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: –
|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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