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For the gigantic nebula discovered in 2006 near the center of the Milky Way Galaxy, see Double Helix Nebula
Helix Nebula

Visible light image of the Helix Nebula, compiled from Hubble telescope and ground-based images in 2004. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply The Double Helix Nebula is a gaseous Nebula near the center of our galaxy. The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into
Observation data
(Epoch J2000)
Right ascension22h 29m 38. In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. Right ascension (abbrev RA; symbol α) is the Astronomical term for one of the two Coordinates of a point on the Celestial sphere 55s[1]
Declination-20° 50′ 13. In Astronomy, declination (abbrev dec or δ) is one of the two coordinates of the Equatorial coordinate system, the other being either 6″[1]
Distance680+150−80 ly (207+46−24 pc)[2]
Apparent magnitude (V)+13. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 5[1]
Apparent dimensions (V)25′[3]
ConstellationAquarius
Physical characteristics
Radius2. In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Aquarius ( Water -bearer or cup-bearer is the eleventh sign of the Zodiac, situated between Capricornus and Pisces. Remote Authentication Dial In User Service ( RADIUS) is a networking protocol that provides centralized access authorization and accounting management for people or computers 87 ly (0. 88 pc)[3]
Absolute magnitude (V)6. In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard 58[a]
Notable featuresOne of nearest PNs
Other designationsNGC 7293[1]
See also: Planetary nebula, Lists of nebulae
Infrared image of the Helix Nebula, taken by the Spitzer space telescope, 2007
Infrared image of the Helix Nebula, taken by the Spitzer space telescope, 2007

The Helix Nebula (also known as NGC 7293) is a planetary nebula (PN) about 650 light-years away in the constellation Aquarius. The New General Catalogue ( NGC) is the best-known catalogue of Deep sky objects in Amateur astronomy. A planetary nebula is an Emission nebula consisting of a glowing shell of Gas and plasma formed by certain types of Stars when they die The Spitzer Space Telescope (formerly the Space Infrared Telescope Facility, SIRTF) is an Infrared Space observatory. A planetary nebula is an Emission nebula consisting of a glowing shell of Gas and plasma formed by certain types of Stars when they die A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Aquarius ( Water -bearer or cup-bearer is the eleventh sign of the Zodiac, situated between Capricornus and Pisces. It is one of the closest planetary nebulae to Earth[4] and was discovered by Karl Ludwig Harding before 1824. A planetary nebula is an Emission nebula consisting of a glowing shell of Gas and plasma formed by certain types of Stars when they die EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 It has a very similar appearance to the Ring Nebula. The famously named " Ring Nebula " is located in the northern Constellation of Lyra, and also catalogued as Messier 57, M57 or It is also similar in size, age, and physical characteristics to the Dumbbell Nebula, with the significant difference in appearance being a consequence of the relative proximity and more nearly equatorial viewing angle of the Dumbbell. The Dumbbell Nebula (also known as Messier 27, M 27, or NGC 6853) is a Planetary nebula (PN in the Constellation Vulpecula [2] The Helix has often been referred to as the Eye of God on the Internet, since about 2003[5]. The Helix Nebula was also featured in the 2004 Battlestar Galactica TV series. Battlestar Galactica is an Emmy and Peabody Award -winning serial drama Television program created by Ronald D

Contents

General information

The Helix Nebula is an example of a planetary nebula created at the end of the life of a Sun-like star. A planetary nebula is an Emission nebula consisting of a glowing shell of Gas and plasma formed by certain types of Stars when they die The Sun (Sol is the Star at the center of the Solar System. The outer gases of the star expelled into space appear from our vantage point as if we are looking down a helix. Perspective, in context of vision and Visual perception, is the way in which objects appear to the Eye based on their spatial attributes or A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i The remnant central stellar core, destined to become a white dwarf star, glows in light so energetic that it causes the previously expelled gas to fluoresce. A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. Fluorescence is a Luminescence that is mostly found as an

