NGC 7027

NGC 7027 is a very young and dense planetary nebula[5] located around 3,000 light-years (920 parsecs) from Earth in the constellation Cygnus. Discovered in 1878 by Édouard Stephan using the 800 mm (31 in) reflector at Marseille Observatory,[4] it is one of the smallest planetary nebulae and by far the most extensively studied.[4]

NGC 7027
Emission nebula
Planetary nebula
Hubble image of NGC 7027
Observation data: J2000 epoch
Right ascension21h 7m 1.7s[1]
Declination+42° 14′ 11″[1]
Distance3,000[2] ly
Apparent magnitude (V)10[3]
Apparent dimensions (V)16" × 12"
ConstellationCygnus
Physical characteristics
Dimensions0.2 × 0.1 ly[4]
Notable featuresYoung (600 years) and unusually massive (3–4 M☉)
DesignationsGummy Bear Nebula

Overview

NGC 7027 is one of the visually brightest planetary nebulae.[6] It is about 600 years old.[7]

It is unusually small, measuring only 0.2 by 0.1 light-years, whereas the typical size for a planetary nebula is 1 light-year.[4] It has a very complex shape, consisting of an elliptical region of ionized gas[8] within a massive neutral cloud.[9] The inner structure is surrounded by a translucent shroud of gas and dust.[10] The nebula is shaped like a prolate ellipsoidal shell and contains a photodissociation region shaped like a "clover leaf".[8] NGC 7027 is expanding at 17 kilometers per second (11 mi/s).[9] The central regions of NGC 7027 have been found to emit X-rays, indicating very high temperatures.[8] Surrounding the ellipsoidal nebula are a series of faint, blue concentric shells.[11]

It is possible that the central white dwarf of NGC 7027 has an accretion disk that acts as a source of high temperatures.[12] The white dwarf is believed to have a mass approximately 0.7 times the mass of the Sun and is radiating at 7,700 times the Sun's luminosity.[6] NGC 7027 is currently in a short phase of planetary nebula evolution in which molecules in its envelope are being dissociated into their component atoms, and the atoms are being ionized.[13]

The expanding halo of NGC 7027 has a mass of about three times the mass of the Sun, and is about 100 times more massive than the ionized central region. This mass loss in NGC 7027 provided important evidence that stars a few times more massive than the Sun can avoid being destroyed in supernova explosions.[4]

NGC 7027 has a rich and highly ionized spectrum caused by its hot central star.[5] The nebula is rich in carbon, and is a very interesting object for the study of carbon chemistry in dense molecular material exposed to strong ultraviolet radiation.[14] The spectrum of NGC 7027 contains fewer spectral lines from neutral molecules than is usual for planetary nebulae. This is due to the destruction of neutral molecules by intense UV radiation.[15] The nebula contains ions of extremely high ionization potential.[16] The helium hydride ion, thought to be the earliest molecule to have been formed in the Universe (about 100,000 years after the Big Bang), was detected in 2019 for the first time in space in NGC 7027.[17][18] There is also evidence for the presence of nanodiamond in NGC 7027.[19]

It has been photographed multiple times by the Hubble Space Telescope since its launch in 1990.[20][21] Prior to these observations, NGC 7027 was thought to be a proto-planetary nebula with the central star too cool to ionize any of the gas, but it is now known to be a planetary nebula in the earliest stage of its development.[4] The progenitor star is believed to have been about 3 to 4 times the mass of the Sun before the nebula was formed.[5]

In 1977 at Yerkes Observatory, a small Schmidt telescope was used to derive an accurate optical position for the planetary nebula NGC 7027 to allow comparison between photographs and radio maps of the object.[22]

In a 6" telescope at around 50× it appears as a relatively bright bluish star. It is best viewed with the highest magnification possible.[23]

