Astronomers using a European telescope on a mountaintop in Chile have discovered the biggest haul yet of alien planets orbiting distant stars. They spotted more than 50 of the new worlds, including 16 that could be bigger versions of Earth.

One of these is particularly exciting because it lies in an orbit where it might host life as we know it. The super-Earth, which is only 3.6 times the size of our planet, is near the edge of its planet’s Goldilocks zone – where it is not too hot and not too cold for liquid water. Skymania News reported on this world last month following publication of a paper about its discovery on arxiv.org.

The record catch of exoplanets was made using a device designed to seek them out on the European Southern Observatory’s 3.6 meter telescope at La Silla in Chile. Called the HARPS spectrograph, it is the most successful planet finder on the ground, competing with other hunters including SuperWASP cameras and space observatories such as NASA’s Kepler and Europe’s Corot probe.

HARPS has now discovered more than 150 planets in the eight years it has been operating by watching tiny wobbles in the light of 376 Sun-like stars as orbiting worlds tug on them. The technique is called radial velocity.

It collected its latest haul, which was announced at the Extreme Solar Systems conference in Wyoming, USA, by making observations over hundreds of clear nights.

Discovery team leader Michel Mayor, of the University of Geneva, said: “The harvest of discoveries from HARPS has exceeded all expectations and includes an exceptionally rich population of super-Earths and Neptune-type planets hosted by stars very similar to our Sun. And even better — the new results show that the pace of discovery is accelerating.”

The team’s results suggest that at least 40 per cent of stars like the Sun have at least one planet lighter that our own gas giant Saturn orbiting them. And most planets the size of Neptune or less appear to be in alien solar systems containing multiple planets.

Scientists are now busy upgrading HARPS’ sensitive hardware and software to make it even more powerful. They want to pinpoint rocky planets where life could exist. Of the total planets found by HARPS, five are already known to be less than five times as massive as the Earth.

More than 550 planets have now been found around other stars by various means. Most are giant gasballs like Jupiter but that is surely because their size makes them easier to detect.

It suggests once again that the galaxy may be swarming with smaller planets much more like the Earth, boosting the prospects of alien life.