Variable Nebulae

Most Deep Sky observers do it for fun. There is not very much science to be derived from this area of astronomy by amateur astronomers, but some areas in which amateurs can do science include: –

Supernova patrolling.
Nova patrolling in Local Group galaxies.
Photometry of the variability in Active Galactic Nuclei.
Measuring binary stars.
Observing Variable nebulae.

So, what are these Variable Nebulae? They are reflection nebulae associated with Young Stellar Objects (YSOs) that have yet to arrive on the Main Sequence (of the Hertzsprung-Russell Diagram). The nebulae themselves show true changes in brightness, shape, or position on observable timescales. They are invariably found on the edge of Dark Molecular Clouds in our Milky Way Galaxy and there are probably many, but very few are observable at optical wavelengths as others are likely to be seen in the infrared. To date, just seven are known, with a handful of other suspects, but more may be discovered now instrumental techniques have become so sophisticated. The current objects are shown in the table: –

Common name	Designation	Constellation	Star	RA	Dec
Hind’s nebula	NGC 1555	Taurus	T Tauri	4hr 21m 57s	+19° 32’ 7”
Hubble’s nebula	NGC 2261	Monoceros	R Mon	6hr 39m 10s	+8° 45’
Thommes’ nebula		Monoceros	V900 Mon	6hr 57m 22s	-08° 23’ 18”
McNeil’s nebula	Near M78	Orion	V1647 Ori	5hr 46m 14s	-00° 05’ 48”
Corona Australis nebula	NGC 6729	Corona Aust.	R & T CrA	19hr 01m 54s	-36° 57’ 12”
Gyulbudaghian’s nebula		Cepheus	PV Cephei	20hr 45m 54s	+67° 57’ 39”
Borisov’s nebula		Cepheus		21hr 37m 18s	+66° 51’ 57”

Of these, all but the Corona Australis nebula can be observed from the UK and are increasingly popular targets for amateurs as they do something on short time scales! In fact, two have been of great interest very recently (2020) as they have faded considerably (McNeil’s and Gyulbudaghian’s) and two are relatively new and in need of monitoring: Thommes’ was discovered in 2009, and Borisov’s just this year (2020).

There are another two variable nebula that have been brought to our attention by Grant Privett, which we will add to our VNe programme:

A variable nebula associated with HBC 340 and HBC 341, which are in the vicinity of NGC 1333 in Perseus looks to be similar to Hubble’s VN, see https://sites.astro.caltech.edu/~lah/hbc340/
In addition, there seems to be a variable nebulosity associated with V347 Aurigae which has some similarity to Hind’s Variable Nebula. There is a paper on Arxiv which you can read at: https://arxiv.org/pdf/2010.02996.pdf

Although both are faint, observations would be appreciated, especially as they are well placed in autumn through to spring.

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