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Asteroid, Meteor, KometRoslizah A.SamadIPG Kampus Perempuan MelayuMelaka

1ASTEROIDBatuan kecil pelbagai saiz dari sekecil debu hingga yang berdiameter beratus kilometer.Ada kalanya dipanggil planet minorTerjadi daripada bahan sisa sistem suriaKebanyakannya beredar di dalam Jaluran Asteroid iaitu orbit di antara Marikh dan Musytari.Ceres adalah asteroid yang paling besar dan yang pertama dijumpai.Kini terdapat lebih 100,000 telah ditemuiGaspra yang terletak dipinggir jaluran asteroid berbenstuk tak sekata dan berdiameter 12 km.

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Ida Dan Gaspra Gambar menunjukkan asteroid Ida yang diambil oleh kapal angkasa Galileo pada 28 Ogos 1993, lebih kurang 3.5 minutes sebelum kapal angkasa itu mendekati asteroid tersebut. Gambar menunjukkan banyak kawah, dan antaranya lebih besar daripada kawah pada Gaspra.

3Ida This view of the asteroid 243 Ida was acquired by the Galileo spacecraft at ranges of 3,057 to 3,821 kilometers (1,900 to 2,375 miles) on August 28, 1993, about 3.5 minutes before the spacecraft made its close approach to the asteroid. This view shows numerous craters, including many degraded craters larger than any seen on Gaspra. The south pole is believed to be in the dark side near the middle of the asteroid. (Courtesy NASA/JPL) More information on asteroids at: http://nssdc.gsfc.nasa.gov/planetary/text/asteroids.txtAnd at http://www.nineplanets.org/asteroids.html

Asteroids

4METEOROIDMerupakan objek berbatu paling kecil yang wujud dalam sistem suria.Mugkin berasal dari serpihan komet atau asteroidSerpihan yang berlanggar dengan permukaan bumi dipanggil meteorit.Terbentuk akibat fregmentasi asteroid terdiri daripada dua jenis iaitu : Siderit (besi) Aerolit (batu)

5METEORTerhasil apabila meteoroid berlanggar dengan zarah dalam atmosfera bumi. Ini kerana meteoroid bergerak pada had laju yang tinggi menghasilkan haba yang banyak.Zarah-zarah di sekeliling meteoroid akan memperolehi cukup tenaga untuk di anionkan.Menyebabkan meteor kelihatan sebagai coretan cahaya di langit.Dikenali sebagai shooting starsHujan meteor boleh dilihat pada masa-masa tertentu dalam setahun.6Sambungan meteor ..Berlaku apabila orbit bumi membawanya ke kawasan aliran meteoroid.Contohnya :Perseid (boleh kelihatan dari 15 Nov 19 Nov)Leonid

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12METEORITKebanyakan meteor akan mengewap sebaik sebelum ia berhentam dengan bumi.Walau bagaimanapun jika batuan meteoroid cukup besar ia akan melepasi atmosphera bumi dan menghentam permukaan bumi. Meteoroid yang jatuh ke bumi dikenali sebagai meteorit.Ini akan menghasilkan satu kawah di muka bumi.Contohnya : di Arizona sedalam 175 meter dan diameternya 1265 meter.13Kawah Meteorit

Kebanyakan meteorite kecil dan tidak meninggalkan kesan kawah yang besar Terdapat lebih 150 kesan kawah dijumpai di bumiContohnya Kawah Barringer yang terbentuk 50,000 tahun lalu oleh meteorit yang berdiameter ~ 80 100m 14Impact Craters on Earth

Impact of a large body formed a crater ~ 180 300 km in diameter in the Yucatn peninsula, ~ 65 million years ago. Drastic influence on climate on Earth; possibly responsible for extinction of dinosaurs.Much larger impact features exist on Earth:15Mencari Meteorit

Good place to find meteorites: Antarctica!.Tempat paling baik untuk ditemui ialah AntartikaFalls = meteorites which have been observed to fallfall time known.Finds = meteorites with unknown fall time

16Menganalysis Meteorit

3 kategori utamaIron meteoritesStony-Iron meteoriteStony meteorites

17Asal Usul MeteoritMungkin daripada solar nebula ~ 4.6 billion tahun laluBukan daripada kometMungkin juga daripada supernova berhampiran iaitu 100,000 sebelum sistem suria terbentukMungkin juga berasal daripada asteroid18KOMETPerkataan komet dari perkataan Yunani kometes yang bermaksud rambut panjang.Terdiri daripada tiga bahagian iaitu nukleus,koma dan ekor.Nukleus komet terbentuk daripada ketulan ais yang mengandungi habuk dan gas beku.Komet tidak selalunya mempunyai ekor.Komet kelihatan berbara dan berekor apabila menghampiri matahari kerana bahan beku di dalam nukleus komet akan mencair dan mengewap.Angin suria akan menolak gas dan habuk ke belakang.Ini menyebabkan ekor komet menjauhi matahari.

