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Dr Lisa Kaltenegger.

There seems to be billions of galaxies out of there, with billions of stars, with billions of planets, a visiting German astronomer told an audience at UKZN recently.

Dr Lisa Kaltenegger of the Max Planck Institute for Astronomy in Heidelberg, Germany, was addressing a full house on the subject of: Super-Earths and Life – Characterising Exoplanets.  The lecture was the final in a series organised by UKZN’s Astrophysics and Cosmology Research Unit (ACRU) on the Westville campus.

‘For the first time in human history we are exploring other worlds, extrasolar planets orbiting stars other than our Sun,’ said Kaltenegger.  She explained that owing to the Kepler Mission, scientists had confirmed that other stars had planets – about 800 had been identified so far.

‘There seems to be billions of galaxies out there, with billions of stars, with billions of planets – this makes for a very exciting search. Our first discoveries shine a light on a fascinating gallery of extrasolar planets, from worlds with potentially permanent lava oceans on their surfaces, to planets with two Suns in their skies, and hot Jupiters, that only need days to orbit their Suns.’

Kaltenegger said some of these planets were orbiting in the habitable zone of their host star, where temperatures may be low enough for liquid water to exist. ‘If they host liquid water, these planets could be the first habitable worlds discovered.

‘We are looking for planets with the signatures of life – planets that are rocky like the earth, and are a distance similar to earth from their star.  Very simple life requires a certain temperature range, roughly between a maximum of 120 degrees Celsius and a minimum of 80 degrees Celsius.  If it is much hotter or colder, life as we know it cannot survive.’

Whether there was life in these worlds was an open question, but the fascinating search would be undertaken with the next generation of telescopes being built, including the James Webb telescope, which would be used to find signatures of life on planets already identified by the Kepler Mission.

Taking her audience on a tour of the closest extrasolar planets, Kaltenegger said astronomers looked for tell-tale signs for life and how these changed through a planet’s history. ‘We are closing in on reading the spectral fingerprint of these worlds – fingerprints that will let us search for tell-tale signs of life in these other worlds, like a detective on a crime scene.’

Kaltenegger explained how astrophysicists analysed the spectral fingerprints of exoplanets. ‘With the use of spectroscopy, we can break up the light waves that reach us from these planets and look at whether any colours of the spectrum are missing.  The missing light tells us what the planet’s atmosphere is made of.  We can tell whether it contains oxygen and methane.  Along with liquid water, the combination of oxygen with methane is the signature for life.’

Kaltenegger presented some interesting astronomical facts for the layperson including:

·         the diameter of the sun is equal to 100 earths placed next to each other

·         it would take 100 000 light years to traverse our galaxy

·         if our whole solar system was compared to the size of a cookie, then our sun would be the size of a sugar grain, and the closest star would be two football fields away.

Kaltenegger leads the research group on Super-Earths and Life at the Max Planck Institute and is also a research associate at the Harvard Smithsonian Center for Astrophysics in Boston, USA.  Among her many awards are the 2012 Heinz Maier-Leibnitz Prize for Physics of Germany.

Whilst visiting UKZN as a guest of ACRU and the School of Mathematics, Statistics and Computer Science, and the School of Chemistry and Physics, Kaltenegger visited local schools to share her love of astrophysics, including Glenwood Boys’ High School and Beaconwood Primary School. Several schools also attended the public lecture.