System of Earth-sized planets spotted

30 January 2015
Posted by Chris Smith.

A clutch of Earth-sized planets discovered around a star 100 light years from Earth means the odds of extraterrestrial life existing have just increased dramatically. Ancient solar system

Using the Kepler space telescope, Birmingham scientist Tiago Campante and his colleagues were able to see tiny dips in the intensity of the light coming from the star Kepler 444. These corresponded to 4 planets, the smallest about the size of Mercury and the largest about the size of Venus, passing at various points in front of Kepler 444 and partially blocking out the light from the star.

The discovery is ground-breaking on two levels. It shows that tiny planets of Earth-size can be detected, according to Campante, "with a precision of within a few tens of miles." More importantly it re-writes the astronomy books because the parent star, Kepler 444, is more than 11 billion years old.

Previously scientists had thought that rocky planets like the Earth couldn't exist this long ago because, so soon after the Universe had formed (a couple of billion years previously) there would have been too few raw materials, like heavy metals such as iron, to seed them.

This is because heavy elements, like iron, are made inside massive stars and then dispersed across the Universe when the star explodes in a supernova at the end of its life.

However, the existence of these newly-discovered rocky worlds shows that Earth-scale planets can and did form this early in the evolution of the Universe, which also means that the odds of an Earth-like planet existing, with liquid water and other correct chemistries needed for life, are significantly higher than previously thought.

At the moment the Birmingham team, who have published their findings in the Astrophysical Journal, don't know the compositions - or what is in the atmospheres, if any, of the planets they have found, but these sorts of studies are on-going by groups internationally.

"It will be an interesting and important next step," says Campante.

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