2. UNIVERSE
The universe is commonly defined as the totality of everything that exists, including all
matter and energy, the planets, stars, galaxies, and the contents of intergalactic space.
Definitions and usage vary and similar terms include the cosmos, the world and nature.
Scientific observation of earlier stages in the development of the universe, which can be
seen at great distances, suggests that the universe has been governed by the same
physical laws and constants throughout most of its extent and history. There are various
multiverse theories, in which physicists have suggested that our universe might be one
among many universes that likewise exist.
The word universe derives from the Old French word Univers, which in turn derives from
the Latin word universum.The Latin word was used by Cicero and later Latin authors in
many of the same senses as the modern English word is used.The Latin word derives from
the poetic contraction Unvorsum — first used by Lucretius in Book IV (line 262) of his De
rerum natura (On the Nature of Things) — which connects un, uni (the combining form of
unus', or "one") with vorsum, versum (a noun made from the perfect passive participle of
vertere, meaning "something rotated, rolled, changed").
3. The night sky
In day time only sun is visible in the sky. As soon as the sun sets sky appear full of twinkling
stars. The twinkling takes place due to atmosphere of the Earth on clear night. There are
billions of stars in the universe it. which are not uniformly distributed. These occur in the form
of huge bunches or clusters. Such a group of stars is a single galaxy.
The Sun ,the Earth and other planets and all the stars that we see in the sky belong to a galaxy
called Milky way. It is also called akash ganga. It assumed that there are some 1011 galaxies in
the universe and each galaxy contains 1011 stars in it.
The fact that the sky is not completely dark at night can be easily observed. Were the sky (in
the absence of moon and city lights) absolutely dark, one would not be able to see the
silhouette of an object against the sky.
MILKY WAY
4. stars
A star is a massive, luminous sphere of plasma
held together by gravity. At the end of its
lifetime, a star can also contain a proportion of
degenerate matter. The nearest star to Earth is
the Sun, which is the source of most of the
energy on Earth.
. Other stars are visible from Earth during the night, when they are not obscured by
atmospheric phenomena, appearing as a multitude of fixed luminous points because of their
immense distance. Historically, the most prominent stars on the celestial sphere were
grouped together into constellations and asterisms, and the brightest stars gained proper
names. Extensive catalogues of stars have been assembled by astronomers, which provide
standardized star designations. For at least a portion of its life, a star shines due to
thermonuclear fusion of hydrogen in its core releasing energy that traverses the star's interior
and then radiates into outer space.
5. Almost all naturally occurring elements heavier than helium were created by stars, either
via stellar nucleosynthesis during their lifetimes or by supernova
Nucleosynthesis when stars explode. Astronomers can determine the mass, age, chemical
composition and many other properties of a star by observing its spectrum, luminosity and
motion through space. The total mass of a star is the principal determinant in its evolution
and eventual fate. Other characteristics of a star are determined by its evolutionary
history, including diameter, rotation, movement and temperature. A plot of the
temperature of many stars against their luminosities, known as a Hertz sprung-Russell
diagram (H–R diagram), allows the age and evolutionary state of a star to be determined.
The colour of star depends upon its temperature. Most of stars are so far away from Earth
that light from them takes millions of years to reach us. The distance of stars is therefore
expressed in terms of light years. One light year is the distance travelled by
Light in one year(the speed of light is
About 3,00,000 kilometer per second
Therefore , 1 light Year= Distance
travelled by light in One year.
6. constellations
In modern astronomy, a constellation is an internationally defined area of the celestial
sphere. These areas are grouped around asterisms, patterns formed by prominent stars
within apparent proximity to one another on Earth's night sky.
There are 88 standard constellations recognized by the International Astronomical Union
(IAU) since 1922. The majority of these go back to the 48 constellations defined by Ptolemy
in his Almagest (2nd century). The remaining ones were defined in the 17th and 18th
century; the most recent ones are found on the southern sky, defined in Coelum australe
stelliferum by Nicolas Louis de Lacaille (1763).
