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ASTRONOMY

ASTRONOMY. LOOK UP. LOOK WAY, WAY UP. WHAT DO YOU SEE?. SUN, MOON, STARS. WHAT DO YOU SEE UP THERE?. Sun crosses the sky at different levels Length of days change (8-16 hrs in Ottawa) Different at different latitude Seasons change Star patterns rotate about “pole” star

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ASTRONOMY

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  1. ASTRONOMY LOOK UP. LOOK WAY, WAY UP. WHAT DO YOU SEE? SUN, MOON, STARS

  2. WHAT DO YOU SEE UP THERE? Sun crosses the sky at different levels Length of days change (8-16 hrs in Ottawa) Different at different latitude Seasons change Star patterns rotate about “pole” star Sun and Moon travel through “zodiac” Moon has phases

  3. WHAT DO YOU SEE? WANDERING BODIES RETROGRADE MOTION SUN MOON EVENING STAR MORNING STAR OTHER MOVING BODIES SOME FASTER THAN OTHERS OCCASIONAL VISITORS: TAILED STARS FALLING STARS BRIGHT FLASHES

  4. SEVEN WANDERERS NAME SPEED BRIGHTNESS (arc-sec/day) (Sirius=1.0 SUN 3550 15,000,000 MOON 48,100 30,000 MERCURY 14,900 0.9 VENUS 5,840 14 MARS 1,910 3.5 (moves the width of the moon in one day) JUPITER 302 2.5 SATURN 102 0.4 They must be gods!

  5. EARLY ASTROMOMICAL OBSERVATION CHINA: Records from 2000 BC Halley’s comet 467 BC Length of Year 365 1/4 days Predicted eclipses BABYLONIANS Star catalogs 1600 BC Eclipse reported 1500 BC continuous records 900 BC

  6. LOOKING FOR PATTERNS Pythagorus 570-490 BC Cosmos model - spheres Plato 428-348 BC Circular paths Eudoxus 400-347 BC First Mechanical model Aristole 384-322 BC Spherical Earth Aristarchus 310-230 BC Sun/Moon dist & size heliocentric model Eratosthenes 275-194 BC Radius of the Earth Hipparchus 160-127 BC Earth-Moon distance Ptolemy 85-165 AD Almegest (120) Geocentric model

  7. ARISTARCHUS MOON Concluded Ds = 20x Dm Actually it is 400:1 Dm 90o SUN a (ang separation of sun and moon on celestial sphere) earth Ds EARTH

  8. ARISTARCHUS (2) If sun and moon look the same size, and the sun is 20x further away, the sun must be 20x larger than the moon. From the size of the Earth’s shadow on the moon during a lunar eclipse, and with his values of the distance from the sun to Earth, he calculated the earth is 3x larger than the moon, and the sun is 7x larger than Earth. Wrong, but clever. Earth’s shadow on moon

  9. ERATOSTHENES Eratosthenes measured the circumference of the Earth by noting that the Sun was at an angle of 6° south of the vertical at Alexandria at the same time that, at Syrene, 800 km south of Alexandria, the sun was observed to be exactly overhead. Based on these data, the circumference of the Earth in kilometers was measured to be 37,200 km or 23,250 miles, very close to the modern value of 40,000 kilometres. 6o shadow SUN Syrene Alexandria

  10. HIPPARCHUS 190-120 BC Hipparchus measured the distance from the Earth to the Moon during a solar eclipse that was a total eclipse at Syene and a partial eclipse at Alexandria. At the same time that an observer at Syene saw the entire Sun blocked by the Moon, one at Alexandria saw 1/5th of the Sun's disk, that is 1/5th of 30 arcminutes of the Sun's disk was visible (The Sun's angular diameter is 30 arcminutes or 1/2 degree). The angular size of the visible Sun seen at Alexandria therefore is 1/10th of a degree (0.1 degree) and this angle, expressed in radians and applying the small angle approximation gives the ratio of the Syene-Alexandria distance to the Earth-Moon distance at 60 earth radii and the moon 1/4 of the earth in size.

