ESA/GAIA/DPAC

Welcome to the age of mass-produced star-gazing. Over 400 million stars have been discovered as part of a project to create the most accurate star map ever. The European Space Agency (ESA) satellite, Gaia, has just released its catalogue of over 1 billion stars in the Milky Way, launching a new era of astronomy.

“In the future we will realise that this was a big day for our understanding of the universe,” says Paolo Tanga from the Côte d’Azur Observatory. “When people will talk about the formation of our solar system, its environment and the nearby stars, our understanding will come thanks to Gaia.”


The huge number of stars that Gaia has made visible to astronomers can hardly be overstated. Of the 1.1 billion stars in the Gaia map, it’s estimated that nearly half are new discoveries. “It’s a 1000 times expansion of what we can see today in the stars” says Tanga. “It’s a completely different sky.”

But the mission aims go beyond just a three dimensional map. “There is a new revolution coming– the 6D revolution of Gaia,” says Antonella Vallenari from the Padua Observatory, Italy. “Gaia is not only going to provide the position of the stars in the sky, but also the motion.”

The craft has managed to catalogue the journey of almost two million stars as they move across the sky, which will allow astronomers to calculate where these stars have been and where they are going. It’s expected that this will lead to a greater understanding of how the Milky Way was formed.

An average day for Gaia

Gaia began its mission in December 2013, when it launched from French Guiana. Its destination: an area 1.5 million kilometres from Earth known as L2. Here the sun and Earth’s gravity are always in balance, allowing a comparatively small object (like Gaia) to stay in the same place relative to these two celestial bodies.

After a three-week journey Gaia reached L2 and started sweeping its two telescopes across the sky, focusing the light into a digital camera capable of capturing nearly a billion pixels. You would need around 500 HD TVs to see all of the detail from a single one of these images.

Each day, Gaia has been performing hundreds of millions of measurements, viewing roughly 70 million celestial objects, and sending around 40 gigabytes of data back home.

But the mission hit some problems early on. More light bent past its sun shield than originally intended, more ice froze onto the telescope mirrors than expected and size changes due to temperature variation were a few nanometres more than initial estimates. This delayed Gaia’s first data release, but the problems were small and didn’t dent the mission objectives.

Although Gaia has produced some fantastic pictures, its legacy will be its calculations. “The main outcome of the mission is not images, but measurements,” says Tanga. “The pretty pictures are just a tiny part of the contribution of Gaia – the one that can easily be conveyed– but the power of Gaia is in the numbers.”

Over the next weeks, months, and years, scientists will sift through the huge dataset. And for the next 20 years or so, we can expect this to lead to new discoveries about our galaxy. “If the Gaia satellite was destroyed today,” says Tanga, “it would have already changed astronomy forever.”