M52 and NGC7635, the Bubble Nebula


Copyright 2005 Hap Griffin

Two intriguing objects in one frame!  M52 at the upper left is an open star cluster of 193 stars in the constellation Cassiopeia.  It's distance is approximately 5000 light years, but is difficult to measure accurately because of the large amount of interstellar dust its light has gone through on its way to us.

At the lower right is the beautiful "Bubble Nebula", known officially as NGC7635.  Is is formed by gas being compressed by a strong stellar wind from massive star BD+602522, forty times as massive as our sun and several hundred thousand times more luminous.  As fast moving gas escapes the star, it compresses surrounding sparse gas into a shell.  The shell, consisting of hydrogen, oxygen and sulphur, is ionized by the radiation from BD+602522 causing it to glow.  The bubble is approximately 6 light-years in diameter.  

BD+602522 is a "Wolf-Rayet" star, a star in the end stages of its life which emits fierce stellar winds (charged particles streaming from its surface) rapidly depleting its mass until it finally dies in a supernova.  Wolf-Rayet stars (named for their discoverers) have surface temperatures between 30,000 and 60,000 degrees Kelvin and emit stellar winds with speeds exceeding 1500 kilometers per second.  There are only about 300 Wolf-Rayet stars known in our galaxy.  


Date/Location:    September 23, 2005     Griffin/Hunter Observatory    Bethune, SC
Instrument:    Canon 350D Digital SLR (modified) through Orion 80mm ED80 APO refractor 
Focal Ratio:   f7
Guiding:    Auto via SBIG ST-237 through 10" Meade LX-200
Conditions:    Very poor visually with haze and passing clouds
Weather:    70 F
Exposure: 145 minutes total (29 x 5 minutes) @ ISO 800
Filters:    Baader UV/IR Block
Processing:    Focused and captured with DSLRFocus.  RAW to TIFF conversion, frame calibrations, alignment, Digital Development, Adaptive Richardson_Lucy deconvolution, scaling and JPEG conversion with ImagesPlus.  Color correction with Photoshop 6.  Noise reduction with NeatImage.