natsci 2014.pptx
TRANSCRIPT
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Motion in the SolarSystem
Chapter 2
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We could imagine that the earth is at thecenter of a large sphere, called the celestialsphere.
The Earth is rotating from the west to east. The circumpolar starts near the north
celestial pole never set. One of the
circumpolar stars, called Polaris, is specialbecause it is very near to the northcelestial pole. Thus it appears to bestationary.
The Motion of the Heavenly Bodies
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elestial Sphere
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Stars do not move on the celestialsphere. Thus , if the earth is notrotating, stars are stationary.
Some stars do move on the celestialsphere which is referred as the propermotion of stars.
The path that the sun traces out on thecelestial sphere is called ecliptic.
Motion of stars
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Twelve constellation that the sun goesthrough are the zodiac.
Ecliptic does also go through theConstellation Ophiuchus, but due tohistorical reason, it is not included inthe zodiac
The sun does not spend equal time oneach ecliptic constellation.
The Constellation
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Due to revolution of the earth, a solarday is longer than a sidereal day.
Solar day- a year has 365. Sidereal days- a year ha 366. It will take about 365.25 days for the
earth to complete its revolution aroundthe sun which is referred to as thesidereal year.
Rotation and Revolution
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Solar and Sidereal days
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The time between successive full Moonsis the synodic Month which is completedevery 29.5 days while the number of the
days required for the moon to completeits revolution around the earth 27.5 daysreferred to as sidereal month.
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Planet in the solar system are classifiedas terrestrial and Jovian. From the eight planets, Mercury and
Venus are classified as inferior planets. Mars, Jupiter, Saturn, Uranus andNeptune are called superior planets.
Motion from west to east called progrademotion .
Motion from east to west calledretrograde motion .
Motion of Planet
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THE RENAISSANCE AND
THE HELIOCENTRICSYSTEMIt was during the renaissance period
that the helio centric system wasproposed and found tobe scientificallytrue.The idea that the earth revolvesaround the sun had been proposed as
during the 3rd century BC by Aristarchus of samos but was not
supported by other greekphilosophers.
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The Earth's axis is tilted fromperpendicular to the plane of the eclipticby 23.45. This tilting is what gives usthe four seasons of the year - spring,summer, autumn (fall) and winter. Sincethe axis is tilted, different parts of theglobe are oriented towards the Sun at
different times of the year.
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The solstices are days when the Sunreaches its farthest northern andsouthern declinations. The winter
solstice occurs on December 21 or 22 andmarks the beginning of winter (this isthe shortest day of the year). The
summer solstice occurs on June 21 andmarks the beginning of summer (this isthe longest day of the year).
Solstices
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Equinoxes are days in which day andnight are of equal duration. The twoyearly equinoxes occur when the Suncrosses the celestial equator.
The moon as the natural satellite of theearth also exhibits motion on its axis(rotation) and its revolution around theearth which causes tides.
Equinoxes
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Karl Schwarzschild 1906 Karl
Schwarzschildmodelled the solaratmosphere fromtheory ofthermodynamic
equilibrium where R.Emden published histheory of gaseousspheres.
Modern Astronomy
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Ejnar Hertzsprung 1906-1912 the
investigation ontemperature-luminosity relationof starsdiscovered
(Hertzsprung-Russell diagram).
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temperature-luminosity
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Arthur StanleyEddington
ChristopherHarrison
1925-1930 intensive studies on stellaratmospheres were pioneered by C.H. Paynewhile stellar structure was investigated by
A.S. Eddington the following year.
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1934 W. Baade and F. Zwicky proposedthe neutron stars hypothesis.
1938 H B h d C F W i k
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1938 H. Bethe and C.F. Weitzsackerproposed that nuclear reactions are stellar
energy sources. Hans Bethe
Carl FriedrichWeitzsacker
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1950 the carbon formation reaction alsoknown as Triple alpha process was
investigated by Opik and Salpeter. Salpeter Opik
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1955 thecomputermodelling ofstellar structureand evolution wasintroduced bySchwarzschildand Hoyle.
O S A O S
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1800 William Herschel
discovered theinfrared radiation.
OBSERVATIONS IN THEINVISIBLE LIGHT AND SPACE
ASTRONOMY
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Johann Wilhelm
Ritter discoveredthe UV radiationthroughdemonstrationshowing some ofits chemicaleffects.
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1931 Karl Guthe
Jansky discoveredradio radiationfrom the MilkyWay.
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1939
Grote Rebermade a follow upin the year 1939showing that thisradiatation isconcentratedwithin the galacticplane and towardthe galacticcenter.
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1942 J.S. Hey and J.
Southward foundthe firstextragalacticradio radiation.
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1963
Radioastronomersdiscovered thefirst quasar.(Maarten.Schmidt)
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1965
E.T. Byram, H.Friedman andT.A. Chubb discovered thefirst cosmic x-rays.
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1967 J. Bell and A.
Hewish discoveredthe first pulsar.
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1970
U.S. satelliteUhuru discovered160 x-ray sources.
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October 4, 1957:1 st Artificial Satellite
The Soviet Union ushers in a newera the space age with the launchof Sputnik 1 . Atechnological feat,
the beach ball-size satellite weighs184 pounds (84 kilograms) andtakes 98 minutes to orbit Earth
SPACE EXPLORATION
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November 3, 1957:First Animal in Orbit
Having stunned the world with the firstorbital space launch, Sputnik 1, less thana month before, the Soviet Union tries fora second coup by launching a dog namedLaika on a one-way journey on a hastilycompleted follow-up mission, Sputnik 2.The dog survives the launch, but Soviet
secrecy masks her ultimate fate for manyyears. It now appears that even thoughshe had a week's supply of food,Laika
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July 20, 1969 :1 st Manned Moon Landing
The lunar module of Apollo 11,nicknamed the Eagle, touches down onthe moon, with 30 seconds' worth of fuel
to spare. Neil Armstrong and Edwin"Buzz" Aldrin, Jr., descend to the
surface. "That's one small step for [a]man, one giant leap for mankind,"
Armstrong says. "Beautiful. Beautiful.Magnificent desolation," Aldrin adds.
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July 20, 1976:First U.S. Mars Landing Viking 1 soft-lands on Mars. Pictures showa stark, rocky landscape much like someEarthly deserts, and chemical testsdesigned to search for life show anomaliesin the soil that have yet to be fullyexplained.
August September, 1977: Voyagers 1 and 2Launched
NASA launches two spacecraft, Voyager 1and Voyager 2, on a grand tour of the solarsystem.
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April 25, 1990:Hubble Space TelescopeDeplo A day after launching, the space
shuttle Discovery opens its cargo baydoors to deploy a unique cargo: the12-ton Hubble Space Telescope