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The Helix Nebula (also known as NGC 7293 or Caldwell 63) is a planetary nebula (PN) located in the constellation Aquarius. Discovered by Karl Ludwig Harding , most likely before 1824, this object is one of the closest of all the bright planetary nebulae to Earth. [ 3 ]
The Helix Nebula has a cometary Oort cloud. Comets, or their precursors, formed in the outer Solar System, possibly millions of years before planet formation. [38] How and when comets formed is debated, with distinct implications for Solar System formation, dynamics, and geology.
Cometary knots in the Helix Nebula. Cometary knots, also referred as globules, are structures observed in several nearby planetary nebulae (PNe), including the Helix Nebula (NGC 7293), the Ring Nebula (NGC 6720), the Dumbbell Nebula (NGC 6853), the Eskimo Nebula (NGC 2392), and the Retina Nebula (IC 4406).
NGC 2685 (also known as the Helix Galaxy) is a lenticular and polar ring Seyfert Type 2 galaxy in the constellation Ursa Major. Its velocity with respect to the cosmic microwave background is 1003 ± 9 km/s, which corresponds to a Hubble distance of 48.2 ± 3.4 Mly (14.79 ± 1.05 Mpc ). [ 1 ]
Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded. According to the nebular theory, stars form in massive and dense clouds of molecular hydrogen—giant molecular clouds (GMC). These clouds are gravitationally unstable, and matter coalesces within them to ...
A nebula that is visible to the human eye from Earth would appear larger, but no brighter, from close by. [6] The Orion Nebula, the brightest nebula in the sky and occupying an area twice the angular diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers. [7]
English: The Helix Nebula: a Gaseous Envelope Expelled By a Dying Star About the Object. Object Name: Helix Nebula, NGC 7293 or "The Eye of God" Object Description: Planetary Nebula; Position (J2000): R.A. 22h 29m 48.20s; Dec. -20° 49' 26.0" Constellation: Aquarius; Distance: About 690 light-years (213 parsecs)
Enormous Lyα nebula (ELAN) Four quasars embedded in the nebula. Likely progenitor of a massive galaxy cluster at z=2.05. Fabulous Nebula [13] 969,000 ly (297,000 pc) [14] Enormous Lyα nebula (ELAN) Also called SDSS J1020+1040 nebula, after the central quasar (aka 4C 10.29), located at z=3.164. Inspiraling material. [14]