Múltiples Dimensiones del Espacio, el Tiempo y la Mente, por Jesús Nieto Palomo: NGC 2359, Asterix's Helmet

I have to admit that in many photos, this nebula really looks like the winged helmet of an ancient warrior or mythological god. But if it is up to me (and why not?), I would call it Asterix's Helmet. Nothing against Thor, but Asterix has been much more important in my life than the remote (to me), scandinavian god. In other words, Asterix is a hero of my childhood and, I admit, adulthood… I still enjoy re-reading those used comic books and seeing how the wings of Asterix helmet seem to be connected to his face, reflecting his expressions so well… For some reason, the old classic episodes of Asterix adventures are more appealing to me than the newer ones, which in my opinion lack some of the freshness and subtle humor of the first ones. Or may be the style of drawing is not the same? Because as it is normal, there has been an evolution in the drawing and the script quality, like with Mortadelo y Filemón, those other great cartoon characters. There must be a Mortadelo nebula somewhere, I need to look for it.

Still this NGC2359 is broadly known as Thor's Helmet or Duck's nebula, although I don't see the bird very clearly. The wings yes, the rest, well, maybe a very fat duck? Anyway, it is a beautiful nebula both in "normal" RGB color photos and in "false color" narrowband photos. I am quite happy with the result because I always had the impression that this Southern object in Canis Major, quite close to Sirius, the brightest star in the sky, would be difficult to photograph for me. Well, it was not easy in the sense that I can only take maximum two hours each night, since it crosses the meridian (which is when I start the session) till it is too low, say less than 25 degress above the horizon.

The nebula is pretty big, about 30 light years in diameter, so its apparent size seen from here is also large, considering that it is located at 15000 light years from us. That is far away, relatively speaking. It is caused by a very energetic "Wolf-Rayet" star. This star, a blue supergiant, emits a lot of radiation mostly as ultraviolet photos. But it also emits matter, or stellar wind, that compresses the gas clouds in the vicinity of the star, thus shaping the cloud into its bubble form. The UV photons excite the gas that then glows in several wavelengths, including the ones corresponding to hydrogen-alpha, ionized oxygen and sulphur, which are the ones that I have registered with the filters I used. This kind of nebulae, created by Wolf-Rayet stars, has nothing to do with planetary nebulae, created by dying stars in their nova stage. Other famous Wolf-Rayet bubbles are of course the Bubble Nebula near Messier-M52 in Cassiopea, and the Crescent Nebula in Cygnus.

The Asterix's Helmet nebula (ok, or Thor's Helmet) emits a lot in OIII, its signal in the central part of the nebula is actually stronger than the H-alpha. But the H-alpha is more extended, meaning there is a broad diffuse cloud of hydrogen in the area. In sulphur-II there is far less signal, which concentrates mostly in the helmet area and its western wing.

In the web there are some nice versions, many of them in NASA's APOD page:

http://apod.nasa.gov/apod/image/0903/Thor4Andreo.jpg

http://apod.nasa.gov/apod/ap140215.html

Much more detailed, by a well renowned group of authors:

http://apod.nasa.gov/apod/ap100605.html

Another group a few years earlier:

http://apod.nasa.gov/apod/ap051119.html

And by the Isaac Newton telescope in the Canary Islands, Spain:

http://www.ing.iac.es/PR/press/ngc2359.html

I have used the normal equipment in the Mar de la Frau Observatory:

Telescope AP 130 Gran Turismo, with Hotech field flattener (f/6.2, 800mm focal length)

Camera QSI 683ws