Astronomers have found a 'Super Earth' planet orbiting a star just like our sun using a ground based telescope for the first time.
The Nordic Optical Telescope on La Palma, off the coast of Africa, detected the planet 55 Cancri E orbiting a star 44 light years from Earth.
The discovery could simplify the search for distant worlds throughout the galaxy.
Discovering a 'Super Earth' sounds like it should be an astonishing, rare event. Actually, it's increasingly common with thousands of planets and dozens of Earth-like worlds already on the books.
It's not easy, though. Finding these planets requires scouring through mountains of data collected by space-based telescopes.
But now astronomers have found one very similar to our own planet using a telescope here on Earth for the first time.
This planet is twice the size of Earth, and orbits its parent star with a much tighter orbit than our own. It is not thought to be habitable, but its size and position make it similar to planets that could support life - and that's a crucial stepping stone for scientists searching the universe for evidence about our origins.
55 Cancri E has a diameter of about 16,000 miles and is eight times heavier than Earth. It completes an orbit around its star every 18 hours, and though that means it is much too hot for life to exist on its surface it also gives scientists a great opportunity to actually find it.
They do this by watching distant stars for subtle changes in light. When light from stars dips, it can indicate that a planet is passing between the star and Earth. These dips are able to tell us a surprising amount about the size, structure and make-up of different planets. When the planet is quite large and close to the star, this is easier than when it is small and distant because the shift is more obvious, and regular.
Exoplanets like Earth are still incredibly hard to find, even for telescopes in space. On the ground, where light from stars can be affected by many other factors it is obviously much harder still - which is why this discovery is so significant.
"We expect these surveys to find so many nearby terrestrial worlds that space telescopes simply won't be able to follow up on all of them. Future ground-based instrumentation will be key, and this study shows it can be done," Mercedes Lopez-Morales, co-author of the new research at the Harvard-Smithsonian Center for Astrophysics said.
With this result, we are also closing in on the detection of the atmospheres of small planets with ground-based telescopes."
The star 55 Cancri is thought to be about 40 light-years from Earth. There are at least four other planets orbiting the star. Other super Earths have been detected from Earth, but not any that orbit a sun like our own -- again, thought to be a crucial ingredient for life.
Earth-based telescopes are an intriguing new frontier for the search for exoplanets, but space-based telescopes are still far superior. Unfortunately they are also expensive. NASA's Kepler Space Telescope was crucial but is out largely out of operation. A new Transiting Exoplanet Survey Satellite mission is due for launch in 2017 and ESA's Planetary Transits and Oscillations of stars mission will be launched in 2024. But until then ground-based systems will be important for continuing the search.
"Our observations show that we can detect the transits of small planets around sunlike stars using ground-based telescopes," Ernst de Mooij of Queen's University Belfast.
"This is especially important because upcoming space missions, such as TESS and PLATO, should find many small planets around bright stars, and we will want to follow up the discoveries with ground-based instruments."