How big is the Solar System? 18th century astronomers tried to find out by sending expeditions around the world to measure a transit of Venus. One of these was Captain Cook's voyage to Tahiti. He went under the auspices of the Royal Society, but he carried secret orders from the British government.

Christmas 2022 is past, but the daily "astro advent" images in the Astronomy Forum are still there to enjoy. The second eight days included both a magnificent aurora and an awesome meteor shower.

Since the name of Nicolaus Copernicus is still well known nearly five hundred years after his death, why was his grave unmarked until 2010? Find out about the life of the quiet revolutionary that turned our view of the universe inside out.

Warm summer nights are a great time to study the sky. Here is a guide to the main summer constellations. You can see all of these things without a telescope, so head outside and look up.

It's the planet most likely to be mistaken for a UFO. It spins backwards on its axis. A year is two days long. It's Venus! Some call it Earth's twin, but it isn't much like home.

Flowers from the florist are popular for Mother's Day. But for really stellar mothers, here is a cosmic floral tribute with links to some dazzling astronomical images.

Rosetta went where no space mission had been before! It caught up with a comet in deep space and went into orbit around it. Its lander Philae was the first ever to land on a comet. At the end of the mission, Rosetta also landed on the comet to join it and Philae on the comet's journey.

In a tilted orbit in the scattered disk, it shook up the traditional Solar System. Was it bigger than Pluto, and therefore a planet? No, both of them ended up as dwarf planets. Eris – named for the Greek goddess of discord – was an apt name for an object whose discovery started so many arguments.

The sky is full of stars, and since prehistoric times humans have known of five nomads – planets – wandering among them. No individual discovered those planets, for they're there for all to see. So why was the sixth one – now called Uranus – not known until 1781?

Christmas 2022 is past, but the daily "astro advent" images in the Astronomy Forum are still there to enjoy. The final eight days – plus a Christmas bonus – included a fire rainbow, ice halos and a spectacular comet.