Astronomers have found the remnants of a thousand dead and dying stars in the southern part of the Milky Way Galaxy they described as a galactic graveyard.
The findings, from a new sky survey, roughly doubles the known number of so-called planetary nebulae. These are a poorly named class of objects that represent the relics of stars that have made their dying gasps by casting waves of gas and dust into space to create often colorful bubble and hourglass shapes.
Having so many new objects to study could eventually help researchers improve their understanding of the geriatric years for most stars.
"There is a currently a severe paucity of observational data of evolved planetary nebulae which our new catalogue should help address," said Quentin Parker of the Institute for Astronomy at the Royal Observatory Edinburgh.
Parker conducted the study with Steven Phillipps of the University of Bristol, and it was presented Wednesday the UK National Astronomy Meeting.
Poorly named
Planetary nebulae have nothing to do with planets. They gained their classification when early astronomers using crude telescopes thought they looked like the planet Uranus because of their greenish tints. They are important to astronomers because they tell various tales of stellar death, shedding light on the final evolutionary stages of our own Sun and about 95 percent of all other stars.
The new survey was done with the Schmidt Telescope at the Anglo-Australian Observatory in New South Wales.
"So far we have identified 1,000 new planetary nebulae from visual scans of 70 percent of the southern galactic plane," Parker said. "This number is now increasing rapidly as the plates are systematically scrutinized by the SuperCOSMOS facility at the Royal Observatory, Edinburgh, so that more compact, fainter candidates are being found."
Inside the nebula
At the center of a planetary nebula is typically a white dwarf or other stellar corpse, a star that now emits very little radiation as it gradually cools. The object once cast off much of its outer material in a gradual process of swelling and contracting known as the red giant phase. (Some 5 percent of stars die more violently, in supernova explosions.)
When our Sun becomes a red giant, its hot atmosphere will reach out to where Earth now orbits. Scientists say the planet will be vaporized unless it's orbit changes, a possibility given the changing gravity of the Sun.
The new study found several rare and unusual variations on the dying-star theme. Some examples:
- Anchoring eight of the planetary nebulae were Wolf-Rayet stars, which are exceptionally hot and rich in carbon or nitrogen. Only 56 Wolf-Rayet stars are currently known.
- Several planetary nebulae so close together they may be considered pairs.
- Several hundred planetary nebulae in the galactic bulge, a densely populated region of stars near the center of the Milky Way.
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