Helix Nebula: Definition, Distance, Comparison, Formation, Structure

Helix Nebula, catalogued as NGC 7293 and Caldwell 63, is a planetary nebula embedded in the Milky Way and ranks among the closest such objects to Earth.  Distance estimates converge near 655±13 light-years, with the most precise value standing at 694.7 light-years, while a generous radius of 2.87 light-years frames its delicate, expanding shell. Molded like a cosmic eye, the nebula mirrors the structures of Ring, Dumbbell and Cat’s Eye Nebulae, offering a nearby laboratory for studying late-stage stellar evolution.

What is the Helix Nebula?

The Helix Nebula is one of the closest bright planetary nebulae to Earth, located in the constellation Aquarius and known as NGC 7293 or Caldwell 63. It is referred to as the “Eye of God” or “Eye of Sauron” and has size, age, and physical characteristics similar to the Dumbbell Nebula.

The Helix Nebula is a typical example of a planetary nebula, a thinly spread cloud of gas expelled by an intermediate to low mass star. Thought to be molded like a prolate spheroid with its major axis inclined 21° to 37° from our vantage point, it subtends an angle of about 20 minutes of arc in the constellation Aquarius. Discovered in the early nineteenth century by Karl Ludwig Harding, it was the first planetary nebula found to contain cometary knots.

Surrounding a hot central star, a fast wind rams into the previously ejected outer layers and sculpts the graceful shell-like filamentary structures that give it the appearance of a fine web of bicycle-spoke features. Sometimes nicknamed the Eye of God or the Eye of Sauron, the nebula glows in radiant colors from ultraviolet to infrared and remains translucent enough for background stars to be visible through the cosmic cloud.

How far away is the Helix Nebula from Earth?

The Helix Nebula lies about 650 light-years away from Earth, a distance refined by the Gaia mission to 655 ± 13 light-years. This measurement places the planetary nebula among the closest of its kind, a mere 200 ± 1 pc from the Sun.

How to find Helix Nebula?

To find Helix Nebula follow the instructions given below.

• Find Helix Nebula just below main star pattern of constellation Aquarius
• Extend imaginary line between Sadalmelik and Ancha beyond Ancha to find the Helix Nebula
• Discover Helix Nebula found in Aquarius constellation
• Search low in autumn sky from Northern Hemisphere for Helix Nebula
• Use space telescope to observe Helix Nebula
• Detect Helix Nebula faintly glowing one-third between Upsilon and 47 Aquarii
• Spot Helix Nebula near center of triangle formed by Fomalhaut Delta Aquarii Delta Capricorni
• Utilize Hubble Space Telescope for Helix Nebula images
• Consult star map for location of Helix Nebula from latitude in August
• View Helix Nebula best in early spring from Southern Hemisphere
• Notice Helix Nebula doesn’t reach 30 degrees over horizon from 43 degrees north
• Track NGC 7293 rising at azimuth 110.7° at 19:41
• Note Helix Nebula Declination −20° 50′ 13.6″
• Record Helix Nebula Right ascension 22 h 29 m 38.55 s

For latitudes around 43° north the nebula never climbs higher than 30° above the horizon, so it sits low in the autumn night sky. Southern observers gain the best view in early spring, when the 7.6-magnitude planetary nebula stands higher. It forms a small equilateral triangle with Fomalhaut, Delta Aquarii, and Delta Capricorni. At magnitude 7.3-7.6 and 25′ across, NGC 7293 is visible with small binoculars, and a small telescope shows its pale blue-gray disk, yet large instruments spread the light too thinly, making it harder to spot.

How is the Helix Nebula compared to Earth?

The Helix Nebula is about 1.5 million times bigger than Earth yet 40,000 times smaller than our galaxy. The nebula is one of the closest planetary nebulae to Earth. Because it lies only a few hundred light-years away, its apparent helix structure can be seen from our planet’s perspective. A white dwarf at its center is compressed into a sphere the size of Earth.

What are the differences between the Helix Nebula and the Ring Nebula?

Differences between the Helix Nebula and the Ring Nebula are explained in the table below.

Helix Nebula and Ring Nebula are both planetary nebulae and at first glance Helix Nebula is similar in appearance to Ring Nebula. Yet the two objects differ in form. Ring Nebula features a round, donut‑like shape and appears almost exactly face-on to observers on Earth. Helix Nebula is seen at an oblique angle. Its major axis is inclined about 21° to 37° from our vantage point, giving it a prolate spheroid rather than a perfect ring outline.

Inside this inclined structure, Helix Nebula has a main ring that contains knots of nebulosity. The entire system is embedded in a much larger disk that surrounds the filled bagel. Ring Nebula also possesses faint knots, but these lie within a cleaner, narrower annulus and lack the extensive outer skirt found around the Helix. Both nebulae trace the late stages of a dying star shedding outer layers, yet their contrasting orientation and internal knot distribution make each a distinctive member of the planetary nebula family.

How did the Helix Nebula form?

The Helix Nebula formed when an intermediate to low-mass star shed its outer layers near the end of its evolution. Shells of gas were blown off from the star’s surface, and a fast wind emanating from the hot core rammed into the ejected atmosphere. This created the nebula’s visible shells and filaments that point back toward the central stellar remnant.

After the outer layers dispersed, the star’s core collapsed to form a compact white dwarf. The explosion resulted in a white dwarf star at the nebula center, now the scorchingly hot central star at 120,000°C (216,000°F).

Is Helix Nebula a dying star?

The Helix Nebula is the remains of a dying star. The dying star at the center of Helix Nebula exhausted its fuel. and threw off its outer layers as a gaseous wind. Helix Nebula is the late stage of a star. The dying star at the center of Helix Nebula transformed into a white dwarf. The white dwarf appears as a tiny white pinprick at the center of Helix Nebula. WD 2226-210 is the central star of Helix Nebula. The glowing shells of gas expand over 10,000 years. Expanding shells thin out and become part of the interstellar medium. Planetary nebulae are the remains of stars that once looked a lot like our sun.

What is the Helix Nebula made of?

The Helix Nebula is composed of dust, ionized material and molecular gas. The blue-green glow in the centre comes from oxygen atoms shining under intense ultraviolet radiation of the 120,000 degree Celsius central star. The red colour farther out is caused by hydrogen emission and nitrogen.

Outermost gaseous bands are composed mostly of hydrogen and helium, gases expelled when the star blew off its outer atmosphere. A white-dwarf central star remains, surrounded by a shell of helium and a core made of carbon, while ultraviolet radiation spreads outward through the nebula and keeps the gas glowing.

Seen from Earth, these gases appear as a helix structure. The Helix Nebula consists of two disks that are nearly perpendicular to each other, giving the planetary nebula its twisted form.

What happens if you enter Helix Nebula?

Entering the nebula places a traveler inside an expanding cloud of ionized gas. Helix Nebula offers a glimpse into the fate of our Solar System in 5 billion years. The expansion of the Helix Nebula knocks planets out of their orbits, swallows them, or incinerates them. Background stars are easily seen through the cosmic cloud.