240709 - NGC 6559 "Chinese Dragon" nebula
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click image to enlarge
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ASTRO:
type=Emission / Reflection Nebula const=Sagittarius mag=(not published) dist~5000 ly size~75 ly IMAGE: location=EB Driveway BrtlCls=4 moon=15% WxCr exposure=CMOS OSC: 66x300s (5.5h), G100 EQUIPMENT: camera=ZWO ASI2600MC-Pro optics=ES102 wStellarview 1.0x flattener, F=714mm, f/7.0 filter=Optolong L-eXtreme Duo NB mount=Celestron AVX guiding=Orion 60x240mm, ZWO ASi224MC SOFTWARE: acquisition=Stellarium, APT, PHD2 processing=PixInsight (RCAstro) (SetiAstro), PhotoshopCC (Lumenzia) (APF-R), LrC |
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Slide your telescope just east of the Lagoon Nebula to find this alluring field of view in the rich star fields of the constellation Sagittarius toward the central core of the Milky Way galaxy. Of course, the nearby Lagoon nebula, known as M8, is the eighth object listed in Charles Messier's famous catalog of bright nebulae and star clusters. Close in the sky but slightly fainter than M8, the complex of nebulae that we see as NGC 6559 was not included in Messier's list; maybe because he could not detect it visually. The nebulae contain the obscuring dust, striking red emission and blue reflection nebula clouds of a star-forming region. Like M8, NGC 6559 is located about 5,000 light-years away along the edge of a large molecular cloud. At that distance, this telescopic view spans about 90 light-years.
As powerful, energetic light from near-by stars bombards interstellar hydrogen atoms, they absorb the photons of star-light, causing the atoms to become more excited and energetic. When enough light energy is absorbed, the protons and electrons within the atoms become so excited that they break apart, leaving the stripped nuclei of those atoms in a highly energetic, and excited state; they have become ionized.
This is not a natural state of equilibrium for Hydrogen atoms. The ions are seeking to recombine back together with any free electrons they might encounter. As they "find" those electrons and recombine, the atoms relax into a more natural and less energetic state of equilibrium; and in so doing, they release energy back into space in the form of photons of light. But light emitted in this way is not the same as that originally absorbed and causing their ionization. Rather, Hydrogen atoms emit light of very specific wavelengths (colors), including the red hue seen in the presented image. This dominant color is referred to as Hα ("Hydrogen-alpha"), indicating a very specific wavelength of red light.
This is the same process that takes place inside a fluorescent light tube as the phosphorus atoms in the inside coatings of the bulb’s glass become ionized by the electrical current passing through them, and then relaxing as they recombine with available electrons, emitting the light we see.
The soft red glow of fluorescent hydrogen is evidence that there are hot young stars associated with the dusty clouds of NGC 6559 that are fueling the emission process. But NGC 6559 is not just made out of hydrogen gas. While the gas in the nebulae clouds, mainly hydrogen, is an essential raw material for star formation, the clouds also contain solid particles of dust made of heavier elements, such as carbon, iron and silicon. When a region inside the nebula gathers enough matter (both gas and solid dust material), it starts to coalesce (gather together) into 'clumps'. As they continue to gather more and more matter, those clumps grow into larger globules. When large enough, a globule will reach a critical point of mass where it collapses under its own gravity. As the matter collapses, pressures rise and heat begins to build. When there is enough gravitational pressure and heat, the mass will ignite into a new star.
The first stars formed by this process tend to be the largest and most massive; and, they will emit fierce stellar winds that erode, fragment, and sculpt their birthplace nebula clouds. The very bright, red arc of gas seen in the foreground of the accompanying image seems to shield several hot stars beneath it. In reality, this is a bow-shock wave, likely the result of the powerful stellar winds from those stars pushing the gas & dust of the nebula into the shape we see.
After tens of millions of years, the gas and dust will get completely consumed into the stars, and all that will remain is a naked open cluster of bright shining stars, free to roam across the galaxy along with billions of their cousins.
