Bumper harvest of exoplanets found by HARPS…

Where is the Death Star? Artist’s impression of a real-life Tatooine spotted by Kepler. (Courtesy: NASA)

By Hamish Johnston

It’s hard to believe that less than 20 years ago we didn’t know if stars other than the Sun had planets. Now it seems that such extra-solar planets (exoplanets) are just about everywhere we look in the heavens.

This week at the Extreme Solar Systems conference in the US, astronomers working on the HARPS instrument at the ESO’s La Silla Observatory in Chile announced the discovery of 50 more exoplanets. This puts the total of known exoplanets at about 680. The newcomers include 16 “super Earths”, which are up to 10 times more massive than Earth and expected to be rocky.

When astronomers first started looking for exoplanets, they tended to find gas giants like Jupiter in very close orbits around their stars – very different from our own solar system. However, it’s becoming clear that this was simply because such exoplanets were easier to find. Now that telescopes have improved, astronomers are finding much more familiar looking systems

Indeed, when HARPS looked at nearly 400 Sun-like stars, it found that about 40% of them have at least one planet less massive than Saturn. Furthermore, HARPS found that the majority of exoplanets of Neptune-mass or smaller existed in multiple-exoplanet systems.

When HARPS focused on 10 nearby sun-like stars, it found five super-Earths orbiting three stars. And one of these super-Earths is in the habitable zone of its star, where the conditions are just right for life – at least as we know it here on Earth

Given this rapid increase in our knowledge of worlds beyond ours, it can’t be very long before an exoplanet with signs of life is spotted. However, it won’t be extraterrestrial beings coming into view, but rather hints of liquid water and atmospheric gases such as oxygen that could be the by-products of life.

Also at the conference, astronomers working on NASA’s Kepler space telescope announced the first direct evidence of a “circumbinary” exoplanet – that is, a planet that orbits two stars.

Much comparison has been made to Tatooine, the circumbinary home planet of Luke Skywalker in the 1977 film Star Wars. Indeed, when the finding was unveiled at the conference, John Knoll of Lucasfilm, which made Star Wars, was on hand to comment. “Working in film, we often are tasked with creating something never before seen,” said Knoll. “However, more often than not, scientific discoveries prove to be more spectacular than anything we dare imagine.”