This object is the Bubble Nebula, located about 7,000 light years away in the constellation of Cassiopeia at a declination of +61 degrees. The bubble diameter is 7 light years across.

The bubble is caused by a stellar wind emitted from the source star, which is the brightest star inside of the bubble (shown on the mouseover). This star is a Wolf-Rayet star, which is an O-type (hot and blue-white) star that is nearing supernova stage. These stars expel a significant amount of mass in this stage, resulting in the expanding gas bubble which is contained by the molecular cloud.

The surrounding cloud has been shaped by the gas velocity into orangish dust pillars which all point back to the source star. The pillars are similar to the iconic columns in the “Pillars of Creation” Eagle Nebula. As seen with the structures in the Eagle Nebula, the Bubble Nebula pillars are being illuminated by the strong ultraviolet radiation from the brilliant star inside the bubble. A bright pillar, located behind the bubble, can be seen shining through the bubble just right of the source star. Cometary knots are seen throughout the image at the tips of the pillars.

Note the shape of the bubble, which is not quite symmetric. The bubble has a point towards the right side. This asymmetry is likely due to polar directional outflow from the star, but could also be due to differences in the density of the surrounding gaseous material. Looking closely, you can see the faint outline of an even larger bubble which is over twice as large as the main bubble. The larger, fainter bubble also has a bit of a point on the right side, which coincides with the brightest foreground star in the image. This larger bubble was likely formed by earlier gas releases from the source star. Hints of even larger bubbles, in the form of faint arcing wave fronts, can also be seen in the image.

I like the 3-D look of the bubble, especially how the curved outer surface is highlighted by white reflected starlight. This is seen most brightly at the top left quadrant of the bubble. I also like how the bubble seems to serve as a type of magnifying glass on the background immediately behind it.

I have attached a comparison of this image with the Hubble image.