what is milky way galaxy?
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➡ The Milky Way is a large barred spiral galaxy. All the stars we see in the night sky are in our own Milky Way Galaxy. Our galaxy is called the Milky Way because it appears as a milky band of light in the sky when you see it in a really dark area.
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Answer:
Explanation:
The Milky Way is the galaxy[nb 1] that contains our Solar System. The name describes the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος (galaxías kýklos, "milky circle").[17][18][19] 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.[20] Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis,[21] 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).[22][23][24][25] It is estimated to contain 100–400 billion stars[26][27] and more than 100 billion planets.[28][29] The Solar System is located at a radius of 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*, assumed to be a supermassive black hole of 4.100 (± 0.034) million solar masses.
Milky Way Galaxy
ESO-VLT-Laser-phot-33a-07.jpg
The Milky Way's Galactic Center in the night sky above the Paranal Observatory (the laser creates a guide-star for the telescope)
Observation data
Type
Sb, Sbc, or SB(rs)bc[1][2] (barred spiral galaxy)
Diameter
150–200 kly (46–61 kpc)
Thickness of thin stellar disk
≈2 kly (0.6 kpc)[3][4]
Number of stars
100–400 billion [(1–4)×1011][5]
Mass
0.8–1.5×1012 M☉[6][7][8][9]
Angular momentum
≈1×1067 J s[10]
Sun's distance to Galactic Center
26.4 ± 1.0 kly (8.09 ± 0.31 kpc)[11][12][13]
Sun's Galactic rotation period
240 Myr[14]
Spiral pattern rotation period
220–360 Myr[15]
Bar pattern rotation period
100–120 Myr[15]
Speed relative to CMB rest frame
631 ± 20 km/s[16]
Escape velocity at Sun's position
550 km/s[9]
Dark matter density at Sun's position
0.0088+0.0024
−0.0018 M☉pc-3 or 0.35+0.08
−0.07 GeV cm-3[9]
See also: Galaxy, List of galaxies
Nature timeline
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-13 —–-12 —–-11 —–-10 —–-9 —–-8 —–-7 —–-6 —–-5 —–-4 —–-3 —–-2 —–-1 —–0 —
Reionization
Matter-dominated
era
accelerated expansion
water
Single-celled life
photosynthesis
Multicellular
life
Vertebrates
Dark Ages
←Universe (−13.80)←Earliest stars←Earliest galaxy←Earliest quasar/sbh←Omega Centauri←Andromeda Galaxy←Milky Way spirals←Alpha Centauri←Solar System←Earliest life←Earliest oxygen←Atmospheric oxygen←Sexual reproduction←Earliest plants←Cambrian explosion←Earliest mammals←Earliest apes
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Axis scale: billion years
The image above contains clickable links(See also: Human timeline, and Life timeline.)
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 (about 90%)[30][31] of the mass of the Milky Way is invisible to telescopes, neither emitting nor absorbing electromagnetic radiation. This conjectural mass has been termed "dark matter".[32] The rotational period is about 240 million years at the radius of the Sun.[14] 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.
