Transcript Document
Stellar Evolution Part III 1 Planetary Nebulae Dr. Bill Pezzaglia Updated March 23, 2009 I. Introduction According to CNN the world will end Dec 21, 2012 2 3 As usual, they got it wrong The world will end: Dec 21, 5,000,002,012 The sun will…. 4 Planetary Nebulae I. II. III. IV. V. Introduction Discovery Spectra Evolution Summary 5 II. Discovery A. Messier’s Catalog B. Herschel names them C. Nebular Hypothesis Interpretation A. Messier Catalog Charles Messier (1730-1817) was hunting for comets. People kept reporting the same fuzzy blobs that were NOT comets, so from 1758-1782 he made a catalog of about 100 of these fuzzy things to “ignore”. In fact, these 110 objects are nebulae, star clusters and galaxies, which are the best things to look for in an amateur telescope! 6 The Summer Triangle Deneb Cygnus The Swan Vega Lyra The Harp Altair Aquila The Eagle M57 (1779) Ring Nebula In Lyra 1’ in diameter Made of stars? M27: July 12, 1764 Dumbbell Nebula In Vulpecula 6’ in diameter B. 1781: Uranus Discovered 8 (accidentally!) by William Herschel using a 6 inch telescope Herschel Classifies Nebulae • 1785 Catalog of 1000 objects • 1788 another 1000 objects • 1802 another 500 objects Classifies objects into star clusters and nebulae. The “types” were: 1. 2. 3. 4. 5. 6. 7. Bright Nebulae Faint Nebulae Very faint Nebulae Planetary Nebulae (Uranus-like in color & shape) Very large Nebulae Very compressed and rich star clusters Compressed clusters of small and large (i.e., faint and bright) stars 8. Coarsely scattered clusters of stars 9 C. Nebular Hypothesis • Herschel (1786) thought that “Planetary Nebulae” might be a cloud of gas coalescing into a star to be surrounded by planets (hence the name) • “Nebular Hypothesis” had been theoretically proposed earlier (1734 Swedberg, 1755 Kant) 10 11 III. The Message in the Light A. Atomic Spectra Lines B. Huggins & Nebulium C. Central Stars are White Dwarfs A.1. Dark Line Spectra • 1802 Wollastan sees lines in solar spectra • 1814 Fraunhofer Labels them A, B, C, D • Later measures over 500 lines! 12 A.2. Solar spectrum 13 A.3. Bright Line Spectra • • • 1857 Bunsen’s burner, a clean flame with no color 1859 Kirchhoff suggest using it to study spectra of elements in flame Each element has a unique set of “bright line” (emission) spectra 14 A.4. Kirchhoff’s Laws 15 B. 1786 Herschel discovers: 16 Draco the Dragon Ursa Major H IV 37 (NGC6543) Cats Eye Nebula Ursa Minor Polaris B.2 William & Margaret Huggins • (1864) Spectra of Cat’s Eye Nebula shows single emission line in green • Implies it’s a gas, NOT made of stars (which would have absorption lines) • Unknown element “Nebulium” makes greenish color 17 Tom Lehrer: Elements B.2 William & Margaret Huggins • (1864) Spectra of Cat’s Eye Nebula shows single emission line in green • Implies it’s a gas, NOT made of stars (which would have absorption lines) • Unknown element “Nebulium” makes greenish color • (1926) Bowen shows Nebulium is really Oxygen & Nitrogen under extraordinary conditions 19 C. Central Star: White Dwarf! • 1800 Friedrich von Hahn discovers central star of Ring Nebula (very faint) • Central Stars have Hydrogen, Helium and sometimes Carbon & Oxygen lines. • 1918 Wright identifies as type “O” [VERY HOT 125,000 C], hence must be very very small to be so faint! 20 21 IV. Evolution & Age A. Age of Planetary Nebula B. Distance to Planetary Nebula C. Did it explode? A. Exploded Stars • (1956) Iosif Shklovsky proposes that red giant stars explode and form a planetary nebular • In 100 years, M27 has expanded 2” • Today it is 5’=300” in size • How old is it? • (300”)(100 yr/2”)= 15,000 years 22 B.1. Doppler Effect with Sound 1842 Christian Doppler shows “detected” frequency fd depends upon: 23 v f d f s 1 fs frequency of source c v relative speed between detector and source • • • c velocity of sound in medium • So if moving 10% speed of sound towards you, the frequency will be increased 10% B.2. Doppler Effect with Light Amount of shift of color is proportional to speed: v/c = / A 10% shift in wavelength means 10% speed of light 22 C.1. Size of Dumbbell • • (1970) Dumbbell has Doppler shift of 0.01% (0.0001)c=(0.0001)(300000km/s)=30 km/sec • In 1 year expands: 30 3600 24 365 Billion km km sec • sec hr hr day day year In 15,000 years has expanded to size: 15,000 yr billion km 15 trillion km (1.5 light year) 25 C.2. Distance to Dumbbell • Recall the “parallax triangle” • Hence if the size is 100,000 AU and makes an angle of 300”, how far away is it? size 100,000 AU 333 parsecs D 300" angle 26 27 Review • • • • • • First Planetary Nebula Discovered was (a) Ring Nebula (b) Cats Eye Nebula (c) Double Helix Nebula (d) Dumbbell Nebula (e) Orion Nebula Vega Lyra The Harp Cats Eye Nebula Type: Planetary Nebula Where: DRACO 6 Dumbell Nebula Catalog: M27 Type: Planetary Nebula Where: VULPECULA 6 Double Helix Nebula Type: Planetary Nebula Where: AQUARIUS 6 Hourglass Nebula Type: Planetary Nebula Where: MUSCA 6 33 Review • • • • • • First Planetary Nebula was discovered by (a) Huggins (b) Herschel (c) Fraunhofer (d) Messier (e) Kant 34 Review • • • • • • Age of a planetary nebula is about (a) 100 years (b) 10,000 years (c) 100,000 years (d) 10 Million years (e) 10 Billion years 35 Review • • • • • • Size of a planetary nebula is about (a) 1 AU (b) 1 km (c) 1 light year (d) 1000x size of sun (e) 1 MPC 36 Review 4. Planetary Nebula (a) are the disk of material left over from a star formation that will form its planets (b) are made of a close group of stars that are hard to resolve (c) Are exploded stars (d) are a nebula that has yet contracted to form a star (e) Are Uranus-like planets 37 V. Summary • • Discovered by Messier (first one M27) Herschel interprets as planetary systems forming 2 VI References • Historial M27 http://www.maa.clell.de/Messier/Mdes/dm027.html • Huggins http://www.maa.clell.de/Messier/E/Xtra/Bios/huggins.html • History: http://en.wikipedia.org/wiki/Planetary_nebula#Observations