This is the Helix Nebula, as imaged by the Spitzer telescope. Another wonderful eye in the sky. See links at bottom for a couple more dramatic eye images. This is a planetary nebula, with a white dwarf star at its core, left over as the late stages of the life of a once vibrant star. (See also here.) What’s the story? Well, you can read at their site, and at the BBC about the fact that new studies are uncovering a bit of a mystery about this object. There’s a lot more dust than there really should be. This object is what’s left over from a star having gone through its expansion phase where at the end of its life it swells into a red giant and blows off its outer layers, leaving only the white dwarf core. So most material surrounding should have been blown away or swallowed. Recent work has shown that there’s a huge amount of dust surrounding the white dwarf, which is rather surprising. The current idea is that there’s activity from comets remaining in the star system (the planets – if it ever had any – are probably all long gone: swallowed or blown away), colliding and leaving lots of debris. This matches earlier studies from last year about another dead star. It also matches with other observations:
Previous observations with the German X-ray telescope RÃ¶ntgensatellit and NASA’s Chandra X-ray Observatory indicated that the white dwarf was throwing out highly energetic X-rays. While the white dwarf is hot, about 110,000 Kelvin (nearly 200,000 degrees Fahrenheit), it is not hot enough to explain the energetic X-rays.
Material in the form of this surplus dust may be falling onto the star and triggering the extra X-ray activity. It all fits together rather nicely.
And it’s an awfully pretty picture too!
P.S. I’m guessing that Amara – an expert on such activity in our local system – might be quite excited about this and maybe can tell us what she thinks the comments? [Update: she has her doubts, and makes a suggestion - see here.]
Some Related Asymptotia Posts (not exhaustive):