Updated census of Sun-like stars

Artist's impression of a star like our Sun

Artist's impression of a star like our Sun with an orbiting planet in the foreground. The Kepler mission is studying such stars by tracking changes in their brightness.

  • Kepler is a space observatory that measures star brightnesses
  • Brightness oscillations reveal secrets of stars’ sizes, ages and composition

USING NASA’S KEPLER SPACE TELESCOPE, scientists have detected changes in brightness in 500 Sun-like stars, giving a much better idea about the nature and evolution of the stars.

Prior to Kepler’s launch in March 2009, astronomers had identified changes in brightness, or oscillations, of only about 25 stars similar to our Sun in size, age, composition and location within the Milky Way galaxy.

Although Kepler’s primary job is to find Earth-like planets that might be able to support life, it also provides a big boost to ‘asteroseismology’…the study of stars by measuring their natural oscillations.

Those oscillations provide clues about star basics such as mass, radius and age, as well as clues about their internal structure.

“This helps us understand more about the formation of stars and how they evolve,” said Steve Kawaler, an Iowa State University professor of physics and astronomy, a co-author of the research paper and a leader of the Kepler Asteroseismic Investigation.

“These new observations allow us to measure the detailed properties of stars at an accuracy that wasn’t possible before.”

Kepler is orbiting the Sun carrying a photometer, or light meter, to measure changes in star brightnesses. The photometer includes a telescope 94cm in diameter connected to a 95-megapixel CCD camera.

Artist's impression of the Kepler spacecraft

Artist's impression of the Kepler spacecraft

The instrument is pointed at the Cygnus-Lyra region of the Milky Way. It is expected to continuously observe about 170,000 stars for at least three and a half years.

Golden age for star studies

The Kepler Asteroseismic Investigation is using Kepler data to study different kinds of stars.

Kepler has provided astronomers with so much new information, the scientists say they’re “entering a golden era for stellar physics.”

Data from the 500 Sun-like stars gives astronomers a much better understanding of the stars, their properties and their evolution. It also gives astronomers data to test their theories, models and predictions about the stars and the galaxy. And it gives astronomers enough data to make meaningful statistical studies of the stars.

“But this is just the start of things,” Kawaler said. “This is a first broad-brush analysis of the data we’ve seen. This is a preview of this new tool and the kind of detailed census that we’ll be able to do.”

Among the projects to come are studies to determine the ages of all these Sun-like stars, and studies of the host stars of the Earth-like planets.

The investigation is led by a four-member steering committee: Kawaler, Chair Ron Gilliland of the Space Telescope Science Institute based in Baltimore, Jorgen Christensen-Dalsgaard and Hans Kjeldsen, both of Aarhus University in Denmark.

Adapted from information issued by Iowa State University. Illustration by Gabriel Perez Diaz, Instituto de Aastrofisica de Canarias (MultiMedia Service). Kepler illustration courtesy NASA.

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