A new exoplanet discovered near us

With Mathilde Fontez, editor-in-chief of the scientific magazine Espiloonwe are talking today about the recent discovery of a planet that revolves around a star close to the Earth.

franceinfo: What is this exoplanet Mathilde, which orbits the star Proxima Centauri?

Mathilde Fontez: An international team of astronomers has just announced the news. Her name is Proxima d. And it revolves around Proxima Centauri: as its name suggests, it is the closest star to us. A small star, a red dwarf star, which is just over four light years from Earth.

It is therefore the discovery of a real small system which orbits very close to us, around Proxima, since two planets had already been detected there: one the size of the Earth, Proxima b. And a bigger one, a bit like our Neptune, Proxima c.

And what does this new planet look like?

Let’s be clear: we don’t know. Proxima d was not photographed by the Very Large Telescope, the Chilean telescope that discovered it. She is much too small.

It was detected thanks to its mass, its gravitational influence: astrophysicists have measured the tiny disturbance it causes in the orbit of its star. She makes her move 40 centimeters per second back and forth: that’s how they were able to detect her presence.

All we know about it is its mass. And it is very small: a quarter of that of our planet. It is a record, it is the lightest exoplanet detected by this method. Which suggests that it is a rocky, like the Earth. But it is probably too small to have been able to retain an atmosphere.

Impossible to find life there so…

Unlikely indeed. Especially since it must be very hot there. This is the other information that astrophysicists have been able to collect on Proxima d: its orbit. It rotates 4 million kilometers from Proxima du Centaure, which is very little.

It is 10 times closer to its star than Mercury, the planet closest to the Sun at home. It only takes 5 days to make a complete turn: on Proxima d, the years last 5 days!

Is it far from being the first exoplanet discovered?

to say the least. The first exoplanet was detected more than 25 years ago, in 1995. And since then, thousands have been discovered. 4.978 to be precise. Astronomers even estimate that there would be some around all the stars, or almost.

But this planet is an event, because it is very close. This planetary system is almost within reach, for us humans.

Moreover, there are projects to explore it. Not within the framework of a manned mission, it remains much too far. Not even with a classic space probe. But with a micro-vessel equipped with a solar sail that could reach a speed close to that of light…