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Date: August. 28, 2025 & - Dark Sky Observatory, Ft. Davis, TX Click on the image below to view at higher resolution. |
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NGC 7293, more commonly known as the Helix Nebula, is one of the closest[1] and most studied planetary nebulae, lying about 655 light-years away[5] in the constellation Aquarius[5]. Planetary nebulae represent the late evolutionary stage of sun-like stars, formed when the aging star expels its outer layers of gas. At the nebula's core lies the remnant of the progenitor star, now a white dwarf. Radiation from this extremely hot white dwarf star continues to energize the expanding gases making them glow in their characteristic colors. Discovered by the German astronomer Karl Ludwig Harding, likely before 1824[2,5], the Helix resembles the more distant Ring Nebula (M57) but reveals a far more intricate structure. High-resolution studies using the Hubble Space Telescope and the Cerro Tololo Inter-American Observatory show that NGC 7293 is composed of at least two nearly perpendicular rings of ionized gas[3]. The origin of this unusual geometry remains uncertain, though one hypothesis suggests that an undetected companion star may have influenced the ejected material[3]. Surrounding the brighter nebula is an extended faint halo[4] of gas, most probably expelled in earlier stages of the progenitor star's stellar evolution. This image is a bi-color narrowband composite created by mapping hydrogen-alpha (Ha) emission to red and doubly ionized oxygen (OIII) emission to both green and blue. Red, Green, and Blue filtered star data was then layered into the image to provide a natural stellar background. This technique, often called HOO mapping, highlights the ionization structure of the nebula while preserving the realistic star field colors, making it a valuable approach on a scientific level as well as aesthetic imaging.
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