ASTRONOMY : *NEW MOON NOW*

WRITERS of science fiction have long assumed that the galaxy is teeming with alien planets. They were correct, but it was only in the past decades that science has been able to confirm this.

The first exoplanet was discovered in 1992 , but the floodgates really opened in 2009, with launch of Kepler, a planet-hunting space probe. Thousands have since been found. Statistics suggests that every star in the galaxy - and, presumably, the universe - has at least one.

Kepler's fuel is now almost exhausted, and the probe is nearing the end of his life.

But a paper published by Alex Teachey and David Kipping in Science, Advances suggest that  data  it has already collected may confirm another science-fiction assumption  - that alien planets have alien moons

In a way, this is not surprising.

Few astronomers would have bet against the existence of exomoons. But they might have been sceptical that  Kepler  was sensitive enough to spot any. What's more,  the moon that Drs Teachey and Kipping propose is strikingly strange.

To find their  moon, the two researchers sifted through data from 284 different exoplanets that Kepler had spotted.

The probe works by monitoring hundreds of thousands of stars, watching for tiny, repeated drops in their brightness caused by a planet moving in front of the star's disk.

A planet with a Moon should produce a subtly different signal, with the moon causing second, much smaller dip just before or just after the one caused by the planet.

Spotting such tiny flickers is on the edge of the Kepler's capabilities. Nonetheless, Dr Teachey and Dr. Kipping found one promising looking planet, with the unromantic name of   Kepler-1625b.

That was intriguing enough for them to be awarded a chunk of coveted observing time on the Hubble Space Telescope, to take a closer look.  The Hubble has a much bigger mirror than Kepler, and so should be able to generate a firmer signal.

After  40 hours of observation, and after putting their data through the statistical wringer to try to remove any possible sources of bias, such a signal is exactly what they think they have found.

Only big moons would cause enough of a dip in brightness to be detectable with today's instruments.  And, with the important caveat that the room for uncertainty is large,  Kepler-1625h's proposed moon seems indeed to be a real whooper.

The Honor and Serving of the latest Operational Research on Astronomy continues. The World Students Society thanks *The Economist*