Waid Observatory

Object: NGC 6781 - Planetary Nebula in Aquila

Date: Sept. 2022   -    Location: Davis Mountains west of Fort Davis, TX
Telescope: 10in, RC    -    Mount: Paramount MX  -  Camera: Apogee Alta F8300M
Exposure: Ha = 200 min. OIII = 135 min. Binned 1x1  R, G, and B = 60 min. each   Binned 2x2

Click on the image to view at higher resolution.


NGC 7129 - Star Forming Nebula in Cepheus

NGC 67811 is a planetary nebula approximately 460 parsecs2 (1,500 light years) from the Earth.  It is located in the constellation Aquila1.  A planetary nebula is formed when an intermediate sized star uses up its supply of nuclear fuel3.  These stars do not have enough mass to end their lives in a spectacular super nova explosion3, however; as their cores collapse they expel their outer layers of stellar matter in expanding shells of gas leaving only an earth-sized, extremely hot, core3 known as a white dwarf star4.  The hot white dwarf radiates intense levels of ultraviolet light.  This radiation excites the surrounding shells of gas causing them to glow in the colors we observe.

NGC 6781 is believed to be a barrel-shaped object and is oriented such that we view it looking down the barrel's axis1.  This gives the nebula a "ring shaped" appearance.  The nebula will continue to expand until it becomes too diffused to be visible.  The central white dwarf star is relatively dim and shines at a magnitude of 16.88.  Without nuclear fuel, it will cool and very gradually, over eons of time, fade away.

The image above was captured using Ha (Hydrogen Alpha) and OIII (Doubly Ionized Oxygen) narrowband filters.  The image was assembled by mapping Ha to red and OIII to green and blue.  The stars were overlaid with RGB filtered data to give them a near true color appearance.

1Wikipedia -  https://en.wikipedia.org/wiki/NGC_6781
2Otsuka et al. 2017 - https://arxiv.org/pdf/1707.06565.pdf
3Cosmic Bubble - https://www.eso.org/public/images/ngc6781-potw/
4White Dwarf Stars - https://www.space.com/23756-white-dwarf-stars.html

Copyright Donald P. Waid