Upload
others
View
0
Download
0
Embed Size (px)
Citation preview
18
‘The Solar System’ is the name given to the planetary system of
which the Earth is part. It comprises 8 planets, moons, comets,
meteors, asteroids & dwarf planets which are all held together by
the gravitational pull of a star, named either the Sun or ‘Sol’.
Formation of the solar system:
The formation of the Solar System is estimated to have begun 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the centre, forming the Sun, while the rest flattened into a proto planetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed.
The Planets:
The known planets in the solar system can be divided into two
groups. The four planets closest to the sun: Mercury, Venus, Earth &
Mars are called the ‘terrestrial planets’. The outer four planets are
called the ‘gaseous giants’ or ‘Jovian planets’. The terrestrial & Jovian
THE SOLAR SYSTEM
19
planets are divided by a belt of asteroids between Mars & Jupiter.
Pluto was demoted to the status of ‘Dwarf planet’ giving it home
among similar sized objects & asteroids which make up the Kuiper
Belt.
End of the solar system:
It is difficult to calculate exactly where our solar system ends. It ends
at a point at which objects are no longer affected by the sun’s
gravitational pull. The farthest reaches of the solar system are
thought to be surrounded by a great halo: Oort cloud; home to
millions of comet nuclei & small icy rocks.
Voyager 1 & 2 are the farthest reaching man-made objects in the
solar system. In 2004, Voyager 1 cleared the termination shock, the
area where solar winds begin to slow down & increase in
temperature as they come up against interstellar winds. Voyager
probes will continue transmitting data for several more decades, but
it would take thousands of years for them to reach the nearest star,
Alpha Centauri.
20
4.1 THE SUN:
In the grand scheme of the universe, the sun in just another middle
aged star. Its stellar classification, G2, denoting its yellowish
colouring & its surface temperature (5000°-6000° kelvin) is not
extraordinary either; there are countless G2-type stars.
Fusion:
In the sun, Hydrogen nuclei collide with one another to form Helium
atoms. In this process, called ‘fusion’, mass is transferred into
energy, which is explained by Einstein’s famous equation: 𝐸 = 𝑚𝑐2.
The period during which sun generates energy through fusion is
called ‘Main sequence’. Our sun is estimated to be 5 billion years old
& its main sequence will last another 5 billion years.
Solar Layers:
The atmosphere of the sun is
composed of several layers, mainly
the photosphere, the chromosphere
and the corona. It's in these outer
layers that the sun's energy, which
has bubbled up from the sun's
interior layers, is detected as
sunlight.
Sunspots:
These are minor regions where the temperature of the photosphere
is cooler than its surroundings. Sunspots are the result of string
localised magnetic field & follow a cycle of 11 years.
21
4.2 MERCURY
Mercury is the smallest and closest to
the Sun of the eight planets in the Solar
System, with an orbital period of about
88 Earth days. Seen from Earth, it
appears to move around its orbit in
about 116 days, which is much faster
than any other planet. It has no
known natural satellites. The planet is
named after the Roman deity Mercury;
the messenger to the gods
Mercury has almost no atmosphere. Its surface is heavily cratered
due to impacts from meteorites.
4.3 VENUS
Venus is the second planet from
the Sun, orbiting it every
224.7 Earth days. It has no natural
satellite. It is named after the Roman
goddess of love and beauty. After
the Moon, it is the brightest natural
object in the night sky, bright enough to
cast shadows. Venus is a terrestrial
planet and is sometimes called Earth's
"sister planet" because of their similar
size, gravity, and bulk composition.
It is the hottest planet in solar system. It rotates on its axis from east to west. Therefore, on Venus the sun rises in west & sets in east.
22
4.4 EARTH Earth, also known as Terra, is the
third planet from the Sun,
the densest planet in the solar system,
the largest of the Solar System's for
terrestrial planets, and the only celestial
body to accommodate life. It is home to
millions of species, including billions of
humans.
The Earth takes 365.26 days to orbit the sun & 23.93 hours revolve
once around its axis which is tilted 23.5° to the planet’s orbit.
4.5 THE MOON
The Moon (Latin: Luna) is the Earth's
only natural satellite. Although not the
largest natural satellite in the Solar System,
it is, among the satellites of major planets,
the largest relative to the size of the object
it orbits and, after Jupiter's satellite Io, it is
the second densest satellite among those
whose densities are known.
The Moon is in synchronous rotation with Earth, always showing the
same face with its near side marked by dark volcanic maria that fill
between the bright ancient crustal highlands and the prominent
impact craters . It is the most luminous object in the sky after
the Sun. It takes moon 27.3 days to revolve around earth.
23
4.6 MARS
Mars is the fourth planet from the Sun
and the second smallest planet in the
solar system, after Mercury. Named
after the Roman god of war, it is often
described as the "Red Planet" because
the iron oxide prevalent on its surface
gives it a reddish appearance.
Mars’s atmosphere is consists of 95%
of carbon dioxide & remaining 5% of Argon & Nitrogen. Average
surface temperature is 60° Celsius. Because of this water exist on
mars in frozen & vapour form.
4.7 JUPITER
Jupiter is the fifth planet from the
sun and the largest planet in the solar
system. It is a gas giant with mass one
thousandth of that of the sun but is
two and a half times the mass of all
the other planets in the Solar System
combined.
Jupiter is primarily composed
of hydrogen with a quarter of its mass being helium. There are also
moons that were first discovered by Galileo Galilei in
1610. Ganymede, the largest of these moons, has a diameter greater
than that of the planet Mercury.
at least 79 moons, including the four large moons called the Galilean
24
The Giant Red Spot is its most notable feature. It is a giant storm
which flows anti-clockwise across in area of 24,000 km in length &
12,000 km in width.
