There May Be a “Super-Earth” Orbiting the Nearest Star to the Sun

A study on low-mass planet candidate orbiting Proxima Centauri by Mario Damasso and colleagues, published in Science Advances, analyzed the cyclical changes of the light emitted by the star Proxima Centauri. This star is the star nearest our Sun. 

Research findings suggest that the star could be orbited by a so-called Super Earth as its second planet.

For more than 15 years, researchers have observed Proxima Centauri with various methods aimed at detecting planetary companions, as mentioned in the publication. 

The search for Earth-like planets with the Red Dots initiative focused on other nearby stars aside from Proxima Centauri, and it led to a recent discovery of a possible super-Earth that may orbit Barnard's star.

The proponents of the study presented data that suggests that this Earth-like candidate planet has a complete orbit of 5.2 years around Proxima Centauri. They think it has a greater mass compared to Earth and a lighter mass compared to Neptune and Uranus. According to the American Association for the Advancement of Science, its existence is yet to be confirmed, but once it is, it could provide valuable insights on how planets with low mass can form around stars with low mass. The study mentions that it can also reverse theories about how so-called super-Earths are formed because, at present, such planets are thought to form near "snowlines," or the closest distance between a star and its planet at which it is possible for water to turn into ice. 

The planet that the researchers discovered is well beyond the snowline area, according to Damasso and his team. They also mention that the planet discovered in Barnard's star is near the snowline.

Damasso and his team cited a previous study where a source of light spectral signals was also discovered in the Proxima Centauri system. The researchers in this study used a Chilean astronomical observatory known as ALMA, or Atacama Large Millimeter / submillimeter Array. They think that the light source may come from a second planet, from a nearby galaxy, or a completely unrelated event.

The team analyzed 17.5 years' worth of data on high precision radial velocities to determine if the light signal came from a planet orbiting the Proxima Centauri star. It is due to the Red Dots campaign that the researchers collected additional radial velocities of Proxima. They used a so-called exoplanet detection technique that tracks the light spectrum of a star. If the light spectrum oscillates in between blue and red, this is indicative of the star regularly nearer and farther away from Earth. This cycle usually occurs due to the presence of a body orbiting it.

The study proponents discovered that the light spectrum signal happens over 1,900 days, which suggests that it may not be related to the cyclical shifts of the magnetic field of the star. Nonetheless, the researchers reiterate that they need more evidence to confirm such a conclusion. If confirmed, this could indicate a nearby habitable planet that humans can colonize in the future.