Mission Gaia measures 1.7 billion stars
The second data release of ESA's mission ‘Gaia’ was yesterday, April 25th 2018, literally the star of the Astro-News. Thanks to it, the positions, brightness and photometric data of 1.7 billion stars of the Milky Way and its surroundings are now available to researchers so that an accurate 3D map can be imaged. In addition to the positions and velocities, parallaxes and proper motions of about 1.3 billion stars were measured. Parallax describes in astronomy a method of determining the distance of celestial bodies. The evaluation of the data now involves several institutes, such as the Max Planck Institute for Astronomy in Heidelberg. Here, the largest star survey so far was conducted, yielding the most detailed three-dimensional dust map of our galaxy until today. Also conditions of star formation could be derived. Particularly interesting is the now existing assumption that the stars did not originate in a dense cluster and then expanded, as explained for a long time by the "monolithic" model. The contrarian "hierarchical" model states that the stars form over extended molecular gas clouds with a wide range of densities. So the accumulation of stars with different densities can be explained without the expansion.
Compared to the first data release in 2016, this time is a significant step forward. Since 2013, Gaia has been traveling in space, measuring stars from the Milky Way and neighboring galaxies. This makes it one of the most important missions in the European Space Agency (ESA) program. The third data release is planned for the end of 2020, the subsequent one for the end of 2022.