August 2026 - Picture of the Month
Supernova remnant W63 (Westerhout 63) in Cygnus
The supernova remnant (SNR) Westerhout 63 (W63) or G82.2+5.3 is rather a large object in the night sky with an angular diameter in excess of a degree. As is sadly the case with many of the largest objects, it's also a very faint making observation difficult. W63 is certainly not a visual target.
A further complication is that W63 is superimposed on that background of H-II nebulosity that you can see in this wonderful image. This nebulosity is designated as LBN 310, or a small portion of that object at least, and it makes W63 challenging to observe optically and in other wavelengths too.
In fact, W63 was original identified in the radio frequency survey of Westerhout in the late 1950s, being too faint to appear on the plates of the Palomar Observatory Sky Survey (POSS) around the same time, and observation remained in the domain of radio telescopes until the 1970s. 1
Fortunately the shell-type structure of W63 is bright in O-III wavelengths, which is blue in this image, which helps to distinguish it from rest of the local nebulae. This O-III structure turns out to be very well correlated to radio observations, particularly on the right side of our image where the H-II nebula is less dense. The O-III emission from the filaments that make up most of W63's structure are the result of shock heated gas, however the more diffuse O-III emission in the upper part of this image seems to be from photoionization processes unrelated to the supernova. 1,2
The distance to this object has been estimated at 1.6—3.3 kpc (5,200—10,800 light-years) and it may be 13,500—26,700 years old. However these estimates appear to be far from certain since the data don't clearly indicate the SNR's stage of development. As such, the age range in particular could be as much as an order of magnitude too short. 1
I'm unaware of any success in identifying the remains of a progenitor for this SNR.
James Whinfrey - Website Administrator.
References
- Mavromatakis, F., Aschenbach, B., Boumis, P., and Papamastorakis, J., “Multi-wavelength study of the {G 82.2+5.3} supernova remnant”, Astronomy and Astrophysics, vol. 415, EDP, pp. 1051–1063, 2004. doi:10.1051/0004-6361:20031694.
- Gao, X. Y., Han, J. L., Reich, W., Reich, P., Sun, X. H., and Xiao, L., “A Sino-German λ6 cm polarization survey of the Galactic plane. V. Large supernova remnants”, Astronomy and Astrophysics, vol. 529, Art. no. A159, EDP, 2011. doi:10.1051/0004-6361/201016311.
