NGC 604, HII- Region in Messier 33
In the Triangulum Galaxy "Messier 33" there are some beautiful HII regions, the brightest and largest of them is NGC 604. It was seen because of its apparent
brightness of 12.0mag already in 1784 by Friedrich Wilhelm Herschel and can be observed even with smaller telescopes. It is located at the end of a spiral arm of
Messier 33 and is about 2.7 million lightyears away from Earth.
The HII region has a diameter of 1,300 to 1,500 light years and is not only about 40 times larger than the Orion Nebula, but also 6,300 times brighter. Wow! NGC
604 was formed about 4-5 million years ago. It contains a large number of young and hot stars: 200 O- stars and about the same number of Wolf-Rayet stars, of which
50 were formed at the same time 4 million years ago. What a spectacle! The total mass of the HII region is given with 100,000 solar masses.
On pictures a hole can be seen in the center of NGC 604. Here the violent stellar winds of the hot stars as well as the shock fronts of single supernovae have driven
the gas outward and created a cavity.
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In a 20" telescope NGC 604 appears quite bright and fuzzy even at low magnification, although relatively featureless. The most beautiful view is at V=270...380x.
Beside the dark center two of the outward arcs are indicated, but it is quite difficult to follow them. Much easier are brighter spots in the interior.
With very good seeing some very faint points of light flash in the gas masses of the HII region from time to time. These are not single stars, but so called SSC (Super
Star Clusters) - immensely luminous young star clusters. Six of them were visible in my telescope.
