1IASS week10 2007

Slide1 : 10-15 m 107 m 1012 m 1019 m 1022 m 10-9 m 10-6 m 10-5 m 10-10 m 10-14 m Telescopes Microscopes


Slide2 : •ATOMS--10-10 m •NUCLEI--10-14 m •NUCLEONS-10-15 m •QUARKS--???


Slide3 : 7p 1n 75% H & 25%He 98% of known matter Where do the rest come from?


Slide4 : Voids on the largest Scale


Slide5 : Hubble Deep Field-A very narrow sample of the sky looking as far back as 10 10 years in some cases.Data taken over 10 consecutive days.


Slide6 : M31-Andromeda Galaxy-2.2Mly from Earth, Part of our Local cluster of galaxies.


Slide7 : Kepler’s Laws 1.The planets orbit the Sun in ellipses with the Sun at one focus. 2.The line joining the Sun and a planet sweeps out equal areas in equal times. 3.The square of the period of a planet is proportional to the cube of the semi-major axis of the ellipse. P2  a3 Note:- Elliptical orbits were an essential innovation but for simple calculations one can assume that the orbits are circles. In general it is a good approximation. Convenient Measure of distance -Astronomical Unit(1 au) = Average Earth-Sun distance = 1.496 x 1013 cm = 1.496 x 1011 m


Slide8 : Plot of a3 versus P2 for the planets in the Solar system - Here a is in AU and P is in Earth Years. All three of Kepler’s Laws are rigorously obeyed wherever two objects move under their mutual gravitational attraction. Kepler’s Third Law P2 a3 Clearly P2  a3


Slide9 : The p-p chain;the reactions which power the Sun Overall - 4p  4He + 2e- +2 + 26.7 MeV


Slide10 : The proton-proton chain 1H + 1H = 2H + e+ + 1H + 1H = 2H + e+ + 1H + 1H = 2H + e+ + 1H + 1H = 2H + e+ + (B) 1H + 2H = 3He +  (C) 1H + 1H = 2H + e+ + (A) 1H + 2H = 3He +  (D) 3He + 3He = 4He + 1H + 1H +  (E) Thus the sequence of reactions turns 4 protons into an alpha particle. 1H + 1H + 1H + 1H 4He + 2e+ + 2e + 3 Since the alpha particle is particularly tightly bound this process of turning 4 protons into an alpha releases about 26MeV of energy. It is this energy which heats the stellar interior,allows it to withstand the gravitational pressure and causes it to shine!


Slide12 : White Dwarf H, N, O ¡¡only!! (Hubble) Fluorescence Helix Planetary Nebula in the constellation of Aquarius


Slide13 : Death of a Red Giant: SUPERNOVA October 1987 1056 Joules of energy This happened 170000 years ago in the nearest galaxy


The Destiny of the Stars… : The Destiny of the Stars… C. THIBAULT (CSNSM) Main Sequence Red Giant White Dwarf Massive Stars Supernova Density/ AÑOS Algún segundo Brown Dwarf 109 109 109 100 kg


Slide15 : Spectrum of Cassiopeia We see here the remnants of a supernova in Cassiopeia.This radio telescope picture is taken with theVery Large Array in New Mexico. From the measured rate of expansion it is thought to have occurred about 320 years ago. It is 10,000 ly away. With optical telescopes almost nothing is seen. The inset at the bottom shows a small part of the gamma ray spectrum with a clear peak at 1157 keV,the energy of a gamma ray in the decay of 44Ti.


Slide16 : The pathways for the s- and r-processes S-process:Neutron flux is low so beta decay occurs before a second neutron is captured.We slowly zigzag up in mass. R-process:Neutron flux is enormous and many neutrons are captured before we get beta decays back to stability.


