Original larger image (8.15 MB)
Poster-sized PDF image (1.77 MB)
Distance: 160,000 light-years
Instrument: WFC3/UVIS and ACS/WFC
Image Filters: F475W (g), F555W (V), F658N (H-alpha+[N II]), F814W (I)
Credits: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
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Floating among the stars, this cosmic bubble might look delicate, but it is the signature of a violent explosion. It is a supernova remnant, the gaseous remains of a star that blew up. Named SNR 0509-67.5 (or SNR 0509 for short), it inhabits a small, nearby galaxy called the Large Magellanic Cloud, roughly 160,000 light-years away. On Earth, stargazers in the southern hemisphere could have seen the explosion about 400 years ago, but so far, no eye-witness accounts have turned up.
This bubble of gas is 23 light-years across and growing. It is expanding at more than 11 million miles per hour (5,000 kilometers per second). Ripples in the edge of the bubble (best seen in the upper left) could be caused by uneven scraps of material ejected by the exploded star, or by clumpiness in the surrounding gas that the supernova material is slamming into as it rushes outward.
This celestial sphere was created by a kind of explosion known as a Type Ia supernova. Type Ia supernovae are valuable for measuring distances across the universe, because they are thought to have a standard peak brightness when they explode.
Astronomers believe Type Ia explosions result from the destruction of a white dwarf — the small, compact core of a once-average star that ran out of the nuclear fuel needed to sustain its high-powered life. One explanation is that a white dwarf self-destructs after using its gravity to steal material from a nearby star, causing it to become unstable under the extra bulk and explode. Another idea is that the detonation happens when two white dwarfs collide, destroying both objects.
To investigate the cause of SNR 0509, astronomers Bradley Schaefer and Ashley Pagnotta of Louisiana State University studied archived Hubble data from the Advanced Camera for Surveys and the Wide Field Camera 3 to search for a surviving star that could have fed the doomed white dwarf. However, the Hubble observations turned up none. If a star were there, it should have shown up.
There’s only one possible explanation, say Schaefer and Pagnotta. For this supernova, the collision of two white dwarfs is to blame.