Astronomers have used NASA’s Hubble Space Telescope, ESA’s XMM-Newton and NASA’s Chandra X-ray observatories to peer at the heart of the planetary nebula Abell 30.
A planetary nebula – so called because it looks like a planet when viewed with a small telescope – is formed in the late stage of the evolution of a Sun-like star. Astronomers now know that as a star with less than eight times the mass of the Sun swells into a red giant towards the end of its life, its outer layers are expelled via pulsations and winds. Ultraviolet radiation shining out from the stripped-down hot stellar core then lights up the ejected shells, resulting in intricate artworks that can be seen by modern telescopes.
Abell 30, one of a small number of planetary nebulae known as born-again planetary nebula, is located in the constellation Cancer some 5,500 light-years away.
A Sun-like star at the heart of Abell 30 experienced its first brush with death 12,500 years ago when its outer shell was stripped off by a slow and dense stellar wind. The remnant of this evolutionary stage is seen in optical light as a large, near-spherical shell of glowing material expanding out into space.
The star suddenly came back to life about 850 years ago, coughing out knots of helium and carbon-rich material in a violent event. Its outer envelope briefly expanded during this born-again episode, but then very rapidly contracted again within 20 years. This had the knock-on effect of accelerating the wind from the star to its present speed of 4,000 km per second. These findings appear in the Astrophysical Journal (arXiv.org version).
As this fast stellar wind catches up and interacts with the slower wind and clumps of previously ejected material, complex structures are formed, including the delicate comet-like tails seen near the central star in this image. The stellar wind bombarding dense clumps of material provides a chilling look at the possible fate of Earth and its fellow planets in our own Solar System in a few billion years’ time.
Bibliographic information: M. A. Guerrero et al. 2012. Rebirth of X-Ray Emission from the Born-again Planetary Nebula A30. ApJ, vol. 755, no. 2, 129; doi: 10.1088/0004-637X/755/2/129