The Milky Way, our galaxy, is a magnificent sight in the night sky, but we know surprisingly little about it for certain. What is its shape? How many stars does it actually contain? What lies at its centre? The Gaia space telescope will answer these questions, being armed with the most advanced camera to leave our planet, and it will allow us to see our galaxy as we've never seen it before. The Sky at Night visits the factory in Chelmsford that made the astonishing sensor at the heart of the mission.

The film looks at the latest understanding of black holes, featuring an interview with Stephen Hawking. Black holes are one of the greatest mysteries in the universe. They behave in a way that is contrary to laws of physics and one has never actually been seen. However, the recent detection of gravitational waves, as predicted by Einstein, proves that black holes exist and provides a way to investigate their remarkable behaviour and properties.

Chris Lintott and Maggie Aderin-Pocock report on the reaction to the dramatic announcement of the discovery of phosphine gas in the clouds of Venus, a gas that could be a sign of life. Venus remains an inhospitable and unlikely host. But if not Venus, where in the solar system is the best place to look for alien life? Chris and Maggie investigate the latest missions to Mars and the icy moons of Jupiter and Saturn. Away from the search for life, Pete Lawrencepreviews the best meteor showers of the year.

A look at two missions attempting one of the most difficult feats of space exploration - to collect a rock from another world. The film checks in on the US and Japanese attempts to bring a piece of an asteroid back to Earth. The missions have taken decades of planning, but the results will be worth it. We find out how studying these space rocks can teach us about the origins of our solar system and may one day help save Earth from a catastrophic collision.

Looking back on the major stories of the year - from the New Horizons mission to the most distant world we have ever visited to the release of the first-ever picture of a black hole. The team relive the highlights and uncover the latest developments.

20 years ago, two astronomers made a remarkable discovery, one which would change the way we view the universe for ever. A planet outside our solar system, orbiting a distant star - an exoplanet. Since then, we have found worlds where it rains diamonds, ones that boil at 3,000 degrees centigrade and even a world with four suns in its sky. But the big question is - will we ever find another Earth? As we close in on the discovery of the 2,000th planet outside our solar system, or exoplanet, we investigates the techniques that are revealing so much about these alien worlds. The documentary asks if we are really any closer to finding another world like our own - a second Earth.