The Sky at Night looks back at the last ten years of astronomy and ponders the most significant milestones and revelations. With the help of six distinguished astronomers, Chris and Maggie consider the state of astronomy in 2020 and wonder what new, exciting discoveries await us across the rest of the decade, as a host of new ground and space telescopes come online. Astronomer Royal Lord Martin Rees is among the guests to walk along the Astronomical Wall of Discovery in this one-hour special.

We are the generation of human beings that are going to know whether or not we're alone in the universe. This episode explores the search of exoplanets, from ancient Greek philosophers to the discoveries made possible with the Kepler Telescope. Unbelievable new worlds, planets made of diamond, planets of raining glass, worlds in collision, some plunging into stars, and others that just might harbor life.
Thanks to today's planet hunters, our views of the universe and of our place in it are undergoing one of the greatest revolutions in scientific history.

NASA may have just gotten one step closer to the answering the question: are we alone? The Spitzer Telescope has made a groundbreaking discovery of exoplanets that could be similar to our own. And as Kepler also continues its search, our understanding of the universe continues to be redefined.

Humans have long gazed up at the night sky, wondering whether other lifeforms and intelligences could be thriving on worlds far beyond our own. But over the last few decades, ultra-sensitive telescopes and dogged detective work have transformed alien planet-hunting from science fiction into hard fact. We expected to find worlds similar to the planets in our own solar system, but we instead discovered a riot of exotic worlds. Vivid animation based on data from the most successful planet hunter of them all, the Kepler space telescope, brings these worlds into view: puffy planets with the density of polystyrene, unstable worlds orbiting two suns and 1,000-degree, broiling gas giants with skies whipped into titanic winds.
But perhaps the most startling discovery was the number of worlds that may be contenders for a second Earth, at the right distance from their sun to have that ingredient so crucial for life as we know it, liquid water. Amongst them, we witness the most tantalizing discovery of all: a so-called ‘super-Earth’, situated in the Goldilocks zone - the area just the right distance from a sun to potentially support life - and with the faint signal of water in its atmosphere.

In just one generation, our ability to search for planets beyond our solar system has transformed. With modern techniques and telescopes, planetary scientists have found thousands of exoplanets in our universe, and many of them have the perfect conditions for life. Are we about to find Earth’s twin?