  11. PTOLEMY: EPICYCLES WITHIN EPICYCLES saturn Field of stars sol jupiter mars venus mercury terra luna PTOLEMAIC GEO-CENTRIC MODEL WITH EPICYCLES

  12. COPERNICUS 1473-1543 THE COPERNICAN REVOLUTION WE ARE NOT “SPECIAL” IN ANY WAY NOT THE CENTRE NOT THE FIRST NOT THE BIGGEST NOT THE SMALLEST WHAT IS THE WORLD COMING TO????

  13. TYCHO BRAHE 1546-1601 Ruler of island of Hveen off the caost of Denmark Built first observatory in Europe (no telescopes) Collected massive amounts of precise measurments

  14. JOANNES KEPLER 1571-1627 Acquired Brahe’s records Kept meticulous records of his own KEPLER’S THREE LAWS: 1. Planets move in ellipses, sun at one focus 2. A vector drawn from the sun to the planet will sweep out equal areas in equal times 3. P2 / a3 = a constant

  15. KEPLER’S SECOND LAW B 2b F2 c Sun A 2a Area A=B=C Planets (and comets) move faster when they are closer to the sun

  16. KEPLER’S THIRD LAW Planet r2 r1 F2 2b F1 2a r1 + r2 = 2a; p2 =k a3; (k= a constant) p=period of rotation

  17. GALILEO 1564-1642 Developed the telescope first to see: Multiple stars (1609) Sunspots (rotation of sun, sun imperfect) Phases of Venus (sphere, reflected light) Moons around Jupiter (1610) (other “centres”) Mountains on moon (“heavenly bodies are imperfect) Rings (handles) of Saturn (did not understand them) Recorded Uranus (in 1617 - but did not know it) Verified Coperican Model

  18. THE PLANETS NAME PERIOD ORBIT RADIUS (days) (A.U.) (km) MERCURY 88 .4 2439 VENUS 225 0.723 6057 EARTH 365.25 1.0 (150MKm)6378 MARS 686 1.52 3393 JUPITER 11.86 yrs 5.2 71400 SATURN 29.5 yrs 9.54 60330 URANUS 84 yrs 19.19 25500 (disc 1781) NEPTUNE 164.8 30.06 24750 (disc. 1846) PLUTO-CHARON ~39.5 1900

  19. BODE’S LAW To find the mean distances of the planets, beginning with the following simple sequence of numbers: 0 3 6 12 24 48 96 192 384 With the exception of the first two, the others are simply twice the value of the preceding number. Add 4 to each number: 4 7 10 16 28 52 100 196 388 Then divide by 10: 0.4 0.7 1.0 1.6 2.8 5.2 10.0 19.6 38.8 the result is very close to the distribution of mean distances of the planets from the Sun: 0.4 0.72 1.0 1.52 2.8 5.2 9.54 19.2 30.1 39.5 M V E M asteroids J S U N P-C

  20. PLANETS Mercury: like the moon, no tectonics, +450 to -270 oC Venus: 500oC, Atm CO2 & H2SO4, 100x earth pressure Mars +30 to -150oC, atm CO2, 0.01% earth p., ice cap Asteroids: more than 10,000, various sizes Jupiter: largest gas giant, 600kph winds, storms, rings, moons Saturn: gas giant, least dense, prominent rings, large moons Uranus, mid size gas giant, blue/green methane atm Neptune: mid sized gas giant, winds and storms Pluto-Charon: odd orbit, out of plane, eccentric, small

  21. SCALE OF THE SOLAR SYSTEM If the earth-sun distance is set as one metre Mercury is 30 cm away from the sun Neptune is 30 meters away (four light-hours) and the entire solar system fits inside a 60 metre circle Alpha Centauri, the nearest star, is 271 km away! (4.3 light-years)

