UNIVERSE
Universe is everything around you, includes all space, time and its content forming supercluster galaxies, galaxies, stars, planets, and all other forms of matter and energy. There are various theories that explain the origin and evolution of universe and its characteristics. Multiple scientific theories try to explain the universe. Single universe theory is most popular explains its characteristics 1) Big Bang theory expanding universe and 2) steady state theory constant universe. Multivariate theory of universe consider many parallel universe. The most popular theory is the BigBang Theory .
Origin of universe : Big Bang Theory
BigBang theory states that every thing began with hot and infinitely dense point similar to a super charged black hole about 13.78billion years ago with explosion. This creates matter , energy, time and space. There are two phases of evaluation 1) radiation era and 2) matter era that shape the universe.
Radiation era occurs just after Big Bang explosion it is a short periods called as epochs such as plank, grand unified, inflationary, electroweak, quark, hadrons, leptons, nuclear. Earliest is the plank epoch here temperature 10*40,no matter existed only energy. Super force binds all 4 forces of nature: gravity, strong nuclear, weak and electromagnetic force. In the end of plank epoch gravity splits with rest of the 3 forces. In Grand unification epoch all three forces (strong nuclear, weak, and electromagnetic forces) are together and in the end strong nuclear force broke away then Inflationary epoch came here size of the universe expanded rapidly from atom size to balloon that produce electrons, quarks, and antiquarks very hot, then came electroweak epoch when last two forces get split off weak and electromagnetic forces. During the quark epoch all ingredients are present however too hot and dense to form subatomic particles, and then hadron epoch ,temperature reduced to 10*10 sufficient to bind quarks to form neutron and protons. In leptons and nuclear epoch the proton and neutron fuse together to form nucleus and then elements helium .
Matter era consist of 3 epochs which expand for billions of years atomic epoch, galactic epoch and stellar epoch. In atomic epoch temperature falls to 3000k which leads to the formation of hydrogen elements by recombination of subatomic particles just after 50,000 years after BigBang. This hydrogen along with helium elements doted the universe with atomic clouds. This clusters of atoms under gravity form the seeding of galaxies around the 200million years ago. Inside these galaxies star formations take place around 3 billion after Big Bang . The formation of star has ripple effects by combining hydrogen to form helium and other elements which is the building blocks of universe. These heavier elements formed planets and all the other heavenly bodies. Because of BigBang expansion the distance between objects are increasing. If the process of universe expansion continues then how the universe end ? Rate of expansion is also increasing, there are 3 possible end of universe
1) big rip 2) Heat death/Big freeze and 3) Big Crunch and big bounce . In big rip, case new spaces is being created , gravity can’t hold the particles together as a result galaxies, black holes ,etc all collapse and matter dissolve into minute particles without interaction and timeless situation .in the Heat death or big freeze scenario, entropy is increasing that means temperature is decreasing, universe is getting colder and colder.
Summary
The big bang theory explains the origin of our universe. According to this theory, 13.82 billion years ago, cosmic matter was in a compressed state from
which expansion started by a primordial explosion. The super-dense ball broke to form galaxies, which again broke to form stars and finally stars broke to form planets including earth.
conventional units for measuring distances are not suitable.
Hence new units as follows are used:
• Light Year: Distance covered by light in one year in vacuum at a speed of 3x10*12 m/s. One light year is equal to 9.46 × 10 kilometers.
• Astronomical Unit: The Mean distance between the Sun and the Earth (1.49 x10*8 km). One light year is equal to 60,000 AU.
• Cosmic Year: Sun's period of revolution around the galactic centre (250 million years). Also called as 'galactic year'
• Parsec: Distance at which the mean radius of the Earth's orbit subtends an angle of one second of an arc. It is equal to 3.26 light years.
Steady state theory of universe : theory of universe, an alternative to bigbang ,here universe is still expanding but density is constant with time due to creation of new matter in new spaces. Which is opposite of decreasing density as proposed under Big Bang .this theory was promoted by Influential papers on steady-state cosmologies were published by Hermann Bondi, Thomas Gold, and Fred Hoyle in 1948. But, in debate Big Bang theory is more acceptable due to following scientific
proves/evidences :-
Red shift : by Edwin Hubble
The galaxies (or galaxy clusters) are systematically moving away from us such that the farther away galaxies are moving faster away from us. As a result of General Relativity this means that space itself is expanding carrying the galaxies with it. Both the Big Bang Theory and its major competitor, the Steady State Theory, could explain it. Recall that the Steady State Theory used the perfect cosmological principle while the Big Bang uses the cosmological principle.
The cosmic microwave background radiation can be explained only by the Big Bang theory. The background radiation is the relic of an early hot universe. The Steady State theory could not explain the background radiation, and so fell into disfavor.
