Press release: Planet found in habitable zone around nearest star
Nr. 166/2016 - 24.08.2016
Pale Red Dot campaign reveals Earth-mass world in orbit around Proxima Centauri
(pug) An international team of Astronomers with participation from the University of Göttingen has found clear evidence of a planet orbiting the closest star to Earth, Proxima Centauri. The long-sought world, designated Proxima b, orbits its cool red parent star every eleven days and has a temperature suitable for liquid water to exist on its surface. This rocky world is a little more massive than the Earth and is the closest exoplanet to us – and it may also be the closest possible abode for life outside the Solar System. The results were published in Nature.
Just over four light-years from the Solar System lies a red dwarf star that has been named Proxima Centauri as it is the closest star to Earth apart from the Sun. This cool star in the constellation of Centaurus is too faint to be seen with the unaided eye and lies near the much brighter pair of stars known as Alpha Centauri AB. During the first half of 2016 Proxima Centauri was regularly observed and simultaneously monitored by several telescopes around the world within the Pale Red Dot campaign. The scientists were looking for the tiny back and forth wobble of the star that would be caused by the gravitational pull of a possible orbiting planet. As this was a topic with very wide public interest, the progress of the campaign between mid-January and April 2016 was shared publicly as it happened. The reports were accompanied by numerous outreach articles written by specialists around the world.
“The first hints of a possible planet were spotted back in 2013, but the detection was not convincing,“ explains leading author Dr. Guillem Anglada-Escudé from Queen Mary University of London. “Since then we have worked hard to get further observations off the ground with help from ESO and others. The Pale Red Dot campaign had been about two years in the planning.”
The Pale Red Dot data, when combined with earlier observations made at ESO observatories and elsewhere, revealed the clear signal of a truly exciting result. At times Proxima Centauri is approaching Earth at about five kilometres per hour – normal human walking pace – and at times receding at the same speed. This regular pattern of changing radial velocities repeats with a period of 11.2 days. Careful analysis of the resulting tiny Doppler shifts showed that they indicated the presence of a planet with a mass at least 1.3 times that of the Earth, orbiting about seven million kilometres from Proxima Centauri – only five percent of the Earth-Sun distance.
Although Proxima b orbits much closer to its star than Mercury does to the Sun in the Solar System, the star itself is far fainter than the Sun. As a result Proxima b lies well within the habitable zone around the star and has an estimated surface temperature that would allow the presence of liquid water. Despite the temperate orbit of Proxima b, the conditions on the surface may be strongly affected by the ultraviolet and X-ray flares from the star – far more intense than the Earth experiences from the Sun. “We do not know yet if Proxima b has an atmosphere,“ says Prof. Dr. Ansgar Reiners from Göttingen University’s Institute for Astrophysics. “This will be the subject of intensive research in the future. The high-energy ultraviolet and X-ray flares probably influence the surface conditions on Proxima b. Nevertheless, it is not impossible that Proxima b has a life-friendly atmosphere.“
This discovery will be the beginning of extensive further observations, both with current instruments and with the next generation of giant telescopes such as the European Extremely Large Telescope (E-ELT). Proxima b will be a prime target for the hunt for evidence of life elsewhere in the Universe. Indeed, the Alpha Centauri system is also the target of humankind’s first attempt to travel to another star system, the StarShot project.
Original publication: Guillem Anglada-Escudé et al. A terrestrial planet candidate in a temperate orbit around Proxima Centauri. Nature 2016.
Contact:
Prof. Dr. Ansgar Reiners
University of Göttingen – Institute for Astrophysics
Phone +49 551 39-13825
Email: ansgar.reiners@phys.uni-goettingen.de
Prof. Dr. Stefan Dreizler
University of Göttingen – Institute for Astrophysics
Phone +49 551 39-5041
Email: dreizler@astro.physik.uni-goettingen.de
Dr. Mathias Zechmeister
University of Göttingen – Institute for Astrophysics
Phone +49 551 39-9988
Email: zechmeister@astro.physik.uni-goettingen.de