An global team of astronomers has detected a candidate super-Earth planet orbiting Proxima Centauri, the nearest star to the Sun. This is largely due to the fact that the red dwarf is the nearest star to the Sun, meaning that future interstellar missions like Breakthrough Starshot will likely start by venturing to the Proxima Centauri system first.
Finding a second planet around Proxima Centauri not only increases the appeal of exploring the system more closely, it also raises some important questions about a feature of planetary systems called the snow line.
According to the researchers, the discovery of Proxima c could provide insights into how low-mass planets around low-mass stars form, especially when the planets begin their lives well beyond a star's "snow line", where water turns to solid ice. This small, cool star is not visible to the naked eye and lies near to the much brighter pair, Alpha Centauri AB. A previous study of Proxima Centauri using the Atacama Large Millimeter/submillimeter Array (ALMA)-an astronomical observatory in northern Chile-reported an unknown source of light spectrum signals that could belong to a second planet or may simply have been the product of a neighboring galaxy or an unrelated phenomenon. If this spectrum oscillates between red and blue, it indicates that the star is moving towards and away from the Earth at regular intervals, a cycle usually caused by an orbiting body's presence. However, the authors emphasize that more evidence is needed to confirm their conclusion.
Dubbed Proxima c, it has an orbital period of 5.21 years and a surface temperature of minus 234 degrees Celsius (minus 389 degrees Fahrenheit).
"The proximity of the planet and its orbit at a relatively great distance from its star, means it is one of the best possible chances for direct observations that will enable detailed understanding of another planet", said team member Professor Hugh Jones, an astrophysicist at the University of Hertfordshire.