Four-for-one: Bubble Nebula, Salt and Pepper cluster, Northern Lagoon Nebula and Nova Cassiopeiae 2021

[Padraic M]

One area of space includes Messier 57 Cassiopeia Salt and Pepper Nebula; Caldwell 11 Bubble Nebula; NGC7538 Northern Lagoon Nebula; and by special request also contains the Nova Cassiopeia 2021, back again to magnitude 6.96.

Captured on 23rd July 2021 in HaRGB.

The nova is the red star in the lower centre. Do novas radiate extra energy in the Hydrogen-alpha band?

Image comprises:
9x 300s each of red, green, blue Baader
6x 300s Baader 3.5nm Ha

Esprit 80, ASI1600mm Pro, HEQ5 Pro
Starwave 50mm guidscope, ASI290mm Mini
AstroPixelProcessor, PHD2, Nina, Gimp.

Edited July 24, 2021 by Padraic M

[vlaiv]

1 hour ago, Padraic M said:

supernova Nova Cassiopeia 2021

Nova and supernova are two different things.

Supernova is exploded star, while nova is transient phenomena that does not destroy the star. It is usually pair of stars orbiting close enough so that smaller (usually dwarf) star stars pulling material from larger neighbor. This material is then heated by rapid rotation and at some point runaway fusion event is triggered - on that material, but not on either of two stars. This process emits bright light that brightens whole star couple of magnitudes.

1 hour ago, Padraic M said:

The supernova is the red star in the lower centre. Do supernovas radiate energy in the Hydrogen-alpha band?

As this is regular nova - I expect that it gives off same amount of Ha radiation as any star with similar temperature - meaning not significant amount.

Very nice image by the way.

[Andy R]

Just finished these targets myself, as yet still unprocessed due to 8 nights of imaging and no sleep. nice capture. 

[Padraic M]

Thanks @vlaiv for that explanation, I actually hadn't understood the differences. Good to know.

I get your point about Ha vs other wavelengths compared to any other star but it seems to have a stronger Ha-Red tint in my subs (which could of course be poor processing). However, there does seem to be some evidence that its Ha emissions have remained bright while other visible wavelengths have faded somewhat. AAVSO spectroscopy charts show strong H-alpha and H-beta spikes (below), and measurements by Hugh Allen at BAA show Ha increasing from Mar-April while other visible wavelengths decreased.

9 hours ago, vlaiv said:

Very nice image by the way.

Thanks! As ever, more data would be good.