Test 04 Chapters 15-20 Limited Copies Are available Griffith Observatory Samuel Oschin Planetarium June 4 th from 8:00 pm - 10:00 pm Covering ALL Tests Slide 1 Slide 2 Griffith Observatory Samuel Oschin Planetarium Griffith Observatory Samuel Oschin Planetarium Slide 3 Slide 4
What will be on the final Only questions from the four tests. It will consist True/False Multiple Choice Fill In the Blank Matching Short Answer It will be L O N G around 250 questions Study the Tests Study the Tests Study the Tests Study the quizzes Study your notes Read the book» Try to understand everything Slide 5 Slide 6 HOW TO STUDY FOR THE FINAL ALL OF THE TESTS WILL BE ONLINE Most of the answers will be online All of the true/false, multiple choice and matching will be online Study the last test as a LOT of the questions will come from this test Extra Credit!!! Before the final Go to the Griffith Observatory See the Planetarium Show Bring me the ticket receipt Earn an extra 5% credit on your grade! Slide 7 Slide 8
Chapter 19: s, Asteroids, and Shooting Stars or Meteors? Slide 10 Fig. 19-1, p.412 Meteoroid A Rock In Space that will enter the earth s atmosphere s s Meteor The Light In The Sky (Shooting Star) Stony Metallic A Rock In Space that makes it to earth Carbonaceous Achrondritic Chrondrite All Metal Stony Metal Chrondrites Slide 11 Slide 12
Analysis of s 3 broad categories: Iron meteorites Stony meteorites Stony-iron meteorites Slide 14 Slide 15 Slide 16
Meteor Showers Most meteors appear in showers, peaking periodically at specific dates of the year. Slide 17 Fig. 19-2d, p.413 Slide 19 Radiants of Meteor Showers Tracing the tracks of meteors in a shower backwards, they appear to come from a common origin, the radiant. Common direction of motion through space. Meteoroid Orbits Meteoroids contributing to a meteor shower are debris particles, orbiting in the path of a comet. Spread out all along the orbit of the comet. Comet may still exist or have been destroyed. Slide 20 Only few sporadic meteors are not associated with comet orbits.
The Origins of s Probably formed in the solar nebula, ~ 4.6 billion years ago. Almost certainly not from comets (in contrast to meteors in meteor showers!). Probably fragments of stony-iron planetesimals Some melted by heat produced by 26 Al decay (half-life ~ 715,000 yr). 26 Al possibly provided by a nearby supernova, just a few 100,000 years before formation of the solar system (triggering formation of our sun?). The Origins of s (II) Planetesimals cool and differentiate; Collisions eject material from different depths with different compositions and temperatures. s can not have been broken up from planetesimals very long ago Remains of planetesimals should still exist. Asteroids Slide 25
Slide 26 Slide 27 Slide 28 Slide 29
Impacts on Earth Over 150 impact craters found on Earth. Impact Craters on Earth (II) Barringer Crater: ~ 1.2 km diameter; 200 m deep Famous example: Barringer Crater near Flagstaff, AZ: Much larger impact features exist on Earth: Impact of a large body formed a crater ~ 180 300 km in diameter in the Yucatán peninsula, ~ 65 million years ago. Slide 30 Formed ~ 50,000 years ago by a meteorite of ~ 80 100 m diameter Slide 31 Drastic influence on climate on Earth; possibly responsible for extinction of dinosaurs. Impacts on Earth (III) Comet nucleus impact producing the Chicxulub crater ~ 65 million years ago may have caused major climate change, leading to the extinction of many species, including dinosaurs. Chicxulub crater 300 km Slide 32 Gravity map shows the extent of the crater hidden below limestone deposited since the impact. Slide 33
Slide 34 Slide 35 The NEOWISE Project (Near Earth Object Wide-field Infrared Survey Explorer) Finding, Tracking and Characterizing Asteroids Slide 36 Slide 37
