Some Nebulae Turned Out to Be Whole Galaxies
A nebula is a cloud of gas and dust in space. Until 1925 nobody knew that some were galaxies far outside our own.
A nebula is a cloud of gas and dust in space. The word once covered anything fuzzy in a telescope, which caused a historic confusion: the Andromeda Nebula turned out to be a galaxy of hundreds of billions of stars, two and a half million light years away. Edwin Hubble settled it in 1925, and the universe abruptly became vastly larger.
- A cloud of gas and dust. *The Orion Nebula.*
- Nebulae — the plural. *Distant nebulae.*
- Nebulous — vague. *A nebulous plan.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | nebula | A planetary nebula. |
| Plural | nebulae | Bright nebulae. |
| Plural | nebulas | Also used. |
| Adjective | nebulous | A nebulous idea. |
| Related | nebulise | A nebulised drug. |
How it is used in a sentence
- Andromeda was called a nebula.Until 1925.
- A planetary nebula has nothing to do with planets.They just looked like discs.
- Nebulous means vague or cloudy.Figurative.
Types of nebula
- Emission — gas glowing from nearby hot stars
- Reflection — dust reflecting starlight
- Dark — dense dust blocking light from behind
- Planetary — a dying star's shed outer layers, misleadingly named
- Supernova remnant — the expanding debris of an exploded star
From Latin *nebula*, mist or cloud, related to Greek *nephele* and to English *nebulous*.
Why are they called planetary nebulae?
Because early observers saw small round discs resembling planets. They are actually the shed outer layers of dying stars.
When did we learn galaxies were separate?
Edwin Hubble showed in 1925 that Andromeda lay far outside the Milky Way, proving that some nebulae were separate galaxies.