NOT TOO cold and not too hot. Scientists searching for Earth-like planets circling distant stars have finally found a “Goldilocks” planet – one that orbits its sun at a distance where the temperature is just right.
The discovery was announced yesterday by Nasa, which operates the Kepler satellite. Its sole purpose is to keep its telescope fixed on 150,000 distant stars, watching continuously for evidence that these stars have their own orbiting planets.
Although the satellite has discovered more than 2,300 planet candidates, the newcomer, named Kepler-22b, is the first confirmed to be close to Earth size, orbiting a star like our own sun and lying in the “habitable zone”.
Being in the zone in a planetary sense means it is far enough away from its sun to avoid desiccation, yet close enough to avoid being frozen solid. This increases the possibility that the planet could have liquid water on its surface, making it something of a home from home for Earthlings.
If there is water, could there be life? Potential life on Kepler-22b is unlikely to look like the three bears of the Goldilocks tale, but scientists remain very excited about the discovery. “This is a major milestone on the road to finding Earth’s twin,” said Dr Douglas Hudgins, a Kepler programme scientist at Nasa.
It isn’t quite a twin, though, having almost 14 times the volume of our own planet. Its sun is of the same class as our own, but is somewhat smaller and cooler, according to the research results, which were released by Nasa yesterday.
Astronomers have no idea yet whether Kepler-22b is a rocky planet like Earth, predominantly liquid, or just a ball of gas wrapped around a core.
Kepler-22b will be remembered as the first Earth-like planet located in its star’s habitable zone, but we are unlikely ever to visit the place, given that it lies 600 light years away.
The research team will be kept busy, because the satellite has located 54 planets that lie in the habitable zone. Each of these will in turn be studied in the coming months to see if they can be classed as Earth-like.
And Kepler has a back catalogue of more than 2,000 probable planets that await further study to see if they too might be considered just right to a discerning Earthling.