Astronomers using NASA’s Kepler space telescope have succeeded for the first time in finding a planet with a surface temperature that, in principle, is favourable for life. The newly discovered planet is 600 light years from Earth.

2011.12.07 | Christina Troelsen

News of the discovery was recently released in connection with the Kepler Science Conference at NASA’s Ames Research Center in California. The result is based on almost two years of work studying KIC 10593626, a star located in the Milky Way, 600 light years from Earth. The researchers have called the new planet Kepler-22b.

It takes 290 days for Kepler-22b to orbit its mother star at a distance of 127 million kilometres from the star (corresponding to 85% of the distance between Earth and the Sun). If the planet orbited in our own solar system, its path would lie between the paths of Venus and Earth. Precise measurements of Kepler-22b indicate a diameter of 30,400 kilometres, which makes it more than twice the size of Earth. Measurements of the mother star show that it emits an amount of energy corresponding to 79% of the Sun’s total energy emission. On this basis, the researchers have calculated Kepler-22b’s surface temperature as being favourable for liquid water to exist on its surface. As liquid water is regarded as an essential prerequisite for the existence of life, precisely this measurement means that Kepler-22b can be considered a so-called habitable planet. However, the researchers are unable to say as yet whether or not life exists on its surface.

“This is an incredibly big discovery and we’ve been waiting for it for a long time,” says Hans Kjeldsen, Aarhus University, enthusiastically. “We’ve now got evidence for the first time that there are planets in the universe where there’s a possibility of finding life,” he adds.

In addition to NASA’s team of researchers, a group of Danish astronomers – mainly from Aarhus University – were involved in the discovery of Kepler-22b. The Danish astronomers’ measurements have been crucial for determining this new planet’s properties.

The Aarhus astronomers were responsible for measurements of the exact diameter of the planet. This was done by using seismological studies of the star to precisely measure its size. Taking part from Aarhus University are Jørgen Christensen-Dalsgaard, Hans Kjeldsen, Torben Arentoft, Christoffer Karoff, Mia Lundkvist, Mikkel Lund and Rasmus Handberg. Lars A. Buchhave, University of Copenhagen, also took part in measuring the surface temperature of the star and the chemical composition of the matter the star and planet are composed of.

Contact information 

Professor Jørgen Christensen-Dalsgaard, Aarhus University, +45 2338 2374, jcd@phys.au.dk

Associate Professor Hans Kjeldsen, Aarhus University, +45 2338 2160, hans@phys.au.dk

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NASA’s Kepler Satellite – a precise light meter

The Kepler Satellite was launched by the USA in March 2009 to carry out very precise measurements of the brightness of many thousands of stars. These very precise light measurements were intended to reveal the existence of planets that pass in front of stars during their orbit around them, and shadow a small part of their luminous surface. In this way, the Kepler Satellite has found a number of new planets and, within the next few years, the satellite’s measurements are expected to reveal the existence of planets the size of Earth.

Kepler almost continuously observes the same field in the sky in the constellations of the Swan and the Lyre. It must surely be described as one of the most successful missions undertaken by the American space organisation NASA.

Asteroseismology – looking into the stars

Ever since Kepler was launched, astronomers all over the world have used the measurements to look for starquakes on the surface of the many different stars observed by the satellite. By measuring periodical light variations from starquakes, the astronomers can determine which physical conditions prevail deep inside the stars via a type of investigation called asteroseismology. The asteroseismology studies of the Kepler Satellite’s measurements are led by a group of researchers at Aarhus University. 
In the last two years, they have succeeded in revealing more and more details of the inner structure and development of the stars. The satellite’s measurements show us the stars in a previously unknown way, and make it possible to carry out in-depth studies that would have been impossible to dream of before the satellite was launched.