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Dying star’s last gasps provides new Kepler target
by Dr Emma Rigby
Posted: 26 July 2011

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A new planetary nebula, recently discovered thanks to the combined efforts of amateur and professional astronomers and within sight of the Kepler spacecraft, could hold the key to understanding how our own Sun's life will end.

The detection of the nebula, Kronberger 61 (Kn 61), along with a striking new image of it from the Gemini Observatory, was presented this week at the International Astronomical Union symposium in Tenerife. It's named after its discoverer, Matthias Kronberger, a member of a group of amateur astronomers called the Deep Sky Hunters, who devote their spare time to hunting through existing datasets to find objects like this. Such a search is difficult because they are "extremely rare and each, a valuable gem," according to George Jacoby of the Giant Magellan Telescope Organization and the Carnegie Observatories.

The planetary nebula Kronberger 61 in a new image from the Gemini North Observatory in Hawaii. The glowing blue gas is primarily due to the emission from twice-ionised oxygen. Image: Gemini Observatory/AURA. Image processing by Travis Rector.

Planetary nebulae are giant shells of ionised glowing gas shed from the outer layers of geriatric stars. Their misleading name is a relic of their original 18th Century observers, and their small telescopes, who mistakenly thought they were similar to the gas giant planets in our own Solar System. Over 3,000 have been identified, making them common throughout our galactic neighborhood, but questions remain about their formation.

"Explaining the puffs left behind when medium sized stars...expel their last breaths is a source of heated debate among astronomers, especially the part that companions might play," says team-member Orsola De Marco of Sydney's Macquarie University. "Some recent theories suggest that planetary nebulae form only in close binary or even planetary systems — on the other hand, the conventional textbook explanation is that most stars, even solo stars like our Sun, will meet this fate. That might just be too simple."

Currently companions have only been found around a low percentage of the central stars associated with planetary nebulae. However, as Jacoby points out, "this is quite likely due to our inability to detect these binaries from the ground." This situation will soon improve thanks to the sensitivity of NASA's Kepler planet-finding mission. It currently monitors more than 150,000 stars within the constellation of Cygnus, looking for the small fluctuations in brightness which indicate the presence of a companion, planetary or otherwise.

To increase the odds of finding good planetary nebula candidates to add to Kepler's monitoring list, professional astronomers enlisted the help of the Deep Sky Hunters. Kn 61 is their second confirmed detection to date, with a possible third to come. As Kronberger comments “…the field where Kepler points to is very scarce in PNe (planetary nebulae) so Dr. Jacoby approached me at the beginning of this year and asked me if I could do a quick survey of the Kepler field for any overlooked planetaries in order to improve statistics. Which I did - and only a few hours of surveying I came across a very faint, bluish shell with a very pronounced blue central star that perfectly fit into this category. And yes – the image tells the rest of the story!”

Jacoby adds: "Without this close collaboration with amateurs, this discovery would probably not have been made before the end of the Kepler mission. Professionals, using precious telescope time, aren't as flexible as amateurs who did this using existing data and in their spare time. This was a fantastic pro-am collaboration of discovery".