Milky Way

Cosma / Communication / Knowledge / Realm / Physical / Universe / Galaxy / Milky Way
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Introduction1

Life and Death of a Planetary System (NASASolarSystem, YouTube Playlist)

Dictionary

Milky Way : the galaxy of which the sun and the solar system are a part and which contains the myriads of stars that create the light of the Milky Way — Webster   See also   OneLook

Encyclopedia

Milky Way is the galaxy that contains our Solar System. The descriptor “milky” is derived from the galaxy’s appearance from Earth: a band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies.

The Milky Way is a barred spiral galaxy with a diameter between 150,000 and 200,000 light-years (ly). It is estimated to contain 100–400 billion stars. There are probably at least 100 billion planets in the Milky Way. The Solar System is located within the disk, 26,490 (± 100) light-years from the Galactic Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust. The stars in the innermost 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The galactic center is an intense radio source known as Sagittarius A*, likely a supermassive black hole of 4.100 (± 0.034) million solar masses.

Stars and gases at a wide range of distances from the Galactic Center orbit at approximately 220 kilometers per second. The constant rotation speed contradicts the laws of Keplerian dynamics and suggests that much of the mass of the Milky Way does not emit or absorb electromagnetic radiation. This mass has been termed “dark matter”. The rotational period is about 240 million years at the position of the Sun. The Milky Way as a whole is moving at a velocity of approximately 600 km per second with respect to extragalactic frames of reference. The oldest stars in the Milky Way are nearly as old as the Universe itself and thus probably formed shortly after the Dark Ages of the Big Bang.

The Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which form part of the Virgo Supercluster, which is itself a component of the Laniakea Supercluster. — Wikipedia

Milky Way Galaxy (Encyclopædia Britannica)

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Innovation

Science

V101 Science (YouTube Channel)

The 360-degree video below immerses viewers into a simulation of the center of our Galaxy. This visualization was enabled by data from Chandra and other telescopes and allows viewers to control their own exploration of this region. From the vantage point of the Milky Way’s supermassive black hole, Sgr A*, the viewer can see about 25 Wolf-Rayet stars (white, twinkling objects) as they continuously eject stellar winds (black to red to yellow color scale). These winds collide with each other, and then some of this material (yellow blobs) spirals towards Sgr A*. The movie shows two simulations, each of which start around 350 years in the past and span 500 years. The first simulation shows Sgr A* in a calm state, while the second contains a more violent Sgr A* that is expelling its own material, thereby turning off the accretion of clumped material (yellow blobs) that is so prominent in the first portion.

Note: This is a 360° Video — press and hold to explore it!

Chandra X-ray Observatory (YouTube Channel)

The Milky Way Galaxy (JPL, NASA)

Milky Way (Wolfram Alpha)

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Preservation

History

Objectivity (YouTube Channel)
Royal Society (YouTube Channel)
Royal Society (Official Site)

Library

Library of Congress # QB856 Galaxies (UPenn Online Books)

WorldCat, Library of Congress, UPenn Online Books, Open Library

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Participation

Education

Milky Way (Cosmos4Kids)

MERLOT: Multimedia Educational Resource for Learning and Online Teaching
OER Commons: Open Educational Resources

Course

Crash Course Astronomy (YouTube Playlist)

News

Milky Way (Astronomy Magazine)
Milky Way (Phys.org)
Milky Way (NPR Archives)

Government

Document

Milky Way (USA.gov)

returntotop

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Related

Here are links to pages about closely related subjects.

Knowledge Realm

Physical

“Fundamentals”
Law (Constant) Relativity
Force Gravity, Electromagnetism (Light, Color)
Matter (Microscope) Molecule, Atom (Periodic Table), Particle

“Space”
Universe (Astronomical Instrument)
Galaxy Milky Way, Andromeda
Planetary System Star, Brown Dwarf, Planet, Moon

Our Neighborhood
Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Trans-Neptunian Object
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid

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Notes

1.   The resources on this page are are organized by a classification scheme developed exclusively for Cosma.