Astronomers discover Earth-sized planet just 11 light years away

The newly-discovered exoplanet shows promising signs for habitability


Ross 128b is the second-closest temperature planet, behind Proxima b. Image credit: ESO/M. Kornmesser

A new and exciting exoplanet has been discovered just 11 light years from our Solar System. Discovered using the European Southern Observatory (ESO)’s High Accuracy Radial Velocity Planet Searcher (HARPS) instrument, Ross 128b – as it’s known – is a temperate Earth-sized world orbiting a red dwarf star. The new world is the second closest ‘Earth-like’ planet discovered after Proxima b, and also the nearest orbiting an inactive star. As the star has very little activity, Ross 128 could potentially sustain life, making it a prime target for ESO’s Extremely Large Telescope.

The team using the HARPS instrument at the La Silla Observatory in Chile found Ross 128b orbiting its host star every 9.9 days. The surface temperature of the planet is thought to be mild, possibly close to Earth’s surface temperature.

“This discovery is based on more than a decade of HARPS intensive monitoring together with state-of-the-art data reduction and analysis techniques. Only HARPS has demonstrated such a precision and it remains the best planet hunter of its kind, 15 years after it began operations,” explains Nicola Astudillo-Defru, of the University of Geneva, Switzerland.

Red dwarf stars are often the subject of study in the search for exoplanet; this is because they are the coolest, faintest and most common stars in the universe. By using the HARPS instrument, astronomers believe that detecting cool exoplanets like Earth is easier around red dwarfs, rather than Sun-like stars

ESO’s La Silla Observatory in Chile accommodates the HARPS instrument that made this discovery. Image credit: Iztok Bončina/ESO

The issue with habitability on Proxima b, the closest exoplanet just four light years away, is that Proxima Centauri is subject to flares from its red-dwarf host star. This would shower its accompanying planet is harmful radiation such as ultraviolet radiation, killing life as we know it. Ross 128 is much less active, meaning the exoplanet stands a greater chance of sustaining possible lifeforms.

Even though Ross 128b is 11 light years away from us, it is travelling at relatively rapid speeds in universal terms. In 79,000 years, it will surpass Proxima b as the closest exoplanet. The data collected by HARPS has also shown that the new exoplanet orbits Ross 128 at a distance that is 20-times closer than Earth to the Sun. Even taking this close proximity into account, the planet only receives 1.38 times more irradiation than Earth. From this, astronomers estimate that the average temperature lies between minus 60 to 20 degrees Celsius (minus 76 to 68 degrees Fahrenheit), making it almost ideal for habitability. Astronomers still have yet to discover if the planets lies within the star’s habitable zone, which is the region around a star where water can exist as a liquid.

With the number of temperate exoplanets ever-increasing, the next step in determining their true habitability is to understand their atmosphere. ESO’s Extremely Large Telescope will have the capabilities to study an exoplanet’s atmosphere, composition and chemistry. For example, if there were a detection of oxygen molecules in an exoplanet’s atmosphere, it would be a monumental discovery for astronomers.

“New facilities at ESO will first play a critical role in building the census of Earth-mass planets amenable to characterisation. In particular, NIRPS, the infrared arm of HARPS, will boost our efficiency in observing red dwarfs, which emit most of their radiation in the infrared. And then, the ELT will provide the opportunity to observe and characterise a large fraction of these planets,” concludes Xavier Bonfils of the Institute of Planetology and Astrophysics of Grenoble, France.

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