top of page
  • Siddharth Madhan

Clouds of Dust

A nebula is a massive cloud of dust and gas that exists between stars and serves as a nursery for young stars. The word is derived from the Latin word nebula, which means "mist, vapour, fog, smoke, or exhalation." Dust, basic elements like hydrogen, and other ionised gases make up nebulae.

The great majority of nebulae are hundreds of light-years in diameter. From a near distance, a nebula visible to the naked eye from Earth would look bigger, but not brighter. The Orion Nebula, the brightest nebula in the sky, can be seen with the naked eye and covers an area twice the angular diameter of the full Moon, although it was overlooked by early astronomers.

The various forms of nebulae have a range of formation mechanisms. Some nebulae are created by stars, while others are formed by gas already present in the interstellar medium. Giant molecular clouds, the coldest and densest phase of interstellar gas, can arise as a result of the cooling and condensation of more diffuse gas. Planetary nebulae, for example, are produced from material shed by a star in the last phases of its stellar evolution.

When a massive gigantic star reaches the end of its life, a supernova occurs. The star collapses inwards when nuclear fusion in the centre of the star ceases. The inward falling gas either bounces back or becomes so hot that it bursts outwards, exploding from the core, causing the star to explode. A supernova remnant, or diffuse nebula, is formed by the expanding shell of gas.

Some notable examples of nebulas are:

  • Ant Nebula

  • Barnard's Loop

  • Boomerang Nebula

  • Cat's Eye Nebula

  • Crab Nebula

  • Eagle Nebula

  • Eskimo Nebula

  • Carina Nebula

  • Fox Fur Nebula

  • Helix Nebula

  • Horsehead Nebula

  • Engraved Hourglass Nebula

A planetary nebula is an expanding, bright disc of hot gas (plasma) ejected by a low-mass star near the end of its existence. They have nothing to do with planets, despite their name, and were given that name because early astronomers thought they looked like planets via a small telescope.

When low-mass stars reach the end of their red giant phase, they become planetary nebulae. The star becomes extremely unstable at this time and begins to pulsate. The stellar winds that arise expel the outer layers. Planetary nebulae have a brief lifetime, lasting only tens of thousands of years.

The surviving core burns brilliantly and is extremely hot (100,000°C+) when the outer layers drift away from the star. The core is now a white dwarf star. The white dwarf's UV radiation causes the ejected outer layers to glow, forming the planetary nebula.

The enriched material from the planetary nebula will eventually spread into space and be used to create subsequent generations of stars.

25 views0 comments

Recent Posts

See All


Post: Blog2 Post
bottom of page