The most detailed 3D map yet of a billion stars in the Milky Way galaxy was released last week on September 14, along with a sneak peek at brand-new data on millions of stars collected by ESA's Gaia spacecraft.
The spacecraft, launched in December 2013, was named after the Greek Mother Earth goddess, known by the Romans as Terra. It has been circling the Sun 1.5 million kilometres beyond Earth's orbit and has been discreetly snapping pictures of the Milky Way. The satellite's billion-pixel camera, that has a resolution over 50 times greater than the one onboard the Hubble Space Telescope, is so powerful it would be able to gauge the diameter of a human hair at a distance of 1,000 kilometres, meaning nearby stars have been located with unprecedented accuracy.
Just over half-way through its five-year mission, Gaia's two telescopes have located a billion stars, scattered over an area 100,000 light years in diameter. While this may be the biggest and most ambitious galaxy-mapping endeavor yet, the vast amount of stars observed in this mission will represent only about 1 percent of all of the stars in the Milky Way galaxy. But it's enough to keep professional stargazers busy for years to come.
The Gaia spacecraft is controlled from the European Space Operations Centre in Darmstadt, Germany, using ground stations in Cebreros, Spain and New Norcia in Australia. According to chairman of the Gaia consortium Anthony Brown of Leiden University in the Netherlands "Gaia data will allow researchers to investigate our place in the Universe, from our local neighborhood, the Solar System, to Galactic and even grander, cosmological scales."
The space-based probe maps the position of the Milky Way's stars in a couple of ways. Not only does it pinpoint their location, the probe—by scanning each star about 70 times—can plot their movement as well. This is what allows scientists to calculate the distance between Earth and each star, a crucial measure. Both types of data are now available for more than two million stars. By the end of 2017, Gaia will have done the same for a billion.
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At the same time, Gaia will collect vital data about each star's temperature, luminosity and chemical composition, vastly expanding current knowledge. Tens of thousands of previously undetected objects will be discovered, including asteroids that may one day threaten Earth, planets circling nearby stars, and exploding supernovas.
By identifying stars from smaller galaxies long ago swallowed up by our own, Gaia will also help scientists better understand the Milky Way's origin and evolution. Astrophysicists, meanwhile, hope to learn more about the distribution of dark matter, the invisible substance thought to hold the observable universe together. They also plan to test Albert Einstein's general theory of relativity by watching how light is deflected by the Sun and its planets.
In a statement, ESA's Science Director Alvaro Giménez said that "Gaia is at the forefront of astrometry, charting the sky at precisions that have never been achieved before."
Image credit: ESA