Orbiting the Proxima Centauri system about 4 light-years from us, a team of astronomers has found evidence of a third planet: Proxima d , which is also one of the lightest exoplanets ever detected , presenting only a quarter of its size. the mass of our planet.
Using the Very Large Telescope in Chile, the team observed how the star wobbled under the gravitational pull of orbiting planets (known as the radial velocity method) and Proxima b and c were discovered. From the oscillations of the star, they deduced the more than probable presence of a third planet in the system.
third planet of the system
The planet Proxima D orbits between the star and the habitable zone , that is, in a region where liquid water can exist on a planet’s surface (because it’s not too hot or too cold for surface liquid water to exist). Of course, it is exceptionally close to its star, about 4 million kilometers away, since it takes only five days to complete an orbit around Proxima Centauri, located in the southern constellation of Centaurus with a radius of 14% of the radius of the Sun, a mass of around 12% with respect to our star and an effective temperature of only 2,777 ºC (the Sun has a surface temperature of 5,505 ºC).
“After obtaining new observations, we were able to confirm this signal as a new planet candidate. I was excited by the challenge of detecting such a small signal and, in doing so, discovering an exoplanet so close to Earth”, explains João Faria, from the Instituto Astrofisica e Ciências do Espaço de Portugal in their study collected by the journal Astronomy and Astrophysics.
The proximity to Proxima Centauri suggests that its surface temperatures are around 90ºC, which is much less than what we can find in places like Venus, but it is still a very hot place.
Another feature that has caught the attention of experts is its mass: 26% of that of Earth or twice the mass of Mars, that is, much lighter than any other planet in this system. (Although it’s not the only extralight planet we’ve discovered or the lightest of them all: PSR B1257+12 b, for example, has a mass of only 2% that of Earth.)
While the measurements are solid, more data is needed to firmly confirm the discovery , says Faria. “It needs to be confirmed by other instruments and other detection techniques.”
But his finding is hopeful
“The discovery shows that our closest stellar neighbor seems to be full of interesting new worlds, within the reach of further study and future exploration,” explains Faria, from the Instituto de Astrofisica e Ciências do Espaço de Portugal in his study published by the magazine.
The scientists behind the recent discovery also hope to find lighter planets using the same instruments that were used to find Proxima d.
“ This achievement is extremely important. It shows that the radial velocity technique has the potential to reveal a population of light planets, like our own, which are expected to be the most abundant in our galaxy and which can potentially host life as we know it”, explains Pedro Figueira, scientist of ESPRESSO instruments and co-author of the study.
The search for other worlds will be complemented by ESO’s Extremely Large Telescope (ELT), currently under construction in the Atacama Desert, Chile, which will be crucial for discovering and studying many more planets around nearby stars.
A very interesting neighbor
We already know that our neighbor Proxima Centauri hosts two other planets: Proxima b, a planet with a mass comparable to that of Earth that orbits the star every 11 days and is within the habitable zone, and Proxima c , which is in a greater distance and takes five years to complete one orbit of its star.
The discovery of Proxima d confirms that there is no doubt that it is a star system worth visiting. If we humans develop the right technology to travel beyond the confines of the solar system and reach interstellar destinations, this should be one of the first targets for such a mission.
Referencia: J.P. Faria et al. 2022. A candidate short-period sub-Earth orbiting Proxima Centauri. Astronomy and Astrophysics 658, A115; doi: 10.1051/0004-6361/202142337
