An image of the Bubble Nebula and M52 with some Ha data. Exposures was very short due to summer light in Sweden.
Exposure time: Lum: 4x5min. RGB: 4x5min. Ha: 4x10min
Equipment: Tec Apo 140, AP MachOne, QSI 583wsg with Lodestar.
Bubble Nebula.
NGC
7635, also called the Bubble Nebula and Sharpless 162, is a H II region emission
nebula in the constellation Cassiopeia. It lies close to the direction of the
open cluster Messier 52. The "bubble" is created by the stellar wind from a
massive hot, 8.7 magnitude young central star, the 15 ± 5 M☉ SAO 20575 (BD+60
2522). The nebula is near a giant molecular cloud which contains the expansion
of the bubble nebula while itself being excited by the hot central star, causing
it to glow. It was discovered in 1787 by Friedrich Wilhelm Herschel. The star
SAO 20575 or BD+602522 is thought to have a mass of 10-40 Solar masses.
With
an 8 or 10-inch (250 mm) telescope, the nebula is visible as an extremely faint
and large shell around the star. The nearby 7th magnitude star on the west
hinders observation, but one can view the nebula using averted vision. Using a
16 to 18-inch (460 mm) scope, one can see that the faint nebula is irregular,
being elongated in the north south direction.
Messier 52.
Discovered 1774 by
Charles Messier.
Messier 52 (M52, NGC 7654) is a fine
open cluster located in a rich Milky Way field. It is one of the rich clusters
for which amateur Jeff Bondono has proposed the name "salt and pepper" clusters.
Ake Wallenquist (1959) found 193 probable members in a region of 9'
radius, and the density near the center is about 3 stars per cubic parsec.
The brightest main sequence star of this cluster is of mag 11.0 and spectral
type B7. Two yellow giants are brighter: The brightest is of spectral type F9
and mag 7.77, the other of type G8 and mag 8.22. The Sky Catalogue 2000.0 gives
an age of only 35 million years, which coincides with the value given by
Woldemar Götz, who mentions that this cluster contains one peculiar Of star,
i.e. an extremely hot star with peculiar spectral lines of ionized helium and
nitrogen.
The distance of this cluster is not very well
known; Kenneth Glyn Jones adopts 3,000, Mallas/Kreimer 7,000 light years, while
the Sky Catalogue 2000.0 gives 5,200 (i.e., 1,600 pc) and Götz 5,050 light
years. Robert Garfinkle, in his "Star Hopping", quotes about 3,000, Harvey
Pennington and George Kepple and Glen Sanner's Night
Sky Observer's Guide 3,900 light years. This
uncertainty is mainly due to the high interstellar absorption its light has
suffered on its way to us, which is complicated to estimate reasonably. M52 is
classified as of Trumpler type I,2,r (Sky Catalog 2000) or II,2,r (Glyn Jones,
Götz).