Glossary term: Milky Way
Description: The Milky Way is the galaxy in which the Solar System resides. It is an aggregate of about 100–400 billion stars. The Solar System is located about 26,600 light years from the center of the Milky Way. In the night sky we can see it as a faint band extending across the sky with its center in the Sagittarius constellation.
The Milky Way is a relatively large barred spiral galaxy, and the distribution of stars in it extends to about 100,000 light years along the disk with a thickness of about 1000 light years. The galactic disk formed 8–10 billion years ago.
This disk is surrounded by a much more sparse halo of stars, including globular clusters of stars. These globular clusters are some of the oldest objects in the Galaxy, with ages of about 12.5 billion years. In addition to stars, the Milky Way is comprised of the gas and dust of the interstellar medium and dark matter. While the interstellar medium is limited mostly to the disk, the surrounding dark matter halo extends to much larger distances than the stellar halo.
The center of the Milky Way hosts a supermassive black hole which is about 4 million times the mass of the Sun. Surrounding the galactic center is a bulge of mostly older stars that is elongated in one direction, forming a bar.
Related Terms:
- Dark Matter
- Galactic Bulge
- Galactic Center
- Galactic Disk
- Galactic Halo
- Galaxy
- Greenwich Mean Time Zone (GMT)
- Solar System
- Interstellar Medium
- Sagittarius
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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher
The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".
Related Media
Milky Way Arch over Lut Desert, Iran, by Amirreza Kamkar, Iran (Islamic Republic of)
Credit: Amirreza Kamkar/IAU OAE
License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
Constellations from the World
Credit: Stephanie Ye Ziyi/IAU OAE
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Flowing Night Sky
Credit: Robert Barsa/IAU OAE
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Credit: Jianfeng Dai/IAU OAE
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Cen-Lup-Cru-Panorama: Centaurus Carrying the Beast and Riding Along the Milky Way
Credit: Uwe Reichert/IAU OAE
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Credit: Amirreza Kamkar/IAU OAE
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Credit: Marcin Zajac/IAU OAE
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Milky Way Arch over Amboseli National Park
Credit: Amirreza Kamkar/IAU OAE
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Most Brightest Stars of the Sky
Credit: Giorgia Hofer/IAU OAE
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The Milky Way Across the Zenith
Credit: Ohnishi Kouji/IAU OAE
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Warm Winter Night Over Spiš Region
Credit: Robert Barsa/IAU OAE
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Teide Observatory
Credit: Curd-Christian Tengeler/IAU OAE
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Credit: Marcin Zajac/IAU OAE
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Equatorial Milky Way
Credit: Giorgia Hofer/IAU OAE
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Milky Way Arch over La Palma
Credit: Amirreza Kamkar/IAU OAE
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The Moon and Milky Way arch Above the Golden Hall
Credit: Likai Lin/IAU OAE
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The Milky Way Over Anglers Reach
Credit: Lucy Yunxi Hu/IAU OAE
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Winter Milky Way
Credit: Giorgia Hofer/IAU OAE
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The Pillar of Creation
Credit: Giorgia Hofer/IAU OAE
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Lyrid of the Lake
Credit: Jianfeng Dai/IAU OAE
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Milky Way Over Quiver Tree
Credit: Jianfeng Dai/IAU OAE (CC BY 4.0)
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Milky Way Over H.E.S.S Observatory
Credit: Jianfeng Dai/IAU OAE (CC BY 4.0)
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Lugu Lake Without Cloud
Credit: Liu Yang/IAU OAE (CC BY 4.0)
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The Milky Way in the Smart World
Credit: Biagio Meli/IAU OAE (CC BY 4.0)
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Milky Way Stargazer
Credit: Jianfeng Dai/IAU OAE (CC BY 4.0)
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Sailing the Celestial Seas
Credit: Lucy Yunxi Hu/IAU OAE (CC BY 4.0)
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Related Diagrams
Sagittarius Constellation Map
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope
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Related Activities
Glitter Your Milky Way
astroEDU educational activity (links to astroEDU website) Description: Explore the Milky Way and characteristics of galaxies using glitter drawing.License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
Tags: Art , Creativity , Hands-on , Handcraft Age Ranges: 6-8 , 8-10 Education Level: Middle School , Primary Areas of Learning: Fine Art focussed Costs: Medium Cost Group Size: Group Skills: Communicating informationLiving in the Milky Way
astroEDU educational activity (links to astroEDU website) Description: Build a model of the Milky Way to discover what our galaxy contains.License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
Tags: Hands-on , Model Age Ranges: 6-8 , 8-10 Education Level: Primary Areas of Learning: Problem-solving , Social Research Costs: Medium Cost Duration: 1 hour 30 mins Group Size: Group Skills: Asking questions , Communicating information , Developing and using models