Ancient Earth-size planets found, by a little bit of Essex

University of Birmingham scientists have found a solar system with Earth-sized planets from the dawn of the Galaxy – 11 billion years ago.

They used data from sensors on NASA’s Kepler space telescope, made by E2V of Essex.

Kepler’s telescope stares fixedly at a +/-6° cone of space with the largest NASA image sensor ever, assembled by Ball Aerospace, and consisting of 42 28x55mm back-illuminated CCD arrays made by E2V. Each has 2,200×1,044 27µm pixels responding across visible and near-IR wavelengths (400-850nm).

This sits behind a 0.95m aperture Schmidt telescope with a 1.4m primary mirror – see the Society of Photo-Optical Instrumentation Engineers (SPIE) website for chapter and verse.

Although it is a telescope, it is not used to take pictures. Instead it is used to continuously monitor the intensity of all stars in its field of view above a certain brightness – all 100,000 of them. To improve its photometry, it is deliberately slightly out of focus (by 10arcsecond).

To prevent saturation, charge on the CCDs it read out every 3s and the resulting data is integrated over 30 minutes for each star.

“The instrument has the sensitivity to detect an Earth-size transit of a solar-like (mv=12 G2V) star at 4 sigma in 6.5 hours of integration,” said NASA.

Data is stored on the spacecraft and sent to Earth once per month.

To work out the age of the star, the Birmingham team used asteroseismology – watching pulsations in the intensity of the star that indicate the way seismic waves are resonating around inside it. From this, we are told, the star’s age can be deduced.

The existence and size of planets is deduced from variations of star intensity cause by the planets passing between the star and the CCD array.

Details of the ancient star system (called Kepler-444) have been published in the Astrophysical Journal. The planets are actually said to be between the size between Mercury and Venus.

The pale yellow-orange star is 25% smaller than the Sun and substantially cooler. Its age is estimated at 11.2+/-1.0 billion years, two and a half times older than the Earth.

‘By the time the Earth formed, the planets in this system were already older than our planet is today. We now know that Earth-sized planets have formed throughout most of the Universe’s 13.8 billion year history, which could provide scope for the existence of ancient life in the Galaxy,” said Dr Tiago Campante of Birmingham’s school of physics and astronomy.

According to the Univeristy, the planets orbit in under 10 Earth days, indicating they are close to the star – less than one-tenth Earth’s distance from the Sun.

Kepler is a 3.5 year mission, which could be extended to 6 years.

steve bush

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via Yuichun