Pear Tree Observatory

The constellation Cygnus (the Swan) has 5 bright stars that forms the shape of the bird in flight. The star at the intersection of the swan’s wings and body is named Sadr; the Arabic word for chest. The Bayer designation is Gamma Cygni (γ Cyg, γ Cygni). The constellation is bright and easy to identify in the Northern sky. What is not so easy to see is the very large emission nebula located near γ Cyg. Although γ Cyg lies near the center of the nebula, it is only a chance alignment. The star lies about 1,500 ly’s from Earth but the estimated distances to the nebula average about 3,000 ly’s.

By IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg) via Wikimedia Commons

(IC 1318)[C:60x60s]

Since γ Cyg is so bright, I positioned it out of the FOV to prevent it overwhelming the image. Also, this image is only a small part of the nebula since my telescopic field of view is much too small to view the entire object. The dark area that crosses the image is not a lack of stars but is instead a very dense part of the nebula which blocks the background light from reaching us.

Chart generated with Cartes du Ciel

Quite often, astronomers adopt a common name for a celestial object based on what it ‘looks’ like to them. Just as often it takes a very vivid imagination to see what the astronomer saw. Most of the common names were based on photography using fairly primitive cameras, equipment and techniques. Modern imagery taken with today’s CCD cameras and processed with computer software, look nothing like the common names associated with the celestial objects.

This is not one of those times.

This nebula quite obviously has a bubble blown in it. The star right of the bubble’s center and slightly above and right of the bright knot of gas is the guilty party. This young star has about 20 times the mass of the Sun and its energy output is several hundred thousand times that of our star. This is what is blowing the bubble in to the surrounding molecular cloud. The cloud of gas and dust is more dense on the right side of the bubble and thus is constraining the expansion more on that side.

Bubble Nebula (NGC 7635)[Ha:76x35s]

Chart generated with Cartes du Ciel

Some of the most photogenic objects in the universe are planetary nebulae. As a star runs low on the fuel it uses to power its fusion furnace, the star starts to shed the outer layers of its atmosphere. The gas is expelled into space at several kilometers per second. This will ultimately bare the star’s core. Now classified as a white dwarf the core is no longer creating energy. Once exposed, the core’s remaining heat energizes the surrounding expelled gas causing it to glow. It is these glowing shells of gas that we call planetary nebula. They come in all shapes and sizes. There are several theories accounting for the varied shapes. Some appear to be shaped by the original star’s magnetic fields and some appear to be shaped by companions to the original star (planets or secondary stars).

In a relatively short time (10,000 years or so) the dwindling ultraviolet output fails to energize the increasingly distant shells of gas. Eventually, the planetary nebula dissipates and the white dwarf remains alone and spends the rest of its existence slowly cooling, becoming less and less visible.

Known as the Dumbbell Nebula due to the brightest portion’s pinched shape, this planetary nebula is located in the northern constellation Vulpecula (The Little Fox) at an estimated distance of 1360 ly. It is the first planetary nebula discovered, being cataloged by Charles Messier in 1764. Viewed under dark skies, it is bright enough and large enough to be seen with binoculars. This image is sixty 60 second exposures through a Hydrogen Alpha filter.

M 27 (Dumbbell Nebula) [Ha:60x60s]