Spring 2009 Course Observing the Moon, Planets and Stars 1 Osher: Spring 2009 Course: Observing the Moon, Planets and Stars Dates: Wednesdays (April 8, 15, 22, 29, May 6) Time: 7:30-9:30 pm, Kenna 109 Instructor: Dr. Bill Pezzaglia, (Pat Maloney deleted) http://www.clifford.org/drbill/osher Pending weather, each week we will spend an hour observing the sky using telescopes after a short introductory lecture (if cloudy the lecture will be extended). Participants will have the opportunity to learn how to use the telescopes themselves if they wish, or can let the instructors find objects for them to view. Available in spring are the planets Mercury, Mars & Saturn, plus of course our moon and various star clusters & nebulae. The last meeting coincides with a conjunction of the Moon & Mercury (and observation of our sun). 2 Notes Lecture Notes can be downloaded at: http://www.clifford.org/drbill/osher/spring09.html Contact: Information DrBill@clifford.org http://www.clifford.org/~drbill 650-430-0342 (cell) 3 2008 2009 The International Year of www.astronomy2009.org 4 Suggested Materials: The Night Sky (Planisphere) [30-40 degree] Available in SCU Bookstore (physics 2 or 3) Or order directly from www.davidchandler.com/nightsky/htm 100 hours of astronomy (April 2-5) The Potato Discovery of Planetary Nebulae 5 I. Introduction 6 March 25, 2009 Dr. Bill Pezzaglia www.clifford.org/~drbill According to CNN the world will end Dec 21, 2012 1
As usual, they got it wrong 7 Planetary Nebulae 8 The world will end: Dec 21, 5,000,002,012 The sun will. I. Introduction II. Discovery III. Structure IV. Measurements V. Summary NGC2392 (Eskimo) II. Discovery 9 A. Messier Catalog 10 A. Messier s Catalog B. Herschel names them C. Nebular Hypothesis M97 Owl Nebula Ursa Major 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! The Summer Triangle Deneb Cygnus The Swan Altair Vega Lyra The Harp 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 11 M76 Barbell Nebula Perseus (1780) (Not recognized as Planetary Nebula until 1918) Perseus The Hero Schedar Cassiopeia Queen of Ethiopia Algol Pleiades 12 2
Ursa Major The Big Bear Alcor & Mizar 13 B. 1781: Uranus Discovered (accidentally!) by William Herschel using a 6 inch telescope 14 M97 Owl Nebula Discovered 1781 6000 years old? Polaris Ursa Minor The Small Bear Herschel Classifies Nebulae 15 1785 Catalog of 1000 objects 1788 another 1000 objects 1802 another 500 objects Classifies objects into star clusters and nebulae. The types were: I. Bright Nebulae II. Faint Nebulae III. Very faint Nebulae IV. Planetary Nebulae (Uranus-like in color & shape) V. Very large Nebulae VI. Very compressed and rich star clusters VII. Compressed clusters of small and large (i.e., faint and bright) stars VIII. Coarsely scattered clusters of stars C. Nebular Hypothesis 16 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) III. The Message in the Light 17 A.1. Dark Line Spectra 18 A. Atomic Spectra Lines B. Huggins & Nebulium 1802 Wollastan sees lines in solar spectra 1814 Fraunhofer Labels them A, B, C, D Later measures over 500 lines! C. Central Stars are White Dwarfs 3
A.2. Solar spectrum 19 A.3. Bright Line Spectra 20 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 A.4. Kirchhoff s Laws 21 B. 1786 Herschel discovers: 22 Draco the Dragon Ursa Major Ursa Minor H IV 37 (NGC6543) Cats Eye Nebula (made of stars?) Polaris Gemini The Twins Castor 23 B.2 William & Margaret Huggins 24 Pollux (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) NGC2392 (1787) Eskimo Nebula (Herschel) Unknown element Nebulium makes greenish color 4
