![]() ![]() Gaia also stared at 158,000 asteroids in our own solar system and even gathered data on millions of other galaxies in our local universe. This data set also includes information about 1.1 million quasars, super-bright active nuclei of galaxies outside our own, each so far away they appear to not move, making them wonderful waypoints for navigation. In 2020, the Gaia team released some of its third data dump early, but this month’s official release offered the finest set of details yet about our more than 1.8 billion stellar neighbors. The mission also collected the radial velocity of stars-which combined with “proper motion” data shows where each one is going and how fast-for 7 million objects. This allowed scientists to better understand each star’s temperature, luminosity, and more. It also collected the accurate brightnesses and colors of these stars. Gaia’s second release in 2018 jumped to 1.6 billion objects, with 1.3 billion measurements of parallax distance and proper motion. ![]() “So we decided to share this with the community to get the maximum out of the data.” (Proper motion is the apparent movement of a star in the sky.) “There are so many more stars than astrophysicists to analyze them, in this case,” says Aerts. (This instrumentation is relatively similar to the Hubble Space Telescope’s in that regard.) But unlike Hubble, which carries a range of heavy instrumentation that was designed to train its gaze on tiny areas of space, Gaia’s mission is expansive: Survey the whole sky and collect massive amounts of data.Īfter some initial hurdles-a “wobble” that impaired the craft’s precision instruments was eventually repaired using data processing and calibration-the Gaia team dropped its first data in 2016, representing parallax and “proper motion” measurements for 2 million stars. Gaia, a nearly $1 billion mission, was approved in 2000 as an upgrade, with two much larger 1.5-meter telescopes and 106 charge-coupled devices, or CCDs, sensitive photon detectors. “But we knew we could do better, even while Hipparcos was working,” says Anthony Brown, an astronomer at the University of Leiden and the lead of Gaia’s data processing team. The amount of shift indicates how far away objects are.) Hipparcos increased the number of those measurements to 120,000 by the end of the mission in 1993. (Parallax means that as Earth moves, nearby stars appear to shift in the sky, just as a lamppost appears to shift relative to the background hills as you cross the street. Precision astrometry of the entire sky is difficult on Earth before Hipparcos launched, there were fewer than 9,000 accurate “parallax” measurements of stars. Its predecessor, the Hipparcos mission, was launched in 1989 to measure the positions, distances, and motions of stars with unprecedented precision-a field called “astrometry” that the mission pioneered in space. The Gaia mission launched in 2013, but its history runs much deeper. “As a survey of stars in our galaxy, it blows all other surveys out of the water,” says Conny Aerts, a stellar astrophysicist at Katholieke Universiteit Leuven and member of the Gaia consortium. It’s the most comprehensive star map humankind has ever made, and scientists are already using it to unlock new secrets about our galactic neighborhood. The mission’s latest result, Data Release 3, which came out two weeks ago, maps 1.8 billion stars in and around our galaxy-covering about 1 or 2 percent of all stellar objects in the Milky Way. ![]() Since 2013, the European Space Agency’s Gaia probe has been doing just that. But if you could find the ideal point in space to stare at these stars around the clock for, say, eight years, tracking their movements and studying their brightness with highly accurate astronomy tools, you’d have created a pretty good moving, living map of the galaxy. It’s so big that, traveling at the speed of light, it’d still take you 100,000 years to traverse it. There are probably 200 billion stars in the Milky Way, stretched across space in a disk shaped like a ninja’s throwing star. ![]()
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