Universe, Solar System
||Radius x 103km
||Mean distance from the sun x 106 km
||Mass as compared to earth M planet / M earth
||Time period of revolution around the sun
||Time taken to complete one rotation about its own axis
||Number of satellites|
||23h 56 min
||24h 27 min
||9h 50 min
||10h 14 min
||10h 49 min
The limitless expanse of space around us consisting of solar system, stars galaxies etc is called universe.
Solar system the sun the planets revolving about the sun in elliptical orbits and the satellites moving around the planets is our solar system. It also includes asteroids comets and meteors. The above table gives the radius, distance, time of revolution time of rotation and number of satellites of the planets of the solar system.
Moon the natural satellite of earth, is 3.84 x 105 km always, its mean diameter is 3480 km, and mass 7.35 x 1022 kg.
The gravity of moon = g / 6 = 1.66 ms2. The temperature during the day is 1000˚ C and during the night is 150˚C, no atmosphere or water exists, hence no possibility of life.
Asteroids group of more than 1600 tiny rock ices moving around the sun between mars and Jupiter. The largest amongst these is cares with a radius of 350 km. the smallest one has radius 50m. It is believed that asteroids are pieces of a planet which broke up due to gravitational pull of Jupiter.
Comets are composed of rock like materials surrounded by large masses of easily vaporized substances like ice, water, NH, and CH4they revolve around the sun in highly elliptical orbits. The time period of revolutionist very large. For example, Halley comet has a time period of 76 years. They appear to have a bright head and a long tail while passing close to the sun.
Meteors are the smaller pieces of stones and metals which may be produced due to the breaking up of comets while approaching the sun. Then they reach reach’s atmosphere due to friction they start bring.
Keller’s law can be used to find distance
T21 / T22 = R31 / R32
Distance can also be determined using specter - scope method I1 / I2 = r22 / r21
Inferior planets mercury and venues are closer to the sum than earth.
The mass of the sun
GMs ME/ R2SE = MERSEω2
Or Ms = (RSE)3 / G (2π / T)2
Where RSE distance of the earth from the sun ME = mass of the earth, MS mass of the sun ω --> angular velocity of the earth.
Mass of a planet = 4 π2 R3PM / GT
Where RpM is the distance of its moon, T time period of revolution of the moon about the planet.
Surface temperature can be determined using Stefan’s law or wein’s displacement law.
Stefan’s law I = σT4 or power P = AσT4
A is area receiving radiation
Wein’s displacement law λm T = (b) constant where, b = 2.89 x 10-3 m– K.
Acceleration due to gravity g = GM/R2,
Orbital velocity = GM/R = gR
Escape velocity 2 (GM/R) = 2gR
Surface temperature of the sun = 5800 K.
Solar constant (S) is the amount of solar energy received per second by a unit area of a perfectly black body surface held at right angles to the direction of sun rays at the mean distance of the earth from the sun. The value of solar constant is 1388 wm-2 or 2 cal cm-2 min-1
Solar luminosity = 4πr2S
Where r = distance of earth from the sun
S = solar constant
T =( r2S / R2σ)1/4 where , R = radius of the sun
Solar flare during solar flare a rich emission of protons is found
Sun spots many dark spots visible on its disc are called solar spots.
1 AU (astronomical unit) = 1.5 x 1011m,
L parsecs = 3.26 light year.
Closest star (after sun) is alpha century, 4.3 light years from the earth. One can see 2500 to 5000 stars with naked eye on a clear night. Star is a self luminous body emitting radiations due to nuclear fusion reaction going on in. it
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