Astronomy 10 - Fall 2003 - Filippenko - Midterm 2

Astronomy 10 - Fall 2003 - Filippenko - Midterm 2 -...

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Unformatted text preview: Astronomy 10, Section 1 — Fall 2003 — Professor Alex Filippenko Midterm Exam #2 — 3 November—2003 Print name: _____-__-_______s..r__r__w___ Sign names Student ID #: Print your GSI’s Name: -_.._.-___. ________m_____"____ Discussion section # (or day, time): ___________ Print and sign your name on your SCAN-TRON 882 form. Under “subject,” please put your GSI’s name and your discussion section number. ‘CLOSED BOOK, CLOSED NOTES, NO CALCULATORS Mark all answers on SCAN-TRON form 882. Use a #2 pencil. Completely fill in the appropriate bubble. Be sure to thoroughly erase all altered answers and stray marks." For true/false questions: mark bubble A if the statement is true, and bubble B if false. For multiple choice questions: mark the bubble corresponding to the single best answer. All 25 questions carry equal weight. Read each question carefully before answering. There is no penalty for guessing. If mm need extra room. for work, use the last {blank} page. Turn in both this multivpage set of questions and your SCAN-TRON form. DO NOT OPEN THIS EXAM UNTIL TOLD TO DO 80!! Time limit: 42 minutes — budget your time appropriately. GOOD LUCK! Possibly Useful Information 03 (pc) = 1/3) (arcsec) d = et density ,0 : M/V c z 3 X 105 km/s For a Sphere, V = firm, Amrfac, : «4st For a circle, A = «R2, C : ZnR There are about 3.2 X 107 seconds per year, and 86,400 [roughly 105) seconds per day Degrees Kelvin = degrees Centigrade —i— 273; Fahrenheit : (9/5)Cent. —|— 32 1 A.U. = 1.5 x 108 km 1 light year (1y) :3 63,000 A.U. e 9.5 x 1012 km a 1013 km 1 pc = 3.261)! m 3 x 1013 cm a: 3 X 1013 km 1 A : 10”S em = 10‘“J In 60” (arcsec) = 1' [arcmin), 60' : 1° (degree), 360° 2 full circle 2 2r: radians '2 24 hours AmarTm3X107AK=03ch AVZC P=1/u 520114 E=hu z:(A—A0)/A0 2mm 'zev/cifvsoac z: if—gg—g—i forallec. F=GM1M2/d2 erlezrg LocM'4 Rocl‘l/l'fl'75 p+e_—>n+v R5 : 9Gll/l/c2 Rphomn sphere = 36'Mr/e2 MC}, : 1.4 M3. F = ma Lmdbody : 4nR20T4 (for a sphere) b = L/(4rrd2) E : nae2 = mne2[1 — ('uz/c2)]_1"2 v = Hod, where H0 2 50—80 km/s/Mpc Q = p/pcm-t per“ 2 3Hfi/(81TG) M : UZR/G N = R*fpnef;fgch, where R* m N*/T (N... = # stars in galaxy, T 2 age of galaxy) P2 z kR3 [k a constant 2 4n2/(G'M1) if M; >> M2]; in general, P2 = (4n2R3)/[G(M1 + M2)] For planets, 1; oc l/x/ITE tmoving = (trest)[1 — ('az/czfll’!2 Lmoving = (Lrest)[l — Caz/(22)]1”2 i Be sure you answer question #1 correctly (6 points off if incorrect)! (1) Ryan Foley, the Head GSI for this class (Astronomy 10, Section 1, Fall 2003), (a) lives on a moon orbiting Uranus. (b is actually a punk rock star in disguise. d is a graduate student in astronomy at UC Berkeley. (d) can‘t possibly be human, because he’s made of pure niobium and plutonium. (e) thinks that UC Berkeley’s TALC (The Astronomy Learning Center) is the silliest thing in the world, and nobody should waste their time going to TALC. (2) T or F. Humans on the planet Earth could not exist if supernovae didn’t occur in the Universe. fl, / (3) Katie is falling into a stellar-mass black hole. Luckily (for you), you are observing her from a safe distance. Which one of the following phenomena would you observe first? ”Katie crossing the event horizon. (b) Katie’s clock stopping because of extreme warping of space-time. (9’) Katie waving at you from the region interior to the event horizon. Katie “evaporating” out of the black hole through Hawking radiation. ((2)5 Katie being ripped apart by tidal forces. Core-collapse supernovae tend to be found in, or near, regions where massive stars are med. , Every White dwarf in a binary system will eventually become a supernova when the companion star fills its Roche lobe. )c) Supernovae are the only way to create the important elements hydrogen, carbon, and oxygen. _(,d’) Supernovae are rather common, occurring about 80-100 times a year in our galaxy. {(6’)- Some types of supernovae can recur, as the surface layers of the white dwarf repeatedly undergo nuclear runaway. (4) 'ch one of the following statements about supernovae is TRUE? (3-) fo (5) T or F. Many astronomers don‘t consider Pluto to be a genuine planet, largely because they claim it is only one member of a swarm of Kuiper Belt Objects. A (6) Which one of the following would have the largest Schwarzschild radius, if compressed to form a black hole? (Notes: In some cases, it is already a black hole. 1 kg = 2.2 pounds.) (a) A 10 kg black hole. (b) A 20 kg black hole. (c) A 