Solar System-Planets-Inner Planets-Outer Planets-Solar System Facts

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In this post we will study about Solar System-Planets-Inner Planets-Outer Planets-Solar

System Facts.

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You can ignore these concepts if you found them too scientific.

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SOLAR SYSTEM

The nebula from which our Solar system is supposed to have been formed, started its

collapse and core formation some time 5-5.6 billion years ago and the planets were

formed about 4.6 billion years ago.

Our solar system consists of the sun (the star), planets, satellites, millions of smaller

bodies like asteroids, meteorites and comets and huge quantity of dust-grains and

gases.

Out of the nine planets, Mercury, Venus, Earth and Mars are called as the inner

planets as they lie between the sun and the belt of asteroids the other five planets are

called the outer planets.

Alternatively, the first four are called Terrestrial, meaning earth-like as they are made

up of rock and metals, and have relatively high densities.

The rest five are called Jovian or Gas Giant planets.

Jovian means Jupiter-like. Most of them are much larger than the terrestrial planets

and have thick atmosphere, mostly of helium and hydrogen.

The orbits of the planets are nearly circular, but many comets, asteroids, and Kuiper

belt objects follow highly elliptical orbits

Why are the inner planets rocky while others are mostly in

gaseous form?

http://www.pmfias.com/universe-big-bang-redshift-blueshift-inflation-big-crunch-cosmic-microwave-background/

http://www.pmfias.com/star-formation-stellar-evolution-life-cycle-of-a-star-nebula-protostar-t-tauri-star-main-sequence-star-red-giant-supernova-white-dwarf-black-dwarf-brown-dwarf-neutron-star-black-hole/

http://www.pmfias.com/solar-system-formation-nebular-theory-of-laplace-milky-way-galaxy/


The terrestrial planets were formed in the close vicinity of the parent star where it was

too warm for gases to condense to solid particles. Jovian planets were formed at quite a

distant location.

The solar wind was most intense nearer the sun; so, it blew off lots of gas and dust from

the terrestrial planets. The solar winds were not all that intense to cause similar removal

of gases from the Jovian planets.

The terrestrial planets are smaller and their lower gravity could not hold the escaping

gases.

Components of the Solar System

1. Sun

2. Eight major planets,

3. Dwarf planets (Pluto, Ceres, Eris etc.),

4. Satellites and countless minor planets

5. Asteroids,

6. Meteors, and

7. Comets

8. Debris etc....

Nicolaus Copernicus was the first to develop a mathematically predictive heliocentric

system (Sun at the center). [Geocentric: Earth at the center]


Sun

Age => 4.6 billion years

Diameter => 13,91,785 km (~1.3 million km)

Temperature => 6000 C on surface and 16 million C in core


Density => 1.41 times that of water…[Density of water = 999.97 kg/m³; Density of

Iron = 7870 kg/m³] => Iron is (7870/999.97) = 7.87 times denser than water

Period of rotation => 25 days 9 hrs

Speed of rotation => 7179.73 km/hr (Earth’s rotational velocity => 1675Km/hr)

Equivalent to 3,32,900 Earth masses.

Compared to the majority of stars in the Milky Way, the Sun is rather large and bright.

Sun are rare, whereas substantially dimmer and cooler stars, known as red dwarfs, are

common, making up 85% of the stars in the galaxy.

Sun is located in Orion arm of Milky Way galaxy.

The vast majority of the system's mass is in the Sun, with most of the remaining mass

contained in Jupiter and Saturn.

Sun is rotating (counter-clockwise, as viewed from a long way above Earth's north

pole).

Kepler's laws of planetary motion describe the orbits of objects about the Sun.

A body's closest approach to the Sun is called its perihelion, whereas its most distant

point from the Sun is called its aphelion.

Although the Sun dominates the system by mass, it accounts for only about 2% of the

angular momentum due to the differential rotation within the gaseous Sun.

The Sun, which comprises nearly all the matter in the Solar System, is composed of

roughly 98% hydrogen and helium. Jupiter and Saturn, which comprise nearly all the

remaining matter, possess atmospheres composed of roughly 99% of these elements.

Those objects closer to the Sun, which are more affected by heat and light pressure, are

composed of elements with high melting points.

Objects farther from the Sun are composed largely of materials with lower melting

points.

Planets

A celestial body moving in an elliptical orbit round a star, the Earth is known as planet.

