Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 September 26

Gaia: Here Comes the Sun
Image Credit: Galaxy Illustration: Nick Risinger (skysurvey.org), Star Data: Gaia Mission, ESA, Antoni SagristÓ SellÚs (U. Heidelberg) et al.

Explanation: What would it look like to return home from outside our galaxy? Although designed to answer greater questions, recent data from ESA's robotic Gaia mission is helping to provide a uniquely modern perspective on humanity's place in the universe. Gaia orbits the Sun near the Earth and resolves star's positions so precisely that it can determine a slight shift from its changing vantage point over the course of a year, a shift that is proportionately smaller for more distant stars -- and so determines distance. In the first sequence of the video, an illustration of the Milky Way is shown that soon resolves into a three-dimensional visualization of Gaia star data. A few notable stars are labelled with their common names, while others stars are labelled with numbers from Gaia's catalog. Eventually the viewer arrives at our home star Sol (the Sun), then resolving the reflective glow of its third planet: Earth. The featured video is based on just over 600,000 stars, but Gaia is on track to measure the parallax distances to over one billion stars over its planned five year mission.

Tomorrow's picture: jupiter's europa


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