By Adam McMaster and Andrew Norton for The Conversation
The European Space Agency’s (Esa) Gaia mission has just released new data. The Gaia satellite was launched in 2013 to measure the exact positions of a billion stars. In addition to measuring the positions, speeds and brightness of stars, the satellite has collected data on a huge range of other objects.
There are many things that excite astronomers. Here are five of our favorite insights that data can provide.
1. The secrets of the past and future of our galaxy
Everything in space is moving and the stars are no exception. The latest edition of the data contains the largest three-dimensional map of the Milky Way ever created – showing how the stars travel in our galaxy. Previous data includes the movements of stars in two dimensions: up and down and left and right (known together as the stars’ own movements). But recent data also shows how fast stars move away from us or toward us, something we call radial velocities of stars.
By combining radial velocity with proper motion, we can understand how fast stars move in three dimensions as they orbit the Milky Way. This means that we now have not only the best map of where the stars of the galaxy are now, but we can trace their forward movement to see how things will change, and backward to see how things were.
This can tell us things about the history of our galaxy, such as which stars may have come from other galaxies and merged with ours in the past. Radial velocity measurements can also help us find hidden objects, such as planets and brown dwarfs (extremely pale, low-mass stars), from the small oscillations they cause as they orbit the host star.
2. Details of how stars die
Gaia not only measures the stars in our own galaxy, but also measures those in the neighboring Andromeda Galaxy. The data includes something called Gaps: Gaia Andromeda’s photometric study. Photometric research measures the brightness of stars and how they change over time. With Gaps, Gaia measured the brightness in time for each star in the direction of the Andromeda Galaxy.
That includes 1.2 million stars. Some of them will be stars in the foreground of the Milky Way, which they accidentally obstructed, but should include approximately the brightest 1% of the stars in the Andromeda galaxy. This will allow us to explore the way in which the largest, brightest stars in Andromeda change their brightness, telling us about their evolution and where they are in their life cycle.
This can tell us more about the old stars who are reaching the end of their lives – some of whom may eventually continue to produce supernovae (huge explosions).
3. The truth about the strange expansion of the universe
Quasars, extremely energetic nuclei of galaxies on the edge of the visible universe, are the brightest objects in the universe and the most distant objects we can see. And new data includes measurements of 1.1 million of them. Quasars contain supermassive black holes that are caught in a raging eating rage. In addition to these confirmed quasars, Gaia has identified another 6.6 million quasar candidates.
This potentially significantly increases the number of known quasars, and this can be very important because they allow us to measure the distance to the farthest reaches of the universe. This in turn allows us to measure how fast the universe is expanding. The ability to measure this more accurately is important because we have two conflicting measurements of expansion and we don’t know which is right – the problem is called Hubble stress.
4. How many asteroids have moons
Not everything Gaia teaches is that far from home. The data contains 158,000 objects in our own solar system. This includes new measurements of 156,000 known asteroids that tell us exactly what paths they follow as they orbit the Sun.
Not only that, but the Gaia team has shown that they are able to detect moons orbiting asteroids based on how the moons cause asteroids to sway. Several hundred asteroids with moons are already known, but Gaia can find asteroid moons even when the moon is too small to see directly. He can also measure the positions of asteroids so accurately that he sees a slight fluctuation in position caused by the moon’s gravity. Esa says the latest figures contain at least one such new moon, but there could be many more.
Collecting better data on asteroids can tell us about the chaos in the early solar system, when larger planets threw smaller planets and asteroids into new orbits around the Sun and led to today’s solar system.
5. How stars are formed and work
Our Sun is a lone star, but many stars have satellites – orbiting each other around a common center. The new data contains the first taste of Gaia’s catalog of such multi-star systems. This is an initial list, with the full catalog coming in a later version of the data, but it already contains 813,000 binary (two star) systems.
Binary stars can tell us a lot about how stars work and how they form. This is especially true for so-called dimming binary systems. These are binary systems that are arranged so that the stars pass in front of each other from our point of view. Dimming binaries are special because we can measure them to calculate all the physical properties of the system, such as the masses and sizes of the stars and how far they are. This allows us to learn much more than we could from studying single stars.
This new data will excite astrophysicists around the world, and we can’t wait to dig into it to see what we can find. We may have some of these answers over the next few months, while others may take longer.
The authors are from the Open University, UK
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