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SIX-ARM SPIRAL OF NGC 309 A.D. Chernin

SIX-ARM SPIRAL OF NGC 309 A.D. Chernin Sternberg Astronomical Institute Moscow University. NGC 309. BLUE ARMS MADE OF STAR COMPLEXES. NGC 309. Van den Bergh (1960):

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SIX-ARM SPIRAL OF NGC 309 A.D. Chernin

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  1. SIX-ARM SPIRAL OF NGC 309 A.D. Chernin Sternberg Astronomical Institute Moscow University

  2. NGC 309 BLUE ARMS MADE OF STAR COMPLEXES

  3. NGC 309 Van den Bergh (1960): d = 75 kpc Luminosity class I One of the largest and most luminous spirals

  4. NGC 309 Elmegreen & Elmegreen (1984): Extreme grand design

  5. Red & Blue Block & Wainscoat (1991) 20 kpc h = 50

  6. M51: Red & Blue Zwicky (1957)

  7. Two-Fold Symmetry Grand Design 1. Two-arm density wave traced by old red stellar population 2. Two coherent patterns of three arms in each traced by young blue stars of Efremov’s complexes NGC 309: giant Hubble type Sc

  8. How two red arms drive six blue arms * Density wave in old-star population generates non-evolutionary jump in disk gas * This kind jump transforms into two shock fronts & contact jump between them * Star formation develops along three overdensity ridges

  9. TWO SHOCKS & CONTACT JUMP Landau & Lifshitz (1979)

  10. Other multi-arm spirals NGC 753, NGC 2997, NGC 4535, NGC 5247, NGC 5584, NGC 5494, NGC 1566, NGC 3423, NGC 6878, NGC 6946, NGC 7125, NGC 7689, etc.

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