The Apple Core Nebula: Messier 27 in Vulpecula (2020) | WIYN Telescope

The Apple Core Nebula: Messier 27 in Vulpecula (2020) | WIYN Telescope

This image of the Apple Core Nebula (M27, NGC 6853), a planetary nebula in the constellation of Vulpecula, was taken at the 3.5-meter WIYN telescope in 2020 using the mini-mosaic imager. The Apple Core Nebula is about 850 light-years away from Earth and about 1.5 light-years in diameter (although both distance and size are very poorly constrained). This nebula was formed when an evolved, red giant star ejected its outer envelope near the end of its lifetime. The expanding cloud of gas becomes visible once the hot core of the star, visible near the center, is exposed and the high-energy, ultraviolet light from the core causes the cloud to fluoresce. As a result, the cloud emits light at discrete wavelengths resulting in an emission-line spectrum. 

The strongest of the spectral lines are at visible wavelengths are those of singly and doubly ionized oxygen (372.7 nm, OII, and 500.7 nm, OIII, respectively) and hydrogen (656.3 nm, H alpha). This color image was obtained by combining three separate pictures, each one taken through a narrow filter centered at these wavelengths, choosing red to be H alpha (30 minute exposure), green to be OIII (30 minutes) and blue to be OII (60 minutes). The combination produces an unusual, semi-realistic image of the Apple Core Nebula. The green regions indicate locations within the gas cloud where the highest energy radiation is absorbed and doubly ionized oxygen is present. In contrast, regions that are predominantly blue and red indicate where lower energy radiation is being absorbed and the line from doubly ionized oxygen is weaker compared with those of singly ionized oxygen (blue) and hydrogen (red). Since the hot central star emits the same spectrum in all directions, these differences are thought to originate from variations in the density of the expanding cloud. 

The Wisconsin-Indiana-Yale-NOIRLab (WIYN) Observatory is situated atop Kitt Peak National Observatory, a partnership consisting of University of California Irvine, Purdue University, the National Science Foundation’s NOIRLab, and NASA.

Learn more about the WIYN Observatory:
https://www.wiyn.org/0.9m/index.html

Credit: Michael Pierce, Robert Berrington (Indiana University), Nigel Sharp, Mark Hanna (NOAO)/WIYN/NSF
Release Date: June 30, 2020

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