Thanks to Elisa Quintana and Sean Raymond, I was able to take part in an exciting adventure:

The discovery of a planet!

This discovery was published in Science (Quintana et al., 2014). Along with Elisa and people of the Laboratoire d’Astrophysique de Bordeaux, we also recently submitted a follow-up article focused on the formation, evolution and habitability of Kepler-186 (Bolmont et al., 2014).


This planet is called Kepler-186f. It’s an Earth-sized planet within the habitable zone of a cool star.

Just to clarify things, the habitable zone is here defined as the region around a star where a planet with the right atmospheric conditions can have surface liquid water. This represents only the very first step to habitability!

Here’s the comparison with our Solar System:
Kepler186f_ComparisonGraphic NASA/Ames/JPL-Caltech/T. Pyle


Here are a few fun facts about this planet:

  • Why the name Kepler-186f?

    The discovery was made thanks to the Kepler Space Telescope.
    The planetary system Kepler-186 is the 186th to be confirmed from the Kepler Space Telescope data.
    Kepler-186A refers to the star, Kepler-186b to the closest planet from the star, then c, d, e and finally the fifth planet of the system is Kepler-186f

  • How was is discovered?

    The Kepler Space Telescope observed from 2009 to 2013 the light coming from about 100,000 stars. When a planet passes between its star and the telescope, it hides a part of the light coming from the star so that for a while the star appears dimmer.
    The decrease in luminosity due to the passage of a planet is called a transit (like an eclipse) and this is what this telescope is capable of detecting!

  • Why can’t we call it a Earth twin?

    Simply because its host star is different than the Sun: its less hot, less big and redder. Kepler-186A is colder than the Sun, so you need to be closer than the Earth-Sun distance to be at the right temperature. In other words, the habitable zone is closer.

  • What makes it even more interesting than the others discovered so far?

    A planet this size is very likely to be rocky, and so likely to have a surface on which you could have oceans. The previous planets in the habitable zone were much larger: 2 times the size of the Earth for Gliese 581 d for example. For such large planets, the doubt remains on their nature: they could be super Earths or mini Neptunes.

  • Can we go there?

    Alas, no… It’s much too far. Light, which is the most rapid thing in the Universe, takes 500 years to come from there. If you can travel in Space at the speed of Voyager 1 (17.26 km/s), you’ll need about 8.5 million years to get there. So forget it, you’ll never be able to build a summer house there.

  • Is there life?

    Unfortunately, there is no way to tell with our current technology. The only sure things we know about this planet are its size and its orbital period (the duration of Kepler-186f’s year). As we can infer the distance between Kepler-186f and its star, we can say its in the habitable zone, so if the planet has water and good atmospheric conditions, it can host surface liquid water. That’s all we can say for now.
    However, we cannot rule out the possibility that life could develop there. So feel free to dream about that!

  •  Will we ever know more?

    Not for a while… The star is faint and far away, our instruments are not good enough to allow other kinds of measurements on the system. However in the future, with better instruments, we can imagine that we will be able to measure the wobble of the star created by the presence of the planets (radial velocity technique). This would allow us to have the masses of the planets, which is very important because it can give us an idea of their composition: mixture of rock and iron, rock and ice…

  • So what now?

    We wait! Scientists are analysing the four years of Kepler data: it’s a long job. They are looking for transits and making sure that the signals they see correspond to real planets.
    This planet is hopefully the first of many others confirmed in the future looking more and more like our Earth!

Links about Kepler-186f

This discovery has created a lot of publicity in France!

Here are a few links to French media which broadcasted these news:
Voici quelques liens vers des médias français qui ont plus ou moins bien relayé: 



  • RTL (à partir de 9:30 min: attention, celui-là est drôle)
  • France inter, la tête au carré (à partir de 5 min)

Presse écrite (interne/externe):


With Sean, we were invited to give a TEDx conference in October 2014, it was a wonderful experience!
The complete show can be seen here: TEDx_LaRochelle_2014. It’s in french but in a few weeks, the YouTube video will come out with english subtitles.