planetarium

noun

plan·​e·​tar·​i·​um ˌpla-nə-ˈter-ē-əm 

plural planetariums or planetaria ˌpla-nə-ˈter-ē-ə 

1

: a model or representation of the solar system

2

a

: an optical device for projecting various celestial images and effects

b

: a building or room housing such a projector

Examples of planetarium in a Sentence

Recent Examples on the Web

Its stops include five observatories, a planetarium, and a space museum, two state parks, and Saguaro National Park (which was certified as the newest Urban Night Sky Place in late 2023). —Mark Ellwood, AFAR Media, 7 Feb. 2025

For the most accurate location-specific information, consult online planetariums like Stellarium. —Jamie Carter, Forbes, 20 Jan. 2025

Rafting trips, aquariums, planetariums … all of these seem like science fiction to someone who has only ever lived in a giant concrete tube. —Noel Murray, Vulture, 15 Nov. 2024

Tucson by night All told, Tucson’s Astro Trail features five observatories, a planetarium, a laboratory, an aviation and space museum, two state parks, and one national park. —Bailey Berg, AFAR Media, 4 Feb. 2025

Word History

First Known Use

1860, in the meaning defined at sense 1

Kids Definition

planetarium

noun

plan·​e·​tar·​i·​um ˌplan-ə-ˈter-ē-əm 

plural planetariums or planetaria -ē-ə 

1

: a device that projects images of heavenly bodies on a ceiling shaped like a dome

2

: a building or room housing a planetarium