Celestial hemisphere:  Southern  ·  Constellation: Aquarius (Aqr)  ·  Contains:  Helix nebula  ·  NGC 7293
NGC 7293: A Relatively Deep View, Fernando
NGC 7293: A Relatively Deep View
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NGC 7293: A Relatively Deep View

NGC 7293: A Relatively Deep View, Fernando
NGC 7293: A Relatively Deep View
Powered byPixInsight

NGC 7293: A Relatively Deep View

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Description

NGC 7293 aslso known as The Helix Nebula is a 10 thousand years old planetary nebula of about 5.75 light-years across, located roughly 700 light-years away from Earth in the constellation of Aquarius. It is one of the closest to the Earth of all the bright planetary nebulae.



When a star with a mass up to eight times that of the Sun runs out of fuel at the end of its life, it blows off its outer shells and begins to lose mass. This allows the hot, inner core of the star (collapsing from a red giant to a white dwarf) to radiate strongly, causing the outward-moving cocoon of gas to glow brightly. They are called “planetary” nebulae because early observers thought they looked like planets.

From our sight of view, NGC 7293 appears as if we are looking down a helix structure, hence its name. However, the nebula is shaped like a prolate spheroid with the outer-most ring flattened on one side due to its colliding with the interstellar medium.



More than 20,000 tadpole-like objects are found within the nebula, dubbed “cometary knots” because their glowing heads and gossamer tails resemble comets. Each gaseous head is at least twice the size of our Solar System; each tail stretches 100 billion miles (160 billion kilometers), about 1,000 times the Earth’s distance to the Sun.



The most visible gaseous fragments are embedded along the inner rim of the nebula, trillions of miles from the central star, which is a small, super-hot white dwarf called WD 2226-210. The comet-like tails that are pointing back toward the central star, form a radial pattern around the star like the spokes on a wagon wheel.



These gaseous knots are probably the results of a collision between gases. The doomed star spews the hot gas from its surface, which collides with the cooler gas that it had ejected 10,000 years before. The crash fragments the smooth cloud surrounding the star into smaller, denser finger-like droplets, like dripping paint. Eventually, the gaseous knots will dissipate into the cold blackness of interstellar space.

It can be noted a bow shaped feature in the outer halo of NGC 7293. It has been found this bow shaped is a real bow-shock caused by the motion of NGC 7293 as it ploughs through this medium. The proper motion of the central star also points towards this halo feature which substantiates this interpretation of its origin.

It also has been found the feature is indeed a collimated outflow, as suggested by its morphology, at around 300 km/s with turbulent widths of around 50 km/s.

Some handbook data:

Visual Magnitude 7.3

Angular Size core: 16'; halo: 28'

Linear Diameter 2.5 light-years

Distance ~650 light-years

Position

R.A. 22h 29m 38.6s;

Dec. -20° 50' 13.6"

Image Details:

Ha: 26 x 20min

O3: 26 x 20min

Telescope: Skywatcher Esprit 120mm f/7

CCD: ST-8300M

CCD Guiding: Lodestar

Capture and guiding software: MaxIm DL

Mount: EQ-6 Pro

Processing: PixInsight

Bias, Darks and Flats applyed



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NGC 7293: A Relatively Deep View, Fernando