Astrophysicist Jackie Faherty Breaks Down New Data from the Gaia Mission

Astrophysicist Jackie Faherty Breaks Down New Data from the ESA’s Gaia Mission – Transcript

INTERVIEWER: So Jackie you're pretty excited about data lately particularly a set of data from the Gaia observatory. What is Gaia and why is it such a big deal?

JACKIE FAHERTY: Gaia is the biggest deal astronomy has ever seen in my opinion. That feels like a big statement, but I also would stand by it as a true statement. Gaia is the name of an observatory that's in space right now, it's about a million miles away, and it has been imaging the sky–the entire sky–and reporting back positions of stars. On April 25, 2018, Gaia, the observatory—more specifically, the European Space Agency that runs Gaia—released something: they released a catalog. And that catalog may be considered one of the greatest catalogs astronomy has ever seen. It contains within it 1.4 billion parallaxes, which is another way of saying a way to estimate the distance. So 1.4 billion distances to stars.

The reason why that is so important is that the foundation of astronomy, the foundation of astrophysics, the foundation of our understanding of the universe, requires a precise measurement of distances. And up until Gaia we kind of had based all of astrophysics, all of the laws of how stars evolved, all of the laws about how the universe is changing, on the distances that we had accumulated from another European Observatory called Hipparcos. And that had given us a hundred thousand stars, which was the gold standard. The gold standard was a hundred thousand, and that was blown out of the water on April 25, when Gaia released 1.4 billion distances to stars.

So anything you can bring up in astronomy I could tell you how Gaia will improve that. It is distances that Gaia is giving us, but there's another important parameter, and that's how they move. So when you measure the distance to the star, you can also get its velocity in the plane of the sky. So two-dimensional velocities. We call it proper motion. And Gaia’s also given us 1.4 billion stars with their motions. And so we not only know exactly where they are, but we also know how they're moving.

And so that gives you what's called the dynamics of the galaxy. You're watching the stars in their kind of natural environment moving around the galaxy. And so now we can really dig deep into questions about the history and the future of our galaxy.

INTERVIEWER: You were part of a three-day Gaia data event. Describe the scene for me. Who was there? What were you doing? Is that usually how astronomers work?

FAHERTY: So what I was at was initially going to be kind of a gathering, almost like a celebration of astronomers that wanted to work on Gaia data as soon as it's released. So the way that this mission worked is that the European Space Agency that was running this mission, they’ve been looking at the data, they've been calibrating the data, they've been making sure that they believe their numbers, that there's no mistakes that are going to be glaring and cause scientific inaccuracies. And then they set a date of April 25 for it to go public.

Now that's public both for you or anybody else that has a computer and internet connection, and for astronomers. All of us got access to the data at the exact same time. And so several of us, knowing that this was such a massively important mission in astronomy, wanted to get together and immediately open the catalog together and start digging into it and looking at it. In astronomy, this has become more and more popular to do. They're called “hack days.” Most people think “hack,” they think of people coding, and that is what we do. We sit there with our computers, we write code, we use that code to figure something out about a data set.

And so a bunch of us were going to hack together. And then I think there was a little bit of FOMO going on– fear of missing out–by other astronomers. When it started to catch wind that some people were going to be getting together in a room working on it together, more people wanted to come. So what started out as maybe like 10 people ended up being about 65. People were coming in from Princeton, from Yale, I had a colleague that flew in from Italy, I had another colleague that trained in from DC, and we had a colleague that flew in from Australia.

And so what was going to be one day then then became three days. And it was both a celebration and it was a day of exploration of the data together with a lot of experts in the room. We learned a lot about the data. Several of us made immediate discoveries. I had a paper that I published almost right away. And the excitement kind of like has continued since then.

INTERVIEWER: And what kinds of things will Gaia help us understand about our galaxy?

FAHERTY: There's a couple of basic things that I can tell you. The one that I like the most is if you- once you know how stars move and you've got velocity, you can actually see the recent history and the coming future of where things are going to pass each other, how things might be related to each other, because you can trace back their motions now. So what has the sky looked like in the recent past and in the coming years? If we move backwards in time a million years, how different was the sky? You can see that. But also, what was the closest star? What is the difference in our solar neighborhood? The nearby solar neighborhood, especially stars that come in close, affect the dynamics of our own solar system. So anything that flies close has the ability to invoke, or to gravitationally influence, our solar system. And that tells us the dramatic history, the dramatic tales, that might be unfolding with how life evolves, how life forms, how material transfers from one system to another.

It also tells you about the dynamics of stars in general. What's the recent star-formation history of the Milky Way? What stars formed when? And what stars are currently forming? What's the most common kind of star that's forming? Right now, we think it's a very low mass star, and that may be true, but we can test that across loads of different nearby groups of stars that we can now identify

INTERVIEWER: And is there another Gaia release coming out in the future? And where does the mission go from here?

FAHERTY: This is only the second data release. There was a first data release and that happened in September of 2016. And that was also a big deal, but not quite as big of a deal as what we–not even close actually–to the kind of big deal that we just had. Over the next several years, we're going to get a couple more data releases, each one will either have an improvement in the parameters–so even better precision than what they've currently given us–or it's going to give us parameters that we don't currently have access to.

For instance, one parameter that many of us are waiting for is the astrometric signature of a planet around a star. It's a predicted way that you can find a planet, similar to how Jupiter actually orbits the Sun at a point that causes the Sun to wobble. You can see that if you can measure the position of a star really, really carefully, but you have to do that over a couple of years, and you have to be very careful in your interpretation of the data. And while we've predicted that you could detect planets this way–and you can detect small planets this way, rocky planets like our own Earth–but no one's found one yet in this manner. Gaia will definitely find them. And so in future data releases, probably the very last data releases, Gaia will reveal the astrometric solutions that will tell us how many stars out there have the astrometric signature of a giant or terrestrial planet or everything in between around them.

That's in the future, so we have way more to look forward to. This mission doesn't go away, it's not like very exciting in this moment and then we move on to the next thing. You will hear about what Gaia has discovered for as long as you listen to space-based news.

INTERVIEWER: So it sounds like we have a lot of discoveries to look forward to.

FAHERTY: Definitely more discoveries are waiting.

INTERVIEWER: Thank you so much.

FAHERTY: You're welcome.