Imaging the Neutron star at the heart of the Crab Nebula

[tomato]

This is a bit different although the idea and practical experiment are certainly not new. While recovering from Covid, @Tomatobro came across a BAA article which described using a rotating shutter to capture the variation in optical brightness of the Crab Nebula Pulsar. By using a spinning chopper disk such that the light path is interrupted 30 times a second it is possible to capture  variations in brightness with extended exposures. The original setup called for a hefty scope (14" SCT) but with more sensitive cameras now  available we thought it might be possible to capture something using a 6" refractor.

@Tomatobro made a stepper motor driven 8 vane disk mounted in a light proof alloy enclosure which could be mounted between the Esprit 150 and an ASI 178 camera. He also constructed a programmable control module to achieve the required RPM for the disk. The challenge was to make an accurately balanced disk so no unwanted vibrations were transmitted to the imaging train when it was in operation.

Last night 3 sessions were completed, each of 100 x 20 sec subs. There was visibly some change in the brightness of the pulsar on individual subs but this has been enhanced by stacking the brightest and dimmest subs to make a crude gif animation. So far I have only analysed the best session, the pulsar actually exhibits 3 discrete brightness levels but I'm not sure this set up is sensitive enough to capture this.

Is it a genuine capture? Well, the varying brightness of the nebula is a concern, but it is the pulsar that is varying in brightness while qualitatively at least the other stars have a constant light output.

It's not much to look at but when you know that the photons are coming from a star about as big as a city but 1.5x the mass of the sun and spinning at 30 times a second, it's quite something.

 

Rotating disk housing and stepper motor

Control Unit

 

[Sunshine]

Wow! that is some effort but I can clearly see the variation in the stars brightness which is more obvious than other stars and feature within the frame so I would say in my eyes it is a legit capture. Amateurs like yourself exemplify what can be done with some ingenuity and determination, impressive.

Edited January 26, 2023 by Sunshine

[peter shah]

Great work

[gorann]

Yes, quite a capture indeed! Something good finally came out of COVID!

[gorann]

PS. sorry to disclose my ignorance, but Is that pulsating neutron star what exploded and caused the nebula?

[900SL]

Ingenuity at work. Well done 👍

[tomato]

Yes, the pulsar  is indeed the highly energetic remnant from the supernova recorded by the Chinese in 1054. 

[Craney]

9 minutes ago, gorann said:

PS. sorry to disclose my ignorance, but Is that pulsating neutron star what exploded and caused the nebula?

I think it's more of the case that the massive star that was, exploded and left the nebula  ( outer stellar atmosphere )  with the pulsar embedded  ( remains of a super crushed core ).

[markse68]

Yes it is: https://www.nasa.gov/feature/goddard/2017/messier-1-the-crab-nebula

HST made an incredible animation of the ripples the pulsar creates:

 

 

[tomato]

5 minutes ago, markse68 said:

Yes it is: https://www.nasa.gov/feature/goddard/2017/messier-1-the-crab-nebula

HST made an incredible animation of the ripples the pulsar creates:

 

 

Not seen this before, thanks very much for sharing.

[markse68]

Hey Tomato, according to Wiki the star does an intermediate blip too so might be worth looking for that too

https://en.wikipedia.org/wiki/Crab_Pulsar#/media/File:Crab_Lucky_video2.gif

https://en.wikipedia.org/wiki/Crab_Pulsar

(Edit sorry you mentioned 3 discrete brightness levels in op)

Edited January 26, 2023 by markse68

[tomato]

Yes, that’s the reference I made to the pulsar exhibiting three levels of brightness, the minimum level, the maximum level and the two interpulses of equal brightness, either side of the main peak. With sufficient data and resolution these should be discernible, I need to analyse all of the data to see if they are present.

[Laurin Dave]

Brilliant work @tomato and @Tomatobro 

[wimvb]

Excellent. Do you have a link to the BAA article describing the method you used?

[tomato]

21 minutes ago, wimvb said:

Excellent. Do you have a link to the BAA article describing the method you used?

Hi Wim, I’m sure @Tomatobro will respond with the details when he reads this.

[josefk]

Super impressive - enjoyed reading that!

[Tomatobro]

1 hour ago, wimvb said:

link to the BAA article describing the method

Go to the British Astronomical Association website (no need to log in), click on journals, scroll down to the December 2022 edition and click on it to open the list of contents

Near the bottom of the list is "Measuring the light profile of the Crab nebula pulsar". If you are a member you can download as a PDF or click on the view now if not.

Enjoy

[wimvb]

@tomato & @Tomatobro, thanks. I got it. Plus now I've also got good source for online reading.

[Richard_]

Great work guys! Looks like the setup worked exactly the way you wanted it to. 

[teoria_del_big_bang]

Brilliant work, such dedication, and some great skill in achieving a working setup 🙂 

Steve

[tomato]

Thanks Steve, @Tomatobro deserves all the credit, he did all the work making the rotating disk and speed controller, I just pointed the scope and took the pictures. I’m currently trying to find if there are any other suitable candidates to try the technique on, but the only one I’ve found so far, the Vela Pulsar, is too far South.

[wimvb]

9 hours ago, tomato said:

I’m currently trying to find if there are any other suitable candidates to try the technique on, but the only one I’ve found so far, the Vela Pulsar, is too far South.

You can always follow up with a magnitude vs time curve. 😉

Edited January 29, 2023 by wimvb