Not for the first time we return to a spectacular nebula that has been dubbed the Eye of God. But this time the “eye” is looking decidedly bloodshot.
That is because this new image of the Helix Nebula, the wreck of a star in its death-throes, has been catured in infrared light, revealing strands of cold gas that are usually invisible.
It was taken by a telescope called VISTA that Skymania visited last year at the European Southern Observatory’s Paranal site in Chile. VISTA sits almost literally in the shadow of ESO’s more famous VLT instruments, being just down the hill. But it is no-less a world-class telescope with a 4.2-metre mirror to collect faint starlight.
Its powerful detectors, working above much of the astronomically unfriendly atmosphere, easily recorded the glow from the thinly-spread filaments of gas radiating from the centre. The brightest part of the ring – actually a shell – of gas measures around two light-years from side to side. But fainter material can be traced to a distance of at least four light-years – the faint red glow of molecular gas that spreads across much of the photo.
These shells of gas and dust have been blow off by the central star as it prepares to become a white dwarf in a dramatic demise that is expected to meet our own Sun around five billion years in the future. Such a gas cloud is termed a planetary nebula, though they have nothing to do with planets and the term came from the planet-like disk that many of them seemed to show.
The strands of gas are molecular hydrogen and known as cometary knots to scientists. They survive because they are shielded by dust and other gas but astronomers are not yet certain how they came to form.
The Helix Nebula lies around 700 light-years away in the constellation of Aquarius, and can be dimly seen in small backyard telescopes by amateur astronomers. It covers an area of sky around a quarter the size of the full moon.