Exoplanet Kepler 37b

Astronomers have smashed the record for the smallest planet beyond our Solar System - finding one only slightly larger than our Moon.

To spot the tiny, probably rocky planet, they first needed to precisely measure the size of its host star.

They did so using "astroseismology" - effectively, turning tiny variations in the star's light into sounds.

A report in Nature describes the blistering, probably rocky planet, which orbits its star in just 13 days.

It is joined in this far-flung solar system by two other planets, one three-quarters Earth's size and one twice as large as Earth - all circling their star too closely to harbour liquid water or life.

Moving target

The record for smallest "exoplanet" is routinely being broken, as astronomers get better and better at finding them.

The best tool in the planet-hunters' toolbox is the Kepler space telescope, which stares at a fixed part of the sky, trying to detect the tiny dips in stars' light that happens when planets pass in front of them: what is called a transit event.

In its earliest days, the Kepler team tended to find large planets - Jupiter- and Neptune-sized behemoths. In more recent years, the catalogue of exoplanet has seen an increasing number of so-called super-Earths, up to about twice the radius of our planet.

Only recently has something definitively Earth-sized been found.

found here-- http://www.bbc.co.uk/news/science-environment-21471908