An Australian-led team of astronomers has found hundreds of colourful glowing objects that might help solve a cosmic accounting problem: why the matter from some old stars seems to vanish.
When stars like our Sun get old they have a final fling, transforming themselves into “planetary nebulae”. These are regions of glowing gas, and have nothing to do with planets. They can take on weird and wonderful shapes, with some looking like an eye, an ant, an hourglass, or a wedding ring.
Now an international team using the UK Schmidt Telescope at Siding Spring Observatory has boosted the number of planetary nebulae known in our Galaxy by 60%, adding 900 to the 1500 already on the books.
And they’ve netted even more in a neighbouring galaxy, the Large Magellanic Cloud, finding almost 500 to add to the 300 known.
The new objects cover a much wider range of types than the ones previously catalogued, ranging from tiny faint ones to the large and ghostly.
When a star becomes a planetary nebula, some of its mass seems to go missing.
Astronomers can see some being shed into space, and some remaining in the star’s core.
“But up to 85% of the mass just disappears from sight,” said Dr Quentin Parker of the Anglo-Australian Observatory and Macquarie University, who led the new surveys. “So we are quite keen to find more planetary nebulae and image them in more detail, to see if we can find this missing stuff. We have found extremely faint haloes around 60% of our new planetary nebulae in the Large Magellanic Cloud, and so we suspect this is where much of the missing mass resides.”
Called the AAO/H-alpha survey, the trawl for planetary nebulae covered
the Southern Galactic Plane in our Galaxy, and parts of the Large Magellanic
Cloud, which is visible only from the Southern Hemisphere. Work began in
1998 and finished in 2006. The research team came from nine institutions,
in Australia, the UK, France and the USA.
Dr Quentin Parker, Anglo-Australian Observatory and Macquarie University
Reid, Warren A.; Parker, Quentin A. “A new population of planetary nebulae discovered in the Large Magellanic Cloud - II. Complete PN catalogue.” Monthly Notices of the Royal Astronomical Society, Volume 373, Issue 2, pp. 521-550. (2006 December).
Parker, Quentin A.; Acker, A.; Frew, D. J.; Hartley, M.; Peyaud, A. E. J.; Ochsenbein, F.; Phillipps, S.; Russeil, D.; Beaulieu, S. F.; Cohen, M.; Kppen, J.; Miszalski, B.; Morgan, D. H.; Morris, R. A. H.; Pierce, M. J.; Vaughan, A. E. “The Macquarie/AAO/Strasbourg Halpha Planetary Nebula Catalogue: MASH.” Monthly Notices of the Royal Astronomical Society, Volume 373, Issue 1, pp. 79-94. (2006 November).