Milky Way

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

The latest star map from the Gaia spacecraft plots 1.7 billion stars (Lisa Grossman, Science News)


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

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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

Encyclopædia Britannica






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

This 360-degree movie 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.

Our Galactic Core Has Thousands of Black Holes (Daniel Starkey,
New Study Suggests Tens of Thousands of Black Holes Exist in Milky Way’s Center (Jessica Guenzel, Columbia News)





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The Milky Way (Ask an Astronomer, Cornell University)
Milky Way (Cosmos4Kids)


Crash Course Astronomy (YouTube)

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  • Astronomers focus robotic eyes on the Milky Way,...
    on January 21, 2022 at 2:50 pm

    Thanks to a breakthrough robotic innovation, an international collaboration that includes the University of Toronto has advanced the Sloan Digital Sky Survey (SDSS), a 20-year-long research project that has been investigating the structure and evolution of our cosmic home, the Milky Way galaxy.

  • Hubble finds a black hole igniting star formation...
    on January 19, 2022 at 8:12 pm

    Black holes are often described as the monsters of the universe—tearing apart stars, consuming anything that comes too close, and holding light captive. Detailed evidence from NASA's Hubble Space Telescope, however, shows a black hole in a new light: Fostering rather than suppressing star formation. Hubble imaging and spectroscopy of the dwarf starburst galaxy Henize 2-10 clearly show a gas outflow stretching from the black hole to a bright star birth region like an umbilical cord, triggering […]

  • Astronomers shed new light on birth of stars and...
    on January 19, 2022 at 2:30 pm

    A star is born—but how? Astronomers are unravelling the mysteries of how clouds of gas ignite to become stars and form spiral galaxies near our own.

  • Globular cluster Messier 14 and its peculiar...
    on January 17, 2022 at 4:10 pm

    Using the Hubble Space Telescope (HST), astronomers have observed the globular cluster Messier 14 and its peculiar multiple stellar populations. Results of the observational campaign, published January 7 on, deliver important insight into the nature of this cluster.

  • Hubble views a tranquil galaxy with an explosive...
    on January 15, 2022 at 8:43 am

    The lazily winding spiral arms of the spectacular galaxy NGC 976 fill the frame of this image from the NASA/ESA Hubble Space Telescope. This spiral galaxy lies around 150 million light-years from the Milky Way in the constellation Aries. Despite its tranquil appearance, NGC 976 has played host to one of the most violent astronomical phenomena known – a supernova explosion. These cataclysmically violent events take place at the end of the lives of massive stars and can outshine entire […]



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Here are links to pages about closely related subjects.

Knowledge Realm


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

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


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