Definition of nebula in US English:


nounPlural nebulae, Plural nebulas

  • 1Astronomy
    A cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter.

    • ‘Based on the nebula's distance of 650 light-years, its angular size corresponds to a huge ring with a diameter of nearly three light-years.’
    • ‘Until recently, it was thought that shells around planetary nebulae were a rare phenomenon.’
    • ‘A planetary nebula forms when Sun-like stars gently eject their outer gaseous layers to form bright nebulae with amazing twisted shapes.’
    • ‘The reason why most planetary nebulae are not spherical is not well understood.’
    • ‘The composition of Phoebe should reflect the composition of the region of the solar nebula where it formed.’
    • ‘For example, consider the shapes of nebulae - those swirling clouds of gas and dust in which newly hatched stars begin to shine.’
    • ‘Evolutionists believe that the solar system condensed out of a cloud of gas and dust called a nebula, hence the nebular hypothesis.’
    • ‘By what principle the ship created and continued to produce the bubble shielding it from the nebula's gasses.’
    • ‘Astronomers suspect that the distant emissions may emanate from the same type of nebulas.’
    • ‘We have missions that include active nebulas, swirling dust clouds, moving asteroids and asteroid fields.’
    • ‘Edwin Hubble quickly began a detailed study of the spiral nebulae.’
    • ‘"Planetary nebulae are shells of gas ejected by dying stars, " Kastner explains.’
    • ‘Thus, meteorites represent a fossil record of the early conditions of the solar nebula.’
    • ‘Jupiter's core formed rapidly relative to the rate at which gas was lost from the solar nebula.’
    1. 1.1dated (in general use) any indistinct bright area in the night sky, for example, a distant galaxy.
      • ‘I can see the stars outside, the swirling patterns of distant nebulae.’
      • ‘A number had been discovered in deep space, but to an ordinary telescope each nebula looked like a faint blur; it was difficult to determine whether it was a cloud of gas or a multitude of stars.’
      • ‘The picture has widened and deepened ever since; fuzzy nebulae were revealed to be other galaxies, as full of stars as our own, and the chemistry of the stars yielded to spectrum analysis.’
      • ‘Hubble's discovery showed that spiral nebulae are entire systems of stars in their own right, as huge and as packed with stars as our own Milky Way.’
      • ‘It was only in the 1920's that the American astronomer Hubble established that some of these nebulae were indeed distant galaxies comparable in size to our own Milky Way.’
      • ‘One of the nicest sectors I ever saw is Ocean of Fantasy, a sector rounded by a bright green nebula.’
      • ‘But soon, performing a visual diminuendo, they drift well astern, a distant nebula of glittering pinpoints at the planet's indistinguishable edge.’
      • ‘The colours of unreachable nebulas mingled with the darkness and desolation of space.’
      • ‘Originally, the word nebula referred to almost any extended astronomical object (other than planets and comets).’
      • ‘Then if he'd looked farther, deeper, he saw star systems, colorful nebulas never before seen in his dreams.’
      • ‘Smudges like this are called nebulae, because they look nebulous - like hazy clouds.’
      • ‘More distant nebulae and galaxies require longer exposure times, and more fiddling.’
      • ‘The large globe with clustered nebulas and speckled stars and solar systems that were scattered with planets, suns and moons rotated slowly and gently.’
      • ‘It is a nebulae system, planets and stars bobbing in and out of blue, purple, and pink stardust.’
      • ‘In early 1845, before his telescope was completed, Rosse had resolved his first nebula, discovering it to be a spiral galaxy of stars.’
      • ‘Heber Curtis had been correct in the 1920 debate; many of the nebulae were indeed remote galaxies.’
      • ‘Hubble realized that these spiral nebulae were so far away they were actually galaxies - separate cities of stars - far beyond our own Milky Way.’
      • ‘Stars, as far as the eye can see, and two of them, pretty close, with a string of planets orbiting between them, the whole family swimming in a pink, blue, and purple nebula.’
      • ‘Then Edward Hubble discovered that the nebulae were other galaxies like ours only much further away than was thought possible.’
      • ‘In further studies, he showed that these nebulas are actually other galaxies, and he went on to classify them.’
      • ‘We sometimes use the word nebula to refer to galaxies, various types of star clusters, and various kinds of interstellar dust or gas clouds.’
      star system, solar system, constellation, cluster
      View synonyms
  • 2Medicine
    A clouded spot on the cornea causing defective vision.

    • ‘The bruise over his eye had settled in to a purple nearly matching the nebula itself, but the swelling had reduced dramatically.’
    • ‘It treats conjunctivitis, pterygium, nebula and pain in the eyes.’


Mid 17th century (as a medical term): from Latin, literally ‘mist’.