Saturn is the sixth planet from the
sun and the second largest planet in
the Solar System, after Jupiter. It is
named after the Roman god of
agriculture. Saturn is gas giant with
an average radius about nine times
that of Earth. While only one-eighth
the average density of Earth, with its
larger volume Saturn is just over 95 times more massive.
One of the greatest fascinations of the solar system is the Rings of
Saturn. They have often earned Saturn the title of the most attractive
planet in solar system.
larger than the planet Mercury and is the only moon in the Solar
System to retain a substantial atmosphere.
4.9 URANUS
Uranus is the seventh planet from the Sun. It
has the third-largest planetary radius and
fourth-largest planetary mass in the Solar
System. Uranus is similar in composition
to Neptune, and both are of different
chemical composition to the larger gas
giants Jupiter and Saturn. For this reason,
astronomers sometimes place them in a
4.8 SATURN - 82 Moon
Titan, Saturn's largest and the Solar System's second largest moon
25
separate category called "ice giants".
It is the coldest planetary atmosphere in the Solar System, with a
minimum temperature of −224.2 °C and has a complex, layered cloud
structure, with water thought to make up the lowest clouds, and
methane the uppermost layer of clouds. In contrast, the interior of
Uranus is mainly composed of ices and rock.
4.10 NEPTUNE
Neptune is the eighth and farthest
planet from the sun in Solar System.
It is the fourth-largest planet by
diameter and the third-largest by
mass. Among the gaseous planets,
Neptune is the densest. Neptune is
17 times the mass of Earth and is
slightly more massive than its near-
twin Uranus, which is 15 times the
mass of Earth but not as dense.
Neptune orbits the Sun at an average distance of 30.1 astronomical
units. It is named after the Roman god of the sea.
Neptune's atmosphere is notable for its active and visible weather
patterns. For example, at the time of the 1989 Voyager 2 flyby, the
planet's southern hemisphere possessed a Great Dark Spot
comparable to the Great Red Spot on Jupiter.
4.11 PLUTO & THE KUIPER BELT
Discovered in 1930, Pluto was originally classified as the ninth planet
from the Sun. Its status as a major planet fell into question following
further study of it and the outer Solar System over the ensuing 75
years. Starting in 1977 with the discovery of the minor planet 2060
26
Chiron, numerous icy objects similar to Pluto with eccentric orbits
were found. The most notable of these was thes cattered disc
object Eris, discovered in 2005, which
is 27% more massive than Pluto.
Pluto has five known moons: Charon (the largest, with a diameter just over half that of Pluto), Nix, Hydra, Kerberos & Styx.
On July 14, 2015, the Pluto system is due to be visited by spacecraft for the first time. The New Horizons probe will perform a flyby during which it will attempt to take detailed measurements and images of the plutoid and its moons.
KUIPER BELT:
Kuiper Belt is a region of the Solar System beyond the planets,
extending from the orbit of Neptune (at 30 AU) to approximately
50 AU from the Sun. It is similar to the asteroid belt, but it is far
larger—20 times as wide and 20 to 200 times as massive. Like the
asteroid belt, it consists mainly of small bodies, or remnants from the
Solar System's formation. Although most asteroids are composed
primarily of rock and metal, most Kuiper belt objects are composed
largely of frozen volatiles (termed "ices"), such as methane,
ammonia & water. The Kuiper belt is home to at least three dwarf
planets: Pluto, Haumea, and Makemake. Some of the Solar System’s
moons, such as Neptune's Triton and Saturn's Phoebe, are also
believed to have originated in the region.
27
4.12 MINOR BODIES IN SOLAR SYSTEM
4.12.1 ASTEROIDS
Asteroids are fragments of rock & metal which are greater than 50m
in diameter. On New Year’s Day 1801, the Italian astronomer,
Giuseppe Piazzi, discovered the first asteroid Ceres. Initially he
thought it was a comet, but its orbit was too slow & uniform. Some
scientists suggested it might be a planet between Mars & Jupiter. But
in 1802, second asteroid was discovered, named Pallas. This 2nd find
led William Herschel, the discoverer of Uranus, to offer a collective
name ‘asteroids’, meaning ‘Star-like’.
Many of the asteroids in the solar system are located in a band
between Mars & Jupiter called the ‘Asteroid Belt’. It is believed that
the belt is failed planet- the chunks of rock & metal were unable to
group together & form 5th terrestrial planet because of the strong
gravitational pull of Jupiter.
4.12.2 METEOROIDS
Meteoroids can be found throughout the solar system. They are
small fragments of rock & minerals, often the size of a grain of sand.
28
Meteoroids are either the chipped away parts of grater bodies or are
remnants from the creation of the solar system.
SHOOTING STAR
When meteoroids collide with the Earth they burn up in the upper
atmosphere, creating a striking spectacle called Meteor.
METEOR SHOWERS
29
4.12.3 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. Comet nuclei range from a few hundred
metres to tens of kilometres across and are composed of loose
collections of ice, dust, and small rocky particles. The coma and tail
are much larger and, if sufficiently bright, may be seen from the
Earth without the aid of a telescope. Comets have been observed
and recorded since ancient times by many different cultures. Comets
are known as the ‘dirty snowballs’.
Comets have a wide range of orbital periods, ranging from several
years to several millions of years. Short-period comets originate in
the Kuiper belt or its associated scattered disc, which lie beyond the
orbit of Neptune. Longer-period comets are thought to originate in
the Oort cloud, a spherical cloud of icy bodies extending from
outside of the Kuiper belt to halfway to the next nearest star.