A group of scientists, led by Guillem Anglada-Escudé at Queen Mary University in London, have detected what they believe is the nearest terrestrial planet to our Solar System.
Using the radial velocity technique, aided by instruments at the European Southern Observatory, astronomers have produced a lightcurve of a nearby variable star. The red dwarf, Proxima Centauri, in the southern constellation of Centaurus, is a mere 4.25 lightyears (1.295 parsecs) distant, making it the nearest star to our Sun. The lightcurve shows a periodicity of 11.2 days which could indicate an orbiting planet. This hypothetical planet, with at least 1.3 Earth masses, has been named Proxima Centauri b.
After 16 years of observations, including an intense period between January and April 2016 known as the Pale Red Dot campaign, Anglada-Escudé and his team used the High Accuracy Radial velocity Planet Searcher (HARPS) to measured the push and pull influence Proxima Centauri b has on its host star. This ‘Doppler effect’ measured the star approaching and receding from Earth at about 1.4 m per second, with a repeating pattern every 11.2 days, which has been measured with a precision of about 1 m per second.
Proxima Centauri is a low mass star, about 12% the mass of the Sun; its planetary companion occupies an orbital semi-major axis of about 0.05 AU, placing it within Proxima’s habitable zone – meaning that if conditions were right, liquid water could be stable on the surface of this exoplanet. But habitability is dependent on many factors, including tidal locking, strong magnetic fields, solar flares, and intense UV and X-ray radiation.
The results of the research must, however, be treated with caution; with positive detection only possible through observational data. This could be achieved when the European Extremely Large Telescope (E-ELT) comes online in 2024. With a segmented primary mirror measuring almost 40m, the E-ELT will have enough resolution to image Proxima Centauri b directly. This would, indeed, determine whether this tantalising Earth-like world exists within our stellar neighbourhood.
© Melanie Davies 2017