Question

Extragalactic nebulae such as the Great Nebula in Andromeda were not immediately recognized as galaxies similar to our own Milky Way because they were thought to be ________.

1) Stars
2) Planets
3) Comets
4) Clouds of gas and dust

Answer 1

Extragalactic nebulae were once thought to be clouds of gas and dust, a misconception corrected by Edwin Hubble's discovery in the early 20th century.

Step-by-step explanation:

Extragalactic nebulae, such as the Great Nebula in Andromeda, were not immediately recognized as galaxies similar to our own Milky Way because they were thought to be clouds of gas and dust. This misunderstanding persisted into the early twentieth century because these objects appeared faint and indistinct, even when observed with the best telescopes of the time, making it difficult to determine their true nature and distance. It was only when Edwin Hubble measured the distance to the Andromeda galaxy in 1924 that the existence of other galaxies was conclusively established, leading to a revolutionary understanding of the universe and its composition.