In 2016, astronomers discovered a potentially habitable, roughly-Earth-sized exoplanet just four light-years away – and now new observations suggest it isn’t alone. Scientists in Chile have detected hints of a second planet orbiting Proxima Centauri, the closest star to the Sun.
Following convention, the new planet (if it exists, that is) has been dubbed Proxima c. Observations indicate that it would have at least six times the mass of Earth, and orbit at a distance of 1.5 astronomical units (AU), which puts it about as far from the star as Mars is from the Sun. At this distance, Proxima c would fall in the system’s Habitable Zone.
The discovery was made using the Harps spectrograph installed on the 3.6-m Telescope at La Silla Observatory in Chile. While most exoplanets are spotted when their shadows pass in front of their host star – known as the transit method – Proxima c was detected using the radial velocity method. Basically, this means astronomers watch a star for telltale wobbles as it spins, which indicate that the gravity of an orbiting planet is tugging on it.
Researchers from the National Institute of Astrophysics (INAF) in Turin and the University of Crete analyzed the data taken from Proxima Centauri and found strong evidence of a second planet. That said, it’s by no means a sure thing, and the researchers say that follow-up observations will be needed to confirm the presence of Proxima c.
“According to our analysis, the presence of the periodic signal appears very convincing, and the data available to us do not seem to indicate a clear alternative physical cause to the presence of a planet, even if we still cannot completely rule out other explanations," says Mario Damasso, co-lead researcher on the study. “It is indeed very difficult to reveal a planet with a relatively small minimum mass and such a long orbital period using only the technique based on radial velocities. A signal like the one we found could be due to a cycle of magnetic activity by Proxima, which can mimic the presence of a planet. So to confirm our discovery, more observations are needed over the next few years.”
As intriguing as it may be to discover new potentially habitable planets around our nearest neighbor, it’s worth keeping in mind that these worlds are probably not exactly Earth 2.0. Proxima Centauri is a very different star to the Sun, being smaller and dimmer and giving off far more radiation. Other studies have suggested that this radiation has probably baked off any atmosphere the Proxima planets may have had, and the detection of huge stellar flares aren’t helping either.
Satellites such as Gaia could help confirm the presence of Proxima c in the near future.
The research was published in the journal Science Advances.
Source: INAF