See also

References
  1. "NASA/IPAC Extragalactic Database". Results for NGC 7027. Retrieved 2 April 2008.
  2. Latter, William B. (12 March 1998). "Staring into the Winds of Destruction: HST/NICMOS Images of the Planetary Nebula NGC 7027". SIRTF Science Center. Archived from the original on 7 September 2008. Retrieved 11 October 2008.
  3. "NGC 7027". SEDS NGC Database. Retrieved 15 October 2017.
  4. O'Meara, Stephen James (2007). "104: NGC 7027". Hidden Treasures. Cambridge University Press. pp. 514–516. ISBN 978-0-521-83704-0.
  5. Salas, J. Bernard; et al. (March 2001). "The ISO-SWS spectrum of planetary nebula NGC 7027" (PDF). Astronomy & Astrophysics. 367 (3): 949–958. Bibcode:2001A&A...367..949B. doi:10.1051/0004-6361:20000435.
  6. Kaler, James B. (2002). The 100 Greatest Stars. New York: Springer-Verlag. p. 133. ISBN 978-0-387-95436-3.
  7. Cox, P. (January 1997). "Planetary Nebulae". Astrophysics and Space Science. 255 (1–2): 489–497. Bibcode:1998Ap&SS.255..489C. doi:10.1023/A:1001511603093.
  8. Kastner, Joel H.; et al. (April 2001). "Discovery of Extended X-Ray Emission from the Planetary Nebula NGC 7027 by the Chandra X-Ray Observatory". The Astrophysical Journal. 550 (2): L189–L192. arXiv:astro-ph/0102468. Bibcode:2001ApJ...550L.189K. doi:10.1086/319651.
  9. Masson, C. R. (January 1989). "The structure of NGC 7027 and a determination of its distance by measurement of proper motions". The Astrophysical Journal. 336: 294–303. Bibcode:1989ApJ...336..294M. doi:10.1086/167011.
  10. "NGC 7027". NOAO. Retrieved 11 March 2010.
  11. "Hubble Telescope Photo Reveals Stellar Death Process". Hubblesite.org. 16 January 1996. Retrieved 11 March 2010.
  12. Gurzadi︠a︡n, Grigor Aramovich (1997). The physics and dynamics of planetary nebulae. Springer-Verlag. p. 464. ISBN 978-3-540-60965-0.
  13. "Hubble Captures the Shrouds of Dying Stars". Hubblesite.org. 19 March 1998. Retrieved 11 March 2010.
  14. Liu, X.-W.; et al. (October 1997). "An ISO Long Wavelength Spectrometer detection of CH in NGC 7027 and an HeH+ upper limit" (PDF). Monthly Notices of the Royal Astronomical Society. 290 (4): L71–L75. Bibcode:1997MNRAS.290L..71L. doi:10.1093/mnras/290.4.l71.
  15. Kwok, Sun & Sandford, Scott (2008). Organic Matter in Space. Cambridge University Press. p. 170. ISBN 978-0-521-88982-7.
  16. Gurzadi︠a︡n, Grigor Aramovich (1997). The physics and dynamics of planetary nebulae. Springer-Verlag. p. 45. ISBN 978-3-540-60965-0.
  17. Güsten, Rolf; et al. (April 2019). "Astrophysical detection of the helium hydride ion HeH+". Nature. 568 (7752): 357–359. arXiv:1904.09581. Bibcode:2019Natur.568..357G. doi:10.1038/s41586-019-1090-x. PMID 30996316.
  18. Fisher, Christine (17 April 2019). "NASA finally found evidence of the universe's earliest molecule – The elusive helium hydride was found 3,000 light-years away". Engadget. Retrieved 17 April 2018.
  19. Reddy, Francis (17 January 2006). "Seeing red with nanodiamonds". Astronomy.com. Retrieved 11 March 2010.
  20. "Planetary Nebula NGC 7027: A Sun-Like Star Burning Out". Hubblesite.org. 19 March 1998. Retrieved 30 May 2019.
  21. "NGC 7027". Hubble Legacy Archive. Retrieved 30 May 2019.
  22. Cudworth, K. M.; Oravecz, M. (June–July 1978). "Astrometry with a small Schmidt telescope: The position of NGC 7027". Astronomical Society of the Pacific. 90: 333–334. Bibcode:1978PASP...90..333C. doi:10.1086/130337.
  23. "NGC 7027 – Gummy Bear Planetary Nebula". Stargazerslounge.com. 26 September 2016.


This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.