Slide17 : The Abundances of the Elements for A = 70 - 210 Note the double peaks at N = 46/50, 76/82, 116/126 They are due to production by the two separate processes


Slide19 : The Solar System Sun - a Main Sequence Star of mass 2 x 1030 kg - radius = 696,000 km and mass = 1.989 x 1030 kg - Luminosity = 3.86 x 1026 W - Distance to centre of galaxy = 8000pc = 26,000ly - density = 1410 kg/m3 Nine planets 137 known moons Asteroids Comets Gas and dust


Slide20 : The Solar System


Slide21 : The Solar System We again see the solar system below but this time without the Sun. On the right we see the scales of the orbits of the various planets. Distance-109 m


Slide22 : The Solar System The formation of the Solar System has been a topic of great interest for a long time. As yet there is no definitive theory but there is an emerging consensus. There have been (are) theories that start with a) A comet colliding with the Sun and knocking the material that composes the planets out of it, b) A close encounter with another large body, with the resulting tidal effects causing part of the Sun’s material to be ripped out. These theories face a variety of problems such as the differences in composition between the Sun and the planets. Other theories rely on the accretion of material from interstellar space. This solves the difference in composition from the Sun but not between planets. The basis of the models that are popular now is the idea that Sun and planets all formed from the same material. Differences in composition arise during the formation of the system. [Does not preclude a mixture of these ideas] Many problems remain but now there seems to be convergence on a theory of this kind.


Slide23 : The Solar System Before looking at the theories we should remind ourselves of some of the facts. The Solar System consist of a very large number of objects, held together by gravity and obeying Kepler’s Laws. The picture is not to scale. It shows the Sun with the four, inner Terrestrial planets, followed further out by the Asteroid belt then the Gas giants. Then we have comets , a large number of moons etc.


Slide24 : Kepler’s Laws 1.The planets orbit the Sun in ellipses with the Sun at one focus. 2.The line joining the Sun and a planet sweeps out equal areas in equal times. 3.The square of the period of a planet is proportional to the cube of the semi-major axis of the ellipse. P2  a3 Note:- Elliptical orbits were an essential innovation but for simple calculations one can assume that the orbits are circles. In general it is a good approximation. Convenient Measure of distance -Astronomical Unit(1 au) = Average Earth-Sun distance = 1.496 x 1013 cm = 1.496 x 1011 m


Slide25 : Plot of a3 versus P2 for the planets in the Solar system - Here a is in AU and P is in Earth Years. Reminder:All three of Kepler’s Laws are rigorously obeyed wherever two objects move under their mutual gravitational attraction. Kepler’s Third Law P2 a3 Clearly P2  a3 Asteroids Asteroids lie in belt from 2-3.5AU from Sun.


Slide26 : Planetary Orbits Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Semi-major axis (106 km) Sidereal Period Orbital Eccent. Direction of revn Angle to plane to ecliptic(degs.) Angle of Plane to spin axis(degs) Rotation Period (Days) Surface Temp. Mass(1024 kgm) 57.9 108.2 149.6 227.9 778.4 1424 2871 4499 5906 0.241 0.615 1.0 1.88 11.9 29.5 84.0 165 248 0.21 0.01 0.02 009 0.05 0.06 0.05 0.01 0.25 7.0 3.4 0 1.8 1.3 2.5 0.8 1.8 17.1 0.1 178 23.5 25.2 3.1 26.7 97.9 29.6 122 58.7 243 1.0 1.03 0.41 0.43 0.72 0.67 6.4 100-620 730 300 220 130 97 58 58 50 0.33 4.87 5.98 0.64 1900 569 86.8 102 0.013 They are all the same


Slide27 : Formation of Solar System Key piece of evidence:- Sun and planets orbit in same direction and lie almost in the same plane. This suggests Sun and planets all formed at the same time from a mass of gas and dust, which was rotating. Why did this mass come together? What triggered this process? Here there is no clear answer – Perhaps a shock wave from a supernova or some other event.


