The Hubble Space Telescope would be widely recognized if all it did was take pictures of planetary nebulae. It photographs many other objects, of course, but few are as attractive or intriguing.
A new image shows what astronomers say is one of the longest of these objects ever seen. In addition, length means intrigue with planetary nebulae, because astronomers don't know why they are sometimes stretched out instead of circular.
Planetary nebulae have nothing to do with planets. They were misnamed early on in astronomy because in crude telescopes they resembled the objects in our solar system that had come to be called planets. What they are, instead, are dying stars that have cast a lot of the gas from their outer atmospheres into space in sort of a last gasp. This gas forms wild structures that range from circles to the elongated shape seen in Henize 3-401, the subject of the new photo.
The aging star can be seen in the center of activity.
Some theorists suspect the streaks and filaments of gas emanating from the star are sculpted by powerful magnetic fields, which funnel the material. Others say a second star, some unseen companion orbiting around the central star, is needed to create the jet-like streamers.
Astronomers do know that the process is one way elements are distributed through our galaxy. Stars are like big recycling factories. Their thermonuclear fusion converts huge amounts of light elements (mostly hydrogen and helium) into heavier ones (such as carbon, nitrogen and oxygen). These heavier elements, once cast into interstellar space, may become part of other stars.
Each type of gas glows in a different color.
Henize 3-401 is in a phase that is very short, in astronomical terms, and there are not very many similar objects around for similar study. It will take only a few thousand years for the central star to exhaust its nuclear fuel and become a cooling, fading white dwarf star that will become so dim as to be nearly invisible.
Astronomers associated with the European Space Agency (ESA) produced the image.
"We are studying stars at a crucial moment in their life -- as they die," said ESA Spanish researcher Pedro García-Lario. "Our ultimate goal is to find out exactly how the dying stars spread these huge amounts of processed material throughout the universe. How can a perfectly round star undergo a rapid metamorphosis to become such an elongated object as Henize 3-401? These are key questions to answer if we want to find out how our Milky Way evolves chemically."
Despite the ongoing efforts of García-Lario and others studying Henize 3-401 with Hubble and other telescopes, the detailed nature and origin of this nebula remain deep mysteries, they say.
Henize 3-401 is located in the constellation of Carina (the Keel) and is about 10,000 light-years away. This picture, released today, is composed of three exposures obtained with Hubble's Wide Field Planetary Camera 2 in 1997.
The Hubble Space Telescope project is an international cooperation between ESA and NASA.
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