2. PLANET
The solar system has a large variety of planets with different features, characteristics and unique
qualities.
The word planet derived from a Greek word “Planetes” that means wanderers or moving stars.
A major object which orbits around a star.
In our solar system there are eight such objects which are called planets.
3. CLASSICAL PLANETS
The Sun ,Moon, Mercury, Venus, Mars, Jupiter and Saturn this seven bodies
continuously moving is called as classical planets.
They were perceived as mighty Gods and the seven weekdays were named
them.
They were not discovered but known from ancient time.
The sun and moon also move in the sky they were included in the list of
planets.
6. URANUS
Uranus is the first planet to be discovered using telescope.
Sir Frederick William Herschel, an English musician and an avid astronomy
enthusiast discovered the planet.
Uranus was discovered accidently on March 1781.
Uranus was named after the Greek God of the sky.
7. NEPTUNE
The eight planet of the solar system is the Neptune.
Neptune was discovered in September 1846
Three astronomers independently worked for discovering the eight planet.
English Astronomer John Couch adams and French Astronomer Urban lee Verrier, German
Astronomer Johan Galle.
John Couch adams and Urban lee Verrier, founded the location and orbit of Neptune.
Johan Galle provided great triumph for mathematical or calculative astronomy
Neptune was named after the God of Ocean.
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10. PLUTO
Slight variations in the movement of Neptune prompted astronomers to
presume that there was another planet behind Neptune.
Clyde Tombaugh discovered it in February 1930 from the Lowell
observatory in Arizona USA.
Pluto was named after the Roman God of the dead and the underworld.
11. Terrestrial Planets
The Latin word terra means earth or land thus terrestrial planets are those
which have land on them or are earth like they are called as terrestrial
planets.
This group of planets are all the solid planets located between the sun and
the asteroid belt.
The terrestrial planets are Mercury, Venus, Earth and Mars.
All these planets have common characteristics such as
1. They are made up of rocks or metals with a hard surface
2. Heavy surface features like valleys, volcanoes and craters.
3. They have a molten heavy metal core.
4. These four planets have an atmosphere which is of a different composition
of gases and density of each planet.
5. All these planets are also faster moving, Smaller and the hotter planets of
our solar system.
12. These are the most studied and visited by our rockets and probes.
The prominent features of all these planets is that they have very few
moons orbiting them.
Mercury and Venus having no moon, Earth has one moon and mars has
two moons.
13. Gas Giants
This group of planets are all giants compared to the tiny terrestrial planets
and are made up almost entirely of Gases.
The Gas Giants planets are Jupiter, Saturn, Uranus and Neptune.
The Gas Giants are made up of gas and have no hard surface for any
spacecraft to land on.
Gas Giants have a rocky core with the presence of metal alloys and the
majority of its mass is in the form of gases like hydrogen and helium with
traces of water, methane, ammonia, and other hydrogen compound.
All these planets are bigger , faster moving and colder planets of our solar
system all orbiting outside the asteroid belt.
A prominent feature of all the gas giants is that they have a huge number
of solid moons and massive ring systems composed of dust and icy rocks
encircling them near their centres.
14.
15. Trans-Neptunian objects (TNOs)
After 20006 a new group of planets has come to prominence and this group is
called the Trans-Neptunian objects, dwarf planets or simply TNOs.
The planet which is located beyond the Neptune falls in this group.
Pluto is now considered as TNO. As Eris is the dwarf planet located behind the
pluto.
There are around 70,000 TNOs each atleast 100km across or smaller,lying between
30 to 50 astronomical units from the sun,many have their own moon orbiting them.
The largest known Trans-Neptunian objects are Pluto and Eris, followed by Haumea
and Makemake all of them being officially recognized as dwarf planets by the
international Astronomers union.
16. Unique characteristics of planets
MERCURY
Mercury’s axis of rotation is tilted just 2 degrees with respect to the plane of its orbit
around the sun,that means it spins nearly perfectly straight and upright and so is the
only planet that does not experience seasons like other planets do.
17. VENUS
The greenhouse effect was not discovered on earth but on Venus when
astronomers were studying it.
In fact Venus has the thickest atmosphere causing the highest Global warming
making it the hottest planet.
18. EARTH
The only known place in the universe to have life.
This is made possible by the exact distance of 150 million kms from the sun
allowing water to exist in liquid state on the planet and this was what gave rise to
life and sustained it.
19. MARS
Strongly believed to have evolved some sort of life forms millions of years ago
Mars is for this very reason the most studied visited and probed planet in the solar
system.
Man even has a remote dream of colonizing it one day.
20. JUPITER
Believed in some theories to be a “failed star” more than a planet.
The concept is that it evolved with the sun as its twin star but did not have enough
internal pressure and temperature to trigger nuclear fusion and cooled off and is
now recognized as a planet.
21. SATURN
The gas inside Saturn is so loosely spread that this planet is even less dense than
water.
If at all there were an ocean of water large enough to hold Saturn, the planet
would literally float on it.
No other planet in the solar system has this property.
22. URANUS
The axis of rotation of Uranus is parallel with the plane of the solar system with a
tilt of 97.77 degree.
Uranus is almost like a fallen down planet rolling around on its stomach.
This causes the strangest effect of one pole in darkness for 42 years, then in
sunlight for the next 42 years causing weird seasons.
