An artist's impression of the Kepler spacecraft at work.
Aussie scientists study stars with NASA
14 Mar 2009
On Saturday, March7, NASA successfully launched the Kepler Spacecraft into orbit around the Sun from the Kennedy Space Centre in Florida.
Using Kepler, NASA expects to answer a very fundamental question—do Earth-size planets exist in orbit around other stars? The Kepler Spacecraft is equipped with a large telescope that will measure the variations in brightness of 170,000 stars simultaneously and continuously for a period of at least 3.5 years.
NASA's Kepler mission will not only be able to search for planets around other stars, but also yield new insights into the parent stars themselves. Kepler's measurements of changes in stellar brightness can also be used to study stars and their interiors, helping scientists answer a host of questions about stars in our galaxy—How old are stars? How do they evolve? Is our Sun a typical star? How does matter behave under the extreme conditions in stars?
Astronomers at the University of Sydney's School of Physics are part of the Kepler Asteroseismic Science Consortium. Dr Dennis Stello, an astrophysicist at the University of Sydney says: "We will now get the opportunity to study a large variety of stars, which will lead to a much improved understanding of the evolution of stars and ultimately of the Universe in which they reside."
The University of Sydney team is leading the effort to understand stars much older than the Sun, and stars located in stellar clusters. "We are tremendously excited to extend our seismic techniques to measure ages of stars much older than the Sun," says Dr Stello.
Stars, such as our sun, can "ring like a bell" due to pressure waves which result in oscillations of the whole star. Kepler's will be able to measure these oscillations by recording small variations in a star's light, and conducting "stellar seismology" in a similar way geologists study how earthquakes make waves move in Earth's interior.
If the surface of the star is oscillating, Kepler will detect periodic variations in the brightness of the star, and by measuring the brightness fluctuations over weeks, months and years, the Kepler team will be able to measure the precise periods of those stellar oscillations.
< Kepler's main job is to watch as planets move in front of stars, causing mini-eclipses.
The Kepler team will use seismic techniques to probe the cores of a large number of stars in order to determine the size of stars, and to measure a star's chemical composition and rotation rate. For many of the stars where accompanying planets will be detected, the astronomers expect to use stellar seismology to determine the parent star's age.
The quality of the Kepler data and the large number of stars observed are expected to lead to a huge step forward in understanding of stellar evolution.
During the first nine months in space Kepler will survey more than 5,000 stars for oscillations. Based on those measurements, around 1,100 stars will be followed for detailed studies throughout the full mission. The accuracy with which Kepler will be able to measure stellar oscillations is so high that the science team expects for the first time to watch directly the change in stars as they age.
In order to allow scientists worldwide to contribute to analysing the huge dataset, the Kepler Asteroseismic Science Consortium (KASC) has been formed, which includes more than 200 researchers from 50 institutions all over the world.
Adapted from information issued by the University of Sydney.
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