OK, I should admit right from the start that while I feel as though I have “discovered” a Wolf-Rayet star, it turns out to be very well-known to science, so I don’t think there is any chance that I will be invited to give it a name, less yet have it named after me!
I wanted to capture a single spectral image with a group of several stars of comparable brightness but varying spectral classes, to illustrate the different spectral “signatures” side-by-side. I decided to go for a small open cluster - "small" because of the small capture area of my set-up (about 0.3 degrees wide x 0.24 degrees), and "open" so that I might capture perhaps 10 comparably bright stars with their spectra, spread over the frame. I selected NGC 6231 (a.k.a. Caldwell 76) as a candidate - approximately 0.25 degrees across, and with a good spread of stars with Magnitude 6 to 7, well within my capability to capture.
So I aimed my telescope (with QHY5 mono camera and Star Analyser SA100 grating), and captured the attached spectral image.
At a quick glance, you can see about 12 stars on the left side of frame, with their spectra on the right of frame. (And even more stars and spectra can be extracted with a bit of post-processing and enhancement.) As I was hoping, you can see a few different stellar “signatures” - some spectra are longer than others, some show some strong absorption lines, and so on - perfect, just what I was hoping for!
But then I noticed the spectrum of the bright star at the mid-height of the frame - it looks very different to the others. I saw that it has several intense bright emission lines - what could this mean?
So I loaded my image into RSpec, calibrated the wavelength scale, and corrected for instrument response, and yes, those bright points that I saw in the original image have come through as strong emission lines, at wavelengths of about 4650, 5690, 5810, 6560 and 6730 Angstroms.
And when I superimposed the characteristic lines of a Class WC Wolf-Rayet star, I saw excellent correlation with 4 of the classic WC emission lines - the bright emission lines that I spotted in the original image correspond to Carbon emission at 4650, 5696 and 5805 Angstroms, and Hydrogen-alpha emission at 6563 Angstroms.
Mystery solved - Open Cluster NGC 6231 (C 76) contains a Wolf-Rayet star, with Spectral Class WC!
This was an exciting “discovery” for me (even more so than my recent “discovery” of methane on Neptune), so I started doing a bit of research - and discovered that NGC 6231 actually contains at least three Wolf-Rayet stars: HD 151932 (Mag. 6.48), HD 152270 (Mag. 6.61), and HD 152408 (Mag. 5.82).
https://en.wikipedia.org/wiki/NGC_6231
Sure enough, my “discovery” turns out to be the well-documented HD 152270 (a.k.a. HR 6265).
Oh well - I guess my first real discovery will have to wait for another day!
Nevertheless, I hope this little story expresses some of the genuine thrill that can be experienced in doing “real science” in your backyard!
