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NEAT SOUTHERN PLANETARIES : 03
NGC 3699 & He2-67 in Centaurus


This next part of the series includes two planetaries. NGC 3699 is the most northern, followed by He2-67 Both planetaries are separated by merely 11.1 arcmin, make an interesting pair. Together, that I name these together as the The Double Planetaries of Centaurus.


NGC 3699 / He2-65 / Sa2-74 / Wray 16-90 / PK 277+7.1 / PN G292.6+01.2 (11279-5957) lies within the eastern portion of Centaurus next to western Crux. Visible in 20cm., this bright 11.0p magnitude planetary subtends the visual diameter of about 45.0 arcsec. This is a strange looking object, and you would be forgiven to easily mistake it for some small emission nebula. Using Sky Catalogue 2000.0 or Sky Atlas 2000.0, it is still remarkably printed as an emission nebula. Interestingly, AOST1 also states NGC 3699 this too.

From what I can ascertain, NGC 3699 was first recognised as a true planetary around 1978. A photograph can be seen in Plate 10 in AOST1, which was taken by Westerland and Henize, whose description (and photograph) can be seen in AJ.Sup.Ser., 14, 154 (1969)

This PN is contained within a fairly starry field, extending in the telescope to some 60 arcsec across. NGC 3699 is likely just visible in 10.5cm, though 20cm vastly improves its appearance. Dividing the image into two portions shows a dark rift, slightly south of centre, at PA 80° to 200°. This can be seen in 20cm and O-III filter, and is visible in all telescopes above 25cm. NGC 3699 does remind me of some smaller version of Centaurus irregular galaxy, NGC 5128 (Centaurus A).


NGC 3699 Wider Field
NGC 3699 Small Field

AOST2 says the appearance appear mottled, but this effect I could be just begin to see using 30cm. At the edge of the PNe appears to me as irregular and wavy.

NGC 3699 is also considered among the Peimbert Type 1 Bipolar (BPNe) exhibiting extreme filamentary structures. Earlier, the structural details of these PNe types were thought to be caused by extreme shocks and instabilities. Modern theory says they are produced by high velocity dense shell(s), catching up and overtaking the circumstellar envelope previously ejected in the AGB phase. In turn, this produces the seemingly chaotic and bizarre appearance of the nebula. All BPNe progenitors of this type are suspected to weigh between 3M⊙ and 5M⊙. NGC 3699s surface temperature is above 140,000K. All BPNe, are in essence, are among the hottest of all the known PNNe.


Observational Descriptions



Technical Data



He2-67 / Sa2-76 / Wray 16-92 / ESO 129-22 / PK 292+1.2 / PN G292.8+01.1 (11288-6007) lies towards the direction SE of NGC 3699. Such planetaries in the sky, like this one are literally a dime a dozen, but extraordinary other descriptions about NGC 3699 never mention this particular nearby one! At 13.2 magnitude, it is just visible in 20cm, and like most of these planetaries the O-III filter is a godsend. Its 5 arcsec stellar-like appearance jumps out at you while flickering the O-III filter over the visible field. To find it, it is recommended using any wide-field eyepiece and with the field diameter between 0.4° and 0.5° (c.80×). Place NGC 3699 at the very top south-western edge of the field, then this PNe becomes obvious — very close to the centre of the field. Appearance-wise, I saw what looked like a smallish grey disk, though I suspect that one of the large Dobsonians could perhaps see some colour. In 30cm, I could not see any apparent structure, except for glimpsing an uneven edge.

He2-67 own PNN is of 15.8 magnitude and could be glimpsed in 40cm telescopes, though I I have never seen it. Although not physically related to NGC 3699, it has the same similar Type 1 structure as its neighbour. Distance of this galactic planetary is likely to be many kiloparsecs.


He2-69 Wide Field
He2-69 Small Field : 
c.2.5x2.5 arcmin

Observational Descriptions



Technical Data


Very little is known about this faint object, with scant details in the literature. It is moving a the radial velocity of +59.5 km.s-1

References.

  1. Stanghellini, L., Shaw, R.A., Villaver, E., The Magellanic cloud calibration of the Galactic planetary nebula distance scale.”, AJ., 689, 1942 (2008)


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Last Update : 04th November 2011

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