Planets are generally divided into:

(i) the Inner Planets (Mercury, Venus, Earth and Mars), and

(ii) the Outer Planets (Jupiter, Saturn, Uranus, Neptune, and Pluto-dwarf planet).

Inner Planets


The inner Solar System is the traditional name for the region comprising the terrestrial

planets and asteroids.

Composed mainly of silicates and metals.

The four inner or terrestrial planets have dense, rocky compositions, few or no

moons, and no ring systems.

They are composed largely of refractory minerals, such as the silicates, which form

their crusts and mantles, and metals, such as iron and nickel, which form their

cores.

Three of the four inner planets (Venus, Earth and Mars) have atmospheres substantial

enough to generate weather; all have impact craters and tectonic surface features,

such as rift valleys and volcanoes.

The term inner planet should not be confused with inferior planet, which designates

those planets that are closer to the Sun than Earth is (i.e. Mercury and Venus).

Mercury

Surface gravity: 1kg = 0.38 kg

Mercury is similar to the Moon with a surface dominated by craters and a younger

area of dark plains presumably made from floods of lava.

Venus

Surface gravity: 1kg = 0.88 kg

Venus is often considered to be the Earth's twin, but the two planets are not identical.

Venus has high plateaus, folded mountain belts, numerous volcanoes, and

relatively smooth volcanic plains.

The surface of Venus is totally obscured by a thick atmosphere composed mostly of

carbon dioxide, with clouds of sulfuric acid.

It is much drier than Earth, and its atmosphere is ninety times as dense.

Earth

Surface gravity: 1 kg =1 kg

The force of the Earth's rotation makes the world bulge very slightly at the equator

and go a little flat at the North and the South poles. So the Earth is actually a flattened

sphere, or a ‘geoid’.

It is large enough to develop and retain an atmosphere and a hydrosphere.


The Pacific Ocean contains the deepest places on the Earth's surface-the ocean

trenches.

The very deepest is the Challenger Deep in the Mariana Trench which plunges 11022

m into the Earth's crust.

A ray of light from the sun takes about eight minutes to reach the earth. Light takes

only a second to reach us from the moon.

Mars

Surface gravity: 1 kg = 0.38 kg.

Surface has been dynamic. Almost every geologic feature is gigantic. Three huge

volcanoes, one more than 28 km high exists at Mars.

There is evidence not only of stream action, but of catastrophic flooding .

Wind action is also an important process on Mars.

In addition polar regions are covered with alternating layers of ice and windblown

sediment.

It possesses an atmosphere of mostly carbon dioxide.

Its surface, peppered with vast volcanoes, such as Olympus Mons, and rift valleys, such

as Valles Marineris, shows geological activity that may have persisted until as recently

as 2 million years ago.

Its red colour comes from iron oxide (rust) in its soil.

Mars has two tiny natural satellites (Deimos and Phobos) thought to be captured

asteroids.

Asteroid belt

Millions of objects, remnants of planetary formation, circle the Sun in a zone lying

between Mars and Jupiter. They are known as asteroids.

Fragments of asteroids break off to form meteoroids, which can reach the Earth's

surface.

Asteroids are small Solar System bodies composed mainly of refractory rocky and

metallic minerals, with some ice.

The asteroid belt occupies the orbit between Mars and Jupiter, between 2.3 and 3.3 AU

from the Sun.

It is thought to be remnants from the Solar System's formation that failed to coalesce

because of the gravitational interference of Jupiter.


Asteroids range in size from hundreds of kilometres across to microscopic.

All asteroids except the largest, Ceres, are classified as small Solar System bodies.

Ceres

Ceres (2.77 AU) is the largest asteroid, a protoplanet, and a dwarf planet.

It has a diameter of slightly under 1,000 km, and a mass large enough for its own

gravity to pull it into a spherical shape

Outer Planets

The four outer planets, called the gas giants, are substantially more massive than the

terrestrials.

The two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium; the

two outermost planets, Uranus and Neptune, are composed largely of substances with

relatively high melting points (compared with hydrogen and helium), called ices, such

as water, ammonia and methane, and are often referred to separately as "ice giants".

Outer Planets are Jupiter, Saturn, Uranus, Neptune and the dwarf planet - Pluto.

The four outer planets, or gas giants (sometimes called Jovian planets), collectively

make up 99% of the mass known to orbit the Sun.