  22. THE SUN 99.8% OF THE TOTAL MASS OF THE SOLAR SYSTEM MOSTLY HYDROGEN, SOME HELIUM; 2 X 1030 Kg SURFACE TEMP = 5800K. FUSION OF HYDROGEN INTO HELIUM POWERS THE SUN AT T= 107 K IT HAS ENOUGH FUEL FOR 1011 YEARS SUN AND PLANETS FORMED OUT OF A ROTATING CLOUD OF INTERSTELLAR GAS. MOST WENT INTO THE SUN, PLANETS ARE JUST SCRAPS LEFT OVER

  23. TELESCOPESLIGHT BUCKETS REFRACTORS: LARGEST 1 METRE DIAMETER LENS MIRROR LARGEST SINGLE 6 M LARGEST MULTIPLE 10 M

  24. DETECTION ASTRONOMERS DO NOT LOOK THROUGH THEIR TELESCOPES ANY MORE. THEY USE FILM, CCDs, OR SPECTRUM ANALYSERS

  25. RADIO ASTRONOMY THE ELECTROMAGNETIC SPECTRUM EXTENDS WELL BEYOND THE VISIBLE IN BOTH DIRECTIONS. RADIO TELESCOPES DETECT RADIO TRASNMISSIONS FROM THE STARS. LARGE DISH ANTENNAE OR MULTIPLE ARRAYS OF ANTENNAE

  26. X-RAY , U-V & I-R THE ATMOSPHERE IS OPAQUE TO MANY WAVELENTHS. SPACE TELESCOPES ARE NEEDED FOR MUCH OF MODERN ASTRONOMY

  27. STARS VISIBLE STARS RANGE FROM BRIGHT TO TOO DIM TO SEE THEY VARY IN ABSOLUTE BRIGHTNESS BY UP TO 100,000 MORE THAN OUR SUN.

  28. STELLAR DISTANCES PARALAX METHOD, CHANGE OF ANGLE AGAINST BACKGROUND STARS WHEN VIEWED SIX MONTHS APART, THAT IS FROM OPOSITE SIDES OF EARTH’S ORBIT STARS OF DIFFERENT CLASSES HAVE DIFFERENT TEMPERATURES, COLOURS, SPECTRAL LINES THEIR BRIGHTNESS GIVES THEIR DISTANCE LIFE-CYCLE OF STARS IS PRETTY WELL WORKED OUT

  29. SUPERNOVAS WHEN CERTAIN STARS BURN OUT, THEY EXPLODE ALL ATOMS LARGER THAN HELIUM COME FROM THE ASHES OF EXPLODED STARS. YOU ARE MADE OF STARDUST!!!

  30. MASS OF THE UNIVERSE HEAVIER ATOMS MAKE UP 0.01% OF THE MASS NEUTRINOS ARE 0.03% OF THE MASS STARS (75% H, 25% He) ARE 0.5% OF THE MASS COLD.DARK MATTER IS 25-35% Dark Energy is 60-70% OF ALL MASS

  31. GALAXIES MILKY WAY: GALAXY: 100 BILLION STARS MASS IS 1012 SOLAR MASSES A LARGE DISC WITH SPIRAL ARMS SUN: 2/3 OF THE WAY FROM THE CENTRE ONE BILLION OTHER GALAXIES SPIRALS AND ELLIPTICALS EACH HAS FROM ONE BILLION TO ONE TRILLION SOLAR MASSES

  32. THE HUBBLE CONSTANT DISTANT GALAXIES ARE MOVING AWAY FROM EACH OTHER (AND US) AT A SPEED PROPORTIONATE TO THEIR DISTANCE THIS OBSERVATION, AND A MEASURE OF THAT SPEED, LED TO THE “BIG BANG” THEORY AGE OF THE UNIVERSE IS 10-20 BILLION YEARS

  33. OTHER PLANETS? SO FAR 100+ EXTRA-SOLAR SYSTEM PLANETS HAVE BEEN FOUND, MOSTLY LARGE AND CLOSE TO THEIR STARS, REVOLVING RAPIDLY THESE ARE DETECTED BY MEASURING CHANGES IN THE OUTPUT OF THE STARS: CHANGES IN BRIGHTNESS, WOBBLE, GRAVITATIONAL LENSING

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