NASAさんのインスタグラム写真 - (NASAInstagram)「Resting on the tail of the Great Bear in the constellation of Ursa Major lies NGC 5585, a spiral galaxy that is more than it appears. The many stars and clouds of dust and gas that make up NGC 5585, shown here in this @NASAHubble image, contribute only a small fraction of the total mass of the galaxy. As in many galaxies, this discrepancy can be explained by the abundant yet seemingly invisible presence of dark matter, a mysterious material that astronomers can’t directly observe. The stellar disk of the galaxy extends over 35,000 light-years across. When compared with galaxies of a similar shape and size, NGC 5585 stands out by having a notably different composition. Contributing to the total mass of the galaxy, it contains a far higher proportion of dark matter. Hot spots of star formation can be seen along the galaxy’s faint spiral arms. These regions shine a brilliant blue, contrasting strikingly against the ever-black background of space. Credit: ESA/Hubble & NASA, R. Tully; acknowledgment: Gagandeep Anand #nasagoddard #Hubble #space #science #astronomy #spaceimage #spacepic #nasa #galaxy」9月27日 22時35分