The (even) bigger picture

We have heard some of the things scientists everywhere will be using Gaia to do - but how does this fit into the bigger picture, and why do we need a better map of our home-galaxy? Mark McCaughrean is the Senior Science Advisor at the European Space Agency - ESA.

Chris - So what are you at ESA anticipating that Gaia's legacy is going to be?

Mark - I think the first thing you have to realise is that this is just the first release of the data from Gaia. It was launched at the end of 2013 and here we are in 2016. It's actually just the first year's worth of data and in that big pile what we've been able to do is establish the 2D positions and the brightnesses of a billion stars but we've also already given out two million stars with their full three dimensional positions and their motions. And that's because we've been able to connect the Gaia data with data from an older mission of ours called Hipparcos that was flying at the end of the 1980s.

And that is actually where a lot of the science is getting done now because that complete data set - the two million stars - that's about a factor of twenty more than ever done before. And that's just a taster because, at the end of next year, the Gaia catalogue will contain the same information for the full billion.

One of the kind of strange things actually, legacy wise, I suspect some of the scientists won't want to hear this, but the ideal thing about Gaia would be that it would disappear, that it would become invisible. By which I mean is that it's so fundamental, it's so linked into every form of astronomy moving forward from today that Gaia will just underpin all of those things and effectively become part of the infrastructure.

Chris - And what is it going to lead to? You've sort of eluded to it there but where do you see this leading next?

Mark - Well, we have a whole range of missions in the European Space Agency - astrophysics missions, planetary missions, solar missions. So, for us, Gaia is deeply linked into all of those missions by definition because it's so fundamental by establishing the scales, the motions, the history of our Milky Way. As Gerry explained earlier on, that helps you understand galaxy evolution across cosmic distances and across cosmic time.

And, in fact, a future mission of ours, which we're now building, called Euclid will in essence, do a similar sort of survey, not for stars in the Milky Way, but of galaxies themselves across the whole of the universe. And by measuring the positions and slight distortions in the shapes of those galaxies, we'll be able to understand both dark matter, but also the even more elusive dark energy.

So these giant surveys gathering huge amounts of data, processing them, making the results available to everybody is becoming a very key part of modern astronomy.

Chris - Now the price tag for this is something in the region of, north of, a billion euros so when it goes to completion that will have notched up a price tag of something like one euro per star or maybe a bit more since Brexit, I'm not sure. But how do you justify that sort of spend?

Mark - Well, let's keep in mind that this is money coming from twenty two member states in the European Space Agency. So there's roughly five hundred million people across those countries and this mission, by the end, will have been running more than twenty years so the amount of money that's spent each year is actually very small indeed per citizen.  But it's not spent in space either: it's spent on the ground, in industry, in academia. It's spent, in fact, even in schools because there's very strong outreach programmes run all across Europe to try to engage students in the science that Gaia is doing.

And, from my perspective in ESA, we do some amazingly exciting things - flying through the solar system investigating the far distant reaches of the universe. But perhaps one of the most fundamental aspects of what we do is to inspire people and to inspire kids, in particular, to go into science, technology, engineering, and maths. Because those are skills we desperately need on the Earth where we have many problems, as we know,  and if we can inspire kids to get involved in those kinds of subjects through missions like Gaia, then it's a win-win. We do brilliant science and we can help with many of the problems we face on the Earth.

Chris - And tell us what the school kids who you're getting involved can do because this is really high level space science - what can someone in the classroom contribute?

Mark - Well, not really, in a sense it's very basic. We have positions of stars and movements of stars and the data are all free and accessible. We have nice interfaces that people can actually go and download the data and play with. And we're building educational tools around that so people will be able to actually make, if you like, a movie of the Milky Way and understand how it was put together by tracing it backwards in time and tracing it forward in the future.