15 kg piece of uranium (which is very dense). (d A fly doing a pushup. GSI Evan (after Thanksgiving dinner). (7) Which one of the following statements about extrasolar planets is FALSE? (3L Extrasolar planets can sometimes be detected by monitoring the brightness of a star, and eing it decrease as the planet blocks part of the star’s light. Sills) Many extrasolar planets discovered thus far have elliptical orbits that are far more 9 centric than the orbits of most planets in the Solar System.. ( Most extrasolar planets discovered thus far were detected by measuring periodic Doppler 250 ”3/2, 7 0/5-7 shi ts in the spectra of stars. é? As in our Solar System, large (Jupiter-like) extrasolar planets are not found close to the st that they orbit. (e) The apparent observed absence oflow-nlass, Earth-like extrasolar planets is not surprising, because with current technology we are unable to detect them. (8) A star that is now a white dwarf may have been, at one time, which of the following? (Assume the star has always been solitary —~ i.e., never in a binary system.) ,_. / (I ' A star of 2 solar masses. A star of 20 solar masses. ,Irl’l. A hot, blue, “type 0” main-sequence star. (IV; A pre-main-sequence star. . I I only. 7 I and IV only. / (c) I and III only. ((1) III and IV only. ( l e I, II, and III only. 9 T or F. One type of supernova occurs when a red iant’s mass reaches the critical 3 Chandrasekhar limit, and the red giant undergoes nuclear runaway. 7 (10) If the Sun magically turned into a black hole tomorrow, Earth would (a) be sucked into the black hole within about two years. /(b.) be ejected from the Solar System. ({3}) retain the same orbit that it currently has. (Ll) be flung through the black hole’s ergosphere, emerging with additional energy of motion. (p) throw a big party that night. (11) Two stars (Joe and Linda) have exactly the same intrinsic properties (specifically, the same mass, temperature, radius, and age), but Joe’s parallax (measured flow-His. three times larger 1 than Linda’s parallax. What is the ratio of Joe’s luminosity to Lindas urrliriosity?___."' (a) 1/9 a - x ., ___________ (b) 1/3 _-... a. I -- st s1 3 a. r. .- (c) 9 J ., (12) IWhich one of the following statements about pulsars and neutron stars is FALSE? (a’)’ Most neutron stars are formed as the result of the death of a massive star. (Eb?) Pulsars are neutron stars that are rapidly, and periodically, oscillating in size. (C) It is sometimes possible to see pulsars in the visible (optical) range of the electromagnetic 7 spectrum. ’ 4.4%) All pulsars are neutron stars, but not all neutron stars are seen by us as pulsars. y If the magnetic axis and rotational axis of a “pulsar” are perfectly aligned, the “pulsar" oesn’t pulse. - (13) Which one of the following is currently NOT possible evidence that Mars may have had con ' 'ons suitable for life at some time in its past? (a) Substantial quantities of complex organic compounds such as proteins were found on the s ace of Mars by the Viking lander. There are substantial quantities of water ice, currently present in the polar caps and in permafrost, that may have been liquid long ago. J(,e’)/ Ancient river beds, which probably once had running water, were seen by spacecraft. ,Ld) Ancient flood plains were seen by spacecraft. 1/02) A meteorite believed to be from Mars has been found, and it might contain fossilized )act eria and chemical evidence of life. fl ,1 L/ (14) Which of the following is a consequence of Jupiter’s enormous tidal forces? (I? The breakup of Comet Shoemaker-Levy 9 (which later crashed into Jupiter] into many fragments. II. Jupiter’s oblate (squashed) shape. III. Io’s extreme volcanic activity. IV. The presence of a thin ring around Jupiter where there could have been a meon. jail" I and II only. I ' I and III only. c) I, III, and IV only. II, III, and IV only. (e) I, II, III, and IV. (15) Star Brandon and Star Mo are main-sequence stars in a binary system with circular orbits. Brandon is twice as far away from the system’s center of mass than Mo. What is the ratio of Bran 1s luminosity to Mo’s? / _ __ J}. _ - . 