Asteroids Small, irregular objects, mostly in the apparent gap between the orbits of Mars and Jupiter. Last remains of planetesimals that built the planets 4.6 billion years ago! Asteroids Colors of Asteroids Colors to be interpreted as albedo (reflectivity) at different wavelengths. M-type: Brighter, less reddish asteroids, probably made out of metalrich materials; probably iron cores of fragmented asteroids C-type: Dark asteroids, probably made out of carbonrich materials (carbonaceous chondrites); common in the outer asteroid belt S-type: Brighter, redder asteroids, probably made out of rocky materials; very common in the inner asteroid belt Asteroids The Origin of Asteroids Distribution: S-type asteroids in the outer asteroid belt; C-type asteroids in inner asteroid belt may reflect temperatures during the formation process. However, more complex features found: Images of the Asteroid Vesta show a complex surface, including a large impact crater. probably fragmented from Vesta Vesta shows evidence for impact crater and lava flows. Heat for existence of lava flows probably from radioactive decay of 26 Al. Asteroids Slide 41 Asteroids
Slide 42 Asteroids Slide 44 Comet C/2001 Q4 Comet Soup The Geology of Comet Nuclei Comet nuclei contain ices of water, carbon dioxide, methane, ammonia, etc.: Materials that should have condensed from the outer solar nebula. These "comet soup" ingredients are pictured above: (in the back from left to right) a cup of ice and a cup of dry ice; (in measuring cups in the middle row from left to right) olivine, smectite clay, polycyclic aromatic hydrocarbons, spinel, metallic iron; (in the front row from left to right) the silicate enstatite, the carbonate dolomite, and the iron sulfide marcasite. Those compounds sublime (transition from solid directly to gas phase) as comets approach the sun. Densities of comet nuclei: ~ 0.1 0.25 g/cm 3 Not solid ice balls, but fluffy material with significant amounts of empty space. Slide 45 Slide 46
Slide 47 The Origin of are believed to originate in the Oort cloud: Spherical cloud of several trillion icy bodies, ~ 10,000 100,000 AU from the sun. Oort Cloud Gravitational influence of occasional passing stars may perturb some orbits and draw them towards the inner solar system. Interactions with planets may perturb orbits further, capturing comets in short-period orbits. Slide 48 Two Types of Tails Ion tail: Ionized gas pushed away from the comet by the solar wind. Pointing straight away from the sun. Dust tail: Dust set free from vaporizing ice in the comet; carried away from the comet by the sun s radiation pressure. Lagging behind the comet along its trajectory Gas and Dust Tails of Comet Mrkos in 1957 Comet Hale- Bopp in 1997 Streaked Gas Tail Dust Tail Slide 49 Slide 50
Dust Jets from Comet Nuclei Jets of dust are ejected radially from the nuclei of comets. Comet Hale-Bopp, with uniform corona digitally removed from the image. Slide 51 Slide 52 Comet dust material can be collected by spacecraft above Earth s atmosphere. Fragmenting Fragmentation of Comet Nuclei Comet Linear apparently completely vaporized during its sun passage in 2000. Comet nuclei are very fragile and are easily fragmented. Only small rocky fragments remained. Comet Shoemaker-Levy was disrupted by tidal forces of Jupiter Two chains of impact craters on Earth s moon and on Jupiter s moon Callisto may have been caused by fragments of a comet. Slide 53 Slide 54
Deep Impact Deep Impact is a NASA space probe launched on January 12, 2005. It was designed to study the composition of the comet interior of 9P/Tempel, by releasing an impactor into the comet. At 5:52 UTC on July 4, 2005, the impactor successfully collided with the comet's nucleus. The impact excavated debris from the interior of the nucleus, allowing photographs of the impact crater. The photographs showed the comet to be more dusty and less icy than had been expected. The impact generated a large and bright dust cloud, which unexpectedly obscured the view of the impact crater. Slide 55 Slide 56 A total of 11 million pounds of water and between 22 and 55 million pounds of dust were lost from the impact. Deep Impact Just before collision Just after collision Slide 57 Slide 58
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