1.8 billion objects: Gaia mission presents atlas of the Milky Way – Wikipedia

Climatic zones, soil types, land use – geologists love to immerse themselves in thematic maps. Now astronomers have this fun too, thanks to Gaia. The Milky Way has been mapped in 3D using a telescope aboard the spacecraft since 2014.

The mission’s largest data package to date was released on Monday. It’s much more than a map: a comprehensive atlas of our galaxy.

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There used to be more hydrogen

The atlas is based on location and brightness data from about 1.8 billion objects, mostly stars, that were published two years ago. More details are now available, such as chemical compositions, stellar temperatures, colors, masses, ages, and speeds at which stars are moving toward or away from us. This makes it possible to find out which of them have been orbiting the black hole in the center of the Milky Way for a long time and which ones were formed in other galaxies and came to us.

The European Space Agency (ESA) also provides a catalog that aims to provide information about the mass and development of more than 800,000 binary star systems. It has also captured tens of thousands of asteroids, more than ten million variable stars, black holes called quasars, and galaxies outside our cosmic neighborhood.

The researchers owe much of the new data to spectroscopy. In the process, the starlight splits into its individual colors. This creates a kind of individual imprint of the orbs. The spectra depend, among other things, on the chemical composition and motion of celestial bodies in relation to the observer.

“Using this data, we can understand the evolution history of the Milky Way,” says Roelof de Jong of the Leibniz Institute for Astrophysics in Potsdam (AIP), which is heavily involved in the Gaia mission. After the Big Bang there was initially only hydrogen and helium, heavy elements formed inside stars and were thrown into intergalactic space by supernovae. The stars of subsequent generations were formed from dust.

Earthquake target

“Depending on the original material that today’s stars are made of, they have different numbers of heavy elements,” the researcher explains. Based on the Gaia data, various groups of objects can be identified, some of which come from other galaxies and migrate to the Milky Way.

Starlight is often very weak and instruments are operating within what can be measured. There are also disturbances. This is how it turned out after the start of the telescope: individual fibers protrude from the collapsible shield that protects it from the sun’s rays. “These work in part to direct sunlight into the sensitive optics,” de Jong explains. The problem with software developed in AIP has been resolved.

There were also positive surprises. Although not specifically designed for this purpose, Gaia has proven to be a sensitive instrument for detecting stellar earthquakes. These are frequent surface changes that vary greatly by star and also occur in the Sun. “Just as seismologists use earthquakes to explore the interiors of planets, stellar tremors can help us learn more about temperature, density, and rotation within stars,” said Connie Aerts of the University of Leuven in Belgium, presenting the findings.

The observatory has tracked more than 100,000 stars that “buzz” in this way. The most promising of them should be observed from 2026 by the Esa “Plato” probe, which specializes in stellar seismology. “The Gaia and Plato measurements are a real goldmine for studying these phenomena.”

The Hubble Gold Standard Telescope is outdated

Data from the current mission could also help track down the mysterious dark matter. So far no one can say exactly what it consists of. But it is very likely that it is. The motion of stars and galaxies is determined by gravity – and cannot be explained solely by the movement of visible matter. So there must be more.

“When a dwarf galaxy enters the Milky Way, it is being stretched by tidal forces in the galaxy,” de Jong says. But the movement of the stars is complex, something invisible is pulling them. dark matter? “We don’t know,” says the AIP researcher. “But with accurate measurements from Gaia, we can for the first time test the effects of suspected dark matter at smaller scales.”

According to de Jong, the data available so far may not be enough yet. But there’s more on the horizon: The mission has already been extended several times beyond its original five-year operating period. The telescope is still intact and continues measurements.

The scientific return is already enormous. On average, five specialist articles based on Gaia data have been published per day since 2020, said Günther Hasinger, Esa’s director of science. “We’ve already surpassed the previous gold standard, the Hubble telescope.”

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