Sosters S4

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  • 1. Strange but true!The Sun is a yellow dwarf star.Its energy comes from nuclear fusion.The centre of the Sun is 15 million C.The Sun accounts for 99.9% of the Solar Systems mass.Helium (very rare on Earth) makes up about 24% of the Sun,where it was first observed. The rest of the Sun is mostly hydro-gen.The Sun, along with the rest of the Solar System, is about 4.6 bil-lion years old. Kuiper BeltType of Star G2V yellow main se- quence dwarf NeptuneNumber of Planets 8 SituationNear Orion Arm about Uranus25,000 light-years from centre of Milky Way Gal-axySaturnAgeAbout 4.5 billion years Images courtesy of NASA Jupiter ParameterActualCompared to Earth Asteroid BeltDiameter 1,400,000 km 110 x bigger Mars Mass2*1030 kg 330,000 x heavierEarth VenusMercuryCreate your own modelBritish Science Associationcharity no. 212479 & Sun

2. Oort CloudThe Oort Cloud is a huge collection of billions of objects around the Sunat 300-100,000 Earth-Sun distances. The furthest of Oort Cloud objectsare 1.5 light-years away, about 1/3 of the way to the nearest star.Its a spherical cloud not a flat disk like the Kuiper Belt.It is 1000 times further away than the Kuiper-belt, although the transitionbetween the two is not clear: they might merge into each other.Most of these objects are stony, dusty or icy particles of different sizes.StarsThe closest star to the Sun at 4.22 light-years distance is Proxima Cen-tauri. It is a red dwarf and so faint it is not even visible to the naked eye.New stars are forming all the time in the dense spiral arms of our Galaxy.Old ones run out of hydrogen fuel and die, sometimes in spectacular ex-plosions (supernova) and sometimes swelling to large red giants (as theSun will in 5 billion years).Galaxies and the UniverseThere are an estimated 400 billion stars in our own galaxy, theMilky Way, a flat disc with a diameter of 100,000 light-years! Inour model this is 100 times the distance from here to theMoon.There are an estimated 100 billion galaxies in the Universe.They are arranged in clusters which lie in flat sheets lining theoutside of huge almost empty regions lacking even traces ofgas. The seeds of this sponge-like structure might have beenlaid down just after the Big Bang. Those filaments and voidsare the largest structures we can see in the universe. Create your own model courtesy of NASA British Science Association charity no. 212479 & SCO39236 3. these conditions. For dwarf planets like Pluto thisnumber is about a million times smaller than for thetrue planets. Strange but true!So Pluto is not a true planet. Instead it is a memberof the Kuiper Belt.There are many other small bodies orbiting the Sun at 30-50 Actually what we know as Pluto are two objects,Earth-Sun distances.Pluto (diameter 2390 km) and its (comparably verylarge) moon Charon (about 1200 km).They consist mostly of ices (frozen methane, ammonia and wa-ter). Pluto is now classified as a dwarf planet, althoughPluto and Charon form a double-object. A nameSome comets originate here, some in the Oort Cloud (see Be- for this has not yet been decided on and is stillyond the Solar System poster).subject of discussion.Plutos orbit sometimes brings it closer to the sunMost Kuiper Belt Objects are on fairly eccentric orbits.than Neptune.There are believed to be around 70,000 objects with diametersPluto isnt the biggest object outside Neptune. Erisgreater than 100km. We already know the location of about (2400 km diameter) is bigger.1000 of them.Pluto, Eris, Makemake, Haumea and Ceres (in theThe furthest point of some short-period comets (e.g. Halley) is inasteroid belt) form the group of known dwarf plan-this belt.ets. Most of the other big ones are candidates, butnot yet confirmed. PlutoThe most famous of these objects is Pluto.According to the International Astronomical Union (IAU) an object Kuiper Beltmust meet three conditions to be considered a planet:It must be in orbit around the Sun.It must be massive enough that its own gravity should pull it into asphere.It must have cleared the neighbourhood around its orbit (by sweepingNeptuneup all other objects).The Stern-Levison parameter shows that Pluto has not met the third of Uranus Type of Object Icy objects similar to SaturncometsSurface Temperature - 220C(approx) Year Length 100s of Earth yearsImages courtesy of NASA Jupiter ParameterActualCompared toEarth Asteroid Belt Diameter (approx)30 1500 km 0.2% - 12%Average distance 4500 - 800030-50 x further Marsfrom Sunbillion metres EarthTotal Mass (approx) 6.0*1023 kg10%Venus Mercury Create your own modelBritish Science Associationcharity no. 212479 & Sun 4. Strange but true!Traces of methane in the atmosphere account for the blue col-our of both Neptune and Uranus.Neptune has very active weather systems, driven by the strong-est winds of any planet in the Solar System, with