19Sambungan kometLama-kelamaan ia akan menyusut sehingga hilang.Sebahagian komet mempunyai orbit berbentuk elips.Mengambil masa beberapa tahun hingga berjuta-juta tahun untuk membuat satu orbit yang lengkap.Bentuk ekornya sentiasa kelihatan menjauhi matahari.Ekornya semakin panjang apabila komet semakin cerah.Kemudian ekornya menjadi pendek dan hilang.Menjadikan ia kelihatan seperti bebola api yang berekor.Setiap kali komet melintasi matahari sebahagian gasnya, hilang dan butir-butir habuk sahaja jatuh ke bumi.

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21Jenis komet Komet ShoemakersKomet HalleyKomet EnkeKomet HyakutakeKomet Shoe_Levy

22Comets

Mostly objects in highly elliptical orbits, occasionally coming close to the sun.Icy nucleus, which evaporates and gets blown into space by solar wind pressure.23COMETS

Comet Halley in 1910

Comets are sometimes called dirty snowballs or "icy mudballs". They are a mixture of ices (both water and frozen gases) and dust that for some reason didn't get incorporated into planets when the solar system was formed. This makes them very interesting as samples of the early history of the solar system. Comets have elliptical orbits.When we see a comet, weare seeing the tail of the cometas comes close to the Sun.24Comets are icy planetesimals formed in the outer solar system.They are composed mainly ice and dustThey have highly elliptical orbits which take them very close to the Sun and back out into deep space, often far beyond the orbit of Pluto. Their orbit duration can be from less than 200 years to more than several millions of years.Composition of comets: Nucleus- Main body of the comet: composed of dust particles trapped in a mixture of ices of water, carbon monoxide, carbon dioxide, methane, and ammonia. Typically only a few kilometers in diameterComa- A halo of evaporated gas and dust which forms when the comet approaches the inner solar system. The coma grows larger as the comet gets closer to the sun.CometsChunk of ice and dirt following an elongated elliptical orbit. DVD Weather- Wind Chp 9 (Solar Wind)Has a tail only when it comes close to the sun. The heat melts it and the solar wind sweeps the tail away.The tail always points away from the sun. 25CometsDirty snowballs - small objects of ice, gas, dust, tiny traces of organic material

26More information at http://www.lpi.usra.edu/education/explore/comets/

What does a comet nucleus look like? Formed from the primordial stuff of the solar system, it is thought to resemble a very dirty iceberg. But for active comets, telescopic images only reveal the surrounding cloud of gas and dust, the comet's coma, and the characteristic cometary tails. In 1986, the European spacecraft Giotto encountered the nucleus of Halley's comet as it approached the sun. Data from Giotto's camera was used to generate this enhanced image of the potato shaped nucleus which measures roughly 15 kilometers across. It shows surface features on the dark nucleus against the bright background of the coma as the icy material is vaporized by the Sun's heat. Every 76 years Comet Halley returns to the inner solar system and each time the nucleus sheds about a 6 meter deep layer of its ice and rock into space. This debris composes Halley's tails and leaves an orbiting trail responsible for the Orionids meteor shower.

Appearances of comet Kohoutek (1973), Halley (1986), and Hale-Bopp (1997) caused great concern among superstitious.Comet Hyakutake in 1996Throughout history, comets have been considered as portents of doom, even very recently: Comets of History27Comet PartsNucleus, ComaDust tail white, smoke, reflects sun. 600,000 to 6 million miles longIon tail Solar UV breaks down CO gas, making them glow blue. 10s of millions of miles