The bright stars around the nebula illuminate tiny solid dust particles, producing the blue reflection nebula we see near the brightest stars. The dust is also evident in silhouette, both as sinuous dark lanes winding through the luminous gas (known as Barnard 303, or B303) and as dark patches and filaments. These absorption nebulae are mostly dust clouds consisting of the heavier elements outlined above. They obscure parts of the visible red emission nebula. The dark structure resembles a Chinese Dragon; hence, the reason for the common name. The cooler and heavier dust absorbs background radiation from the surrounding ionized hydrogen gas. The intricate details and wispy structure in the dark cloud is determined by turbulence and flow dynamics influenced by variables such as nearby star radiation and motions of other nearby gas and dust. These kinds of clouds illustrate how past generations of stars are dispersing heavier elements into our galaxy, material that will eventually seed future generations of stars, and possibly protoplanetary disks and planetary systems.
As powerful, energetic light from near-by stars bombards interstellar hydrogen atoms, they absorb the photons of star-light, causing the atoms to become more excited and energetic. When enough light energy is absorbed, the protons and electrons within the atoms become so excited that they break apart, leaving the stripped nuclei of those atoms in a highly energetic, and excited state; they have become ionized.
This is not a natural state of equilibrium for Hydrogen atoms. The ions are seeking to recombine back together with any free electrons they might encounter. As they "find" those electrons and recombine, the atoms relax into a more natural and less energetic state of equilibrium; and in so doing, they release energy back into space in the form of photons of light. But light emitted in this way is not the same as that originally absorbed and causing their ionization. Rather, Hydrogen atoms emit light of very specific wavelengths (colors), including the red hue seen in the presented image. This dominant color is referred to as Hα ("Hydrogen-alpha"), indicating a very specific wavelength of red light.
This is the same process that takes place inside a fluorescent light tube as the phosphorus atoms in the inside coatings of the bulb’s glass become ionized by the electrical current passing through them, and then relaxing as they recombine with available electrons, emitting the light we see.
The soft red glow of fluorescent hydrogen is evidence that there are hot young stars associated with the dusty clouds of NGC 6559 that are fueling the emission process. But NGC 6559 is not just made out of hydrogen gas. While the gas in the nebulae clouds, mainly hydrogen, is an essential raw material for star formation, the clouds also contain solid particles of dust made of heavier elements, such as carbon, iron and silicon. When a region inside the nebula gathers enough matter (both gas and solid dust material), it starts to coalesce (gather together) into 'clumps'. As they continue to gather more and more matter, those clumps grow into larger globules. When large enough, a globule will reach a critical point of mass where it collapses under its own gravity. As the matter collapses, pressures rise and heat begins to build. When there is enough gravitational pressure and heat, the mass will ignite into a new star.
The first stars formed by this process tend to be the largest and most massive; and, they will emit fierce stellar winds that erode, fragment, and sculpt their birthplace nebula clouds. The very bright, red arc of gas seen in the foreground of the accompanying image seems to shield several hot stars beneath it. In reality, this is a bow-shock wave, likely the result of the powerful stellar winds from those stars pushing the gas & dust of the nebula into the shape we see.
After tens of millions of years, the gas and dust will get completely consumed into the stars, and all that will remain is a naked open cluster of bright shining stars, free to roam across the galaxy along with billions of their cousins.
The bright stars around the nebula illuminate tiny solid dust particles, producing the blue reflection nebula we see near the brightest stars. The dust is also evident in silhouette, both as sinuous dark lanes winding through the luminous gas (known as Barnard 303, or B303) and as dark patches and filaments. These absorption nebulae are mostly dust clouds consisting of the heavier elements outlined above. They obscure parts of the visible red emission nebula. The dark structure resembles a Chinese Dragon; hence, the reason for the common name. The cooler and heavier dust absorbs background radiation from the surrounding ionized hydrogen gas. The intricate details and wispy structure in the dark cloud is determined by turbulence and flow dynamics influenced by variables such as nearby star radiation and motions of other nearby gas and dust. These kinds of clouds illustrate how past generations of stars are dispersing heavier elements into our galaxy, material that will eventually seed future generations of stars, and possibly protoplanetary disks and planetary systems.