NGC40, also known as the bow tie nebula, is a planetary nebula (PN) in the constellation of Cepheus. It lies at a distance of roughly 3500 light years and spans 1.25 light years in diameter and is only 4500 years old.
At the centre of the PN lies a white dwarf at 0.7 times the mass of the sun. The gases surrounding the white dwarf have a temperature of about 10.000°C and expand at 29 km/s.
While NGC40 spans only some 1.23’x1.23’ the bigger structure that can be seen in this image is the supernova remnant (SNR) G119.5+10.2, also known as CTA 1, being named after the pulsar that can be found in the middle of the SNR. It is suspected to lie at a distance of 4600 light years from earth and be 10.000 years old.
CTA 1 spans about 1°30’, making it a relatively big SNR. The vast abundance of Ha and Oiii make this SNR look somewhat similar to the Cygnus Loop - in contrast to the Cygnus loop though, this SNR is extremely faint and is rarely imaged by amateurs. In fact, even after nearly 14h in both Ha and Oiii at f/3 the signal still was relatively weak. The central source of the SNR is the pulsar named “CTA 1” and as pointed out earlier, it’s also name-giving for the name of the SNR. This Pulsar can also be found in our image, but more on that later.
This image was captured as part of the NHZ project by Felix
@SomeAstroStuff and me
@Tim Schaeffer using our shared remote setup in Spain. As we still have some problems with stars we need to fix, Carl
@Palmito was so kind and helped us out, shooting a bit over 3h of RGB stars for us to use in this image.
Whereas we were busy gathering data on this unusual target,
@William Ostling was the editor for this image, pulling out the faintest of things in this picture with his amazing skills.
Big thanks to everyone involved!
Interesting features in our image- The Supernova G119.5+10.2.
As pointed out earlier this supernova is only very rarely imaged and only a few pictures of the wider region near CTA 1 exist. For this image we went with a HOO palette, giving it the popular red and blue look just like it’s known for the cygnus loop.
In addition, we captured the most visible portion of the SNR in our image; the small part that isn’t included in our frame is not as filled with gas - this can be seen in the radio image below. (NGC40’s position is marked by the white circle)
- The central pulsar, CTA 1
As for every supernova, there has to exist a central source. In this case the source is the pulsar named CTA 1, also known as PSR J0007+7303. Pulsars are highly magnetised, rapidly rotating neutron stars that emit beams of electromagnetic radiation from their magnetic poles. In the case of CTA 1 the pulse period is relatively long at 1.6s per rotation. CTA 1 is associated with a pulsar wind nebula (PWN) - PWNe are regions of high-energy particles and magnetic fields that result from the interaction between the pulsar's outflowing wind of particles and the surrounding interstellar medium, resulting in a “small” nebula surrounding the pulsar. This PWN is so small however, that it’s not visible in our image.
The planetary nebula NGC40, also known as the bow-tie nebula, can be found in the lower middle of the image. The bow-tie nebula got its name from the distinctive appearance - The central star, which is shedding its outer layers, illuminates the surrounding gas and dust. This creates a structure that, in certain views, resembles a bow tie. The central star, now a white dwarf, emits intense ultraviolet radiation that ionises the surrounding gas, causing it to glow and emit light at various wavelengths such as Ha or O[iii].Below is a crop of the PN found in our image.
For any further questions, feel free to leave a comment!
We hope that you enjoy this image!
Text written by Tim
@Tim Schaeffer and proofread by the team.
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