There are also numerous historical constellations not recognized by the IAU, or
constellations recognized in regional traditions of astronomy or astrology, such as Chinese,
Hindu or Australian
Aboriginal. We can easily identify some
constellation with Naked eyes. Some
Important constellations are-
7. URSA MAJOR
Ursa Major (Latin: "Larger Bear"), also known as the Great Bear, is a constellation visible
throughout the year in most of the northern hemisphere. It can best be seen in April. It is
dominated by the widely recognized asterism known as the Big Dipper or Plough, which is a
useful pointer toward north, and which has mythological significance in numerous world
cultures.
URSA MINOR
Ursa Minor (Latin: "Smaller Bear", contrasting with Ursa Major), also known as the Little
Bear, is a constellation in the northern sky. Like the Great Bear, the tail of the Little Bear
may also be seen as the handle of a ladle, hence the name Little Dipper. It was one of the
48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88
modern constellations
8. ORION
Orion, sometimes subtitled The Hunter, is a prominent constellation located on the
celestial equator and visible throughout the world. It is one of the most conspicuous, and
most recognizable constellations in the night sky. Its name refers to Orion, a hunter in Greek
mythology.
SCORPIO
Scorpio, sometimes known as Scorpio, is one of the constellations of the zodiac. Its name is
Latin for scorpion, and its symbol is (Unicode ♏). It lies between Libra to the west and
Sagittarius to the east. It is a large constellation located in the southern hemisphere near the
center of the Milky Way.
10. The planets
mercury
Mercury is the innermost of the eight planets in the Solar System. It is also the smallest, and
its orbit has the highest eccentricity of the eight. It orbits the Sun once in about 88 Earth
days, completing three rotations about its axis for every two orbits. Mercury has the
smallest axial tilt of the Solar System planets. The perihelion of Mercury's orbit precesses
around the Sun at an excess of 43 arc seconds per century beyond what is predicted by
Newtonian mechanics, a phenomenon that was explained in the 20th century by Albert
Einstein's General Theory of Relativity.
Mercury, being an inferior planet, appears as
a morning star and an evening star, but is much
more difficult to see than the other inferior
planet, Venus. At its brightest, Mercury is
technically a very bright object when viewed
from Earth, but it is not easily seen in practice
because of its proximity in the sky to the Sun.
11. Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is
named after Venus, the Roman goddess of love and beauty. After the Moon, it is the
brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright
enough to cast shadows. Because Venus is an inferior planet from Earth, it never appears
to venture far from the Sun: its elongation reaches a maximum of 47.8°. Venus reaches its
maximum brightness shortly before sunrise or shortly after sunset, for which reason it has
been known as the Morning Star or Evening Star.
Venus is classified as a terrestrial planet and it is sometimes called Earth's "sister planet"
owing to their similar size, gravity, and bulk composition. Venus is covered with an opaque
layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen
from space in visible light. Venus has the densest atmosphere of all the terrestrial planets
in the Solar System, consisting of mostly carbon
dioxide. The atmospheric pressure at the planet's
surface is 92 times that of the Earth. Venus has no
carbon cycle to lock carbon back into rocks and
surface features, nor does it seem to have any
organic life to absorb it in biomass. Venus is believed
to have previously possessed oceans, but these
evaporated as the temperature rose owing to the
runaway greenhouse effect..
12. earth
Earth (or the Earth) is the third planet from the Sun, and the densest and fifth-largest of the
eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial
planets. It is sometimes referred to as the world, the Blue Planet, or by its Latin name, Terra.
Earth formed approximately 4.54 billion years ago by accretion from the solar nebula, and
life appeared on its surface within one billion years. The planet is home to millions of
species, including humans. Earth's biosphere has significantly altered the atmosphere and
other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as
well as the formation of the ozone layer which, together with Earth's magnetic field, blocks
harmful solar radiation, permitting life on land. The physical properties of the Earth, as well
as its geological history and orbit, have allowed life to persist. The planet is expected to
continue supporting life for another 500 million to 2.3 billion years.
