This confusing name arose because many of them show small bright discs when observed visually and resemble the outer planets in the Solar System, such as Uranus and Neptune. *Planetary nebulae have nothing to do with planets. Please note that this text was modified on 18 January 2012 to correct some minor errors. It is currently unclear how the cometary knots may have originated. The molecules in them are able to survive the high-energy radiation that emanates from the dying star precisely because they clump into these knots, which in turn are shielded by dust and molecular gas. The material clumps into filaments that radiate out from the centre and the whole view resembles a celestial firework display.Įven though they look tiny, these strands of molecular hydrogen, known as cometary knots, are about the size of our Solar System. The infrared light picks out how the cooler, molecular gas is organised. The powerful vision of ESO's VISTA telescope also reveals fine structure in the nebula's rings. The 4.1-metre telescope is also able to detect an impressive array of background stars and galaxies. While hard to see visually, the glow from the thinly spread gas is easily captured by VISTA's special detectors, which are very sensitive to infrared light. This is particularly clear in this infrared view since red molecular gas can be seen across much of the image. However, material from the nebula spreads out from the star to at least four light-years. The main ring of the Helix is about two light-years across, roughly half the distance between the Sun and the nearest star. The nebula itself is a complex object composed of dust, ionised material as well as molecular gas, arrayed in a beautiful and intricate flower-like pattern and glowing in the fierce glare of ultraviolet light from the central hot star. It is evolving to become a white dwarf star and appears as the tiny blue dot seen at the centre of the image. Unable to hold onto its outer layers, the star slowly shed shells of gas that became the nebula. ![]() This strange object formed when a star like the Sun was in the final stages of its life. It lies in the constellation of Aquarius (The Water Bearer), about 700 light-years away from Earth. Values of He/H and N/O, and a solar level of C/O are consistent with a 6.The Helix Nebula is one of the closest and most remarkable examples of a planetary nebula*. The central star properties, the super-solar The S/O ratio which we derive is anomalously low such values are found in onlyĪ few other planetary nebulae. Our carbonĪbundance measurements represent the first of their kind for the Helix Nebula. Measurements indicate the following values: He/H=0.12 (+/-0.017), ![]() Star effective temperature and luminosity of 120,000K and 100L_sun, and weĮstimate a lower limit to the nebular mass to be 0.30M_sun. The outer visible ring structure is of lower ionization and temperatureĪnd is brighter because of a thickening in the disk. Whose thickness is roughly one-third its diameter with an inner regionĬontaining hot, highly ionized gas which is generally invisible in narrow-band Nebula support the recent claim that the Helix is actually a flattened disk Detailed models of the observable ionized ![]() Of NGC 7293, the Helix Nebula, a nearby, photogenic planetary nebula of largeĭiameter and low surface brightness. With UV and optical spectrophotometry measurements from 1200 to 9600 Angstroms Kwitter (Williams College), R.J Dufour (Rice U.) Download PDF Abstract: We present new narrow-band filter imagery in H-alpha and 6584 along
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