speeds as highas 2100 km/h.Neptunes outer atmosphere is one of the coldest places in theSolar System, with temperatures of 218 C.Neptune is named after the Roman god of the sea.Like Jupiter and Uranus, Neptune has a faint ring system.Neptune was FIRST calculated to exist from small wiggles in Ura-nus orbit and THEN observed!In 1613 Galileo observed Neptune very close to Jupiter, but ei-ther thought it was a star in the background or one of Jupitersmoons. Kuiper Belt Type of PlanetIce Giant Number of Moons13 Neptune Surface Temperature - 201C(varies with depth)UranusDay Length 16.1-18.3 hours (sunrise to sunrise)Year Length 165 Earth yearsSaturnTilt of Axis of rotation28.3 Angle of orbit against 1.77 Images courtesy of NASA plane of Earths orbit Ovalness of orbit0.011Jupiter (0=circular)ParameterActualCompared to Asteroid BeltEarth Diameter 49,500 km 3.9 x bigger Mars Average distance4500 billion30 x further from Sunmetres EarthMass 1.0*1026 kg17 x heavier VenusMercuryCreate your own model British Science Association charity no. 212479 & SCO39236 Sun 5. Strange but true!Uranus is only just visible with the naked eye and moves slowlyso ancient astronomers never recognized it as a planet.The Greek god Uranus was father of Saturn and grandfather ofJupiter, so it is an appropriate name for the third largest planet.Uranus is lighter than its neighbour Neptune yet bigger in di-ameter. Traces of methane in the atmosphere account forboth planets blue colour.Its rotation axis is tipped over so it rotates nearly in the plane ofhis orbit around the sun. That means it rolls along its orbit in-stead of spinning round it like the Earth does.Uranus had been observed on many occasions before its dis-covery as a planet, but it was generally mistaken for a star. Theearliest recorded sighting was in 1690 when John Flamsteed ob-served the planet at least six times, cataloging it as 34 Tauri.Kuiper BeltType of Planet Ice GiantNumber of Moons27Surface Temperature-197C Neptune (varies with depth) Day Length 16-17 hours Uranus(sunrise to sunrise) Year Length84 Earth yearsSaturnTilt of Axis of rotation 97.77 Angle of orbit against 0.77 plane of Earths orbitImages courtesy of NASA Ovalness of orbit0.044 Jupiter (0=circular) Parameter ActualCompared toAsteroid Belt EarthDiameter 51,000 km4 x biggerMarsAverage distance2870 billion 19 x furtherfrom Sunmetres EarthMass8.7*1025 kg 15 x heavierVenus MercuryCreate your own modelBritish Science Associationcharity no. 212479 & 6. Strange but true!Saturn has a prominent system of rings, consisting mostly of iceparticles with a smaller amount of rocky debris and dust.Over sixty moons (e.g. Titan) orbit the planet, not counting hun-dreds of "moonlets" within the rings. Telesto, Tethys and Calypsoshare one orbit, following each other at 60 distance. Thatseems to be unique in the Solar System.Jupiter, Saturn, Neptune and Uranus all consist mostly of hydro-gen gas so they are called the gas giants.Saturns mean density is so small it would float in water (if youwould find enough of it!)Saturn and Saturday are both named after the Roman god ofagriculture and justice, Saturnus.The rings are only about 20 metres thick!Kuiper BeltType of Planet Gas Giant Number of Moons About 200Neptune Surface Temperature -139C(varies with depth)UranusDay Length 10 hours 14 min (sunrise to sunrise) (at equator)Year Length29.5 Earth years Saturn Tilt of Axis of rotation 26.7 Angle of orbit against 2.49 plane of Earths orbitImages courtesy of NASAOvalness of orbit 0.056 (0=circular) Jupiter ParameterActual Compared toAsteroid BeltEarth Diameter121,000 km 9.5 x biggerMarsAverage distance 1430 billion9.6 x furtherfrom Sun metresEarthMass 5.7*1026 kg95 x heavierVenus Mercury Create your own modelBritish Science Associationcharity no. 212479 & 7. Strange but true!Jupiter is basically a small star which is just too light to start nu-clear fusion but its composition is nearly the same as that of theSun!Galileo first saw the four largest of Jupiters 60+ moons (Io, Eu-ropa, Ganymede and Callisto) 400 years ago which is why weare celebrating astronomy this year!The moon Europa is very likely to host liquid water and is one ofthe likeliest places to find life outside the earth.Perhaps the Romans knew Jupiter was the largest planet in theSolar System because they named it after Jove, king of thegods. Kuiper BeltThe famous red spot is a big storm system known to have ex-isted for at least 300 years. The earth would fit into it entirely.Type of PlanetGas GiantNeptune Number of Moons 63 Surface Temperature -108CUranus (night-day) Day Length 9 hours 50 min Saturn (sunrise to sunrise)(at equator) Year Length11.9 Earth Years Tilt of Axis of rotation 3.13 Angle of orbit against 1.31 Images courtesy of NASA plane of Earths orbit JupiterOvalness of orbit0.049 (0=circular) Asteroid Belt Parameter ActualCompared to Earth Diameter 143,000 km11 x