Earth's crust is divided into several rigid segments, or tectonic plates, that migrate across
the surface over periods of many millions of years. About 71% of the surface is covered by
salt water oceans, with the remainder consisting of continents and islands which together
have many lakes and other sources of water that contribute to the hydrosphere. Earth's
poles are mostly covered with solid ice (Antarctic ice sheet) or
sea ice (Arctic ice cap). The planet's interior remains active,
with a thick layer of relatively solid mantle, a liquid outer
core that generates a magnetic field, and a solid iron inner core.
13. mars
Mars is the fourth planet from the Sun in the Solar System. Named after the Roman god of
war, Mars, it is often described as the "Red Planet" as the iron oxide prevalent on its surface
gives it a reddish appearance. Mars is a terrestrial planet with a thin atmosphere, having
surface features reminiscent both of the impact craters of the Moon and the volcanoes,
valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of
Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is
the site of Olympus Mons, the highest known mountain within the Solar System, and of
Valles Marineris, the largest canyon. The smooth Borealis basin in the northern hemisphere
covers 40% of the planet and may be a giant impact feature.
Until the first successful flyby of Mars occurred in 1965, by Mariner 4, many speculated
about the presence of liquid water on the planet's surface. This was based on observed
periodic variations in light and dark patches, particularly in the polar latitudes, which
appeared to be seas and continents; long, dark striations were interpreted by some as
irrigation channels for liquid water. These straight line features were later explained as
optical illusions, though geological evidence gathered by unmanned missions
suggest that Mars once had large-scale water coverage on its surface.
In 2005, radar data revealed the presence of large quantities of water ice
at the poles, and at mid-latitudes. The Mars rover Spirit sampled
chemical compounds containing water molecules in March 2007. The
Phoenix lander directly sampled water ice in shallow Martian soil on July
31, 2008.
14. Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a
gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of
all the other planets in our Solar System combined. Jupiter is classified as a gas giant along
with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as
the Jovian or outer planets.
The planet was known by astronomers of ancient times, and was associated with the
mythology and religious beliefs of many cultures. The Romans named the planet after the
Roman god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of
−2.94, making it on average the third-brightest object in the night sky after the Moon and
Venus. (Mars can briefly match Jupiter's brightness at certain points in its orbit.)
Jupiter is primarily composed of hydrogen with a quarter of its mass being helium; it may
also have a rocky core of heavier elements. Because of its rapid rotation, Jupiter's shape is
that of an oblate spheroid (it possesses a slight but noticeable bulge around the equator).
The outer atmosphere is visibly segregated into several bands at different latitudes,
resulting in turbulence and storms along their interacting boundaries.
A prominent result is the Great Red Spot, a giant storm that is known
to have existed since at least the 17th century when it was first seen
by telescope. Surrounding the planet is a faint planetary ring system
and a powerful magnetosphere.
15. Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System,
after Jupiter. Named after the Roman god Saturn, its astronomical symbol (♄) represents
the god's sickle. Saturn is a gas giant with an average radius about nine times that of Earth.
While only 1/8 the average density of Earth, with its larger volume Saturn is just over 95
times more massive than Earth.
Saturn's interior is probably composed of a core of iron, nickel and rock (silicon and oxygen
compounds), surrounded by a deep layer of metallic hydrogen, an intermediate layer of
liquid hydrogen and liquid helium and an outer gaseous layer. Electrical current within the
metallic hydrogen layer is thought to give rise to Saturn's planetary magnetic field, which is
slightly weaker than Earth's and around one-twentieth the strength of Jupiter's. The outer
atmosphere is generally bland and lacking in contrast, although long-lived features can
appear. Wind speeds on Saturn can reach 1,800 km/h.
