ESA’s Gaia Mission Reveals a Multi-Dimensional Map of the Milky Way

In Version 3 of the Gaia mission data, over 30 million objects (mainly stars) in the Milky Way are shown to approach or recede from us at varying speeds. Such a phenomenon is known as radial velocity. The newly released mission database shows how objects move over a large part of the Milky Way’s disk, the ESA revealed in a statement.

The rotation of the disk can be seen in the image at the top left as bright and dark areas alternate (facing away from us) and toward us (facing toward us). By contrast, it is possible to observe various objects whose radial velocity differs from that of their surroundings.

A map provided by GAIA showing the radial velocity of stars. © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO.
A map provided by GAIA shows the radial velocity of stars. © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO.

In the lower right corner of the image, the Large and Small Magellanic Clouds (LMC and SMC) are visible as bright spots. Under the Galactic Center is a faint, nearly vertical stripe representing the Sagittarius Dwarf Galaxy. In the image, the dark dot to the immediate left of the SMC is 47 Tucanae, a globular cluster.

About 26 million stars are shown in the lower-left image of the sky map. Along the line of sight, the colors represent the stars’ radial velocities. The blue regions show where the average motion of the stars is toward us, while the red areas show where it is away from us.

In the figure, you can see lines representing the motion of the stars projected on the sky (proper motion). The lines show how galactic latitude and longitude affect the direction of the stars’ velocity. This image has no signs of the Large or Small Magellanic Clouds (LMC or SMC) because only stars with well-defined distances were included.

A map provided by GAIA showing the radial velocity and proper motion of stars. © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO.
A map provided by GAIA shows the radial velocity and proper motion of stars. © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO.

Gaia does much more than map our galaxy’s stars — she tells us what’s between them. The space between stars is not empty but contains clouds of dust and gas, which give birth to stars.

Gaia allows us to map the absorption of starlight by the interstellar medium by using precise measurements of the positions of stars and the scattered light they emit. Our galaxy’s history, and the physical mechanisms of star formation, can be derived from these maps.

The Milky Way is filled with interstellar dust, as seen in the upper right image. The interstellar dust makes the dark areas in the galactic plane, which fade to yellow as the amount of dust decreases in the galaxy’s center.

A map created by GAIA showing the interstellar medium and what is found between the stars. © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO.
A map created by GAIA shows the interstellar medium and what is found between the stars.
© ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO.

We can learn about stars’ birthplaces and journeys by examining what they are made of. This provides insight into the history of the Milky Way. Among the new data released by Gaia is a chemical map of the galaxy (lower right image).

A chemical map of the Milky Way Galaxy and its stars. © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO.
A chemical map of the Milky Way Galaxy and its stars. © ESA/Gaia/DPAC; CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO.

Using Gaia, we discover that some stars in our galaxy were formed from primordial matter, while others, including our Sun, are composed of material enriched by earlier generations of stars. Stars closer to our galaxy’s center and plane are richer in metals than those farther away.

Gaia Data Release 3 shows a sample of Milky Way stars in this all-sky image. Star metallicity is indicated by the color. The redder the star, the more metallic it is.


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