Dying Star Goes Out With a Ring

Release: August 09, 2004

Ring of Stellar Death

[This false-color image from NASA's Spitzer Space Telescope shows a dying star (center) surrounded by a cloud of glowing gas and dust. Thanks to Spitzer's dust-piercing infrared eyes, the new image also highlights a never-before-seen feature -- a giant ring of material (red) slightly offset from the cloud's core . This clumpy ring consists of material that was expelled from the aging star.

The star and its cloud halo constitute a "planetary nebula" called NGC 246. When a star like our own Sun begins to run out of fuel, its core shrinks and heats up, boiling off the star's outer layers. Leftover material shoots outward, expanding in shells around the star. This ejected material is then bombarded with ultraviolet light from the central star's fiery surface, producing huge, glowing clouds -- planetary nebulas -- that look like giant jellyfish in space.

In this image, the expelled gases appear green, and the ring of expelled material appears red. Astronomers believe the ring is likely made of hydrogen molecules that were ejected from the star in the form of atoms, then cooled to make hydrogen pairs. The new data will help explain how planetary nebulas take shape, and how they nourish future generations of stars.

This image composite was taken on Dec. 6, 2003, by Spitzer's infrared array camera, and is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). ]

A new image from NASA's Spitzer Space Telescope shows the shimmering embers of a dying star, and in their midst a mysterious doughnut-shaped ring.

"Spitzer's infrared vision has revealed what could not be seen before - a massive ring of material that was expelled from the dying star," said Dr. Joseph Hora, a Spitzer scientist at the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. "The composition of the ring and how it formed are mysteries we hope to address with further Spitzer studies." The dying star is part of a "planetary nebula" called NGC 246. When a star like our own Sun begins to run out of fuel, its core shrinks and heats up, boiling off the star's outer layers. Leftover material shoots outward, expanding in shells around the star. This ejected material is then bombarded with ultraviolet light from the central star's fiery surface, producing huge, glowing clouds -- planetary nebulas -- that look like giant jellyfish in space.

These cosmic beauties last a relatively brief time, about a few thousand years, in the approximately 10-billion-year lifetime of a star. The name "planetary nebula" came from early astronomers who thought the rounded clouds looked like planets.

NGC 246 is located 1,800 light-years away in the Cetus constellation of our galaxy. Previous observations of this object by visible-light telescopes showed a glistening orb of gas and dust surrounding a central, compact star.

By cutting through the envelope of dust with its infrared eyes, Spitzer provides a more transparent view through and behind the nebula. "What we have seen with Spitzer is totally unexpected," said Hora. "Although previous observations showed the nebula had a patchy appearance, Spitzer has revealed a ring component of this dying star, possibly consisting of hydrogen molecules."

In the new false-color picture, the ring appears clumpy and red and off-center from the central star, while fluorescent, or ionized, gases are green. The central star is the left white spot in the middle of the cloud.

Ultimately, these data will help astronomers better understand how planetary nebulas take shape, and how they nourish new generations of stars. A scientific paper on this and other planetary nebulas observed by Spitzer will be published on Sept. 1 in The Astrophysical Journal Supplement, along with 75 other papers reporting Spitzer early mission results.