National Geographic News
The nebula Kronberger 61.
Planetary nebula Kronberger 61.

Image courtesy Gemini Observatory/AURA

Dave Mosher

for National Geographic News

Published July 27, 2011

A dying star's wheezing cough has puffed out a gas shell reminiscent of a big blue soccer ball, scientists say.

The discovery could shed new light on the shaping of planetary nebulae—so called because 18th-century astronomers using early telescopes mistook the stellar clouds for gas-giant planets.

(Related picture: Hubble spies the Cat's-Eye Nebula.)

Amateur astronomer Matthias Kronberger discovered the soccer-ball nebula, called Kronberger 61, in January 2011 after poring over digitized photos of sky surveys from the 1980s. After he alerted professional astronomers, the Gemini Observatory in Hawaii zoomed in on the region to create the new, color-composite image.

Kronberger 61 lies roughly 13,000 light-years away in the Cygnus constellation and is almost perfectly round—an oddity when compared with the other 3,000 or so planetary nebulae already discovered.

"Very few are this spherical. They're usually elongated and look like butterflies and other objects," said astronomer George Jacoby of the Giant Magellan Telescope Organization in Pasadena, California, who helped image the nebula with Gemini.

When a star similar to the sun fuses most of its hydrogen into helium, then the helium into carbon, the star becomes unstable and puffs out into a red giant. (Related blog: "What Will the Sun Look Like When It Dies?")

The hot core collapses and begins to pulsate, eventually shedding its outer layers of gas to set the stage for the birth of a planetary nebula. When the core is exposed, its radiation heats the ejected gas, making it glow.

(See a jellyfish-like nebula.)

Looking for Soccer-Ball Nebula's Telltale Heartbeat

How planetary nebulae can form such complex structures, however, is a hot debate among professional astronomers such as Jacoby.

One camp suspects a dying star requires the gravitational and/or magnetic "interference" of a celestial partner—perhaps another nearby star or very large planet—to create a planetary nebula's complex shapes.

Another camp thinks that the complex shapes, including butterfly-like clouds, can form without the help of nearby companions.

"In the case of [Kronberger 61], we'll find out a year from now," when NASA's planet-finding Kepler space telescope will have finished staring at the hot star at the center of the nebula, Jacoby said. (See a picture of Kepler's launch.)

If the star seems to periodically dim and brighten over the year, it's likely that a big orbiting companion helped form the soccer ball-like seams. Brightening would imply that the lighted-up side of an orbiting object is facing the Earth, as when sunshine reflects off the moon. Dimming, meanwhile, could mean an object is passing in front of the star, or that the companion (and its lighted side) is passing behind the star.

Our own sun may or may not puff out and light up like Kronberger 61 when it begins to die some five billion years from now.

"The sun is right on the edge of being able to do this. It's not quite massive enough," Jacboy said. "I suspect it'll have trouble."

The soccer-ball nebula findings were presented Monday at an International Astronomical Union symposium in Puerto de la Cruz, Spain.

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