence long-term habitability. These processes are still poorly understood on super-Earths due to the lack of examples in our Solar System.