-Launched in 2013, the European Space Agency's
Gaia mission is building
the biggest and most accurate 3D space catalog ever made,
which maps out over one billion astronomical objects
and provides an unprecedented understanding
of our place in space.
So whether you're a professional space explorer
or a backyard observer,
this new catalog promises to be a star chart like no other.
♪♪
I'm pleased today to be speaking with Timo Prusti.
He is a Gaia Project scientist at the European Space Agency.
Thank you so much, Timo, for joining us.
-Thanks. It's a pleasure to join you.
Well, you know, throughout human history,
we've always been a species that has wanted to explore
and understand our surroundings,
see what's over the next horizon.
I really feel like the Gaia Mission
has taken this to a pretty unprecedented level.
So I just want to start --
if you could just describe what Gaia is
and what are some of the objectives of this mission?
-So Gaia is a billion star map
of our Milky Way,
and, really,
the requirements for the mission
have been set in order to understand our home galaxy,
the Milky Way, better.
So that is set how Gaia is actually working
on what it is measuring.
But then it turns out that it's really useful
for many, many other things
because what they mean for the Milky Way
are very fundamental missions.
-Could you sort of go over what the main ways
that scientists are using this data to kind of discover
new insights about the galaxy and the universe, in general?
-So the really important thing in Gaia
in what we call photometry.
So this is actually a very ancient way to do astronomy.
It's basically measuring the position of stars.
However, it's not only to understand
where the stars are in the sky,
but measuring them very precisely
given us information also of their distances and movements.
And that's really the key thing what Gaia is doing
and what has to be done from space
because all these movements are extremely tiny,
and you have to be extremely stable
to do any of these things.
-Yeah, and that point,
Gaia is located out in the center of Lagrange 2 Point.
Why does it have to be out there
and where is that in relation to Earth?
-So if if you start from the Sun,
first look where Earth is.
Earth is 150 million kilometers from the Sun.
And this Lagrange Second Point
is 1.5 million kilometers from Earth
to the other direction,
so way from the Sun.
It is actually beyond the Moon,
and that is the whole thing why it is interesting
for astronomical measurements,
because if we look from that point towards the Sun,
we will see the Sun, the Earth, and the Moon
roughly in the same direction.
So if we put a big shade, what Gaia is doing --
putting a big shade, blocking that light.
Then we have the whole dark universe
at the other direction,
and that's the art of L2 point.
-So you're able to basically block out
all of the kind of sunlight
and all of the disruptive stuff
and just see this massive galaxy and universe beyond?
-That is exactly the idea,
that we have free view of the dark sky.
-I'm seeing this amazing skyscape behind you here.
Wonderful catalog of stars.
Is that a Gaia image? And if so, what is it?
So, this is, indeed, the number of stars one sees
in a certain part of the sky.
So it is definitely Gaia results.
And of course, there is a personal choice here
that if I can move a little bit, you'll see the black spots.
So those are chameleon clouds in the southern sky,
and that's their area
where I did my thesis a long time ago.
-From my perspective as space reporter,
every single time there's one of these big data release
projects from Gaia --
I think there's been two and like a little bit --
half of one, like an early data release of a third,
it's like Christmas and New Year's
and every holiday you can imagine
for for astronomers, right?
You get this this glut of papers
that starts appearing like a couple of months afterwards
with everyone trolling through all the new data.
So could you just explain
what's been in the two full data releases
that have happened so far and what we can expect
from the full third and fourth release.
-Before Gaia, we roughly had
a map of the city where we lived,
but then everything beyond that
was a little bit unclear and grey.
And what Gaia is doing, actually --
We are not competing just the state or a country,
but we are mapping a continent.
So we are just making this huge leap
from our surroundings of our sun
to really a large fraction of our Milky Way galaxy.
-And even beyond the astronomical community,
if the public wanted to look at this data,
would they be able to try to,
you know, educate themselves on the kind of data
that's coming back from Gaia?
Is it that open?
-It is totally open, so anyone can use it.
And we have, actually --
I mean, we are following the people
who are using the data, and we get countless questions,
and there are teachers who are
making cases for their students at schools.
So it is definitely used not only by the hardcore scientists,
but also by the wider audience.
-That's really wonderful to know that, yeah,
it has this public effect, as well,
because it is, you know --
it's a mission that is helping us understand
where our place in things, and that affects everybody.
You know, to that point,
you mentioned, this is primarily
a mission that's focused on our own galaxy.
But does it ever look at stuff that's extragalactic?
Are there objects that Gaia is mapping
that are in other galaxies or out really just in space?
-By far, most of the billion objects we are observing
are stars in our own Milky Way galaxy.
But then you go really to the extremes.
So, we also see asteroids in our own solar system.
It's only a few hundred thousand.
