Kepler – A milestone in the search for other worlds

The space observatory Kepler has run out of gas and, as a result, has been officially retired by NASA.

By looking out into the galaxy, and feeding back an ongoing stream of stellar data, Kepler brought us closer to the stars than any spacecraft, and stirred the desire for cosmic understanding among professional and amateur alike.

Without the technology and resources of science fiction, we are forced to explore space as observers and, until recently, we have had very little data about the planets orbiting distant stars. By investigating a tiny slice of the sky, Kepler has detected light from many thousands of these stars in its view, and variations in the light received has been an indicator of planets. Further analysis could determine a planet’s distance from the star, its size, as well as its mass, density, and even temperature.

NASA launched the Kepler observatory in March of 2009 and, in less than a decade, raked in more than 2,600 confirmed sightings of these ‘exoplanets’. Kepler was not the first to do this, but it did take astronomy to new heights, accounting for 70 percent of all exoplanet discoveries.

The information received from Kepler was made accessible to the public and resulted in a phenomenal explosion in citizen science – hundreds of thousands of volunteers around the world helped sift through the data, revealing exoplanets that others (and other computers) had missed. These exoplanets have provided us with a link to the cosmos.

Kepler-90 System Compared to Our Solar System (Artist’s Concept)

Knowing for sure that there were worlds out there – some maybe like ours – has given the vastness of the Milky Way galaxy a more neighbourly feel. We are not so alone; in fact, based on the findings of Kepler, it is now estimated that there are more planets than stars in our galaxy.

The sheer variety of planets has been surprising, with some in orbit around two stars, whilst others are candidates for being massive water worlds whose surface may be covered in a global ocean. Strange gas giants – such as our own Jupiter – have been found orbiting too close to stars, and other planets have sibling worlds that pass so close they dominate the sky.

Kepler has also made many discoveries in the ‘Goldilocks Zone’ – the necessary distance from a star to potential have liquid water and life – and some of these are likely to be small and rocky, like our own planet Earth. Kepler may not be able to detect alien life, but it does show that there are certainly places out there that alien creatures may call home.

Kepler’s replacement – TESS – is already space-borne, and along with the upcoming James Webb Telescope, these platforms are hoped to bring our observations of the universe to a whole new level. As for Kepler itself, it has far outlived its original four-year mission, and its passing is an opportunity to reflect on its success.

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