ESA (the European Space Agency) has released a colossal star catalog detailing the precise positions and brightness of over a billion stellar bodies spread across the Milky Way. Created from data harvested by the agency's Gaia satellite, the new catalog, which is by far the largest of its kind, is a significant step on the road to the probe's ultimate mission of creating the most precise and comprehensive 3D map of our galaxy ever.

The new release accounts for data collected by the satellite over the first 14 months of observation, ending in September this year. The task of converting the probe's raw data into a useful tool for the scientific community fell to the Gaia Data Processing and Analysis Consortium (DPAC) – a group of around 450 scientists and software engineers hailing from over 20 countries.


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This highly skilled workforce has striven and succeeded in creating a resource that details the brightness, location and motion of 1,142 million stars, with a precision twice that of any previous large-scale catalog. The general public can appreciate the magnitude of the release in a more accessible format via a visualization of the data that is freely available on the Gaia webpage.

Artist's impression of the Gaia probe in space (Credit: ESA/ATG medialab; background: ESO/S. Brunier)

DPAC was able to provide a more detailed analysis of some 2 million stars by combining Gaia data with that of the 1997 Hipparcos and Tycho-2 catalogs. The new observations, when combined with the old, allowed scientists to account for parallax and apparent motion effects, facilitating accurate estimates regarding the stellar bodies' motion and distance from Earth.

To further demonstrate the capabilities of the new catalog, DPAC carried out a study of open star clusters. Under the Hipparcos and Tycho-2 star catalogs, scientists could only accurately map the disposition, motion, and distance of stellar bodies composing the closest open cluster to Earth, which, known as the Hyades cluster, sits 151 light-years from our planet.

Using the Gaia catalog, DPAC was able to map the distance, distribution and motion of around 400 open clusters up to a maximum range of roughly 4,800 light-years – a massive leap forward.

Gaia has the capacity to improve the accuracy of techniques used to map vast cosmic distances by providing detailed observations of celestial objects such as Cepheid variable stars. These stellar bodies are so named owing to the fact that they periodically expand and contract, brightening and dimming in the process.

Visual representation of Gaia data overlaid with the positions of various galaxies open clusters and globular clusters (Credit: ESA/Gaia/DPAC)

In 1912, American astronomer Henrietta Swan Leavitt discovered that the periodical expanding and contracting of Cepheid stars relates directly to the star's luminosity. With this relationship established, astronomers are now able to work out the actual brightness of a Cepheid star by observing pulsation periods, and then compare this luminosity with the observed brightness of the stellar body as perceived from Earth in order to work out the distance.

During the first 14 months of Gaia's operational life, the satellite has discovered 386 previously unknown Cepheids. It is hoped that further observations will allow astronomers to gain a greater understanding of this unusual breed of star, and thus improve their ability to accurately chart vast cosmic distances.

Gaia may also have a significant role to play in the study of the atmospheres of planets within our own solar system, by providing a greater understanding of the movement of stars across the sky. In July 2016, the early release of data from the satellite was instrumental in allowing astronomers to observe the tenuous atmosphere clinging to the dwarf planet Pluto as it passed between Earth and a distant star.

Scroll down to see a visualization of how Gaia mapped the entire sky.

Source: ESA

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