<p>A combined view of visible and x-ray light from a pair of NASA telescopes has helped astronomers solve a cosmic mystery: What caused the brilliant supernova that left behind this bubble in space?</p><p>Astronomers already knew that the supernova remnant 0509-67.5, seen above, is the product of what's called a Type Ia supernova, which involves a white dwarf star becoming so massive that it explodes. The most common explanation for a Type Ia is that a white dwarf gains mass by siphoning matter from a companion star.</p><p>But in this case, the sharp eyes of the <a href="http://hubblesite.org/">Hubble Space Telescope</a> and the Chandra X-ray Observatory couldn't find any trace of such a companion. Instead, astronomers think that SNR 0509-67.5 was formed when two tightly orbiting white dwarfs spiraled in toward each other and collided, destroying both stars in a cataclysmic blast.</p>

Hubble Bubble

A combined view of visible and x-ray light from a pair of NASA telescopes has helped astronomers solve a cosmic mystery: What caused the brilliant supernova that left behind this bubble in space?

Astronomers already knew that the supernova remnant 0509-67.5, seen above, is the product of what's called a Type Ia supernova, which involves a white dwarf star becoming so massive that it explodes. The most common explanation for a Type Ia is that a white dwarf gains mass by siphoning matter from a companion star.

But in this case, the sharp eyes of the Hubble Space Telescope and the Chandra X-ray Observatory couldn't find any trace of such a companion. Instead, astronomers think that SNR 0509-67.5 was formed when two tightly orbiting white dwarfs spiraled in toward each other and collided, destroying both stars in a cataclysmic blast.

Image courtesy ESA/NASA

Space Pictures This Week: Hubble Bubble, Dusty Dwarf, More

A "soap bubble" in space, stellar royals in hiding, and a new look at an old galactic neighbor are among this week's best space pictures.

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