On April 25, all astronomers in the world are awaiting a second data release from the Gaia satellite. But how many sources will be included in the new catalog?
Gaia's mission started in December 2013. She counted more than a billion stars in the Milky Way and neighboring galaxies, measuring their locations, parallaxes and correct movements with an incredible level of accuracy.
Parallax is a small displacement in the visible position of a star, created by the annual rotation of the Earth around the Sun. Measuring the star location and parallax, you can accurately determine the star in 3D-space. Proper motion is shaped by the actual movement of stars around the galaxy.
Gaia is creating the largest astrometric catalog. The satellite also studied the stellar brightness, colors and spectra of the brightest objects. It is expected that the second release will contain the position and brightness of 1 692 919 135 stars, and also include measurements of parallax and correct motion of 1 331 909 727 stars. Data obtained for 22 months of work (between July 25, 2014 and May 23, 2016). This is a huge leap from the first set. The second release will also contain a wide range of additional information: colors (1.38 billion stars), radial velocities (7,224,631), information on 550,737 variable sources, surface temperature estimates for 161,497,595 stars, dimming (measure of the amount of dust along the line of sight ) 87,873,672 stars, and radius and luminosity of 76,956,778 stars.