Slide28 : Basic Idea of Nebular Hypothesis Here is the idea with which we are already familiar. The system forms from a collapsing cloud of gas and dust If the whole cloud is spinning slowly when the collapse starts then it will speed up as it gets smaller in order to conserve angular momentum.


Slide29 : Formation of Solar System The initial cloud or nebula must have had a small rate of rotation. As the cloud collapses it would speed up to conserve angular momentum. Two results:- the rotation we see today and the formation of a disc with the planets forming in the outer part of the disc as the material clumps together. Protoplanetary disc or Proplyd


Slide30 : Solar System – Role of Condensation Temperature Temperature would play a large role in determining the composition of the planets. For the inner planets T is high so molecules have higher average velocities and Light gases escape from the gravitational field. For outer planets T is lower and masses higher so they retain the light gases. Metals condense out at higher T so the inner planets have more metals or heavy Elements. The angular momentum leads to a flattened disc which explains why all the planets are in the same plane. T rose in centre and stayed at say 50K in the outer reaches. Rocky material stayed solid near the protosun and gases and other icy substances Vapourised. The planetesimals of rock coagulated to form inner planets. The icy grains on outside grew together and then accumulated gases. Note:- Chemical differentiation vs. heterogeneous accretion Former - material accumulated and radioactive decay caused melting and Fe-rich Minerals sank to centre. Latter- Fe and Fe oxides were first to condense so cores formed early. Later Si-rich Material condensed on top.


Slide31 : Formation of Solar System Here is another view of the same process. Initially T = 50K so solar nebula would have been filled with dust grains, small ice particles etc plus H and He as gases. As protosun formed it heated central part leaving outer parts at 50K. In inner section everything except materials with high condensation temperatures were vapourised i.e.Fe,Si,Mg S,Al,Ca and Ni and their oxides remained. Protoplanets formed from planetesimals by accretion, which collided to form planets.


Slide32 : Solar System Question of angular momentum. Most of the angular momentum is in the disc-the ang.mom. of the planets. The Sun has only 0.5% of the total. Why? Rotating solar nebula was gaseous and hot. The molecules move quickly and are ionised in collisions – thus a plasma of ions and free electrons forms. The motion of charged particles creates a magnetic field. The nucleus of the solar nebula thus had a magnetic field associated with it. Matter close to the nucleus was also partially ionised and moved with it. T for disc fell as we moved away from the nucleus so that more and more electrically neutral molecules would have been found as we moved out from the centre. As the charged particles were dragged round they collided with uncharged particles and so they dragged the uncharged particles with them and transferred ang.mom. to the disc. A particle whose ang.mom. thus increased would move out from the centre.so that total ang.mom. is conserved. Nucleus continued to contract and increase its rotational velocity(although at a slower rate due to the ang.mom. Transfer) while the matter moving away slowed as its orbital radius increased. In principle all of the ang. Mom. could be transferred to disc.


Slide33 : Eagle Nebula – Star Formation About 1 light year Enlargement of regions where young stars are forming. Tips are about size of the Solar system. Hubble space telescope pictures of star-forming region in the Eagle Nebula.


Slide34 : Origin of the Solar System A small part of the ORION nebula In which young stars are being formed from small pieces of the giant interstellar cloud. Our solar system presumably Formed as a small part of a gas Cloud collapsed under gravity. This piece of collapsed cloud we call the solar nebula. Before the collapse began it would have been spread out over a few Light years in diameter. It was cold and had a low density. Why did it start to collapse? Perhaps it was the result of a shock wave from an exploding star.


Slide35 : Protoplanetary discs forming in the ORION Nebula. Insets show examples. They are In false colour and the picture is a mosaic of HST pictures. A young star is at centre of each proplyd. Size of Solar system


Slide36 : Jovian Planets Outer planets probably began in same way with accretion of planetesimals. Since T was low this included ice particles. Gas was moving slowly so it got attracted by gravitational force. Process stopped when gas ran out. Result - a small solid core with a large gas envelope. This is thought to be origin of four Jovian planets. Initially they would have been hotter and would have behaved like a miniature solar System and we can imagine their satellites forming like the planets in the solar system. Solar wind plus accretion would have scavenged all of the gas and dust and planets would then have stabilised at present sizes.


