The delicate shell, photographed by the NASA/ESA Hubble Space Telescope, appears to float serenely1(安详地,沉着地) in the depths of space, but this apparent calm hides an inner turmoil2(混乱,骚动) . The gaseous3 envelope(气囊,气膜) formed as the expanding blast wave and ejected material from a supernova(超新星) tore through the nearby interstellar medium(星际物质) . Called SNR B0509-67.5 (or SNR 0509 for short), the bubble is the visible remnant of a powerful stellar explosion in the Large Magellanic Cloud (LMC), a small galaxy4 about 160 000 light-years from Earth. Ripples5 seen in the shell's surface may be caused either by subtle variations in the density6 of the ambient(周围的,外界的) interstellar gas, or possibly be driven from the interior by fragments from the initial explosion. The bubble-shaped shroud7 of gas is 23 light-years across and is expanding at more than 18 million km/h.
Astronomers8 have concluded that the explosion was an example of an especially energetic and bright variety of supernova. Known as Type Ia, such supernova events are thought to result when a white dwarf9 star in a binary10 system(二进制) robs its partner of material, taking on more mass than it is able to handle, so that it eventually explodes.
Hubble's Advanced Camera for Surveys observed the supernova remnant on 28 October 2006 with a filter that isolates11 light from the glowing hydrogen seen in the expanding shell. These observations were then combined with visible-light images of the surrounding star field that were imaged with Hubble's Wide Field Camera 3 on 4 November 2010.
With an age of about 400 years, the supernova might have been visible to southern hemisphere observers around the year 1600, although there are no known records of a "new star" in the direction of the LMC near that time. A much more recent supernova in the LMC, SN 1987A, did catch the eye of Earth viewers and continues to be studied with ground- and space-based telescopes, including Hubble.