Würmer, zwei Kaulquappen, ein Pferdchen, ein Schlüsselloch und ein Weihnachtsbaum home


Worms, two tadpoles, a horse, a keyhole, and a Christmas tree

Five dusty winter nebula


December 2009

Some time ago, I had written a short article on dark clouds in two summer nebula to be published in our local astronomy club's magazine (it was all about pigs, elephants, and queens). The winter sky offers a number of comparable objects for visual observation, and again, it is quite animalistic. One of these objects, the worm holes in the Rosette Nebula, are relatively easy. The tadpoles, the horse, and the keyhole are somewhat more difficult. And the last one, the cone at top of the Christmas tree, is a real challenge.

The Rosette Nebula is one of the biggest emission nebula of the winter skies. Despite its size, it is a conspicuous object even in smaller telescopes employing a UHC or OIII narrow band filter.

The Rosette Nebula is worth to be observed with more scrutiny. With increasing magnification and some patience (depending, of course also on aperture), it reveals dark filaments that stretch from the void central part around the central star cluster to the denser outer parts. In bigger telescopes that do not have the field to show the entire nebula, these wormholes become the most conspicuous details. In the western part is a filament that is superimposed to the brightest parts of the nebula and that is meandering around its center. Toward south, a group of wormholes forms a conspicuous three-foiled structure that is associated with some people profanely as a Mercedes-Benz Star.

Despite not being included neither in Messier's catalog nor in Dreyers NGC, IC 410  in Auriga is a very conspicuous emission nebula. Using UHC or OIII narrow band filters, it is an easy object even with a 4-Incher from my house at the city border of Freiburg.

The tadopoles in IC 410, are actually not dark dust clouds. Rather they are so-called globules, which may be the cradles of new stars. These globules are eroded by the radiation of the central star cluster of IC 410, which excites their gas at the side facing the star cluster and forms a so-called bright rim.

Despite a number of excellent photographs of the tadpoles, as form instance by Richard Crisp here in narrow band technique, there were no visual observing reports available of them. I had them in mind for some time, but always forgot to take along a photograph, when IC 410 was high. In February 2008, I had a photograph with me AND IC 410 was observable. My observing report from that night at Astrotreff appears to be the first one of the tadpoles. In the meantime, they have become more population and the even made it into Sky and Telescope (January issue of 2010, page 65).

The brighter one of the two globules, which also bears the name Simeiz 130 and which is the one to the left of the finder map, is relatively easy and can be seen already with a 12 inch telescope. It responds well to narrow band filters an in particular to the UHC (and also H beta). With filter it appears as a small condensation with a superimposed group of three very faint stars.

The other tadpole with name Simeiz 129 is substantially more difficult, in part also due to a superimposes star at the brightest rim of the globule. However, with my 22 Inch Dob it could be observed with certainty.

A finder chart of IC 410 and of the tadpoles is here.

There is need to write much about the Horse Head in Orion, next to Alnitak, the easternmost of the three belt stars. The Horse is formed by a dark cloud, Barnard 33, which superimposes over the HII curtain of IC 434, which extends from Alnitak almost precisely toward south.

The difficulty of observing the Horse Head is commonly overrated and depends in the end mostly on the use of the right filter and the experience and previous knowledge of the object of the observer. With my 14-Inch Dob and a H beta filter it is easy and can be seen from my garden at the city border of Freiburg. With a UHC filter, it is accessible as well under a darker sky.

As a first step, the bright/dark border of the HII curtain of IC434 must be found (where "bright" is of course relative). Following this border from Alnitak toward south, at some point there is a small, darker indentation. Many people have difficulties seeing this indentation as they expect something substantially bigger or more conspicuous. If you know what to expect, the little horse is not difficult at all. With patience and some serious aperture some more detail can be discerned. You may see how the nose of the horse separates from the dark border and sometimes even the ears can be glimpsed, which render the front side of the indentation concave.

As you are already in the neighborhood, also take a look at the dark filaments of the Flame Nebula east of Alnitak and the small round blobs of NGC 2023 and IC 435 east of the Horse.

NGC 1999 in Orion is famous as a the Keyhole Nebula and is about one and a half degrees south of the Orion Nebula. The picture to the left was taken by Hubble Space Telescope. At the eyepiece, the nebula itself is quite small and easily overlooked at low magnification. At higher magnification, the 11 mag star and a surrounding small reflection nebula can be seen (use no filtering). Within the reflection nebula the keyhole can be discerned as a small dark shadow. As it is quite small, you should try to increase the magnification as much as the light-gathering power of your telescope allows.




The Keyhole Nebula is embedded in a fantastic landscape of dust and gas, which can be seen in the POSS composite to the left or in this image. NGC 1999 is the white overexposed part precisely in the middle.




In this dusty area, there are also two Herbig-Haro Objects, which are gas jets that are expelled by young stars and that excite interstellar matter on their way.

Two of these Herbig-Haro Objects, HH1 und HH2 were examined by Hubble Space Telescope. I was able to observe one of them, HH1, with my 22" Dob. A drawing by Uwe Glahn is here.

A wide field image with finder chart and close ups is here.


Appropriate for the time of the year, the Christmas Tree Cluster in Monoceros must be included.  However, not the tree itself and the reflection nebula around 15 Mon will be the focus here, but rather the  Christmas star at the top of the tree. In the picture to the left, the top of the tree is at the bottom, while in the eyepiece it is oriented the way it should be. Somewhat south of the that Christmas star is another starlet, which is already quite dusty and which forms the top of the so-called Cone Nebula.

The Cone Nebula is once again a stellar nursery, in which the dust conceals newborn stars. Similarly dark Pillars of Creation can be found in the summer pendant, the Star Queen in M16. The Hubble image of the Star Queen is a true  classic, despite its peculiar format due to the WFPC2 camera's  sensor arrangement.

The Cone is clearly the most difficult among the objects introduced here. You invariably need serious aperture, a dark sky, an H beta filter, and lots of patience

According to the definition of a dark nebular, the cone itself is not visible but only its rims, which stand in front of a somewhat brighter background nebulosity.  As this background nebulosity is only weakly excited, an H beta filter is the filter of choice.

My first successful observation of the cone was in December 2004 using the 20-Incher of our local astronomy club and an H beta filter. At that time, I could see the eastern rim of the dark wedge. The eastern boundary is somewhat easier to discern, as there are no superimposed stars and the contrast is somewhat higher. During later observations with my 22-Inch Dob, I could see both boundaries as well as further HII nebulosity extending from the eastern rim to the east.

Some of the introduced dark nebula are parts of much more famous bright nebula, which have been observed probably by most of us. Though these dark nebula are very evident on pictures, they are by far not as obvious in the eyepiece. To see their detail, you usually need some patience to get accustomed to the object. Intelligent use of nebula filters and light gathering power of the telescope are, of course, helpful as well.

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