EU-funded researchers are peering into the depths of the cosmos, studying distant stars to gain a better understanding of how our universe works, what the future of Earth and our solar system might be, and even whether there could be life elsewhere out there.
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Just like people, stars come in many varieties: they have different colours, temperatures, brightness, mass, ages, compositions, behaviours and they are located at different distances from us, says Katrien Kolenberg, an astrophysicist at Universiteit Antwerpen and Katholieke Universiteit Leuven in Belgium. My field of research, asteroseismology, is about obtaining information on the inner structure of stars, enabling us to unravel the mysteries of their interior workings and the properties of the planets that orbit them.
Asteroseismology, a relatively new field of astrophysics, is being led by European researchers, but has been greatly advanced by NASAs Kepler mission. The satellite is seeking Earth-like planets outside our solar system and has provided invaluable data to study how stars work.
The Kepler satellite's data on more than 150 000 stars has so far yielded more than 5 000 exo-planet candidates of which nearly 2 500 have been confirmed. The data are being analysed by scientists from around the world. Kolenberg joined these exo-planet hunters at the Harvard-Smithsonian Centre for Astrophysics for two years as part of the Marie Curie-funded SAS-RRL project, a unique initiative to study a specific class of star called RR Lyraes.
The RR Lyrae stars stand out because they pulsate; they contract and expand as if they are breathing. What is actually happening is these stars are ringing with sound and each star has its own particular sound pattern, which leads to brightness variations that we can record with our telescopes and cameras, Kolenberg explains.
RR Lyrae stars are extremely useful as so-called standard candles or cosmic lighthouses a kind of measuring stick to determine cosmic distances and better understand the history, evolution and behaviour of the universe.
One star has been studied for more than 100 years, but it still holds many mysteries. Its brightness oscillates every 13.5 hours but other cyclical changes occur over timescales of weeks and months. Analysis of the Kepler data has confirmed that this feature, known as the Blazhko effect, is a rule rather than an exception in other RR Lyrae stars.
An eagle-eye view of Lyraes
For asteroseismologists like myself, Kepler is a dream dataset to work on. In the years before, I had been painstakingly organising observing campaigns from Earth for a handful of stars, using many excellent ground-based telescopes, and the data were good, but they had gaps and noise, Kolenberg says. Getting Kepler data of RR Lyraes was like suddenly having an eagle-eyes view on something that we had previously been looking at with blurred vision suddenly we saw things, tiny changes, that we had never seen before.
Keplers data and research stemming from the SAS-RRL project are leading to vastly improved understanding of the interior workings of stars and growing interest in RR Lyraes. This is underscored by more than 30 papers co-authored by Kolenberg during the Marie Curie project as well as numerous presentations at international meetings.
Kolenberg and her colleagues have since launched a bi-annual conference series on RR Lyraes and she continues to present her work to broader audiences. She also contributes to the education of the next generation of scientists through courses at Universiteit Antwerpen and as STEM (science, technology, engineering and mathematics) coordinator for the KU Leuven Association.
Kepler is still active in the K2 mission and another planet-hunting project, TESS, will soon launch, which will deliver more high-quality data on RR Lyrae stars from all over the sky.
Koltenberg is co-chairing the RR Lyrae and Cepheid working groups for both the Kepler/K2 and TESS missions, which will enable asteroseismologists to work on ever-growing data sets, while the European Space Agencys Gaia mission is currently measuring the distances of tens of thousands of RR Lyrae stars.
Our research field is being revolutionised, Kolenberg says. Soon we will be able to calibrate our cosmic measuring sticks with unprecedented precision.