Gaia: Google Maps of the Milky Way publishes the spectra of 200 million stars

The Gaia mission , whose observatory developed a 3D map of the Milky Way , revealed a new version with information on nearly 2 billion objects.


When reading astronomy news, we marvel at the large amount of information that we are capable of obtaining from the Universe. Sometimes we even ask ourselves: “And how do they know that, if no one has gone there to see it?” In trying to figure out the answer to this question, we discovered that much of our recent knowledge of our Galaxy uses data from a space mission called Gaia .

Well, we’re in luck. The European Space Agency has published new data from this mission on June 13, 2022 . These data are now much more precise and complete and add something exceptional, the spectra of 200 million stars in our galaxy. The spectra are like the fingerprints of the stars and with them we can know what they are like precisely. Without a doubt, many more interesting news await us in the coming years thanks to Gaia.

Gaia’s super powers

Gaia has often been described as the “Google Maps” of the Galaxy. With Gaia, a mission with great Spanish participation , we can know the position and distance of each star. The goal is to know all the streets of our cosmic neighborhood, knowing where each block of flats (stars in our case) is. Gaia can measure the position of the stars with a precision equivalent to being able to distinguish from the Earth the eye of an astronaut on the Moon.

In addition, Gaia also measures the amount of light we receive from the stars. By comparing this information, we can begin to marvel at great stars that, despite their distance, emit so much light that we still see them bright in the sky. The opposite can also happen, that stars that we thought were similar to the Sun, are actually much smaller because they are much closer than expected. Some even change brightness due to stellar earthquakes or belong to systems with more than one star .

Actually, the three-dimensional map of Gaia is even more ambitious. Can you imagine that Google Maps incorporated an option to know how far some houses are separated from others due to the tiny movement of tectonic plates? Well, despite the fact that throughout a human life it is very difficult to appreciate it, the stars move around the Galaxy.

Gaia is able to detect this small movement of the stars with a precision equivalent to being able to appreciate how the nails grow on the astronaut before on the Moon. This is very useful to know where the stars are going , where they were formed or to know how the matter that attracts the stars is distributed.

Gaia’s abilities do not end here. The color of the stars gives us information about their temperature without having to go there. This is the same phenomenon that we see when heating a piece of iron to be able to mold it to our liking. As their temperature rises more and more, objects begin to emit light, first of a reddish color, gradually changing its color to a more whitish and even bluish tone.

The color of 200 million stars reveals new information

Gaia obtains color information using two low-resolution spectra (one in the blue range and one in the red range). These spectra are published for the first time for more than 200 million stars in this latest dataset. Thanks to them, we can know the astrophysical parameters of the stars (not only their temperature, but also their surface gravity, chemical composition or interstellar absorption ). It would be equivalent to knowing the fingerprints and the identity card of the inhabitants of the galactic “Google Maps”.

We can also use these spectra to simulate what the stars would look like with any telescope, in our favorite colors. Thus, Gaia’s extensive catalog can be used as a reference for any present or future astronomical instrument. For example, we can simulate what Gaia objects would look like with the James Webb telescope even before their first images are released. We can also simulate observations with future satellites (like Euclid ).

Other Gaia spectra, with higher resolution , provide us with the speed of receding (or approaching) of each object. In the latest published data we already have these speeds for 30 million objects . This represents the largest sample of stars with all their dynamic information complete.