A team of astronomers have discovered evidence for yet another exoplanet orbiting Proxima Centauri, our closest neighboring star just over four light-years away.

The planet, dubbed Proxima d, is the third planet detected in the system. It’s also pretty tiny, at only a quarter of the Earth’s mass, making it one of the lightest exoplanets ever discovered, according to a press release.

“The discovery shows that our closest stellar neighbor seems to be packed with interesting new worlds, within reach of further study and future exploration,” said João Faria, a researcher at the Instituto de Astrofísica e Ciências do Espaço in Portugal and lead author of the study published today in the journal Astronomy & Astrophysics, in the statement.

The tiny planet orbits its star at around 2.48 million miles, less than a tenth of the distance between Mercury and the Sun, completing a full rotation in just five days.

Even more excitingly, its orbit is also within the habitable zone of the Proxima Centauri system, the area where liquid water could exist on its surface.

In other words, Proxima d could theoretically harbor life as we know it.

Faria and his team used the High Accuracy Radial velocity Planet Searcher (HARPS) instrument attached to the European Southern Observatory’s Very Large Telescope in the Chilean desert to make the discovery.

The team got first glimpses of Proxima d during 2020 observations, but the signal was too weak to confirm its existence, requiring follow up observations with the even more precise Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO).

“After obtaining new observations, we were able to confirm this signal as a new planet candidate,” Faria explained in the statement. “I was excited by the challenge of detecting such a small signal and, by doing so, discovering an exoplanet so close to Earth.”

The team was able to find evidence for the tiny planet’s existence by using the radial velocity technique, which involves detecting wobbles in the motion of a star caused by an orbiting planet’s gravitational pull.

The ESO’s instrument was accurate enough to pick up Proxima Centauri wobbling a mere 15 inches per second.

Experts are now excited to use the same technique to “unveil a population of light planets, like our own, that are expected to be the most abundant in our galaxy and that can potentially host life as we know it,” as Pedro Figueira, ESPRESSO instrument scientist at ESO, put it in the statement.

Proxima Centauri is tantalizingly close — and we may only see whether it hosts life once we have a look for ourselves.

READ MORE: New planet detected around star closest to the Sun [ESO]

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