4 1/16 l l0 ' a 6 z (5*. f4 (b) 1/2 (C) 1 , x ' (d) 2 / , 06 (e) 16 (16) Which one of the following properties of a star is the main factor in determining its position on the main sequence? - Its chemical composition. Its mass. (c) Its angular momentum (i.e., spin). ((1) Its age. (e) Its distance from the Sun. (17) Which one of the following statements about sunspots is TRUE? 3,1) It is safe and easy to view sunspots with the naked eye, without filters. during a total olar eclipse. Strong gravitational fields inhibit hot interior gas below the photosphcrc from entering 1e unspot region. *6? Sunspots appear dark because they are extremely cold and don’t emit any light. /(,dj" Sunspots appear dark because they are much hotter than the surrounding area; their on 'ion peaks at ultraviolet wavelengths, which our eyes cannot see. a; Large sunspot groups are sometimes associated with solar flares and prominences. (18) Which one of the following statements about brown dwarfs is TRUE? ha) A brown dwarf is the very cold remnant of a red giant that has lost its outer hydrogen and helium layers through ejections that produced planetary nebulae. ) While cooling to eventually form a black dwarf. a white dwarf goes through the brown dwarf stage. a. Brown dwarfs are about as massive as our Sun, but significantly smaller. Brown dwarfs are formed by the same initial process that forms main-sequence stars. (e) A low rate of sustained nuclear fusion allows brown dwarfs to emit mainly at infrared wavelengths. (19) Which one of the following is NOT a positive test of general relativity? [(3’) The precession of Mercury’s orbit. (,b’) The different apparent positions of stars near the Sun during a solar eclipse. (pl' Light emitted outward from the Earth’s surface shifts to a lower frequency. -\ The orbital period of binary neutron stars decreases with time. Q It takes about 8 minutes for light from the Sun to reach the Earth. (20) T or F. If a helium nucleus has 0.7% less mass than four free protons (each of mass mp), then the equation E : (0.007)(4nr.r.p)c2 represents the amount of energy generated by the Sun each time a new helium nucleus forms through nuclear fusion. x4 (21) Which one of the following combinations of information is sufiicient for determining a star’s radi 5? (Note: the star is not necessarily on the main sequence.) Luminosity. distance, and apparent brightness. (13). Mass, spectral type, and parallax. c Peak wavelength of blackbody emission, parallax, and mass. . Parallax, apparent brightness, and surface temperature. (e) Mass of its binary companion, apparent brightness, and distance. (22) Which one of the following statements about comets is FALSE? The tail of a comet points roughly away from the Sun. (b); The tail of a comet grows as the comet approaches the Sun because more of the comet’s g es start chemically burning. (c) Comets are believed to be leftovers from the formation of our Solar System. (d) Meteor showers occur when Earth crosses the orbit of an old comet that is disintegrating. (e) The sudden extinction of large numbers of species on Earth about 65 million years ago seems to have been caused by a comet or asteroid collision with Earth. (23) T or F. If Star Renbin is twice as luminous as Star Francis, but Renbin is twice as distant as Francis, then Renbin will appear as bright as Francis. P (24) Which one of the following statements about planets in our Solar System is FALSE? TH?)— The narrow rings of Uranus were unexpectedly discovered when astronomers were monitoring the apparent brightness of a star that Uranus occulted (blocked) for a while. “(b)__ The existence of Neptune was predicted by comparing the observed and expected positions of ranus. a. (c) Ignoring the reflective clouds, the atmosphere of genus is more opaque at optical wavelengths than at infrared wavelengths. In) The terrestrial planets are the densest planets since they contain relatively low amounts of gas in relation to the amounts of rocky and metallic material. “(13.) Studies of the atmospheres of planets can help us understand atmospheric phenomena on Earth. (25) T or F. Astronomers can determine the approximate age of a cluster of stars by plotting luminosity VS. surface temperature for all stars in the cluster, and analyzing the resulting graph. A End of Examination - _:_“.o_"_._.>z._. ) 5 2 exam: S: ._. 2%. _...\.u._u.,r.m = - m F > 7. H m 3 Z flora. ZO. mmm-m 2533mmmmIEanmquizfi do cmm mchmnfl<m 1 c211... H E {..:......Z.‘.. .. .I m moon—m mmbacmmu _ . _ H. 33.x 3:: 103.55 magma—..«m 59.23.. _ . 3me on}: Efirzm u. 9% 03¢ 32: .51 35 o: :3. i 1| u m _ .. .mm voiwm 53.13:: I A _ .mmbmmoognrmamc. . mcmgmnd D. _ Soiznm ..I. . mxngmrmOm .. _. l. .,H l . _ .mxraurm” .9 m LI 5 m macomza a ... n... z _ moomm” .. .._. ... .u u :_ —3(]— £20.— '10— r. 1' 6 5 2 1 it 0 '5 2 KEY 40- a 3 E R O C S E W T C E J B U S INSTRUCTOR USE ONLY ;504 9 51 .._.. 3?. me I 5.5.5.. wnmflwwOBH—Oqam 001: mmc dual: .. cw £4.20 ! m 8 E :3 New 8m 3: 623mm The answers are all Comect! ...
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