Helix lies about 650 light-years away towards the constellation of Aquarius and spans about 2. Aquarius ( Water -bearer or cup-bearer is the eleventh sign of the Zodiac, situated between Capricornus and Pisces. 5 light-years. Recent pictures of Helix are a composite of newly released images from the ACS instrument on the Hubble Space Telescope and wide-angle images from the Mosaic Camera on the WIYN 0. The Advanced Camera for Surveys (ACS is a third generation axial instrument aboard the Hubble Space Telescope (HST The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into WIYN Consortium consists of the University of Wisconsin-Madison (W Indiana University (I Yale University (Y and the National Optical Astronomy 9 m Telescope at Kitt Peak National Observatory. The Kitt Peak National Observatory ( KPNO) is a United States astronomical Observatory located on a 2096 m (6880 ft peak of the

It is estimated to be 10,600+2,300−1,200 years old based upon an expansion rate of 31 km/s. [2]

Structure

The nebula is thought to be shaped like a prolate spheroid with a strong density concentration toward a filled disk of the equatorial plane. A prolate spheroid is a Spheroid in which the polar Diameter is longer than the Equatorial diameter The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the Its major axis is inclined about 21° to 37° from our vantage point. In Geometry, the semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae It is composed of an inner disc with a 8′ 19″ diameter (0. 52 pc) and outer torus with a 12′ 22″ diameter (0. 77 pc) and an outer-most ring with a 25′ diameter (1. 76 pc). The outer-most ring is flattened on one side due to its colliding with the ambient interstellar medium. The PN is estimated to have been expanding for 6,560 years for the inner disc and 12,100 years for the outer ring with expansion rates of 40 km/s and 32 km/s respectively.

Knots

The Helix Nebula was the first PN discovered to contain knots. The main ring contains knots of nebulosity which have now been detected in many near-by PNs. In the Helix, these knots are highly radially symmetric (from the central star) and "cometary", they contain bright cusps (local photoionization fronts) and tails which extend away from the star in the radial direction. Photoionisation is the physical process in which an incident Photon ejects one or more Electrons from an Atom, Ion or Molecule Not including the tails, they are (very approximately) the size of the Solar system. At the cusps the knots are optically thick to Lyc photons from the central star. Lyc photon or Ly continuum photon or Lyman continuum photon are a kind of Photon emitted from Stars. [2][3][6]

See also

Notes

  1. ^ 13. The New General Catalogue ( NGC) is the best-known catalogue of Deep sky objects in Amateur astronomy. The famously named " Ring Nebula " is located in the northern Constellation of Lyra, and also catalogued as Messier 57, M57 or 5 apparent magnitude - 5 * (log10(242 pc distance) - 1) = 6. 58 absolute magnitude

References

  1. ^ a b c d SIMBAD Astronomical Database. Results for Helix Nebula. Retrieved on 2006-12-07. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 43 BC - Marcus Tullius Cicero assassinated 1696 - Connecticut Route 108, one of the oldest highways
  2. ^ a b c d O'Dell, C. R. ; Balick, B. ; Hajian, A. R. ; Henney, W. J. ; Burkert, A. (2002). "Knots in Nearby Planetary Nebulae". The Astronomical Journal 123 (6): 3329-3347. doi:10.1086/340726. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  3. ^ a b c O'Dell, C. R. ; McCullough, Peter R. ; Meixner, Margaret (2004). "Unraveling the Helix Nebula: Its Structure and Knots". The Astronomical Journal 128 (5): 2339-2356. doi:10.1086/424621. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  4. ^ Hora, Joseph L. ; Latter, William B. ; Smith, Howard A. ; Marengo, Massimo (2006). "Infrared Observations of the Helix Planetary Nebula". The Astrophysical Journal 652 (1): 426-441. doi:10.1086/507944. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  5. ^ Urban Legends Reference Pages. The Eye of God. Retrieved on 2007-07-16. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 622 - The beginning of the Islamic calendar. 1054 - Three Roman legates fractured relations between the Western and
  6. ^ O'dell, C. R. ; Balick, B. ; Hajian, A. R. ; Henney, W. J. ; Burkert, A. (2003). "Knots in Planetary Nebulae". Winds, Bubbles, and Explosions: a conference to honor John Dyson, Pátzcuaro, Michoacán, México, September 9-13, 2002 (Eds. S. J. Arthur & W. J. Henney) Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias) (http://www.astroscu.unam.mx/~rmaa/) 15: 29-33.  

External links

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