Astronomers have captured a breathtaking new image of the Helix planetary nebula, one of the most spectacular objects in the night sky.
Astronomers have captured a breathtaking new image of the Helix planetary nebula, one of the most spectacular objects in the night sky.
The nebula, which looks like a giant blue eye, is made from shells of gas blasted into space by a dying star.
Lying about 700 light years away in the constellation of Aquarius, the main ring of the Helix is about two light years across - half the distance between the Sun and its nearest stellar neighbour.
It first appeared in a list of new objects compiled by the German astronomer Karl Ludwig Harding in 1824. The name Helix comes from the rough corkscrew shape seen in the earlier photographs.
Astronomers now believe the nebula consists of at least two separate discs with outer rings and filaments.
The brighter inner disc, formed over a period of some 12,000 years, is expanding at about 100,000 kilometres per hour.
Planetary nebulae like the Helix have nothing to do with planets but mark the death throes of Sun-like stars.
Shells of gas are blown off the star's surface, often in intricate and beautiful patterns, and lit up by the ultraviolet radiation. Eventually all that is left of the star is an ashy remnant called a white dwarf.
Because the Helix is relatively close it has been studied in much more detail than most other planetary nebulae.
Astronomers have found its structure to be unexpectedly complex. All around the inside of the ring are small blobs, known as "cometary knots", with faint tails extending away from the central star. Although they look tiny, each knot is about as large as our Solar System.
A careful look at the central part of the nebula reveals not only the knots, but also many remote galaxies visible through the thinly spread glowing gas.
The new image was captured with a special camera attached to the European Southern Observatory's 2.2 metre Max-Planck Society telescope at La Silla, Chile, using blue, green and red filters.
