|
 May 2008. The
images at right (click for larger view) are of the famous planetary
nebula M27 (NGC 6853,
a.k.a. Dumbbell Nebula). They were taken May 5, 2008 using luminance
(clear), red, green and blue, and hydrogen alpha narrow-band filters.
The upper left panel shows a normal tri-color image constructed from
the LRGB filters. It clearly shows the central blue white dwarf, with a
surface temperature T = 85,000K and a radius 6x the Earth's radius -
the largest known white dwarf. The white dwarf emits mostly intensely
in the ultraviolet portion of the spectrum and is responsible for the
glowing ionized gas. The nebula, which is 8' in
angular size, is expanding at 31 km/sec. At an estimated
distance
of 1300 ly, this implies an overall nebula size of 1.1 ly and an age
close to 10,500 yr. The red emission is dominated by the
656.3 nm
spectral line of hydrogen (H alpha) , while the inner bluish
part
of the nebula is due to lines of excited oxygen (OII and OIII). The
image is not particularly well color-corrected, since the oxygen
emission should appear greenish-blue.
The image at upper right
is also a tricolor image, but using narrow-band H-alpha image for the R
filter. It show that the hydrogen gas extends deep into the
central region, which is also seen in the lower left image (enhanced
version). The image at lower right is the hydrogen H-alpha image, at
high
contrast, showing the extension of the hydrogen gas well past the usual
boundary of the tri-color image.
In spite of its suggestive
name, a planetary nebula has nothing to do with planets. It it is a
relatively brief period of mass loss near the end of a star's life as
it runs of out hydrogen fuel at its core. This is the fate of
the
Sun in about 4.5 billion years. |
Science
Archives
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Recent
Rigel Telescope Images
(click image
for larger view) |
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| Emission nebula IC 410 in Taurus |
Spiral galaxy
M63 with H alpha Filter, highlighting HII regions (red) |
Flame nebula
NGC 2024 |
| See tri-color imaging page for
more color images |
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