Slide37 : Extra-Solar Planets Are there other “solar systems”? The unequivocal answer is YES. We now have evidence of at least 100 planets around other stars. There is a systematic search for such objects. For example at the 3.9m anglo-australian telescope. Star Planet planet As the planet orbits the star it will cause it to “wobble” back and forth in space. This will also cause the light from the star to be Doppler shifted. The AAT team can detect a Doppler shift to an accuracy of 3m/sec. This is the basis of their planet-hunting technique. The latest such planet was observed around a star called Tau Gruis and is of the size of Jupiter. It is about 100ly away. It is three times further from its star than Earth is from the Sun.


Slide38 : Extra-Solar planets Star Planet Variety of methods used to look for them. - radial velocity measurement - astrometry – looking for slight variation in position - Imaging – looking for reflection of light from planet - Photometry (occultations) So far we have only been able to detect the effects of Jovian-like planets. Earth-like planets are too small to detect by these methods.


Slide40 : Summary Extrasolar planets known within 200 pc of Earth. This picture shows their distances from the stars they orbit in AU


Slide43 : Formation of Binary Star Systems A large fraction of all stars are binary systems. They are important for astronomers because they allow us to measure masses. The collapsing nebula idea gives a natural explanation.


Slide44 : The Sun Sun - a Main Sequence Star of mass 2 x 1030 kg - radius = 696,000 km - Luminosity = 3.86 x 1026 W - Distance to centre of galaxy = 8000pc = 26,000ly - density = 1410 kg/m3 Aside:- Source of energy. Typical chemical reaction-1eV = 1.6 x 10-19 Joules No.of atoms needed to provide Sun’s luminosity = 3.9 x 1026 / 10-19 = 3.9 x 1045 atoms Length of time to consume all of Sun = 1057 / 3.9 x 1045 = 3 x 1011 s = 10,000 Years!!!


Slide46 : Surface of the Sun Photosphere = layer at which photons finally escape from the surface. Average T is 5850K but close up we see it is granulated. This is the result of convection. The bright areas are where hot gas bubbles upwards and the dark edges are where cool gas descends. It is like the surface of water boiling in a pan.


Slide47 : Sunspots and Solar Surface One of the most striking features of the solar surface-sunspots. T is ~ 4000K, rather cooler than normal surface temp of 5850K. Why is the region not heated? It turns out that these are regions with strong magnetic fields and the fields cause charged particles to spiral along magnetic field lines. No easy motion at rt. angles to field lines.


Slide48 : Solar Prominences . Fields from two sunspots often go high above the photosphere. These loops of Magnetic field sometimes appear as solar prominences in which the field traps gas that can glow for days or even weeks. They can rise to 100,000 kms above the surface Solar flares are even more dramatic – they usually occur in vicinity of sunspots Suggesting they may be due to a collapse in the magnetic field with a large release of energy. This heats the plasma and accelerates the charged particles to high velocity.


Slide49 : Solar Prominence UV photo of this very Large solar prominence. It is 20 times Earth size.


Slide50 : Courtesy of A..King


Slide51 : Courtesy of A.King


Slide52 : Mercury Mass = 3.3 x 1023 kg Distance from Sun = 0.307 – 0.467 AU Orbital period = 87.97 days Rotational Period = 58.6 days Density = 5430 kg/m3 Average surface Temp. = 350 – (-170) degrees centigrade Decent photographs only from Mariner 10 spacecraft in 1974 Surface looks like the moon. With the results of many impacts clearly visible. It has a large iron core and a magnetic field. Mercury is not in synchronous rotation round the Sun. It makes three rotations on its axis for each time it orbits the Sun. This is related to the large eccentricity In its orbit.


