Details: Located between 7,000 and 11,000 light years away, the Bubble Nebula is sometimes misidentified as a planetary nebula, because it appears similar to other planetaries such as M57, the Ring Nebula , the where an old dying star expels vast amounts of material into interstellar space. The Bubble, in contrast, contains not an old dying star, but a very young, hot, massive star. The young, hot star creates its own stellar wind that presses on the surrounding molecular cloud to form an enormous bubble in space. The star is about 44 times the mass of our own sun and appears very much off center within the bubble. This asymmetry is a result of different densities of the surrounding molecular cloud. Where the cloud has greater density (bottom and left), the bubble remains closer to the central star. Where the surrounding cloud has lower density (top and right), the bubble presses further into space.

The Bubble Nebula’s central star, cataloged as BD+602522 or SAO 20575, is an O-type star, blue-white in color, and burns a million times brighter than our own sun. At about 30,000 kelvin and nearly 54,000°F, it produces powerful gaseous outflows forming a stellar wind that travels at more than 4 million miles an hour through space, approaching 1% the speed of light! This star is so massive, so hot, and so bright, that it burns its nuclear fuel very quickly. In only 10-20 million years, a blink of an eye in astronomical time, the star will consume all its energy and then explode as a supernova, thereby destroying the bubble, and perhaps creating an equally interesting vista in the night sky.

While not the Pillars of Creation known from the famous Hubble Telescope image of M16, the Eagle Nebula , the Bubble Nebula does, indeed, have its own pillars similarly formed that may one day collapse to form small stars. Unfortunately, the pending supernova in 10-20 million years, leave little chance that these next generation stars will survive to harbor planets or even life! The Bubble Nebula also finds itself visually close to the open star cluster M52. M52 is an easy target for small telescopes. While M52 and the Bubble are not physically associated with each other, amateur astronomers often use M52 as a jumping point to find and view the Bubble Nebula.

Instinctively one might think of the Bubble Nebula as a reflection nebula where the central star’s light illuminates the gases of the bubble. However, in this case it is an emission nebula, because the central star not only lights up, but energizes the material it encounters, causing it to emit its own light.

Annotations. In the image above, hover a mouse or curser over the image to show annotations of NGC 7635, with several enlarged insets identifying interesting features! Starting at the left is an enlarged inset of the shock wave formed when the interstellar winds encounter more dense gases. The bottom inset shows the pillars of the bubble, similar to the “Pillars of Creation” mentioned above. The right inset shows a close up of the O-type central star, where fine loops of gas are clearly visible close to the star itself. Note also the bright 6.9 magnitude bluish white central star in the upper center of the image. Visually, this star is only half as bright as the faintest naked-eye star at a dark site.

Below Images: In the first image below, is the same image as above, but processed to remove all stars, except for the central star. This is what the view would appear like if no stars existed along our line of sight. Using a mouse to hover over the image brings all the stars back. The second image below shows an enlarged and cropped version of the Bubble Nebula; this time hovering a mouse makes the stars disappear. The next image below is the same data but using old generation 2 processing techniques versus today’s newer generation 4. Hovering the mouse over this image reveals a direct comparison of old and new images. Note how tighter the stars are and how the nebula is more visible with more detail than before. The last image below is taken by the old Celestron 11 telescope and 3 megapixel camera showing a long evolution of both equipement and processing!

Object Statistics: Constellation: Cassiopeia, Right Ascension: 23h 20m 45s, Declination: +61° 12' 42”, Magnitude: 10.0, Size: 15’ x 8', Distance 7000 - 11000 light-years, Size of Bubble 6 - 10 light-years.

The Bubble Nebula is a beautiful example of gas being expelled into space by a giant  star (center) about 40 times the mass of our sun.  The bubble is not uniform, likely due to its encounter with existing gas and dust of differing density.  The gas is expanding at 4 million miles per hour and is about 4 light years (24 trillion miles) across.  The Bubble Nebula is in the constellation Cassiopeia NGC 7635 and has the following statistics:  RA: 23h 20m 40.0s, Dec: +61° 12' 00", Size: 16.0'x6.0', Class: E.