This was the 25th Astrofest – and how things have changed since the first one! No one knew then if other stars had planets. Pluto was still a planet and its discoverer Clyde Tombaugh was still alive. The Rosetta mission was in the very early planning stages, and Cassini-Huygens hadn't been launched.

Shopping
The Kensington Conference and Events Centre in London provides exhibition space on three floors, and some three dozen stands filled the space. There was Astronomy Now, the magazine that presents Astrofest, astronomical societies, book publishers, and universities with astronomy courses. Almost the only limit to what you could buy was your budget. Equipment ranged from telescope eyepieces to a telescope dome for your backyard. But there were also posters, astronomy-themed jewellery, meteorites and much more.

Although many people come only to look at the stands and meet up with friends, there is also a conference program. You can hear – and meet – people who make the discoveries and who work on the space missions we read about.

Conference
An 800-seat auditorium with a big screen is the venue for four sessions over two days. The conference was chaired by Lucie Green, a professor of physics known for her outreach work, and science journalist and author Stuart Clark.

Let's have a look at some of the talks.

Robotic missions – firsthand accounts

Rosetta, ExoMars
Andrea Accomazzo is a head of division at the Space Operations Centre of the European Space Agency (ESA). He was the Flight Director for ESA’s comet chaser Rosetta, and told us about some of the tense moments, including his landing Philae on comet 67P. He also spoke about the ExoMars mission. In October 2016 the first part of the mission arrived at Mars – an orbiter and test lander. The orbiter is orbiting, but the test lander failed its exam and crash-landed. Unfazed, Accomazzo said this is what a test is for, to ensure the main event's success in 2020.

Voyager
Garry Hunt has been, among other things, an astronomer, broadcaster, and businessman. For nearly two decades he was involved in NASA planetary missions, primarily the Voyager missions. The year 2017 marks the 40th anniversary of the launch of Voyagers 1 and 2 to the outer planets. Voyager 2 is the only space mission ever to visit Uranus and Neptune, and Voyager 1 was the first spacecraft to enter interstellar space.

Cassini-Huygens
The Cassini mission ends in September 2017 with the spacecraft plunging into Saturn's atmosphere. Andrew Coates of the Mullard Space Science Laboratory related some of the highlights of this spectacular mission. Cassini has studied the Saturnian system since 2004, and Huygens was the lander that made it to the surface of the large moon Titan. Between the Huygens data and Cassini data, there were some amazing discoveries about Titan, such as its methane-driven weather system. Coates said, “We thought Titan would be the star.” But that was before finding geysers on Enceladus and realizing that it had a liquid ocean beneath the ice.

Exoplanets and the search for life
The discovery of a small planet orbiting one of the Solar System's nearest neighbors was big news in 2016. Guillem Anglada-Escudé, a member of the discovery team, talked about looking for exoplanets, and “Proxima b: the world next door”.

Louisa Preston's interest is astrobiology (extraterrestrial life). She admitted that it was difficult to work in a discipline that has “yet to demonstrate its subject matter even exists.” However biologists think the essential conditions for life to develop seem to exist on Mars, Europa and Enceladus. Extremophiles on Earth show that life can survive in grim environments. This includes ones with extreme temperatures; highly acidic, caustic or saline ones; even those with high levels of radiation. Preston's special favorites, the “water bears” (tardigrades), have been sent into the vacuum of space. After returning they revived with no ill effects.

Worlds beyond Neptune
Scott Sheppard of the Carnegie Institution for Science has discovered more than seventy moons, but his true love is the objects of the Kuiper Belt and beyond. He told us some of the surprising things New Horizons learned about Pluto, and talked about even more distant objects. He also explained why he thinks that the distant objects include a massive planet that hasn't yet been located, Planet X. Sheppard explained the observations that led to this conclusion and suggested that it might already have been imaged, but not identified. Uranus and Neptune had been observed many times before being identified as planets.

Astronomy on the Ground
Most astronomy is still done on the ground. Some of Katherine Joy's work has even involved looking around on the ground as part of a team hunting for meteorites in Antarctica. Meteorites are bits of space rock, a sample return not needing a spacecraft. She liked her first trip and thought herself fortunate to get a second one, though Antarctica isn't for everyone.

The really big astronomy story of 2016 was the LIGO (Laser Interferometer Gravitational Wave Observatory) detection of gravitational waves. Martin Hendry, part of the international team that works on LIGO, said it would “open a whole new window on the Universe”. He explained how the LIGO detectors work, and how the waveform generated by the event could be analyzed. Analysis showed that it was a collision of two black holes about 1300 light years away. They could even calculate the masses of the two black holes.

What a show! Happy 25th birthday, Astrofest.

Note: I attended Astrofest as a guest of the organizers Astronomy Now magazine. Many thanks to Steven Young.