All four gas giants have rings, although only Saturn's ring system is easily observed

from Earth.

The term superior planet designates planets outside Earth's orbit and thus includes

both the outer planets and Mars.

Jupiter


It is composed mostly of gas and liquid swirling in complex patterns.

Jupiter has no solid surface and hence no record of a geologic history.

Its moons are, however, solid planetary bodies that contain geologic wonders.

Number of moons = 67. Planet with highest number of moons.

Jupiter's four large moons (Io, Europa, Ganymede, and Callisto), called the Galilean

satellites because they were discovered by Galileo in 1610

Saturn


It is composed mostly of hydrogen, and helium.

Saturn's rings for long have been considered as its most dramatic feature.

The rings are probably made up of billions of particles of ice and ice-covered rocks

Titan, the second-largest moon in the Solar System, is larger than Mercury and the only

satellite in the Solar System with a substantial atmosphere. (Our Moon is the fifth

largest natural satellite. Ganymede, a moon of Jupiter, is the largest natural staellite in

this solar system. At 5,268 km at the equator, it is larger than Mercury, the dwarf

planet Pluto, and three times larger than the Moon orbiting Earth.)

Number of Moons = 62.

Uranus


No solid surface.

Enveloped by a thick atmosphere of hydrogen and helium.

In contrast to all other planets in the solar system, it is tipped and spun on its sides,

that is its axis of rotation lies nearly the plane of its orbit.

Moons = 27.


Neptune

1 kg = 1.18 kg

Uranus and Neptune are called the twins of the outer solar system.

Surrounded by thick atmosphere of hydrogen, helium and methane.

Moons = 13.

Pluto and Charon

1 kg = 0.30 kg.

The dwarf planet Pluto (39 AU average) is the largest known object in the Kuiper belt.

When discovered in 1930, it was considered to be the ninth planet; this changed in

2006 with the adoption of a formal definition of planet.

Pluto was moved into the list of Dwarf Planets along with Ceres and Eris.

Charon, Pluto's largest moon.

Kuiper belt

The Kuiper belt is a great ring of debris similar to the asteroid belt, but consisting

mainly of objects composed primarily of ice.

It extends between 30 and 50 AU from the Sun.

Other Solar System Objects

Comets

A comet is an icy small Solar System body that, when passing close to the Sun,

heats up and begins to outgas, displaying a visible atmosphere or coma, and sometimes

also a tail.

These phenomena are due to the effects of solar radiation and the solar wind upon

the nucleus of the comet.

Short-period comets originate in the Kuiper belt or its associated scattered disc, which

lie beyond the orbit of Neptune.

Comets, composed of ice and dust, originated outside our solar system. Their elliptical

orbit brings them close to the Sun and into the inner Solar System.

Comets are among the most spectacular and unpredictable bodies in the solar system.

They are made of frozen gases (water, ammonia, methane and carbon dioxide) which

hold together small pieces of rocky and metallic minerals


One of the larger comets is the Halley's Comet. The orbit of Halley's Comet brings it

close to the Earth every 76 years. It last visited in 1986.

Meteorite

Any solid debris origination from asteroids or comets or from outer space that fall to the

Earth, the Moon, or another planet in the solar system.

Meteor is a body of matter travelling at a great speed through space which becomes

luminous when enters into the atmosphere (mesosphere) at about 200 km above the

Earth's surface, because it is heated by friction. Generally, this latter process dissipates

the material into meteoric dust.

A meteor is popularly termed a 'shooting star' or 'falling star'.

Largest Meteor Crater: A meteor crater in Arizona (USA) is 4,200 ft (1,300 m) deep is

the largest meteor crater in the world. It was formed over 10,000 years ago.

Solar System - Relevant Facts

Planets Diameter in kms; Distance from Sun; Distance in Astonomical

Units(AU)


1 AU = Distance between Sun

and Earth = 149.6 milliom kms

Mercury 4,878 = 0.38 57.9 mkm = 0.38

Venus 12,104 = 0.96 108.2 mkm = 0.72

Earth 12,576.3 = 1 149.6 mkm = 1

Mars 6,794 = 0.54 227.9 mkm = 1.52

Jupiter 143,884 = 11.44 778.4 mkm = 5.22

Saturn 120,536 = 9.58 1.426 mkm = 9.57

Uranus 51,118 = 4 2.87 mkm = 19.26

Neptune 50,538 = 4 4.498 mkm = 30.18

Relative size of Planets

The Sun compared to the planets


Planets in the ascending order of proximity to sun Temperature in °C

Mercury +427

Venus +480

Earth +22

Mars -23

Jupiter -150

Saturn -180

Uranus -214

Neptune -220

The reason that Venus is hotter than Mercury is because it has an atmosphere made

of carbon dioxide; it also has clouds of acid inside its atmosphere.

