Hubble image of NGC 7027
|Observation data: J2000 epoch|
|Right ascension||21h 7m 1.7s|
|Declination||+42° 14′ 11″|
|Apparent magnitude (V)||10|
|Apparent dimensions (V)||16" × 12"|
|Dimensions||0.2 × 0.1 ly|
|Notable features||Young (600 years) and unusually massive (3–4 M☉)|
|Designations||Gummy Bear Nebula|
NGC 7027 is a very young and dense planetary nebula 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, it is one of the smallest planetary nebulae and by far the most extensively studied. Helium hydride was detected in the nebula in 2019, the first discovery of that molecule in space.
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. It has a very complex shape, consisting of an elliptical region of ionized gas within a massive neutral cloud. The inner structure is surrounded by a translucent shroud of gas and dust. The nebula is shaped like a prolate ellipsoidal shell and contains a photodissociation region shaped like a "clover leaf". NGC 7027 is expanding at 17 kilometers per second (11 mi/s). The central regions of NGC 7027 have been found to emit X-rays, indicating very high temperatures. Surrounding the ellipsoidal nebula are a series of faint, blue concentric shells.
It is possible that the central white dwarf of NGC 7027 has an accretion disk that acts as a source of high temperatures. 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. 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.
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.
NGC 7027 has a rich and highly ionized spectrum caused by its hot central star. 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. 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. The nebula contains ions of extremely high ionization potential. 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 for the first time in space in NGC 7027. There is also evidence for the presence of nanodiamond in NGC 7027.
It was photographed by the Hubble Space Telescope in 1996[disputed ]. 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. The progenitor star is believed to have been about 3 to 4 times the mass of the Sun before the nebula has formed.
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.
In a 6" telescope at around 50× it appears as a relatively bright bluish star. At magnifications around 180× a vaguely ursine shape has led to the epithet of the "Gummy Bear Nebula". It is best viewed with the highest magnification possible.
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- 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.
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- "NGC 7027 - Gummy Bear Planetary Nebula".
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