Saturn has a ring system that consists of nine continuous main rings and three
discontinuous arcs, composed mostly of ice particles with a smaller
amount of rocky debris and dust. Sixty-two known moons orbit
the planet; fifty-three are officially named. This does not
include the hundreds of “moonlets" within the rings. Titan,
Saturn's largest and the Solar System's second largest moon,
is larger than the planet Mercury and is the only moon in the
Solar System to retain a substantial atmosphere.
16. 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. It is named after the ancient Greek deity
of the sky Uranus (Ancient Greek: Οὐρανός), the father of Cronus (Saturn) and grandfather
of Zeus (Jupiter). Though it is visible to the naked eye like the five classical planets, it was
never recognized as a planet by ancient observers because of its dimness and slow orbit. Sir
William Herschel announced its discovery on March 13, 1781, expanding the known
boundaries of the Solar System for the first time in modern history. Uranus was also the first
planet discovered with a telescope.
Uranus is similar in composition to Neptune, and both are of different chemical composition
than the larger gas giants, Jupiter and Saturn. Astronomers sometimes place them in a
separate category called "ice giants". Uranus's atmosphere, while similar to Jupiter and
Saturn's in its primary composition of hydrogen and helium, contains more "ices" such as
water, ammonia and methane, along with traces of hydrocarbons. It is the coldest planetary
atmosphere in the Solar System, with a minimum temperature of 49 K
(−224 °C). It has a complex, layered cloud structure, with water
thought to make up the lowest clouds, and methane
thought to make up the uppermost layer of clouds. In
contrast, the interior of Uranus is mainly composed of
ices and rock.
17. Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the
Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by
mass. 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. On average, Neptune orbits
the Sun at a distance of 30.1 AU, approximately 30 times the Earth–Sun distance. Its
astronomical symbol is ♆, a stylized version of the god Neptune's trident.
Neptune was the first planet found by mathematical prediction rather than by empirical
observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that
its orbit was subject to gravitational perturbation by an unknown planet. Neptune was
subsequently observed on September 23, 1846 by Johann Galle within a degree of the
position predicted by Urbain Le Verrier, and its largest moon, Triton, was discovered shortly
thereafter, though none of the planet's remaining 12 moons were located telescopically
until the 20th century. Neptune has been visited by only one spacecraft, Voyager 2, which
flew by the planet on August 25, 1989.
Neptune is similar in composition to Uranus, and both have
compositions which differ from those of the larger gas giants,
Jupiter and Saturn. Neptune's atmosphere, while similar to
Jupiter's and Saturn's in that it is composed primarily
of hydrogen and helium, along with traces of hydrocarbons
and possibly nitrogen, contains a higher proportion of "ices“
such as water, ammonia and methane.
18. Pluto (dwarf planet)
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet
in the Solar System (after Eris) and the tenth-most-massive body observed directly orbiting
the Sun. Originally classified as the ninth planet from the Sun, Pluto was recategorized as a
dwarf planet and plutoid due to the discovery that it is one of several large bodies within
the Kuiper belt.
From its discovery in 1930 until 2006, Pluto was classified as a planet. In the late 1970s,
following the discovery of minor planet 2060 Chiron in the outer Solar System and the
recognition of Pluto's relatively low mass, its status as a major planet began to be
questioned. In the late 20th and early 21st century, many objects similar to Pluto were
discovered in the outer Solar System, notably the scattered disc object Eris in 2005, which
is 27% more massive than Pluto. On August 24, 2006, the International Astronomical Union
(IAU) defined what it means to be a "planet" within the Solar System. This definition
excluded Pluto as a planet and added it as a member of the new
category "dwarf planet" along with Eris and Ceres. After the
reclassification, Pluto was added to the list of minor planets and
given the number 134340.A number of scientists hold that
Pluto should continue to be classified as a planet, and that
other dwarf planets should be added to the roster of planets
along with Pluto.
