NGC 1907, Open Star Cluster
The small open star cluster NGC 1907 is located about half a degree south of Messier 38 in the constellation Auriga and can best be seen high in the
firmament on a clear winter night. However, with an apparent brightness of +8.2mag, you will need somewhat larger binoculars or a small telescope
to see the cluster.
The distance to NGC 1907 is given as 5,120 light years. With an apparent diameter of 6', the true diameter is calculated to be 9 light-years. About 290
stars are counted as members of NGC 1907, according to some sources even up to 400. The total mass is estimated to be about 550 solar masses. The
brightest star reaches an apparent visual magnitude of 11.0mag, which corresponds to an absolute magnitude of 0.0mag. Therefore it shines 80 times
brighter than our sun. Since the star cluster is strongly reddened by dust clouds in front of it, the true value will probably be a bit higher. About 25
stars of the cluster are brighter than 13mag and are therefore already visible as faint points of light in an 8" telescope. By the way, the two bright stars
directly south of the cluster do not belong to it, but are most likely foreground objects.
The age of NGC 1907 is estimated at 500 to 700 million years.
Exciting is the fact that it was once assumed that NGC 1907 and Messier 38 form a double star cluster. But they just happen to be in the same direction
at the moment, flying straight past each other. The distance between the two clusters is currently about 1,600 light years. Since they have probably
already passed the closest approach, they should currently be moving away from each other again.
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The view in my 20 inch f/3 Dobsonian is as follows:
Even at a low magnification of 120x the star cluster is already partially resolved. From time to time fainter stars flash out of the background.
NGC 1907 appears most beautiful at a magnification of 270x. The sky background becomes deep black and the two bright foreground stars form a
great contrast to the fainter cluster stars. There are about 35 to 40 individual stars of varying brightness in a roundish area. The cluster is well separated
from the surrounding star field even at this high magnification. The star density is about the same everywhere.
All in all, a nice little star cluster that is definitely worth a visit if you are already in the area. :)
