Nuclear fusion reaction, converts hydrogen into helium in the core of the sun.
Superimposed on sun’s white light are hundred of dark lines called Fraunhofer lines. Each line indicates some elements present in the solar system.
Solar winds: – The sun is continuously emitting streams of proton in all directions either as spiral streams called solar wind or bouts of incandescent material called solar flares. Solar flares being hot ionized gases pose danger to satellite communication.
Aurora: – The constituent particles of the solar wind are trapped by the earth’s magnetic field and enters the earth’s upper atmosphere as aurora. It is described as aurora borealis in northern hemisphere and aurora australis in southern hemisphere.
The surface of sun is continuously changing. Bright spots are called plages and dark spots are called sunspots. The sun spots are cold and dark regions on the sun’s surface with a periodicity of 11 years, these spots greatly influence the global climate.
Planets-
Mercury
Rotation period – 58.65 days.
Revolution period – 88 days. (fastest)
No satellite.
Highest diurnal range of temperature.
Venus
Earth’s twin, morning/evening star.
Brightest after sun and moon because of 70% of albedo.
Closest to earth.
Hottest planet. (97% co2)
Slightly smaller than earth. (500 km in dia)
Rotates east to west unlike others.
No satellite.
Rotation period – 257 days. (slowest)
Revolution period – 224.7 days.
Transit of venus – When it passes directly between the sun and earth, 8 year apart but separated by a century. Last was in 2004, next will be in 2117.
Mars
Revolution period – 687 days.
Rotation period – 24.6 hours.
Satellites – phobos and deimos.
Jupiter
Almost 11 times of earth.
Also called lord of the heavens.
Rotation period – 9.8 hrs. (fastest)
Revolution period – 12 years.
Have 16 satellites. (prominent are europa, ganymede and callisto)
Ganymede is the largest satellite.
Europa resembles living conditions.
Saturn
Least density – 30 times less than earth.
Revolution period – 29 years.
Rotation period – 10.3 hours.
More than 39 satellites. (prominent is titan)
Have system of rings. (three well defined)
Uranus
Identified as a planet in 1781 by William hershal.
Rotates from north to south as it is inclined at an angle of 98 degree to its orbit.
Revolution period – 84 years.
Rotation period – 16.8 hours.
Surrounded by 9 faint rings.
Have 21 satellites. (Miranda, aricl etc.)
Neptune
Greenish star because of methane.
Revolution period – 165 years.
Rotation period – 16.18 hours.
Notified by J g galle of Berlin in 1846.
Prominent satellites are trion and neroid.
Uranus and Neptune are called jovion twins.
Brightest star – Sirius. (dog star)
Comet-
May have originated from a huge cloud, the oort cloud.
Solid matter combined with gases.
Asteroids-
Or minor planets between mars and jupiter.
Also called planetoids or small planets.
Chunks of rock covered in frozen gases.
Meteroids are smaller than asteroids. (mostly are smaller than the size of pebble)
Meteor is a meteroid that has entered the earth atmosphere. (shooting/falling star)
A meteorite is as meteor that has fallen to earth.
The moon-
59% of surface is visible from earth.
Revolution period – 27 days 7 hrs 43 min 11.47 sec.
Rotation period – 27 days 7 hrs 43 min 11.47 sec.
Circumference – 11,000 km.
Distance from earth – 3, 82,200 km.
Moon light takes 1.3 sec to reach earth.
New moon = no moon. (moon is between earth and sun)
Full moon = complete moon. (occurs every 14th day after new moon)
Two full moons in a single month, then second full moon is called a blue moon.
Stars-
Due to novae and supernovae explosion a star will turn into a neutron star or pulsar.
Color indicates the temperature of its surface: – blue color (max temp.) > yellow > red.
Evolutionary sage of a star: – adult star > red giant > white dwarf.