Wolf - Rayet 134 (and WR 135...)

The so-called Wolf-Rayet stars are a rare set of stars that exhibit very uncommon spectra showing outstanding broad emission lines of ionized helium, nitrogen or carbon. Their surface temperatures are between 20.000 K and 200.000 K higher than most other types of stars.

In 1867, from the Paris Observatory and using the 40 cm Foucault telescope, french astronomers Charles Joseph Étienne Wolf and Georges Antoine Pons Rayet observed visually (thus before the systematic use of photographic plates) the spectra of three eighth-magnitude stars in the constellation Cygnus. 

They found that their spectra showed very broad emission lines instead of the much more usual absorption lines or bands. From then on, these stars became known as Wolf-Rayet (WR) stars.

The stars they found were HD 191765, HD 192103 and HD 192641, now designated as WR 134, WR 135 and WR 137. In the first image on the right you can see the location of the first two, which are less than one degree from each other (the third one is outside the field covered by this image but can be found, within the field of my previous RGB image of this area, here).

WR 134 is about 6.000 light-years away from us and is surrounded by a faint nebulous bubble blown by the intense radiation and fast wind from the star (*). It is about five times the radius of the sun, but due to a temperature over 63.000 K, typical of WR stars, it is 400.000 times as luminous as the Sun.

WR 134 is also a variable star and has been classified as an Algol type eclipsing variable and given the designation V1769 Cygni.

(*) Today seems that it is still unclear which of the two stars, WR 134 or WR 135, is primarily responsible for creating the shell (For example, have a look at this).

My image is presented in the Ha-OIII-OIII palette (with RGB stars "taken" from this image) and accumulates 33 hours of exposure time. As usual, I first calibrated the image with SpectrophotometricColorCalibration, but then modified the balance of the G and B channels to get a more pleasing (subjective) view. Since the OIII component of the nebula is so weak, I gave a little more time to the exposure with this filter (18 h OIII vs. 15 h Ha), but it is now clear to me that it was not enough.

Click on the images for a full or higher resolution version, or go to the Gallery section for complete exposure details.

Image processing: Pixinsight.

Observatory automation and remote operation with Talon6

No comments:

Post a Comment