Tom Lehrer: Elements Can you find the element Nebulium? B.2 William & Margaret Huggins 26 (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 C. Central Star: White Dwarf! 27 Helix Nebula, Aquarius 28 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 (magnitude m=15.3)! Not a normal star forming! Discovered 1824, central star is 100,000 degrees Kelvin, m=13.4 It is the closest bright nebula to earth (700 light years) White Dwarfs 29 Hourglass & Double Helix 30 (1956) Iosif Shklovsky proposes that (red giant) stars explode and form a planetary nebula + white dwarf star White dwarfs would have BIG densities. A handful of this electron degenerate matter would weigh several tons on the earth! But are they just science fiction? To PROVE it, you must find one in a binary star system, where you can measure its mass. They found one orbiting Sirius! Earlier theories thought the star blew up once but some nebulas show 2 rings How can there be 2 deaths? 5
Bipolar Planetary Nebula 31 32 One of the stars is pulling matter off its partner and spinning it into a giant disk, about 10 times the diameter of Pluto s orbit. The disk acts like a jet nozzle to accelerate the gas to 200 miles/sec M2_9 HST: Wings of Butterfly Nebula (Twin Jet Nebula) Planetary in Ophiuchus (2100 Lightyears away) About 1200 years old Neutral Oxygen (red), once ionized Nitrogen (green), twice ionized Oxygen (blue) Ant Nebula in Norma, 1000 km/sec gas channeled by magnetic field 2f). Preferential Ejection 33 Hourglass Nebula (Musca) Ejected doughnut shaped cloud of gas and dust from its equator Later ejected gas from entire surface, which was channeled by dust into oppositely directed streams Explains 2 loops! IV. Measurements A. Age of Planetary Nebula B. Doppler and Speed C. Size & Distance 34 NGC3132 Eight-burst Nebula A. Age of Planetary Nebula 35 Compare measurements of size of nebula over several centuries. In 100 years, M27 has expanded 2 Today it is 5 =300 in size B.1. Doppler Effect with Sound 1842 Christian Doppler shows detected frequency f d depends upon: f f s frequency of source d fs 1 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% 36 v = + c How old is it? (300 )(100 yr/2 )= 15,000 years 6
B.2. Doppler Effect with Light 22 C.1. Size of Dumbbell 38 (1970) Dumbbell has Doppler shift of 0.01% (0.0001)c=(0.0001)(300000km/s)=30 km/sec Amount of shift of color is proportional to speed: v/c = Δλ/λ In 1 year expands: km sec hr 30 3600 24 365 day ( )( )( )( )= sec hr day year Billion km A 10% shift in wavelength means 10% speed of light In 15,000 years has expanded to size: 1billion km (,000yr)( )= 15 year 15 trillion km (1.5 light year) 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? D = size angle 100,000AU = = 333 parsecs 300" 39 V. Summary Early confusion if planetary nebulae were close groups of stars or gaseous nebula Then it was thought they were a star forming from a nebula Expanding size and exotic white dwarf core imply its an exploded star 40 VI. Review Questions 41 Question 1 42 (i.e. a test of short term memory ) No grades! First Planetary Nebula Discovered was (a) Ring Nebula (b) Cats Eye Nebula (c) Double Helix Nebula (d) Dumbbell Nebula (e) Orion Nebula 7
Constellation? 43 Question 3 44 Vega 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 Lyra The Harp Ring Nebula M57 NAME?: Cats Eye Nebula Question 5 45 46 First Planetary Nebula was discovered by (a) Huggins (b) Herschel (c) Fraunhofer (d) Messier (e) Kant Where? DRACO NAME?: Barbell (M76) Question 7 47 48 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 Where? Perseus 8
NAME?: Dumbell Nebula Question 9 Catalog: M27 49 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 50 Where: VULPECULA (e) Are Uranus-like planets NAME?: Eskimo Nebula 51 Question 11 52 Herschel 1787 The sun will blow up into a planetary nebula (after being a red giant for a short while) in about how many years from now? (a) Three (year 2012) (b) 15,000 (c) 5 million (d) 5 billion (e) 5 trillion Where? Gemini Question 12 The green color of a planetary nebula is due to and the red is due to (a) Nebulium, Neon (b) Oxygen, Hydrogen (c) Black body radiation, Hydrogen (d) Nebulium, Helium (e) Carbon, Hydrogen 53 Hourglass Nebula 54 Type: Planetary Nebula Where: MUSCA 9
VI References 55 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 10