Astronomers spots over 100 new potential planets

The radial velocity method takes advantage of the fact that the planet's gravity also affects star

Scientists have detected more than 100 new potential exoplanets, including one orbiting a star about 8.1 light years away from the Earth, using one of the most successful techniques for spotting alien worlds.

Astronomers released the largest-ever compilation of exoplanet-detecting observations made using a technique called the radial velocity method.

The radial velocity method takes advantage of the fact that the planet's gravity also affects the star. Astronomers are able to use sophisticated tools to detect the tiny wobble the planet induces as its gravity tugs on the star.

The virtual mountain of data was gathered as part of a two-decade radial velocity planet-hunting programme that uses a spectrometer called HIRES, mounted on the 10-metre Keck-I telescope of the W M Keck Observatory atop Mauna Kea in Hawaii.

The compilation includes almost 61,000 individual measurements made of more than 1,600 stars.

By making the data public, the team is offering unprecedented access to one of the best exoplanet searches in the world.

"HIRES was not specifically optimised to do this type of exoplanet detective work, but has turned out to be a workhorse instrument of the field," said Steve Vogt of the University of California Santa Cruz in the US, who built the instrument.

Now as the survey moves into its third decade, the team members have decided it is time to clean house. With so much data at hand and a limited amount of time, they recognised that more exoplanets would be found by sharing their catalogue with the exoplanet community.

Mikko Tuomi of the University of Hertfordshire in the UK led a sophisticated statistical analysis of the large data set to tease out the periodic signals most likely to be planets.

"We were very conservative in this paper about what counts as an exoplanet candidate and what does not, and even with our stringent criteria, we found over 100 new likely planet candidates," Tuomi said.

One of these probable planets is around a star called GJ 411, also known as Lalande 21185. It is the fourth-closest star to our own Sun and is only about 40 per cent the mass of the Sun. The planet has a very short orbital period of just under 10 days, so it is no Earth-twin.

However, the planet, GJ 411b, continues a trend that has been seen in the overall population of detected exoplanets: the smallest planets are found around the smallest stars.

The team is hoping their decision will lead to a flurry of new science, as astronomers around the globe combine the HIRES data with their own existing observations, or mount new observing campaigns to follow up on potential signals.

The catalogue release is part of a growing trend in exoplanet science to broaden the audience and discovery space, which has emerged in part to handle the aftermath of follow-up discoveries by NASA's Kepler and K2 missions.

The research appears in The Astronomical Journal.