Geography and Universe

Cosmology

The study of Universe

Big Bang Theory

Big bang was an explosion that forms galaxies

Big Bang Theory

Big bang occurred about 15 billion years ago.

Big Bang Theory

Proposed by George Lemaitre.

Black hole

Collapse of the star to form black hole.

Galaxy

A large group of stars.

Milky Way (Akash Ganga)

Name of the galaxy to which our Earth and Sun belong.

Andromeda

Our nearest galaxy.

Light year

Distance travelled by light in 1 year.

1 Light Year

9.46 × 10¹² km

Speed of light

300000 km / sec

1 Parsec

3.26 light years.

1 Astronomical unit (AU)

14960000 km (Earth-Sun Distance)

Stars

Heavenly bodies made up of hot burning gases like Hydrogen and Helium.

Proxima Centauri

Closest star to our solar system (4.2 light years).

Sirius (Dog Star)

Brightest star outside solar system.

Supernova

Explosive death of a star.

Pole star

Located in North direction.

Constellation

It is a group of stars

Number of constellations

88

Ursa Major

Also called Saptarishi (seven stars)

Orion

In the shape of a 'Hunter'.

Leo Major

In the shape of a 'Lion'.

Solar System

Comprises the Sun and its 8 planets.

Sun's main gases

Hydrogen and Helium

Age of the Sun

5 billion years.

Photosphere

The glowing surface of the sun.

Corona

The outermost layer of the sun visible during solar eclipse.

Surface temperature of the Sun

6000° C

Measurement of Sun's temperature

Pyrometer.

Sun's revolution around Milky Way

224 million years.

Distance between Earth and Sun

14.96 crore km.

Time taken by sunlight to reach Earth

8 minutes and 20 seconds.

Inner Planets

Mercury

Composition of Inner Planets

Made of rocks

Outer Planets

Jupiter

Composition of Outer Planets

Made of gases and dust

Planets rotation

Rotates from west to east except Venus and Uranus.

Mercury

Smallest and nearest planet to the Sun.

Mercury's revolution

Fastest Revolution (88 days).

Mercury's satellites

No satellite.

Venus

Brightest Planet.

Venus

Hottest Planet.

Venus

Morning Star

Venus's rotation

Slowest Rotation Speed (243 days).

Venus's rotation direction

Rotates from east to west.

Earth's Twin

Venus.

Venus's satellites

No satellite.

Earth

Only Planet where life exists.

Earth

Densest Planet.

Earth

'Blue Planet' due to the presence of water.

Earth's satellite

Moon is the only satellite.

Mars

Red Planet (due to the presence of iron oxide).

Mount Olympus

Highest mountain in Solar system

Mars's satellites

Phobos and Deimos.

Mars's rotation speed

24 Hours.

Most similar planet to Earth

Mars.

Asteroid Belt

Between Mars and Jupiter.

Jupiter

The largest planet.

Jupiter's rotation speed

Fastest Rotation speed - 10 hours.

Ganymede

Largest satellite in solar system (Jupiter's).

Jupiter

Maximum gravity.

Saturn

Second largest planet.

Saturn's rings

Surrounded by rings made up of gas and dust.

Saturn's density

Least Density (can float on water).

Saturn's satellites

Most Satellites-145.

Titan

Satellite of Saturn.

Uranus

Discovered by William Hershel.

Uranus's inclination

Inclined at 98^{\circ}.

Uranus

Sleeping planet.

Uranus's rolling

It actually rolls from north to south.

Uranus's satellites

27 satellites.

Uranus

Green planet.

Neptune

The farthest planet from the sun.

Neptune's revolution speed

Slowest revolution speed - 165 years.

Neptune's satellites

14 satellites.

Pluto

Not a planet now (Omitted from the list in 2006)

Moon's distance from Earth

384000 km.

Time taken by moonlight to reach Earth

1.3 seconds.

Moon's rotation and revolution speed

Same - 27 days.

Part of moon visible from Earth

59%.

First to reach Moon

Neil Armstrong and Edwin Aldrin in 1969.

Sea of Tranquillity

On Moon.

Comets

They revolve around sun. It has a tail which always points away from the sun.

Halley's comet

Appears after every 76 years.

Halley's comet last appearance

1986.

Meteors

Shooting stars

Meteorites

The burnt part of a meteor which falls on Earth.

Asteroids

Numerous tiny heavenly bodies between the orbits of Mars and Jupiter.

Age of the Earth

4.6 billion years.

Shape of Earth

Oblate spheroid.

Inclination of Earth on its axis

-23.5^{\circ}

Earth's orbit

Elliptical.

Radius of Earth

6400 km.

Earth's Rotation Speed

23 hours

Earth's Revolution Speed

365 days

Earth's surface composition

Water-71%

Perihelion

Nearest distance between Earth and the Sun (14.70 crore km)

Aphelion

Farthest Distance between Earth and Sun (15.20 crore km)

Apogee

Farthest Distance Earth and Moon.