Weltevreden SA
19-05-2014, 06:32 AM
Last dark sky cycle I observed the Dark Doodad a number of times visually. It shows as a very fine black thread against the MW about 15 arcmin to the W of Gamma Muscae & N of the globular NGC 4372. Visually the thread is less than a lunar diameter long. I forgot about the sightings till I saw Nicola Montecchiari's image of the DD in the Deep Sky imaging forum. Her pic of the DD is here (http://skymonsters.net/personal/immagine.php?img=DarkDoodad.jpg). Gauging by her image, I visually detected only the densest portion. I can't visually spot the nearby globular NGC 4372 but it shows up very well along with the DD in a pair of 8x30 binocs. In a 150mm scope at 48x the DD is a black chasm with sharp edges. I looked up the DD in the literature and it seems to be a leftover filamentary fragment after a GMC collapse into several large star clusters. No indication of what those clusters might be today. Filaments of this 'leftovers after the big feast' type are formed when gas pockets stream along magnetic field lines and are compressed by shock waves and external pressure into thin gas cores. They then collapse into small linear aggregates of a few tens of stars that soon dissipate into the field. The DD is unrelated to the nearby Coal Sack, which is just now initiating the starform process that will eventually yield DD-like threads many millions of years from now. (Thanks to Robert for his excellent Coal Sack paper which first drew my attention to dark nebulae in this region.)
Can anyone else confirm an unaided eye DD sighting?
=Dana in SA
Can anyone else confirm an unaided eye DD sighting?
=Dana in SA