ASTRONOMERS HAVE REVEALED the discovery of yet another new planet – the smallest planet that humans have ever identified.
Kepler 37b is smaller than the Earth’s moon – smaller even than Mercury, the smallest planet in our own solar system – and orbits its host star in just 13 days.
It is part of a three-planet solar system, and is so close to its star that it has an estimated surface temperature of about 425°C (800°F).
Though astronomers have identified hundreds of ‘exoplanets’ – planets outside our own solar system – the discovery of Kepler 37b is relatively unusual given its comparatively tiny size: most discovered so far are several times larger than Earth.
The planet – just like the star Kepler 37, around which it resolves – is named after the Kepler mission which identified it. The Kepler extra-terrestrial observatory was launched in 2009 and was due to have been phased out of action by now, but has been maintained due to the significant quantity of data it accrues.
Kepler works by constantly monitoring the brightness of over 150,000 stars – and keeping an eye out for any momentary changes in that brightness. Changes in the light usually mean that a planet has gotten in the way of the star’s light by orbiting in front of it.
The difference in the light emission is then used as the basis to calculate the size of the planet; further monitoring for repeat events can reveal how often the planet revolves around its sun.
This first requires knowledge about the size of the star – which is determined using a technique called asteroseismology, which involves examining sound waves emitted by the stars and measuring the slight ‘flicker’ that it causes to the light.
Small stars like Kepler 37 – which is three-quarters the diameter of our sun – emit sound at a far higher frequency, making them difficult to accurately measure – which is why most of the stars and planets identified by Kepler are significantly larger than our sun or than Earth itself.
“Even Kepler can only detect such a tiny world around the brightest stars it observes,” said Jack Lissauer, a planetary scientist at NASA’s Ames Research Centre.
“The fact we’ve discovered tiny Kepler-37b suggests such little planets are common, and more planetary wonders await as we continue to gather and analyse additional data,” he said.