28What are comets?Comets have been called dirty snowballs. They are small celestial objects, made of ice, gas, dust, and a small amount of organic material, that orbit our Sun. There are about 1000 known comets and more are discovered each year. What are the different parts of a comet?Every comet has a nucleus , a stable, porous central mass of ice, gas, and dust that if often between 1 and 10 kilometers (0.6 to 6 miles) in size. The ice is made of varying amounts of water, carbon dioxide, ammonia, and methane. The dust may contain hydrogen, oxygen, carbon, nitrogen, silica, and some metals. The nucleus may have traces of hydrocarbons. As comets approach our Sun [within about 450 million kilometers (280 million miles)], they heat up and the ice begins to sublimate (change from a solid directly to a gas). The gas (water vapor, carbon monoxide, carbon dioxide, and traces of other substances) and dust forms an atmosphere around the nucleus called a coma. Material from the coma gets swept into the tail. As comets move close to the Sun, they develop tails of dust and ionized gas. Comets have two main tails, a dust tail and a plasma tail. The dust tail appears whitish-yellow because it is made up of tiny particles about the size of particles of smoke that reflect sunlight. Dust tails are typically between 1 and 10 million kilometers (about 600,000 to 6 million miles) long. The plasma tail is often blue because it contains carbon monoxide ions. Solar ultraviolet light breaks down the gas molecules, causing them to glow. Plasma tails can stretch tens of millions of kilometers into space. Rarely, they are as long as 150 million kilometers (almost 100 million miles). A third tail of sodium has been observed on Comet Hale-Bopp.

Comets are enveloped in a broad, thin (sparse) hydrogen cloud that can extend for millions of kilometers. This envelope cannot be seen from Earth because its light is absorbed by our atmosphere, but it has been detected by spacecraft. 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 suns radiation pressure. Lagging behind the comet along its trajectory29Gas and Dust Tails of Comet Mrkos in 1957

30Comet Hale Bopp (1997)

Comet Ikeya-Seki (1965)31Dust 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. Comet dust material can be collected by spacecraft above Earths atmosphere.32Fragmenting Comets

Comet Linear apparently completely vaporized during its sun passage in 2000.Only small rocky fragments remained.33The 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. Those compounds sublime (transition from solid directly to gas phase) as comets approach the sun.Densities of comet nuclei: ~ 0.1 0.25 g/cm3Not solid ice balls, but fluffy material with significant amounts of empty space.34Fragmentation of Comet Nuclei

Comet nuclei are very fragile and are easily fragmented.Comet Shoemaker-Levy was disrupted by tidal forces of JupiterTwo chains of impact craters on Earths moon and on Jupiters moon Callisto may have been caused by fragments of a comet.35The Origin of Comets

Comets are believed to originate in the Oort cloud:Spherical cloud of several trillion icy bodies, ~ 10,000 100,000 AU from the sun.10,000 100,000 AUOort CloudGravitational 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.36The Kuiper Belt

Second source of small, icy bodies in the outer solar system:Kuiper belt, at ~ 30 100 AU from the sun.Few Kuiper belt objects could be observed directly by Hubble Space Telescope.Pluto and Charon may be captured Kuiper belt objects.37Impacts on Earth

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.Gravity map shows the extent of the crater hidden below limestone deposited since the impact.38Comet Planet Interactions

39What happens when Earth passes through the path of a comet?Meteor showers occur when Earth passes through the trail of dust and gas left by a comet along its elliptical orbit. The particles enter Earth's atmosphere and most burn up in a lively light show a meteor shower. Some meteor showers, such as the Perseids in August and the Leonids in November, occur annually when Earth's orbit takes it through the debris path left along the comet's orbit. Comet Halley's trails are responsible for the Orionids meteor shower. For upcoming meteor showers and viewing suggestions, explore Sky and Telescope's Meteor Showers page. What happens when Earth passes through the path of a comet?Meteor showers occur when Earth passes through the trail of dust and gas left by a comet along its elliptical orbit. The particles enter Earth's atmosphere and most burn up in a lively light show a meteor shower. Some meteor showers, such as the Perseids in August and the Leonids in November, occur annually when Earth's orbit takes it through the debris path left along the comet's orbit. Comet Halley's trails are responsible for the Orionids meteor shower. For upcoming meteor showers and viewing suggestions, explore Sky and Telescope's Meteor Showers page.

401. Futurists suggest that we may someday mine the asteroids for materials to build and supply space colonies. What kinds of materials could we get from asteroids? (Hint: What are S-, M-, and C-type asteroids made of?)

2. If cometary nuclei were heated by internal radioactive decay rather than by solar heat, how would comets differ from what we observe?

3. From what you know now, do you think the government should spend money to locate near-Earth asteroids? How serious is the risk? Discussion Questions41