230820 - C63 "Helix" nebula
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click image to enlarge
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ASTRO:
type=Planetary nebula (pre-supernova) mag=7.6 const=Aquarius dist=700 ly size=5 ly IMAGE: location=EB Driveway moon=0.4% (new) BrtlCls=4 exposure=CMOS OSC; 26x360s (2.6h), G100 EQUIPMENT: camera=ZWO ASI2600MC-Pro optics=ES102 w1.73x EP (afocal mode), F(eff.)=1238mm, f/12.1 (eff.) filter=Optolong L-eXtreme DNB mount=Celestron AVX guiding=Orion 60x240mm, ZWO ASi224MC SOFTWARE: acquisition=Stellarium, APT, PHD2 processing=PixInsight, RCAstro, PhotoshopCC, Lumenzia, APF-R, LrC |
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A mere 700 light years from Earth toward the constellation Aquarius, a sun-like star is dying. The dying star's last few thousand years have produced the Helix Nebula (also known as NGC 7293), and is a well studied nearby example of a Planetary Nebula, typical of this final phase of stellar evolution. Combining narrow band image data from emission lines of hydrogen atoms in red and oxygen atoms in blue-green hues, it shows tantalizing details of the Helix, including its bright inner region about 3 light-years across. The white dot at the Helix's center is this planetary nebula's hot, central star. A simple looking nebula at first glance, the Helix is now understood to have a surprisingly complex geometry.
Discovered by Karl Ludwig Harding, probably before 1824, the Helix is one of the closest of all the bright planetary nebulae to the Earth. The distance, measured by the ESA Gaia mission, is appx 655 (rounded to appx 700) light-years. It is sometimes referred to as the "Eye of God" in pop culture, as well as the "Eye of Sauron".
The Helix Nebula is a prime example of a planetary nebula (not to be confused with our solar system's planets), formed by an intermediate to low-mass star shedding its outer corona gaseous layer near the end of its life, and prior to exploding as a super nova. Because this particular Planetary Nebula is positioned "face-on" from our perspective, patterns in the gas clouds from the star in the surrounding space appear as if we are looking down inside a helix structure. Scientists know by studying hundreds of similar objects, the remnant central star core is destined to become a white dwarf star, a largely white-hot piece of iron no longer able to sustain the process of atomic fusion. But even though it is nearing the end of its life, the observed glow of the central star is still so energetic that it causes the previously expelled gases to glow brightly.
How did a star create the Helix? The shapes of planetary nebula like the Helix are important because they hold clues to how stars like our Sun end their lives. Observations by the orbiting Hubble Space Telescope and the 4-meter Blanco Telescope in Chile, however, have shown the Helix is not really a simple helical formation. Rather, it incorporates two nearly perpendicular disks as well as arcs, shock waves, and other features not yet well understood. Even so, many strikingly geometric symmetries remain. How a single Sun-like star created such beautiful yet geometric complexity is a topic of research. The outer ring of the Helix spans about 5 light-years. The nebula's age is estimated to be appx 10,600 years old, based on the ratio of its size to its measured expansion rate of appx 32 km/sec.
Expansion of the outer nebula ring structure is estimated to have occurred in the last 6,600 years, and the inner disk within the last 12,000 years. Scientists have determined using a technique called Spectroscopy that the outer ring is expanding at a rate of about 40 km/s, and the inner ring about 32 km/s.
The Helix Nebula was the first planetary nebula discovered to contain cometary knots. Readily visible in this image, they represent a photographic detail that is highly sought after by amateur astrophotgraphers to resolve in their images. The nebula's main ring contains these knots of nebulosity, which have now been detected in many other planetary nebulae across the Milky Way galaxy. These knots are radially symmetric and are described as "cometary" due to the appearance of each being centered on a core of neutral molecular gas, containing a brightly photoionized nodule facing towards the central star, and with a tail streaming away toward the outer reaches of the nebula. This phenomena somewhat resembles, but is specifically distinct from actual comets. Excluding the tail, each knot is approximately the size of our Solar system. There are about 40,000 cometary knots in the Helix Nebula. Collectively, they make up what resembles the iris of a human eye.
Discovered by Karl Ludwig Harding, probably before 1824, the Helix is one of the closest of all the bright planetary nebulae to the Earth. The distance, measured by the ESA Gaia mission, is appx 655 (rounded to appx 700) light-years. It is sometimes referred to as the "Eye of God" in pop culture, as well as the "Eye of Sauron".
The Helix Nebula is a prime example of a planetary nebula (not to be confused with our solar system's planets), formed by an intermediate to low-mass star shedding its outer corona gaseous layer near the end of its life, and prior to exploding as a super nova. Because this particular Planetary Nebula is positioned "face-on" from our perspective, patterns in the gas clouds from the star in the surrounding space appear as if we are looking down inside a helix structure. Scientists know by studying hundreds of similar objects, the remnant central star core is destined to become a white dwarf star, a largely white-hot piece of iron no longer able to sustain the process of atomic fusion. But even though it is nearing the end of its life, the observed glow of the central star is still so energetic that it causes the previously expelled gases to glow brightly.
How did a star create the Helix? The shapes of planetary nebula like the Helix are important because they hold clues to how stars like our Sun end their lives. Observations by the orbiting Hubble Space Telescope and the 4-meter Blanco Telescope in Chile, however, have shown the Helix is not really a simple helical formation. Rather, it incorporates two nearly perpendicular disks as well as arcs, shock waves, and other features not yet well understood. Even so, many strikingly geometric symmetries remain. How a single Sun-like star created such beautiful yet geometric complexity is a topic of research. The outer ring of the Helix spans about 5 light-years. The nebula's age is estimated to be appx 10,600 years old, based on the ratio of its size to its measured expansion rate of appx 32 km/sec.
Expansion of the outer nebula ring structure is estimated to have occurred in the last 6,600 years, and the inner disk within the last 12,000 years. Scientists have determined using a technique called Spectroscopy that the outer ring is expanding at a rate of about 40 km/s, and the inner ring about 32 km/s.
The Helix Nebula was the first planetary nebula discovered to contain cometary knots. Readily visible in this image, they represent a photographic detail that is highly sought after by amateur astrophotgraphers to resolve in their images. The nebula's main ring contains these knots of nebulosity, which have now been detected in many other planetary nebulae across the Milky Way galaxy. These knots are radially symmetric and are described as "cometary" due to the appearance of each being centered on a core of neutral molecular gas, containing a brightly photoionized nodule facing towards the central star, and with a tail streaming away toward the outer reaches of the nebula. This phenomena somewhat resembles, but is specifically distinct from actual comets. Excluding the tail, each knot is approximately the size of our Solar system. There are about 40,000 cometary knots in the Helix Nebula. Collectively, they make up what resembles the iris of a human eye.