A multinational team of astronomers has determined precise ages and other fundamental properties of 33 Kepler stars with the so-called ‘solar-like oscillations.’ All of these stars host Earth-like planets, giving scientists a clear indication that such planets have formed in the Milky Way long before the Earth and are still being formed out there.

The 33 stars selected for the study are not all similar to our Sun, but they behave in much the same way as the Sun does. They are what technically is called ‘solar-like oscillators.”

“The term solar-like oscillators means that the stars exhibit pulsations excited by the same mechanism as in the Sun: gas bubbles moving up and down,” explained Dr Victor Silva Aguirre, lead author of a new study on the findings accepted for publication in the Monthly Notices of the Royal Astronomical Society (arXiv.org preprint).

“These bubbles produce sound waves that travel across the interior of stars, bouncing back and forth between the deep interior and the surface producing tiny variations in the stellar brightness.”

The stars in this study span distances between 100 and 1,600 light-years from our Solar System. They have been carefully selected from the more than 1,200 stars with exoplanets around them that have been observed with NASA’s Kepler space telescope.

“The stars we studied harbor exoplanets of size comparable to Earth (between 0.3 and 15 Earth radii), and our results reveal a wide range of ages for these host stars, both younger (down to half the solar age) and older (up to 2.5 times the solar age) than the Sun,” Dr Silva Aguirre and co-authors said.

Two of these stars – KOI-281 and Kepler-444 – are older than 11 billion years, and 19 stars are older than our Sun.

“The study gives us values for the selected stars with unprecedented precision. On the average stellar properties are better than the following percentages: 1.2% (radius), 1.7% (density), 3.3% (mass), 4.4% (distance), and 14% (age),” the scientists said.

“If a star e.g. has a calculated age of 5 billion years, the 14% means that it’s true age lies between 4.3 and 5.7 billion years.”

Up to now only the age of the Sun has been determined with high precision (it is 4.57 billion years, with a precision of 10 million years to each side).

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V. Silva Aguirre et al. 2015. Ages and fundamental properties of Kepler exoplanet host stars from asteroseismology. MNRAS, accepted for publication; arXiv: 1504.07992