Discovery of Extra-Solar Planets Has Rocketed

Extra-solar plantes, or "exoplanets", are planets that orbit stars other than our own. Finding exoplanets is important if the human race is ever to succeed in finding life elsewhere in the universe, or indeed settle on another planet.

The discipline of exoplanatology is the attempt to observe such planets in their orbits around distant stars, which is no mean feat given that even the nearest star is 4.24 light years away!

Three Exoplanets imaged by the Hale telescope (Source: Wikipedia)

Whilst exoplanets have been rumoured to exist since the 16th century, it was not until 1988 that the first one was discovered. The problem being that at that distance planets are so tiny as to be invisible even to the Hubble Space telescope directly, and their existence has to be inferred by measuring things like the tiny gravitational wobble they impart on their star or a  minuscule dimming of their star as they pass in front of it.

Even then, scientists were cautious in concluding that a planet had been detected. It wasn't until 1992 that two more were observed orbiting a pulsar, and observed with such a degree of certainty that their discovery was regarded as definitive.

Since then a variety of techniques have been used, including direct imaging, radial velocity, transit and gravitational lensing. And the number of exoplanets spotted has rocketed, if you'll excuse the pun, and in 2014 there were 800 exoplanet discoveries:

Source: The Smithsonian

And this is a field that can only continue to grow, particularly since the James Webb Space Telescope, which is 100 times as powerful as the Hubble Space Telescope, is due to be launched in 2018:

James Webb Space Telescope versus Hubble (Source: Wikipedia)