IC 4997 - Planetary Nebula
IC 4997 is a distant planetary nebula in the constellation "Sagitta". The PN is nearly 25,000 light years away from Earth and was discovered by
astronomer Williamina Fleming in 1896. Despite the great distance, the brightness is 11.2mag, so the PN can be seen even with small
telescopes of 4" aperture and larger.
With an angular extent of just under 2" (arcseconds) IC 4997 appears even a bit smaller than the planet Neptune. If you look at an image of
the HST, you can see two lobes emanating from a brighter central star on both sides.
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To find IC 4997 is quite easy. It also responds very well to the filter blink. The great thing is that just southwest there is a star of about the
same brightness, with the help of which you can compare the brightness of the PN quite well when blinking. At 20", however, the filter
blink is not really necessary for identification because the greenish color is quite noticeable.
While the PN appears stellar at small magnifications of 120x, at 270x you can see a tiny nebular area. Now and then at this magnification
I had the impression that the planetary nebula does not appear circular, but slightly elongated. But to be sure here, I should have chosen
the magnification a little higher.
So there was only the overall impression of a quite bright, greenish, but tiny little disk, which seems to get brighter towards the center -
a hint for the central star.
