By Dave Paiz
Arizona Daily Wildcat
March 25, 1998

UA camera captures dying star's last stages

A UA-designed camera on the Hubble Space Telescope has captured stunning images of a distant star's last days.

"We're investigating the final stages of evolution of stars comparable to the sun," said John Bieging, a UA associate astronomy professor.

Bieging is on the team that took the new images of NGC 7027, a star 3,000 light years away in the constellation of Cygnus the Swan.

The images are among the first of their kind taken by the UA-designed Near Infrared Camera and Multi-Object Spectrometer which was put on the Hubble Space Telescope in February 1997.

"We're trying to understand the processes by which they (stars) throw off large amounts of matter in the final stages of their evolution," Bieging said.

These images have captured the dying star in the process of becoming a planetary nebula.

"Planetary nebulas have nothing to do with planets," Bieging said.

Bieging said the planetary label came from an 18th century astronomer who first identified the objects but had no formal term to describe them. The term nebula refers to their gaseous, cloudy nature.

The images of NGC 7027 are actually the combination of three separate pictures taken at different wavelengths of light.

"These are not the first images, but they're definitely the best," Bieging said.

The wispy red, butterfly shaped wings that surround NGC 7027 are actually expanding layers of dust and cool hydrogen gas that have "blown off" the white-hot central star.

"One of the things we're trying to understand is the physical processes that are responsible for this shape," Bieging said.

Bieging said the material being cast out into space is rich in carbon and other elements that will form the building blocks of future stars and planets.

"It's kind of a giant cosmic recycling process," Bieging said. "We can see things in this structure that I think will tell us how it was created and what will happen to it in the future."

Bieging said as a star exhausts its supply of nuclear fuel - hydrogen and helium - it ejects the material into space in a wind-driven stream of dust and gas.

"When the star blows off this material, what's left is very hot," Bieging said.

As the process unfolds, the temperature of the dying star exceeds many thousands of degrees Fahrenheit.

The energy given off by the star makes the expanding gas clouds glow in a phenomenon called luminescence.

Only part of this phenomenon is visible to human eyes. In order to capture the process in its entirety, scientists need something that can see into the infrared light spectrum.

The ability to see in the infrared is crucial, for it allows scientists to detect molecular gases that can only be seen at certain wavelengths of light.

By analyzing these gases, scientists are better able to understand the processes that dictate a particular star's life cycle.

NGC 7027 will exhaust its fuel in roughly 100,000 years Bieging said. It will then begin to expand and cool before shriveling up and ultimately becoming an ember that will simply vanish from sight.

Scientists predict that our own sun will meet a similar fate in approximately 4.5 billion years.

Bieging and his fellow team members will look at eight other objects in various stages of evolution from now until May.

"Each one of these stars is unique in some regard," Bieging said. "I think there's a combination of being impressed with individuals, as well as with the general nature of stars."