By Dr. Ed Albin
Program Director, Space Studies, American Military University
High above in the late summer evening sky is a beautiful little cloud of dust and gas, affectionately called by astronomers the Apple Core Nebula. It is a favorite viewing target for a telescope’s camera and is this week’s featured celestial object.
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Clearly having the appearance of a well-eaten apple, our image was taken on the evening of September 10 from the APUS observatory.
Found in the indistinct constellation of Vulpecula or the “little fox,” this striking object resides close to 1300 light years from Earth. It was discovered by the great French astronomer Charles Messier in 1764, who designated it as the 27th entry (M27) in his catalog of celestial objects.
M27 has the Distinction of Being the First So-Called Planetary Nebula Ever Discovered
Sometimes referred to as the Dumbbell Nebula because of its shape, M27 has the distinction of being the first so-called planetary nebula ever discovered. But the name is a misnomer since this type of object has nothing to do with planets other than a vague ghostly appearance to one. The great English astronomer William Herschel coined the term in the 1780s when he was surveying the skies for faint objects with his telescope.
A planetary nebula represents a site of stellar destruction, when an aged star has expended its fuel reserves and died. Such stars are not unlike our own Sun in mass and character, passing from existence in a relatively mild puff off its stellar atmosphere. When we look at the Apple Core Nebula, we are seeing a preview of the fate of our own star some five billion years into the future.
When a Star Grows Old, it Swells into What Astronomers Call a Red Giant
What makes these planetary nebulas so remarkable is not so much their stunning shroud of dust and gas, but the tiny object left behind which was once the core of a former shining star. When a star grows old, it swells into what astronomers call a red giant. These bloated suns perish in an implosion that produces a stellar corpse known as a white dwarf.
A dusty sphere of gas surrounds the stellar remnant and this is what we see in the case of the Apple Core Nebula. Its gaseous shell extends almost two light-years into interstellar space. Because they glow in the darkness of space, astronomers classify them as emission nebula, which are clouds of bright gas irradiated by the light of the central white-hot dwarf star.
Such planetary nebula are fleeting features — they only last about 10,000 years — when considered in the context of the long history of our galaxy. As the Apple Core Nebula fades into the inter-stellar vacuum of space, we can for now enjoy its exquisiteness through the cameras of our earth-bound telescopes.
About the Author
Dr. Ed Albin is an Associate Professor and Program Director of Space Studies in the School of STEM (Science, Technology, Engineering and Math) at American Military University. His academic credentials include a Ph.D. in Planetary Geology from the University of Georgia, an M.S. in Geology from Arizona State University and a B.S. in Earth Science from Columbus State University. Ed has also held positions as an assistant professor, a planetarium lecturer, a commercial helicopter pilot and a planetary geologist.