Just in time for World Cup 2014 madness: a dying star puffs out a “soccer ball” in space. This object is known as Kronberger 61 and is an example of a planetary nebula, so named for their resemblance in early telescopes to distant Solar System planets like Uranus and Neptune.
As a star with roughly the mass of the Sun ends the main phase of life, having exhausted its supply of hydrogen fuel, its core contracts and its outer layers expand. For a few tens of millions of years, it shines brightly as a red giant star, fusing the helium ash of its former hydrogen-burning existence into carbon. Eventually even the helium runs out, and the core contracts further; despite vastly increased core temperatures, it is unable to fuse the carbon and the star’s life effectively runs out.
The red giant then sheds its outer layers to space, creating a planetary nebula. The core, consisting mostly of carbon, some oxygen and a little leftover helium, is exposed and becomes known as a white dwarf. A shadow of its former self, this “star” will cool over billions of years as remnant interior heat from the fires of nuclear fusion in its past slowly radiate away. The outer layers of the star blown out into space become seed material for future generations of stars.
The oldest white dwarf stars in the Universe may now have surface temperatures similar to those of household ovens. In the distant future of the Universe, these stars should cool until they come into equilibrium with the cosmic background radiation as “black dwarfs”.
Very few planetary nebulae are this spherical, says astronomer George Jacoby of the Giant Magellan Telescope Organization in Pasadena, California, who helped image the nebula with the Gemini North Telescope in Hawaii. “They’re usually elongated and look like butterflies and other objects,” he said. The origin of the complex structures seen among planetary nebulae is still not well understood by astronomers.
In terms of the mass required to produce a planetary nebula, “The sun is right on the edge of being able to do this. It’s not quite massive enough,” Jacoby said. “I suspect it’ll have trouble.”
The new soccer-ball nebula image was presented Monday at an International Astronomical Union symposium in Puerto de la Cruz, Spain.