So compared to the billion, it's nothing,
but, really, it will be the biggest database
of measurements of asteroids.
We also see galaxies, which are far away.
So in the next release,
two million galaxies.
and the properties of those ones will be published.
And even goes to stars actually in the galaxies
which are close by our Milky Way galaxy.
Some stars are bright enough to be seen by Gaia.
So there are also a few million stars in galaxies around us,
the brightest ones in those galaxies,
which will be also in the catalog.
-That's really exciting. Wow.
Those must be incredibly luminous objects
to be shining across intergalactic space.
-Correct. They are really the most massive stars,
the brightest ones.
-So Gaia was launched in 2013.
It's been doing all of these amazing data releases.
What's the sort of long-term future
of the mission?
Is there a mission-end date?
When will it know as a project that it's done?
-Well, we have a project, actually, end date,
and this is coming from the fact that when we are observing,
we are spinning the satellite,
and you can imagine if you try
to make a very sharp image by spinning --
I mean, everyone who has done photography says
you should not move
when you are making a sharp photograph.
So we are doing that, and we are doing it
by controlling the spin extremely precisely,
and we are moving at the same time
the picture from our camera.
So that might be a little bit difficult
to imagine how it works,
but we are actually making a picture by moving,
but we are moving the picture at the same speed
on the detector as Gaia is spinning.
But that works only if we spin this control
really precisely.
And for that one, we need something --
what we call Cold Gas.
So there is a tank,
and we are making tiny, little puffs of gas
to get the spin precise.
And at some point, that gas, we will run out of it,
and the predicted time
when we will run out of it is early '25.
So, we really hope that nothing else happens before '25
so that we can get more than 10 years of Gaia data.
-Certainly, whenever I report on Gaia data,
it really kind of boggles my mind
how broad the insights are
from so many different fields.
I love the kind of insights about these hyper-velocity stars
that shoot across space,
and what's going on at the center of the galaxy.
What do you think are some of the most exciting discoveries
that have been made so far, in your opinion,
and what else do you think you are looking forward to
along those same lines?
-So, I think maybe one of the important things,
what should be mentioned is that one of the reasons
why we have the Gaia mission
is we try to understand better our own Milky Way,
the structure and also the evolution of it.
And what was one of the results that came out
is that they see some big impact
which our Milky Way had some 10 billion years ago.
And how can we know that there was a big impact?
Because the Gaia data revealed that there is quite a bunch
of stars which are actually orbiting our Milky Way
to the wrong direction.
So, meaning that they go to the opposite direction
in as -- most of the stars.
And the only explanation of this one is that,
10 billion years ago,
the Milky Way was cannibalizing a small galaxy
which hit our Milky Way against the rotation,
and so the stars were captured by our Milky Way,
but they still remember where they came from
because there is nothing to stop them,
so they still circle the galactic center
the wrong direction after 10 billion years.
And you can only tell this one
because the Gaia provides the movement
in that level of accuracy.
So, it really demonstrates
that the idea of measuring the motions of stars
in order to understand our Milky Way,
it works.
We really understand now much better
what has happened in the past,
how our Milky Way has been constructed.
-That actually touches on two of my favorite space terms,
galactic cannibalism, and also galactic archeology,
I think, has some relevance there, too,
where, you know, being able to kind of find
these signs of what the galaxy has been through in the past.
I mean, it's just astonishing to think that our galaxy
has been eating other galaxies and what that means.
Can you tell me a little bit more about
how that plays into our wider understanding
of how galaxies evolve, even beyond the Milky Way?
-So, this was always a big issue
when we looked at other galaxies, extragalactic sky.
We would see all the signs that smaller galaxies
are being cannibalized by the big ones,
so that's the build-up of bigger and bigger galaxies.
But our picture of our own Milky Way was --
simply because we are inside it.
It's very difficult to see when you are inside something.
And we were lacking the information to --
we see the similar kind of science in our Milky Way Galaxy.
And now Gaia data is really demonstrating
that, yes, exactly.
We see the remnants of this 10 billion years ago event.
But we see also, now, there are further articles coming out
where people see signatures of other galaxies
which have been merged to our Milky Way Galaxy.
So in a way, we are showing that our Milky Way,
how it is building, building up.
It fits into the general picture how we think galaxies form,
where the big guys are eating the small ones.
-[ Chuckles ] That's so wild. I love it.
And I don't know, I mean, I know that
there's not a huge amount, I think, of disruption
on the stellar Solar System level when these things happen,
but I'm still glad to be in the big galaxy
that's eating other galaxies rather than the small one.
-Now, watch out, because we might be eaten
by the Andromeda Galaxy in the future.
-Okay, well, if I live five billion years,
then I'll watch out for that.
♪♪