The Soot Enshrouded End of a Sun-like Star
December 15, 2004
Image (96 KB)
Object: Planetary Nebula BD +303639
Telescope: Subaru (Effective Aperture 8.2 m), Cassegrain Focus
Instrument: Coronagraphic Imager with Adaptive Optics (CIAO)
Filters: J(1.25 microns), H(1.65 microns), K(2.2 microns)
Color Composition: J=Blue, H=Green, K=Red
Observation Date: July 9, 2001 (UT)
Exposure Time: 30 sec in each filter
Filed of View: 10'' x 15''
Image Orientation: Top is North, Left is East
Position: alpha=19h35m45.23s delta=+30deg 30'58.9'' (J2000)
Constellation: Cygnus (the Swan)
The Coronagraphic Imager with Adaptive
Optics (CIAO) on the Subaru telescope captured this near-infrared
(wavelengths of 1.25 - 2.2 microns) image of a star at
the end of its life. BD +303639 is a planetary nebula,
similar to the
Ring Nebula in the constellation Lyra, the Harp. It
is about five thousand light years from Earth in the direction
of the constellation Cygnus, the Swan. The surface of
the star in the center of the nebula sizzles at a temperature
of forty two thousand degrees Kelvin, and shines fifty
thousand times brighter than our Sun.
At the end of their lives, comparatively lightweight stars like our Sun shed dust and gas which pile around the star. BD +303639 rapidly puffed off its outer layers about nine hundred years ago. This material, weighing almost a quarter of the Sun, has now expanded into a shell one hundred times more extended than the Solar System. The central star illuminates the material which looks like a life preserver from our point of view.
With visible light we can only see the light from the central star scattering off the dust. In infrared light, we can also see light emitted by the dust itself. CIAO used a technique called adaptive optics, which removes the twinkle of light due to turbulence in Earth's atmosphere, to obtain an extraordinarily sharp image of the dust surrounding the star. (Note 1)
Spectra of the central star from the Subaru telescope's High Dispersion Sepctrogrtaph indicates that the sizzling at the star's surface is generating large quantities of carbon. This carbon is a likely ingredient of the dust surrounding the star.
Shedding of material is an integral part of the life of stars. "Although astronomers have been studying the dust and gas surrounding stars of different ages and types, we are only beginning to be able to observe and understand detailed structures such those in BD +303639," says Dr. Koji Murakawa, an astronomer at the Netherlands Foundation for Research in Astronomy. Murakawa adds that "images like these give us precious insight into the last moments in a stars life."