x Abu Dhabi, UAESaturday 22 July 2017

A planet like ours

Nasa has found a planet, circling another star, where temperatures could permit liquid water. Someday humans will decide to go have a look at such planets.

Kepler-22b is not exactly a holiday resort. The temperature may be pleasant enough - around 22°C degrees, scientists think - but the trip would be awfully long: about 600 years each way, if you could travel at the speed of light.

But Kepler-22b is an important bit of real estate all the same. It is the first identified "exoplanet" - the planet of another star - in the "habitable zone", the radius around its star where liquid water could exist.

The US space agency Nasa has an orbiting telescope, named for the astronomer Johannes Kepler, searching for our planet's twin, or at least distant cousin: someplace about the size of Earth, with temperatures suitable for liquid water, which is essential to all the life forms we know.

Kepler-22b may not be suitable for human life - it has 2.4 times Earth's radius, and it may be all gas. But the Kepler telescope is steadily identifying many more planets, in just the one little patch of sky it is studying. A close match for our home planet can be confidently expected before Earth circles its own star many more times.

Humans haven't even visited the moon since 1972, so manned space travel to exoplanets is still just a dream. For now - but surely not forever - Kepler's discoveries can serve only to increase the essential human appetite to go and see what's on the other side of the hill.