Slide53 : Venus Distance from Sun = 0.723 AU Mass = 4.869 x 1024 kg Orbital Period = 224.7 days Rotational period = 243 days Density = 5243 kg/m3 Surface temp = 733K Surface Pressure = 90 atmospheres Covered by a thick,unbroken layer of clouds. It rotates in retrogade rotation Clouds are transparent to radiowaves and microwaves. Large number of space probes aimed at Venus Strong greenhouse effect so surface is hot. Russian Venera-14 Satellite landed And we see surface


Slide54 : Venus-Second Planet out Terrestrial Type planet. Covered in thick cloud of ammonia etc. Surface is rocky As we can see on the radar maps. Density similar to Earth.


Slide55 : Volcanic activity is probably responsible for Injecting substantial amounts of sulphuric Acid and sulphur dioxide in atmosphere of Venus. Lava flows clearly visible via radar Lots of volcanic activity No evidence of plate tectonics.


Slide56 : Earth Mass = 5.97 x 1024 kg Distance to Sun = 1.496 x 108 km Density = 5515 kg/m3 Surface Temperature = 333K Orbital period = 365.256 days Rotational period = 23.9345 hours. Troposphere-heated only indirectly by Sun. Stratosphere – Lot of ozone so it absorbs UV heavily. T increases with height. Mesosphere – Little ozone so UV is not absorbed. T decreases with height. No defining edge to atmosphere.


Slide57 : Earth Observed from Space Earth seen from Apollo 11 Galileo shot of Earth and its Moon Galileo shot of South America


Slide58 : Structure formed in Differentiation process. After approx 109 years Earth melted due to a) gravitational energy. from formation, b) Meteor bombardment and c) radioactive decay. Whilst molten, gravity concentrated denser material near the centre. When it solidified again apart from outer liquid core it had a layered structure. As the outer layers cooled large cracks developed in the lithosphere because of thermal Stress-this leads to favourable conditions for plate tectonics.


Slide59 : Earth We can study Earth’s interior with seismic waves. P-waves:-Longitudinal waves which propagate in liquids and solids. S-Waves:-transverse waves propagate in solids but not liquids Seismic studies plus “theory” suggest the structure on the left. Solid inner core (Fe + Ni), Liquid outer core(Fe+Ni).Diameter 7000km. Crust = tens of km. Mantle = region between core and crust. Lithosphere = crust + upper part of mantle. Aesthenospshere = region of plasticity


Slide60 : Plate tectonics. Crust is thin (tens of km). Lithosphere is broken into large plates. Aesthenosphere Is plastic and kept so by heating from radioactive decay. This small amount of decay of light elements is enough to keep it plastic. Very slow convection then provides Horizontal force on plates to make them move.


Slide61 : Seismic activity  laser ranging can detect few cms. per century.  fossil record supports theory. Future: Australia will join Asia. Parts of California will “leave” USA. Africa will separate from Middle East. Italian boot will disappear.


Slide62 : Earth’s Atmosphere Sunlight warms surface which heats lower part of troposphere. Resulting vertical T variation causes convection currents which lead to the large variation in the weather. The atmosphere is also strongly affected by the Earth’s rotation, namely by the Coriolis Effect. Oxygen all came from plants. H and He gone at an early stage Coriolis Effects


Slide63 : Solar Heating and Coriolis Forces Winds are driven by solar heating. This would suggest N-S pattern of air flow. Coriolis forces deflect air to the right in N.hemisphere and to left in S.hemisphere. In other words you might expect a natural air flow of hot air from the equator towards the poles. However the Coriolis effect deflects the air molecules. We end up with a very general pattern as shown.


Slide65 : Earth’s Magnetic Field It is like a simple bar magnet. Axis is tilted relative to rotation axis Remember Magnetic field is the result of electrical currents.


