May 2026 - Picture of the Month
Planetary nebula NGC3699 in Centaurus
Around 2015 this planetary nebula was imaged by ESO from its La Silla Observatory in Chile using an instrument on their 3.6-metre telescope. Adam's image was also taken from Chile but, 11 years on, he's using a 0.61m telescope and 32 hours of exposure time to produce this detailed, confusing and fascinating view of NGC 3699 in the southern constellation of Centaurus.
Adam has a great article on this object and his imaging process on Astrobin and, rather than repeat what he's said here, I suggest you read it. As Adam notes, this is probably a polypolar planetary nebula with a binary system at its heart, but there appears to be very little written about it.
The article for NGC 3699 on French Wikipedia claims that the GAIA DR3 parallax corresponds to a distance of about 1228–1534 pc (4,000–5,000 light-years). There's little data available for NGC 3699 anywhere else.
I checked this with Gaia DR3 using Vizier and the location of this particular source (Gaia DR3 5336133687170599040) does appear to be that of Adam's suspected central star. However the estimated effective temperature of around 10,000K seems a little low, although it is easily the highest to be found in the area. Additionally, the Renormalized Unit Weight Error (RUWE) for this star is very close to 1, suggesting that this isn't an unresolved binary system... perhaps Gaia DR4 will help when it arrives.
NGC 3699 is a relatively large and faint object which I suspect puts it beyond the scope of visual observers, and it's location will foil many imagers in the northern hemisphere. Fortunately the availability of remote telescopes under southern skies opens up the possibility to examine many fabulous objects of this kind.
James Whinfrey - Website Administrator.
