Milky Way — LLMpedia

Milky Way
source
Name	Milky Way
Type	Barred spiral galaxy (SBbc)
Distance	~0 kpc (Earth within)
Diameter	~100,000–200,000 light‑years
Mass	~1–1.6×10^12 M☉
Stars	~100–400 billion
Arm structure	Four major spiral arms, central bar
Satellites	Large Magellanic Cloud, Small Magellanic Cloud, Andromeda Galaxy (interaction partner), Sagittarius Dwarf Spheroidal Galaxy, Canis Major Overdensity, Fornax Dwarf, Sculptor Dwarf Galaxy
Notable objects	Sagittarius A*, Kepler space telescope discoveries, Hubble Space Telescope observations

Contents

Milky Way The Milky Way is the barred spiral galaxy that contains the Solar System and Earth, central to studies by Galileo Galilei observers and modern missions such as Gaia (spacecraft), Hubble Space Telescope teams, and surveys like the Sloan Digital Sky Survey. It is a massive stellar system studied alongside neighboring systems such as Andromeda Galaxy and groups monitored by institutions including European Space Agency and National Aeronautics and Space Administration. Measurements from facilities like Very Large Telescope, Arecibo Observatory, and Chandra X-ray Observatory constrain its structure, mass, and dynamics.

Overview

The galaxy is classified as a barred spiral (SBbc) in morphological schemes developed by Edwin Hubble and updated by surveys from Two Micron All Sky Survey and Spitzer Space Telescope, with a central bar revealed by infrared studies from COBE and WISE (space telescope). Historical mapping traces to work by Galileo Galilei, William Herschel, and the Harlow Shapley–Heber Curtis debate, later refined by kinematic studies by Jan Oort and radio mapping by Jocelyn Bell Burnell-era instrumentation. Contemporary parameter estimates rely on astrometric catalogs from Hipparcos and Gaia (spacecraft), dynamical modeling by groups at Caltech, Harvard–Smithsonian Center for Astrophysics, and cosmological context from Planck (spacecraft) results.

The galaxy comprises a thin disk, thick disk, central bulge and bar, stellar halo, dark matter halo, and interstellar medium mapped by teams at Max Planck Institute for Astronomy, Institute of Astronomy, Cambridge, and National Radio Astronomy Observatory. The disk hosts spiral arms named in radio and infrared studies such as the Perseus Arm, Scutum–Centaurus Arm, Sagittarius Arm, and Norma Arm with molecular clouds traced by Atacama Large Millimeter/submillimeter Array and James Clerk Maxwell Telescope. The central region contains the supermassive black hole Sagittarius A* identified in observations by Andrea Ghez and Reinhard Genzel using instruments at W. M. Keck Observatory and Very Large Telescope, with stellar orbits measured by groups associated with UCLA and Max Planck Institute for Extraterrestrial Physics. Globular clusters like Omega Centauri, 47 Tucanae, and M13 populate the halo studied by surveys from Palomar Observatory, Subaru Telescope, and Kitt Peak National Observatory.

Galaxy formation models draw on hierarchical assembly frameworks from Lambda-CDM cosmology developed by researchers at Princeton University and University of Cambridge, enriched by simulations like Illustris and EAGLE and analytic work by James Peebles. The Milky Way’s growth involved accretion events such as the merger with the Gaia Sausage/Enceladus progenitor identified by Gaia (spacecraft), and earlier interactions inferred from stellar streams like the Sagittarius Stream mapped by teams at European Southern Observatory and Sloan Digital Sky Survey. Chemical evolution studies referencing yields from Type Ia supernovae and Type II supernovae use spectroscopy from Keck Observatory and Gemini Observatory to trace metallicity patterns in disk and halo populations characterized by work at Carnegie Institution for Science.

Rotation curve measurements by Vera C. Rubin-inspired programs and radio surveys using Arecibo Observatory and Green Bank Telescope reveal flat rotation curves, evidence for a dominant dark matter halo first emphasized by Oort and Rubin. Proper motion and parallax results from Gaia (spacecraft) constrain solar motion relative to the Local Standard of Rest and orbits of objects including globular clusters studied by teams at Space Telescope Science Institute and University of California, Berkeley. N‑body and hydrodynamic simulations by groups at MIT, Stanford University, and Max Planck Institute for Astrophysics model bar formation, spiral density waves introduced in theories by C. C. Lin and Frank Shu, and dynamical friction effects involving satellites like Large Magellanic Cloud.

Stellar populations include Population I disk stars, Population II halo stars, and distinct subpopulations studied in surveys by Kepler (spacecraft), Transiting Exoplanet Survey Satellite, and spectroscopic campaigns from APOGEE and LAMOST. Star formation occurs in molecular clouds traced by ALMA, Herschel Space Observatory, and Spitzer Space Telescope with feedback processes from Wolf–Rayet stars and supernovae cataloged by Chandra X-ray Observatory and Fermi Gamma-ray Space Telescope. The initial mass function and cluster formation draw on work by Edwin Salpeter and modern revisions from Pavel Kroupa and Gustavo Gilmore with observational benchmarks in regions like the Orion Nebula, Carina Nebula, and Taurus Molecular Cloud.

The galaxy resides in the Local Group dominated by the Andromeda Galaxy and linked to nearby systems including Triangulum Galaxy, M33, and dwarf satellites such as Leo I, Leo II, Draco Dwarf, and Ursa Minor Dwarf. Its motion within the Local Sheet and toward the Great Attractor is measured by peculiar velocity studies from teams at Johns Hopkins University and University of Chicago using data from 2MASS Redshift Survey and Cosmicflows. Future interaction and eventual merger with Andromeda Galaxy predicted by simulations from NASA and ESA teams will reshape the galaxy over gigayear timescales; these scenarios are explored in computational projects at Argonne National Laboratory and Los Alamos National Laboratory.

Category:Galaxies