Slide66 : Van Allen belts Field is thought to be due to electrical currents in the spinning liquid outer core. This Is called the dynamo effect. Rocks formed from molten state retain their magnetism from that time. Accordingly fossil records show field has reversed every million years or so. Charged particles spiral along the field lines and are reflected at Mirror points. Primary source of these particles is the solar wind. They are responsible for Aurora.


Slide67 : Earth’s Magnetosphere Solar wind = stream of ionised gas from Sun. velocity = approx 400 km/second It varies in intensity depending on solar activity. When it encounters Earth’s field it is deflected. Region behind the Bow Shock is called the Magnetosphere. It largely prevents the solar wind entering. Leakage causes Van Allen belts, Aurora etc.


Slide68 : Aurora over Circle, Alaska Delicate colours are due to collisions between energetic electrons and O and N molecules in the atmosphere.


Slide69 : Aurora in UV in Northern hemisphere from Nasa’s Polar satellite.


Slide70 : U.S.A. at night from space. Mount Etna from space Earth Observation


Slide71 : Earth Observation can be at any wavelength. Here it is in Infra-red and we see the distribution of water vapour.


Slide72 : The Moon Mass = 1/80 x Earth’s mass Mean distance = 384,000 km Diameter = ¼ x Earth’s diameter. Orbit eccentricity is approx 0.05 Daytime T = 373 K Nightime T = -160K No atmosphere to store heat. Density = 3.4 g/cc Apollo rock samples show material is as old as Solar system. They are older than Earth rocks because of Volcanic activity here.


Slide73 : Structure of Interior Largely dead geologically No magnetic field in essence Maybe in past it was bigger. Any seismic activity due to tidal effects. Craters from meteor impact Early molten stage Vulcanism ended some 3 billion years ago


Slide74 : How did Moon form? 1.Fission Theory:-Once part of Earth and separated in some way-Pacific basin is favourite site for this. 2.The Moon formed somewhere else and was captured by Earth’s field. 3.Condensation theory:- Moon and Earth condensed together. 4.Colliding planetesimal theory:- Moon condensed from debris. 5.Ejected ring theory:- Large Planetesimal struck Earth and ejected material that formed Moon. First three are essentially ruled out because of differences in the Material on Moon and Earth. Fifth is the currently favoured theory.


Slide75 : Mars from Viking 2 Mars-Fourth Planet Out Mass = 6.418 x 1023 kg Distance from Sun = 1.381 – 1.666 AU Orbital Period = 686.98 days Rotational Period = 24 hours 37 min. Diameter = 6794 km. Average density = 3934 kg/m3 Surface Temperature = 133-293K


Slide76 : Mars-Fourth Planet Out Prominent features on surface - Meteor craters - Huge volcanic cones Gorges larger than Grand canyon Vast sedimentary deposits Valleys that look as if they were formed in water flow No plate tectonics. Note:- craters are thought to have been formed at a very early stage as in the case of the Moon. This process stopped when all the debris in the solar system had been Mopped up.


Slide77 : Frozen carbon dioxide at Pole Valles Marineris 500 m wide and up to 6 km deep. Variation in temperature at site of Viking 1 Surface Atmospheric pressure = 1/200 atmosp. pressure on Earth Atmosphere = 95% CO2 plus 5% N Large Dust Clouds due to seasonal heating


Slide78 : Jupiter Mass = 1.899 x 1027 kg Distance from Sun = 4.95 – 5.455 AU Orbital period = 11.86 years Rotational period = 9 hours 50 mins Diameter = 133.7 – 142.98 x 106 m Average density = 1326 kg/m3 Average Temperature = 165K at cloud tops. Largest object in solar system Large number of Moons Great Red spot is strong feature of surface Weather patterns are due to solar and internal heating and differential rotation. Shape is oblate (6.5%). This due to rotation of core.