The amount of activity (active galaxies, quasars, collisions) was greater in the past than now. This shows that the universe does evolve (change) with time. The Steady State theory says that the universe should remain the same with time, so once again, it does not work.
The number of quasars drops off for very large redshifts (redshifts greater than about 50% of the speed of light). The Hubble-Lemaître Law says that these are for large look-back times. This observation is taken to mean that the universe was not old enough to produce quasars at those large redshifts. The universe did have a beginning.
The observed abundance of hydrogen, helium, deuterium, lithium agrees with that predicted by the Big Bang theory. The abundances are checked from the spectra of the oldest stars and gas clouds which are made from unprocessed, primitive material. Even better observations are those made of light from very distant quasars that have passed through gas in regions of the universe where are no stars that could have contaminated the gas. The intervening intergalactic primordial gas imprints its signature on the quasar light giving us the composition of the primordial gas. All of those places have the predicted relative abundances.
Cosmological constant or lambda cold dense matter.
Age of universe:
According to research the age of the universe is approximate around 13.8billion years. Assuming that the Lambda-CDM model is correct, the measurements of the parameters using a variety of techniques by numerous experiments yield a best value of the age of the Universe as of 2015 of 13.799 ± 0.021 billion years. Age is determined by scientists by two ways:-
1) by studying the oldest objects within the universe.
2) by measuring how fast universe is expanding
Dense collection of stars called as globular clusters. The oldest known globular cluster has stars between 11-14 billion. The expanding rate of universe is known as Hubble constant. To determine it, several factors needs to be noticed:-
Oldest matter, energy, dark matter and dark energy. Older matter of the universe has lower density than younger one
To determine the older matter and lighter matter scientists relying on two space mission: 1) NASA- Wilkinson Microwave Anisotrophy probe (WMAP) and 2) ESA- Planck’s telescopes. In 2012, WMAP— determines the age of universe =13,772 billion years with uncertainty of 59million years. And in 2013, planks- determines the age of the universe as13.82 billion years . So, we say universe has become 80,000 years more older.
Composition of universe:
Both space based telescopes of NASA such as Hubble and Spitzer
ESA planks telescopes , determines that universe consist of 4 parts:—
Electro-magnetic radiation (0.005%), Matter and energy (4.9%), Dark matter(26.8%) Dark energy.(68.3%)
Universe is consist of two things one filaments and second voids.
Filaments are arranged hierarchally, superclusters(50-1000) and clusters galaxies(<50), galaxy consist of stars, solar system consist of planets, asteroids and meteors. And interstellar dust spread in the universe.
Voids is an area between intergalactic region. Contains dark matter and dark energy.
Note : first time photograph of universe was published internationally in 2008 and in 2013 by COBE and WMAP satellite and real shape of universe is defined by global geometry and local geometry.
Galaxies :
Galaxies are cluster of stars, interstellar gas/dust, nebula
Each Galaxy consist of 10^8 to 10^14 stars.
Our milky way galaxy is located into VIRGO supercluster which itself a constellation of 54 galaxies .
Centre of each galaxy is made up supermassive Black Holes.
Our own galaxy is Milky Way and next nearest spiral galaxy is Andromeda.
Galaxy Closest to solar system are :-
Rank 1 Canis Major Dwarf galaxy- Aka, 25000 light years, elliptical shape; 2003 discovered .
Rank 2 Milky Way galaxy centre - 30000 light years (spiral)
Rank 3 Sagittarius dwarf elliptical galaxy- 70000 light years, 1994 discovered.
Rank 4 Large Magellanic Cloud -180,000 light years
Rank 5 Andromeda galaxy-20,00,000 light years, it is approaching towards Milky Way galaxy at the speed of 110km/sec and merge within 40 billion years.
Galaxies can be classified on the basis of structure and shape into 4 categories:
1) elliptical (E1-E-7)
2) spiral (Sa and Sb)
3) lenticular (S0)
4) irregular (Irr1; Irr2)
Galaxies are of two types:-
1) normal galaxy emits energy equivalent to the sum of all the stars of it.
2) active galaxy emits energy more than the sum of all stars of it.
Active Galaxies emits electromagnetic radiation in the range of infrared , gamma rays,UV rays,X-rays, radio waves due to accretion of objects towards the centre supermassive Black Hole. But normal galaxy may or may not have supermassive black hole.
Active galaxies are of different types such as
1) radio galaxy
2) quasars
3) Blazars
Quasars =Quasi-Stellar radio source
It is highly bright object ,
Millions to billions times larger than sun, it emits radio waves, it is explained by Active Galactic Nuclei (AGN) Theory . It contains supermassive Black hole in it centre which results into accretion of matter inward. This process generates electromagnetic radiation of radio waves .it is observed when jet burst away from black holes otherwise it becomes Blazar.
