When you look up at the night sky, do you wonder about what’s out there? Most of the stars we can see with the naked eye reside within our own galaxy. And now we know a lot more about them. The European Space Agency’s (ESA) Gaia mission has just announced the largest, most accurate, most detailed map of the Milky Way ever made.
This is actually the Gaia mission’s third data release. But it blows its predecessors out of the water. This is the richest star catalogue to date, including high-precision measurements of nearly 1.7 billion stars. ESA spokespeople and Gaia scientists revealed the extent of their map today in a press conference, along with a blizzard of nearly fifty related research papers.
Gaia makes its observations using two optical telescopes operating at Earth’s L2 Lagrange point. (It’s in good company there. The James Webb space telescope also orbits L2.) Its dual nature takes advantage of parallax, which the ancient Greeks used to make elegant models of the solar system. For certain stars, especially stars that are close or very bright, it can make measurements of exquisite precision. It’s like an earthly observer being able to spot a Euro coin lying on the surface of the Moon.
The Gaia Project’s Data Release 3: a 3D Map of the Milky Way
The new map of the Milky Way includes information on parallax and proper motion (velocity across the sky) for more than 1.3 billion stars. Using these measurements, astronomers can directly estimate distances to individual stars — and even to objects outside the galaxy.
Using Gaia’s highly precise measurements, mission scientists can separate the wobble of parallax from an object’s true motion within the galaxy.
Beyond details about the stars’ motion, the data release includes information concerning their chemical composition, their burn temperature, and where in their lifespans they might be. This data dump even includes a refined Hertzsprung-Russell diagram, which describes how stars of various colors and temperatures live out their lives.
These four sky maps represent what Gaia sees. They also demonstrate the four key types of measurements that Gaia performs. From top: a) radial velocity, b) radial velocity and proper motion, c) interstellar dust, and d) chemical composition. Image: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO
While Gaia mostly looks outward beyond our solar system, mission scientists also used the array to look at objects within our celestial borders. This third data release includes information on more than 150,000 asteroids, including near-Earth objects, main belt asteroids, TNOs (Trans-Neptunian Objects), and others. But for sixty thousand nearby space rocks, the map coordinates each asteroid’s color, composition, rotation and orbit.
“The observations collected by Gaia are redefining the foundations of astronomy,” said Günther Hasinger, ESA Director of Science.
Were There Any Surprises?
One of the most surprising discoveries coming out of the new data is that Gaia is able to detect starquakes, tiny disturbances on the surface of a star. That wasn’t in its job description. But Gaia has spotted starquakes, making everything from ripples to “large-scale tsunamis.”
Most of the stars we can see come from our own galaxy. However, Gaia’s clarity of vision let it capture millions of objects outside the Milky Way. This map includes a photometric survey of the Andromeda galaxy. It catalogues almost three million other galaxies beyond our own. It also tracks almost two million quasars. Quasars, also known as active galactic nuclei or AGNs, are massive, faraway, insanely high-energy objects powered by supermassive black holes.
What Does It All Mean?
The Gaia map of the Milky Way allows astronomers to reconstruct our home galaxy’s structure and past evolution over billions of years.
“The sheer number of stars alone, with their positions and motions, would make Gaia’s new catalogue already quite astonishing,” said Anthony Brown, of Leiden University in the Netherlands. Brown is a data processing expert and executive with the Gaia mission.
“But there is more: this unique scientific catalogue includes many other data types, with information about the properties of the stars and other celestial objects, making this release truly exceptional.”
The depth and breadth of this survey also allow us to better understand the life cycle of stars and galaxies, and perhaps even our place in the Universe. In addition to all its flashy visual-spectrum observations, Gaia can tell us about the “mysterious macromolecules” that lie between galaxies.
“Unlike other missions that target specific objects, Gaia is a survey mission. This means that while surveying the entire sky with billions of stars multiple times, Gaia is bound to make discoveries that other more dedicated missions would miss,” said Gaia project scientist Timo Prusti.
“This is one of its strengths, and we can’t wait for the astronomy community to dive into our new data to find out even more about our galaxy and its surroundings than we could’ve imagined.”
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