Slide79 : Jupiter-The largest Gas Giant Jupiter has a volume approx 1000 times the Earth’s volume..The mass = 1.9 x 1027 kgm Diameter is 142,800 kms. It has a very dynamic weather system-atmospheric clouds,storms and latitudinal bands. The Great Red Spot The Great Red Spot is a complex storm moving in a counter-clockwise direction. At the outer edge material appears to rotate in 4-6 days. Near the centre motions are small and random. Atmosphere is very deep, maybe including the whole planet. It is very like the Sun. It is composed mainly of H and He with small amounts of Methane, ammonia, water vapour and other compounds. At great depths the pressure is very high and atoms are broken up. In this state H becomes a metal.


Slide81 : The four Galilean Satellites They all orbit more or less in plane of planet’s orbit. Their motions are closely linked. The tidal effects are very strong. They all rotate in same direction as orbit. Large number of other satellites. Although all of “publicity” is for Saturn’s rings we see here that there are rings for Jupiter.


Slide82 : Jupiter Jupiter has 28 known satellites, four of which were observed as long ago as 1610. They are Callisto, Europa, Ganymede and Io. There is also a faint ring system. The image below is a collage of images acquired by Voyager and Galileo spacecraft. We see the Valhalla region of Callisto in the lower right. Inside the four Galilean Moons are Amalthea(top), Metis and Adrastea(to right) and Thebe(left). Jupiter’s rings and moons exist within an intense radiation belt of ions and electrons trapped in the planet’s magnetic field. This field stretches out 3-7 Mkms towards the Sun and 750 Mkms towards Saturn.


Slide85 : Saturn-Another gas Giant


Slide86 : Saturn’s rings are complex


Slide89 : Pluto and Charon


Slide90 : Comets Nucleus = mixture of ice and dust. Ion tail = Ions from comet are swept directly away from comet by solar wind. Dust tail = photons hitting dust particles are absorbed and hence exert a pressure on dust. Tails always point away fro Sun.


Slide92 : Comet Hale-Bopp photographed over Boulder Colorado (1997)


Slide93 : Asteroids Approx 105 asteroids spread Over 1017 square km. Largest is CERES with diameter Of 934 km. It accounts for 1/3 of total Asteroid mass. Probably planet did not form because of huge pull of Jupiter. They occasionally collide with each other and with Earth


Slide94 : Photograph of EROS asteroid from NEAR spacecraft. It is about 40 kms in length. Appearance is probably typical of most asteroids. Note its non-spherical shape, also typical of such small objects.


Slide95 : Solar System Schematic view of the solar System. The insets show a COMET and an ASTEROID Note the asteroid belt between Mars and Jupiter Further out we have the Kuiper belt and much further away the Oort Cloud.


Slide98 : Solar System Montage


Slide99 : Saturn-Another Gas Giant


Slide100 : Solar System The planets of the Solar system are classified as Terrestrial or Jovian. The four inner, terrestrial planets are close to the Sun. They are quite warm- Noon on Mercury = 600K and on Mars = 300K At top of clouds on Jupiter = 150K cf 63K on Neptune. Inner planets – densities 5.4-3.9 gcm-3 . Masses typically 1024kg Outer planets- 0.7-2.0 1026kg Conclusion-terrestrial planets contain a large amount of material denser than rock. Whilst outer planets probably have solid cores of Earth dimensions but with extensive gaseous atmospheres. All the planets except Mercury and Venus have satellites. At least 50 are known. Seven are comparable in size to Mercury – Moon, Io, Europa, Ganymede, Callisto, Titan, and Triton


Slide102 : Artist’s Impression This how the possible scene from a moon around the recently Discovered planet. The star is 6th magnitude and takes 4 years to Orbit at a distance three times the Earth-Sun distance. There is,of course, no evidence of a moon. So far we only see planets of Jupiter-like mass but they fall into two groups-those very close in and those a long way out. So far we have no explanation of this.


Slide103 : 10-15 m 107 m 1012 m 1019 m 1022 m 10-9 m 10-6 m 10-5 m 10-10 m 10-14 m Telescopes Microscopes