Three Steps to the Hubble Constant : 無料・フリー素材/写真
Three Steps to the Hubble Constant / NASA Hubble
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | This Hubble Space Telescope image showcases one of the 19 galaxies analyzed in a project to improve the precision of the universe's expansion rate, a value known as the Hubble constant.The color-composite image shows NGC 3972, located 65 million light-years from Earth. The galaxy contains pulsating stars called Cepheid variables. These stars blink at a rate matched closely by their intrinsic brightness, making them ideal cosmic lighthouses for measuring accurate distances to relatively nearby galaxies. Another reliable milepost marker is a special class of exploding star called a Type Ia supernova. All of these supernovae peak at the same brightness and are brilliant enough to be seen over relatively longer distances. NGC 3972 also hosted a Type Ia supernova.Astronomers search for Cepheid variables in nearby galaxies containing a Type Ia supernova so they can compare the true brightness of both types of stars. That brightness information is used to calibrate the luminosity of Type Ia supernovae in far-flung galaxies so that astronomers can calculate the galaxies' distances from Earth. Once astronomers know accurate distances to galaxies near and far, they can determine and refine the universe's expansion rate.The observations for NGC 3972 were taken in 2015 using Hubble's Wide Field Camera 3.For more information, please visit:www.nasa.gov/image-feature/goddard/2018/hubbles-galaxy-fu...Image credit: NASA, ESA, A. Riess (STScI/JHU)Text: European Space Agency |
| 撮影日 | 2018-02-22 00:00:00 |
| 撮影者 | NASA Hubble |
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