Planets in the ascending order of

proximity to sun

Period of Rotation

Period of Revolution

Mercury 58 days 87 days

Venus 243 days 224 days

Earth 23:56 hrs 365d, 5:48

Mars 1.05 days 687 days

Jupiter 9 hrs 11.86 years


Saturn 10 hrs 29.46 years

Uranus 17 hrs 84.01 years

Neptune 16 hrs 164.8 years

Planets in the ascending order of proximity to sun

Density relative to water (Taking, density of water = 1)

Mercury 5.43

Venus 5.24

Earth 5.51

Mars 3.94

Jupiter 1.33

Saturn 0.70

Uranus 1.3

Neptune 1.76

Planets No of Known Moons

Mercury 0

Venus 0

Earth 1

Mars 2

Jupiter 67

Saturn 62

Uranus 27

Neptune 13

Planets Rank according to

size

Mercury 8

Venus 6

Earth 5

Mars 7

Jupiter 1


Saturn 2

Uranus 3

Neptune 4

Planet Inclination angle to

Ecliptic

Orbital Velocity

in km/s

Mercury 7° 47

Venus 3° 35

Earth 23° 29

Mars 1° 24

Jupiter 1° 13

Staurn 2° 9

Uranus 0° 6

Neptune 1° 5

Pluto (Dwarf

planet)

17° 4

Other related concepts

Heliocentric vs Geocentric

Heliocentric system is an astronomical model in which the Earth and planets revolve

around a relatively stationary Sun at the center of the Solar System. [Remember the

name of the man who first suggested this model?]

Geocentric model (Earth the centre) was proposed by Ptolemy.

Kepler's laws of planetary motion

1. The orbit of a planet is an ellipse with the Sun at one of the two foci.

2. A line segment joining a planet and the Sun sweeps out equal areas during equal

intervals of time.

3. The square of the orbital period of a planet is proportional to the cube of the semi-major

axis of its orbit.


Why is Venus sometimes called Earth's twin?

almost the same size,

have about the same mass (they weigh about the same), and

have a very similar composition (are made of the same material).

They are also neighboring planets.

However, Venus and Earth are also very different

Venus has an atmosphere that is about 100 times thicker than Earth's and has surface

temperatures that are extremely hot.

Venus does not have life or water oceans like Earth does.

Venus also rotates backwards compared to Earth and the other planets.

Mars Compared to Earth

53% the diameter of Earth

10% the mass of Earth

surface gravity on Mars is only 38% the gravity on Earth

A day on Mars lasts 1.03 Earth days

axial tilt on Mars is 25.19 degrees. Very close to Earth’s 23.5 degree tilt

a year on Mars lasts about twice as long as an Earth year, the seasons are twice as long.

The atmosphere of Mars is less than 1% the thickness of Earth’s atmosphere.

Furthermore, it’s made up of 95% carbon dioxide

Ecliptic Plane


Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as

the ecliptic. The planets are very close to the ecliptic, whereas comets and Kuiper belt

objects are frequently at significantly greater angles to it.

Important fact

All the planets except VENUS and URANUS rotate in anti-clockwise direction.

The Moon

The moon is the only natural satellite of the earth.

It is now generally believed that the formation of moon, as a satellite of the earth, is an

outcome of ‘giant impact’ or what is described as “the big splat”.

A body of the size of one to three times that of mars collided into the earth sometime

shortly after the earth was formed. It blasted a large part of the earth into space.

This portion of blasted material then continued to orbit the earth and eventually formed

into the present moon about 4.44 billion years ago.

Its diameter is only one-quarter that of the earth.

It is about 3, 84,400 km away from us.

The moon moves around the earth in about 27 days. It takes exactly the same time to

complete one spin. As a result, only one side of the moon is visible to us on the earth.

Neil Armstrong was the first man to step on the surface of the moon on 29 July 1969.

Solar System-Planets-Inner Planets-Outer Planets-Solar System Facts

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