As the Earth starts on yet another orbit of the big ball of gas that we know as the Sun – the star that sets our clocks and feeds our plants – a new project aiming to map one per cent of the one hundred billion stars that make up the Milky Way has been set into motion. The Milky Way, the galaxy that contains our humble solar system, is a vast beast. It takes one beam of light (something which travels pretty fast , I hear) 100,000 years to travel across it. This is what Gaia is up against.

The Gaia satellite – which was launched from French Guiana at the end of last year – began as an idea by a small group of scientists in the early 1990s, and will be in orbit for the next five years. Its billion-pixel camera will return data for the first map in 2016. The data will allow astronomers to build a history of the Milky Way from its earliest beginnings, producing the first three-dimensional ‘census’ of our night sky.

According to Professor Gerry Gilmore of the Institute of Astronomy, the UK principal investigator for the mission, Gaia “will allow us, for the first time ever, to walk through the Milky Way – to say where everything is, to say what everything is. It is truly a transformative mission.” 

Cambridge is at the beating heart of what has been called “one of the most ambitious space missions in history”. The university is one of the primary Gaia data processing centres and will publish new data on supernovae, black holes and dark matter that has previously been a mystery to astronomers.

The hope is that by measuring the distances of stars relative to other stars, and relative to one million supermassive black holes that the team’s measurements have identified, Gaia will be able to create a ‘reference grid’ that spans three-quarters of our known universe.

Perhaps even more excitingly, Gaia will put to test Einstein’s theory of General Relativity, by measuring the way in which light bends around the Sun. Einstein also predicted the existence of ‘ripples’ in the space-time continuum, which would alter the apparent positions of groups of stars. Gaia will be able to theorise the possible strength of these ripples.

The satellite will also be able to determine the age of each of the stars, allowing scientists to make a comprehensive timeline of the galaxy. In order to produce the exquisitely precise data that Professor Gilmore and his team are searching for, Gaia needs to be locked into an orbit in which heat and gravity are stable. To keep Gaia adequately cold, it has been sent up into space with a shield about the size of half a tennis court, meaning that the temperature difference across the satellite will be less than one-millionth of one degree (that’s 0.000001°C).

It will also be securely locked into an orbit in which the gravity of the Earth and the gravity of the Sun exactly cancel each other out, 1.5 million kilometres into space. These genuinely weightless points are known as Lagrange points, and there are only five such points around our sun. Gaia will be locked onto the second point, and will need almost no fuel – and, crucially, hardly any engine disturbing movement – to keep it in orbit.

Such ambitious aims do not come cheap. The satellite itself, which was funded by the European Space Agency, cost €650 million to build. However, Professor Gilmore believes that the findings will “revolutionise our knowledge of astronomy”. As a bonus, it will also be able to spot any killer asteroids heading our way - not that it will be able to do anything about them.