Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20. Tom Burbine

Transcription

1 Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine

2 Course Course Website: Textbook: Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny. You also will need a calculator.

3 Office Hours Mine Tuesday, Thursday - 1:15-2:15pm Lederle Graduate Research Tower C 632 Neil Tuesday, Thursday - 11 am-noon Lederle Graduate Research Tower B 619-O

4 Homework We will use Spark owebct Homework will be due approximately twice a week

5 Astronomy Information Astronomy Help Desk Mon-Thurs 7-9pm Hasbrouck 205 The Observatory should be open on clear Thursdays Students should check the observatory website at: for updated information There's a map to the observatory on the website.

6 Exam #4 Hard to make questions that everybody gets right: 23 out of 274 (8% of class) got this question wrong Which spacecraft landed on the surface of Venus and took pictures of the surface? Venera 9 8 out of 274 (3% of class) got this question wrong Caloris Basin and Hellas Basin are both large impact craters

7 Class average was 75.4 Exam #4 Grades ranged from 45s to 100

8 Class Averages as of today For people who took all 4 tests: Class average now (80% Exam, 20% HW) is 80.6 Grades range from a 98.3 to a 54.2 This average will go up when the lowest exam grade is dropped after the final and the lowest HW grade is dropped

9 Final Cumulative Monday - 12/14 4:00 pm Hasbrouck 20 Review Session Sunday -12/13 3:00 pm Hasbrouck 134

10 Due today HW #20 and 21

11 HW #18 (late) and #19 (late) I have put HW #18 (late) and #19 (late) All calculations On blog

12 Student Presentations Life on Mars Life on Europa and Titan Life on extrasolar planets

13 Why we should worry about asteroids and comets?

14 2009 DD45 On March 2, 2009: NEA 2009 DD45 came within ~70,000 km of the surface of the Earth Diameter between m Over 36 minutes

15 Tunguska This object is believed to be the same size as the object that exploded over Siberia in 1908 About 1,000 times as powerful as the bomb dropped on Hiroshima

16 2008 TC3 2-3 m object that entered the atmosphere over Sudan on October 7, 2008 Burned up before it reached the ground Fragments found

17 99942 Apophis Initially thought to have a high probability (up to 2.7%) of hitting Earth in 2029 ~270 meters in diameter Impact probability with Earth for April 13, 2036 is calculated as 1 in 45,

18 Comets can also hit us Comets

19 When were comets first discovered? Comets have been known since the earliest days of mankind Usually thought to be unlucky Attacks by heavenly beings on terrestrial people Comet Ikeya-Zhang 153P/Ikeya-Zhang Period of 341 years

20 Chinese, written on silk about 168 BC: Astrological omens, such as war comes, general dies, 'small war, corn plentiful'

21 Roman coin depicting soul of Julius Ceasar as a comet

22 Comet Halley in 1145 From English Monastery

23 Comet Halley in 1066 Bayeaux Tapestry

24 Fresco by Giotto, ca 1300

25 From German manuscript, ~ 1400 AD

26 Moctezuma II in 1516

27 Comet Ikeya-Zhang Copyright 2002 Michael Jager

28 Comet Wild2 By StarDust

29 Comet Tempel 1 before impact from Deep Impact Tempel 1 pre-impact 5 x 7.6 km

30 Halley s Comet Edmund Halley figured out that the orbit of the comet of 1682 was nearly the same as those of two comets which had appeared in 1531 and 1607 Halley concluded that all three comets were in fact the same object returning every 76 years Halley predicted its return for Halley's prediction of the comet's return proved to be correct, although it was not seen until December 25, 1758

31 Comets Usually named after discoverer (or person who computed its orbit) Comet Halley Number given when discover (or discoverers) have discovered numerous comets Comet Shoemaker-Levy 9

32 Types of Comets Short period comets periods < 200 years Long-Period Comets periods > 200 years

33 Comets Comet West Blue tail gases, white tail dust particles

34 Comet Halley Giotto image Dimensions - 16 x 8 x 8 km

35 Comets Called Dirty Snowballs by Fred Whipple Because they are mixtures of ice and dust

36 Composition Rock Dust water ice frozen gases such as carbon monoxide, carbon dioxide, methane, and ammonia.

37 An Icy Conglomerate Nucleus In 1950, Fred Whipple showed that comet activity can be explained by sublimation of water ice from an icy conglomerate nucleus a few km in size. The sublimation rate can be computed as a function of temperature.

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41 Periodic Comet Halley, 1986 Our first look at a comet nucleus Giotto (Comet Halley will return in 2061)

42 Comet P/Halley Giotto HMC

43 Comet West Comet West

44 Where does cometary dust originate?

45 Origin of Cometary Silicates Crystalline olivine and pyroxene condensed at high T, most likely in the inner solar nebula Glassy silicates were not subjected to high temperature, may be ancient interstellar grains

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47 The Importance of Sample Return Missions Science is done on the ground Instrumentation is state-of-the-art and more Ultimate in precision & sensitivity Not limited by mass, power, cost or reliability Results can be confirmed by several methods Instruments can be calibrated Analysis is iterative not limited by pre-conceived ideas Samples - a resource for present and future study

48 Stardust Mission Mission to investigate Comet Wild 2 Return samples of the comet back to Earth

49 Dr. Peter Tsou with aerogel Aerogel - Peter Tsou

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53 Two-micrometer comet particle, collected by the Stardust spacecraft, is made up of the silicate mineral forsterite (Mg 2 SiO 4 ) (olivine)

54 Encounter with Comet 81P/Wild 2 January 2, days post-perihelion Heliocentric distance: 1.86 AU Geocentric distance: 2.6 AU Closest approach: 236 km Encounter speed: 6 km/s

55 72 encounter Images Full range of phase angles ( 70 o - 3 o o ) Alternate 10 & 100ms exposures

56 Comet P/Wild x 4 x 5.5 km Stardust

57 Flat-floor crater - 140m deep stereo

58 Scarps Cliffs imply crust with some strength

59 P/Wild 2 nucleus Wild 2 image superimposed on jets Nucleus image superimposed on image of jets

60 Deep Impact NASA space probe designed to study the composition of the interior of the comet Tempel 1.

61 Deep Impact 2 parts: 370 kg copper-core "Smart Impactor" which impacted the comet "Flyby" section, which imaged the crater created by the impactor.

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63 Videos _Long_ mov Movie.mov act.mov

64 Image from Deep Impact Comet Tempel 1 or Comet 9P/Tempel 1

65 Any Questions?