A Dusty NA & Pelican

[Knight of Clear Skies]

You don't typically see dust in images of the NA and Pelican, but this is an optical/IR composite using data from the WISE space telescope, used to survey the entire sky at infrared wavelengths. It shows that the visible nebulae are just part of a larger complex.

The NA & Pelican are a single large emission nebula obscured by a central dark nebula. The hot massive star lighting up the complex, christened the Bajamar star, has recently been identified. If it wasn't shrouded by dust it would be one of the brightest stars in our sky.

https://cab.inta-csic.es/en/news/escape-from-bermuda-the-ejection-of-its-massive-stars-leaves-a-stellar-cluster-orphan/49/

(The article also mentions that the Veil nebula may well have been created by a star from the same cluster hiding behind the Pelican, it's at about the same distance.)

Having aligned the IR image using Registar I can blend it in at any level, I made this video to show how the ionizing star is lighting up the nebulae we recognise. I think this is the best way to present it.

This is the base HaRGB image I used.

The 200mm lens gives enough resolution to see the dust pillar in the head of the Pelican.

This also got me thinking, why don't we see much visible dust along the plane of the Milky Way, like we do in Cepheus, Taurus or Perseus? I suspect it's because dust outside the plane of the galaxy can be illuminated by many more stars. The IFN at high polar latitudes is very tenuous but is illuminated by the entire galactic disc, whereas dust along the galactic plane is obscured by - more dust. Can anyone shed any light on this please? Where is the illumination of these dusty fields actually coming from?

This image makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, and NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology. WISE and NEOWISE are funded by the National Aeronautics and Space Administration.

IR image credit: unWISE / NASA/JPL-Caltech / D. Lang (Perimeter Institute)

[ollypenrice]

Superb. I wonder if any of this could be picked up by a very fast broadband rig in RGB.

One of the drawbacks of HaLRGB imaging is that it lets us prioritize the hydrogen so easily using an Ha filter. We can get a deep hydrogen image that way without spending so long on the broadband, thereby causing us to miss the deepest broadband signal. I like broadband-only images for precisely this reason. The Ha is downplayed relative to the surrounding dust and emerges from it more naturally.

Olly.

[Knight of Clear Skies]

On 26/11/2022 at 13:30, ollypenrice said:

Superb. I wonder if any of this could be picked up by a very fast broadband rig in RGB.

Would be interesting to see what you could get, I've seen one or two images showing some dust around these nebulae. But I suspect it would be difficult for the reason I give in my post above.

[ollypenrice]

Well, I had a look for brown dust in mine and Paul Kummer's and tried to emphasize it. There is certainly brown dust there to be had and what I found is in partial but by no means full agreement with yours. However, that's to be expected, to some extent, since the Ha will out-shine the brown from the IR. My 'emphasizing' methods were crude so I don't regard this as a published image but just as the result of a quick test.

If our little consortium is in ageement, I think going for this in broadband colour, without Ha, would help swing the balance towards the dust. An interesting project for next season since we should have both RASA and Samyang 135 as fast systems to point at this.

Olly

[Knight of Clear Skies]

On 28/11/2022 at 09:17, ollypenrice said:

Well, I had a look for brown dust in mine and Paul Kummer's and tried to emphasize it. There is certainly brown dust there to be had and what I found is in partial but by no means full agreement with yours.

You definitely have some dust in there. In this case I wouldn't expect the visible dust to line up very well with the IR in my image, as it dependant on the illumination. I bended in the W1 and W2 channel from WISE which shows the warmer dust, which I think is heated by embedded stars and/or gravitational collapse.

I'd be very interested to see what a really deep broadband image would show. There is a lot of scope for using different blends of data to emphasise different features.

[Rodd]

On 26/11/2022 at 08:30, ollypenrice said:

Superb. I wonder if any of this could be picked up by a very fast broadband rig in RGB.

One of the drawbacks of HaLRGB imaging is that it lets us prioritize the hydrogen so easily using an Ha filter. We can get a deep hydrogen image that way without spending so long on the broadband, thereby causing us to miss the deepest broadband signal. I like broadband-only images for precisely this reason. The Ha is downplayed relative to the surrounding dust and emerges from it more naturally.

Olly.

If one uses the Ha in the emission portion of the red channel, one can take advantage of Ha structures without compromising reflective dust.   This is easily done as the red emissions are much brighter than the dust. In PI the two are easily differentiated.