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
See this term in other languages
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".
If you notice a factual error in this glossary definition then please get in touch.
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
License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
Flowing Night Sky
Credit: Robert Barsa/IAU OAE
License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
Chilean Nights
Credit: Robert Barsa/IAU OAE
License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
Southern Sky
Credit: Jianfeng Dai/IAU OAE
License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
Related Diagrams
Sagittarius Constellation Map
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope
License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
Cygnus Constellation Map
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
Triangulum Constellation Map
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons
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 information
Living 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