Earth-based telescope detects super-earth transit

Coimbatore 06/05/2012. Public watching the last transit of Venus in a century through telescopes set up by Coimbatore Astronomy Club with the Perks Astronomy Club at Perks School on Wednesday. The rare celestial spectacle visible only from parts of Earth will not come again until 105 years from now in 2117. Photo: K.Ananthan

Astronomers in Spain have detected the transit of a super-earth transiting across its star — 55 Cancri — using only ground-based detection systems. This detection is significant because it opens the door to ground-based remote sensing of astronomical bodies. Also, as the planet transits its star, observing it can give a clue as to what its atmosphere is made of, according to the lead author of the study, Ernest de Mooij of Queen’s University, Belfast, who was quoted in a Harvard Smithsonian Centre for Astrophysics release.

The detection was through the 2.5 metre Nordic Optical Telescope, in La Palma, Spain. Though moderately-sized by today’s standards, it is equipped with the best instruments. Developing ground-based telescopes such as this is important because it paves the way to interpreting the atmospheres of planets and detection of bio-signatures of Earth-like planets, according to the report which quotes co-author of the study, Mercedes Lopez-Morales of Harvard Smithsonian Centre for Astrophysics.

Super-earths are extrasolar planets that are bigger than the earth, but not as big as the gaseous giants in the solar system, for example, Uranus, which is 17 times as big as the earth. This particular planet, 55 Cancri e, belongs to the group orbiting around the sun-like star 55 Cancri, which is about 40 light years away from the earth. The star can be seen with the naked eye.

During its transit across the star, 55 Cancri e exoplanet blocks about 0.05 per cent of the light coming from the star. Based on the transit time, astronomers have estimated the size of the exoplanet to be around twice that of the earth.

Its proximity to its star makes 55 Cancri e’s surface as hot as 1,700 degree C. Thus, it is hostile to life as we know it. This exoplanet is the innermost of four planets orbiting the star. Dr de Mooij further noted that this detection assumes further significance because when upcoming missions such as space telescopes PLATO and TESS detect stars and planets, it can be followed up with instruments based on ground.