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Astronomers have confirmed the existence of Proxima b, an Earth-size exoplanet orbiting the closest star to our sun.
The European Southern Observatory’s High Accuracy Radial velocity Planet Searcher (HARPS) detected the planet in 2016.
The Very Large Telescope based in Chile has a new and more powerful spectrograph named ESPRESSO, so astronomers decided to use it for more precise measurements of the planet. It stands for Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations.
In fact, ESPRESSO has an accuracy more than three times the precision of HARPS — which is essentially the same instrument, just from a previous generation.
“We were already very happy with the performance of HARPS, which has been responsible for discovering hundreds of exoplanets over the last 17 years,” said Francesco Pepe, study author and University of Geneva professor in the astronomy department, in a statement.
“We’re really pleased that ESPRESSO can produce even better measurements, and it’s gratifying and just reward for the teamwork lasting nearly 10 years.”
The researchers determined that Proxima b is 1.17 times the mass of Earth — and completes an orbit around its star, Proxima Centauri, every 11.2 Earth days. The star, Proxima Centauri, is 4.2 light-years from our sun. Previously, scientists using the HARPS measurements said it was 1.3 Earth masses.
“Proxima b is a very special guy among all the known exoplanets: the closest exoplanet there will ever be to us, terrestrial in size, and within the habitable zone,” said Christophe Lovis, study co-author and researcher in the University of Geneva’s astronomy department.
“In spite of the clear detection achieved by HARPS in 2016, it was necessary to have independent confirmation from the new and much more powerful ESPRESSO, to lift any remaining doubts there could have been.
The study results were published last week in the journal Astronomy & Astrophysics.
Proxima b is 20 times closer to its star than Earth is to the sun. Proxima Centauri is a low-mass red dwarf star, which means that even though the planet is close to the star, it receives similar energy that Earth does from the sun.
“Finding planets around these [stars] has always been difficult because they are faint and emit most of their light in the red and infrared spectral ranges,” Lovis said. “ESPRESSO opens new possibilities for finding many other small worlds around stars very close to the Sun.”
Proxima b is located within the habitable zone of its star, meaning that liquid water, and the suggestion of life, may be possible on the planet’s surface.
However, Proxima Centauri is an active star that lashes the planet with X-rays — 400 times more than Earth receives from the sun. This could impact the chances for water and life on the planet.
Lovis is working on a new instrument called RISTRETTO which will be installed at the Very Large Telescope in Chile. It’s designed to directly detect light emitted by the planet, which will allow researchers to characterize the planet’s atmosphere and its surface composition.
“The ultimate goal is to search for molecules in the atmosphere that could possibly hint at the presence of life, such as oxygen and water vapour,” Lovis said. “On the longer term, we are also building a spectrograph called HIRES for the European Extremely Large Telescope whose main goal will be to study Proxima b and similar exoplanets in the habitable zone.”
