NGC 2467, Sh2-311, Mandrill Nebula, Skull and Crossbones Nebula
H-II region with embedded cluster
Constellation: Puppis
RA: 07h52m 30.0s
DEC: -26° 26' 00"
Visual magnitude: 7.0 (cluster)
Dimensions: 15.0 x 15.0' (cluster)
Many planetarium programs contain confusing information about NGC 2467. Some only include the cluster of stars, others contain two objects (one for the cluster and one for the nebula). In truth the object is far more complex so let's have a look.
NGC 2467 was discovered by William Herschel on December 9, 1784, during sweep 333. He noted it down as number 22 in category IV which means he meant the nebula and not an open cluster! In that respect the designation of Sh2-311 is the correct one. NGC 2467 has been a subject for star formation research, particularly the influence of already existing O and B stars on the star formation rate. Spitzer observations have revealed 47 YSOs (Young Stellar Objects) in the nebula complex.
When examined thoroughly there really isn't one open cluster but according to WikiPedia we see "a superimposition of several stellar groups along the same approximate line of sight that have distinctly different distances and distinctly different radial velocities. One of these is a young and very distant group beyond Puppis OB2, while another, nearer group with later type stars lies at a similar distance as Puppis OB1."
However, it doesn't end there! Several objects of interest lie in the general direction of NGC 2467. First of all there is a massive, young O6 star called HD 64315 (SAO 174700 == V402 Pup). This star seems to be the source of ultraviolet radiation exciting the gas in NGC 2467. And despite the fact that NGC 2467 doesn't represent a cluster, there are in fact two clusters in the complex. One is Haffner 18, which contains the very young star FM3060a which has just come into existence and is surrounded by its birth cocoon of gas. The other one is Haffner 19, which is a compact cluster containing a Strömgren Sphere (a sphere of ionised gas around a young star of which the Rosetta Nebula is the most famous example).
Here is an annotated image (consisting of 49 images with 6 different filters taken with the Wide-Field Imager camera at the 2.2m MPG/ESO telescope, located at La Silla, in Chile) with north up and east to the left for easier reference when observing:
NGC_2467_and_Surroundings.jpg
My observation with my 20" dob at February 29, 2016, reads
"At 256x without filter the brightest part already is visible. At 83x with UHC this is a spectacular nebula which almost fills the 59' field of view! One part of the nebula is bright and oval and at its center lies SAO 174700 = V402 Pup. At the south west edge of the nebula I see a bright rim. On the other side of the star runs a dark lane that almost splits the nebula in two. Almost from the bright rim runs a faint loop around several field stars and it returns to the nebula on the other side of the dark lane. According to pictures there should be another reasonably bright circular nebula around another star on that side but I don't see it."
and on March 30, 2016
"This is a very spectacular nebula! At 83x it already is visible without a filter. UHC improves the view. But OIII really makes it unforgettable. The part that was visible without a filter turns out to be a small part of a very large nebula that fans out to the north east. In the north east of the part with designation NGC 2467 lies a bright star surrounded by a darker inner bit and a brighter ring of gas. To the north runs a dark lane followed by another fainter part of the nebula. When I move the telescope around I seem to be seeing much more nebulous patches around this bright part and the fan. I'll need to make a proper finder chart and return to this area to see what's visible there!!!"
Well, I haven't returned since then which is why I missed the clusters H18 and H19. However, the second time I did see the Strömgren sphere
As always,
"Give it a go and let us know!
Good luck and great viewing!"
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