Astronomers at Aarhus University play a leading role in NASA’s Kepler mission, which has as its most important goal to search for planets that are similar to the Earth, and that therefore might support life.

’Since we began to receive data from the Kepler satellite, our knowledge of the stars and their orbiting planets has been revolutionised to such a degree that it is not impossible that, within a few years, we will find the first indisputable signs of life elsewhere in the Universe.’
So says Hans Kjeldsen, an associate professor at the Department of Physics and Astronomy, who is one of the researchers from Aarhus University who plays a crucial role in the Kepler mission.
The Kepler satellite, launched by NASA in March 2009, performs measurements of the light emitted by stars. These measurements can reveal the existence of planets, which block out a tiny portion of the light coming from the surface of the star as they orbit around it. Thanks to this technique, the Kepler satellite has enabled the discovery of many new planets.

NASA asked for help

To determine the size of a planet, it is necessary to know the size of the star that the planet orbits; this can be determined by measuring the star’s oscillations or ”starquakes”. This branch of science is known as asteroseismology, and Aarhus University has been a leader in this field for the past 25 years.
’When we were planning the Kepler mission, we knew that Kepler would be able to measure the oscillations of a star very accurately, but we also knew that we did not have the necessary expertise in asteroseismology to analyse the data,’ explains Ronald Gilliland of the Space Telescope Science Institute in the United States, one of the driving forces behind the Kepler mission. And so he turned to Aarhus University.
’Jørgen Christensen-Dalsgaard and Hans Kjeldsen of Aarhus University are internationally recognised experts in the field, and it quickly became clear that we were right to ask them for help in planning Kepler and in processing the data from the satellite. As a result of the Danish contribution to the mission, we have succeeded in obtaining totally unique results,’ says Ronald Gilliland.

International consortium led from Aarhus

’Initially, the idea was that we should concentrate on certain specific stars, but our role in the programme was quickly expanded, as it became apparent that many more measurements from many different stars were being produced by the Kepler satellite than originally planned,’ says Hans Kjeldsen.
The data arriving are all quite unique; they cannot simply be analysed by a computer program. The researchers have to examine the data from each individual star to analyse the information it contains. Consequently, in 2006 Hans Kjeldsen and Jørgen Christensen-Dalsgaard set up an international scientific consortium and invited researchers all over the world to participate in analysing the enormous number of measurements being generated, thus maximising the yield from the data. In 2007 this consortium, the Kepler Asteroseismic Science Consortium (KASC), was made up of around 200 researchers; it has now grown to a membership of 540 scientists at over 100 institutions in 30 countries all around the world. The consortium is directed by the Aarhus University researchers.
When data collected by the Kepler satellite are transmitted to Earth, they are sent to Denmark, where data for asteroseismolgical analysis are distributed to researchers using a database maintained by Aarhus University. Through the computers in Aarhus, the over 500 researchers in KASC have access to the raw data from Kepler, and the same computers are also the central coordinating point for the production of the scientific results and articles based on the Kepler measurements.

A central role – now and in the future

The Kepler mission was originally planned to last three and a half years, but has been extended for a further four years. The astronomers in Aarhus will continue to play a central role in the investigation of the secrets of the universe, not only through their cooperation with NASA, but also through the SONG network – a huge network of Earth-based telescopes that will come into use over the coming years.
’The data we are working with give us the opportunity to be right at the forefront of events, so who knows? Maybe a researcher or even a PhD student from Aarhus University will be the first person in the world to find life out there,’ says Hans Kjeldsen.

Scientific publications

The scientific breakthroughs achieved using data from the Kepler satellite have so far resulted in the publication of no fewer than six articles in Science and three in Nature co-authored by astronomers from AU. In total, over 100 academic articles have been produced since 2010 with the participation of Aarhus University astronomers on the basis of data from Kepler.

New centre for stellar and planetary research

The Danish National Research Foundation has awarded a grant of EUR 7.4 million for a new Centre of Excellence to be headed by Professor Jørgen Christensen-Dalsgaard. The centre is set to open in 2012 and, in addition to its main base at the Department of Physics and Astronomy at Aarhus University, consists of five research units spread around the world.  The centre will take a holistic approach to studying the stars and their planetary systems, providing a fuller understanding of conditions in and around stars and their planets - and thus of the possibility of finding life as well. The astronomers will work with both biologists and geologists at Aarhus University, who will contribute their expertise on climate and life forms, and on the conditions necessary for life.