Black Holes : ( think properties and origin)
Strange object in the universe characterised by strongest gravitational pull, highest density, not visible, nothing can escape from it even light.
It is recognised by gravitational forces felt on the surrounding objects since they deviates from path.
Black holes generate from two ways : 1) when large stars(3times the sun) decay- stellar black holes. 2) at the centre of galaxy- supermassive black holes. 3) intermediate black holes.
Recently two news related to black holes gave evidence to Einstein’s theory of general relativity:
1) LIGO experiment observed gravitational waves first time in 2015 when two black holes meet and 2) on (April 2019) black hole photo is being published first time by event horizon telescope of MH87 galaxy as given .
Other famous black holes are : Sagittarius A* of our Milky Way galaxy, Cygnus -X1, Centarus A.
Stars :
Self-luminous celestial objects
Life cycle of star, starts as protostar i.e., nebulae - a gaseous cloud of dust containing hydrogen and helium which undergo accretion under its own gravity.
Thermonuclear fusion process ignite the protostar and become a star.
Mature star consist of 3 parts : 1) core 2) chromosphere and 3) photosphere. See the diagram…
Life cycle of stars :
A star's life cycle is determined by its mass. The larger its mass, the shorter its life cycle. A star's mass is determined by the amount of matter that is available in its nebula, the giant cloud of gas and dust from which it was born. Over time, the hydrogen gas in the nebula is pulled together by gravity and it begins to spin. As the gas spins faster, it heats up and becomes as a protostar. Eventually the temperature reaches 15,000,000 degrees and nuclear fusion occurs in the cloud's core. The cloud begins to glow brightly, contracts a little, and becomes stable. It is now a main sequence star and will remain in this stage, shining for millions to billions of years to come. This is the stage our Sun is at right now.
As the main sequence star glows, hydrogen in its core is converted into helium by nuclear fusion. When the hydrogen supply in the core begins to run out, and the star is no longer generating heat by nuclear fusion, the core becomes unstable and contracts. The outer shell of the star, which is still mostly hydrogen, starts to expand. As it expands, it cools and glows red. The star has now reached the red giant phase. It is red because it is cooler than it was in the main sequence star stage and it is a giant because the outer shell has expanded outward. In the core of the red giant, helium fuses into carbon. All stars evolve the same way up to the red giant phase. The amount of mass a star has determines which of the following life cycle paths it will take from there.
As the main sequence star glows, hydrogen in its core is converted into helium by nuclear fusion. When the hydrogen supply in the core begins to run out, and the star is no longer generating heat by nuclear fusion, the core becomes unstable and contracts. The outer shell of the star, which is still mostly hydrogen, starts to expand. As it expands, it cools and glows red. The star has now reached the red giant phase. It is red because it is cooler than it was in the main sequence star stage and it is a giant because the outer shell has expanded outward. In the core of the red giant, helium fuses into carbon. All stars evolve the same way up to the red giant phase. The amount of mass a star has determines which of the following life cycle paths it will take from there.
the different evolutionary paths low-mass stars (like our Sun) and high-mass stars take after the red giant phase. For low-mass stars (left hand side), after the helium has fused into carbon, the core collapses again. As the core collapses, the outer layers of the star are expelled. A planetary nebula is formed by the outer layers. The core remains as a white dwarf and eventually cools to become a black dwarf.
On the right of the illustration is the life cycle of a massive star (10 times or more the size of our Sun). Like low-mass stars, high-mass stars are born in nebulae and evolve and live in the Main Sequence. However, their life cycles start to differ after the red giant phase. A massive star will undergo a supernova explosion. If the remnant of the explosion is 1.4 to about 3 times as massive as our Sun, it will become a neutron star. The core of a massive star that has more than roughly 3 times the mass of our Sun after the explosion will do something quite different. The force of gravity overcomes the nuclear forces which keep protons and neutrons from combining. The core is thus swallowed by its own gravity. It has now become a black hole which readily attracts any matter and energy that comes near it. What happens between the red giant phase and the supernova explosion is described below.
From Red Giant to Supernova: The Evolutionary Path of High Mass Stars
Once stars that are 5 times or more massive than our Sun reach the red giant phase, their core temperature increases as carbon atoms are formed from the fusion of helium atoms. Gravity continues to pull carbon atoms together as the temperature increases and additional fusion processes proceed, forming oxygen, nitrogen, and eventually iron.
When the core contains essentially just iron, fusion in the core ceases. This is because iron is the most compact and stable of all the elements. It takes more energy to break up the iron nucleus than that of any other element. Creating heavier elements through fusing of iron thus requires an input of energy rather than the release of energy. Since energy is no longer being radiated from the core, in less than a second, the star begins the final phase of gravitational collapse. The core temperature rises to over 100 billion degrees as the iron atoms are crushed together. The repulsive force between the nuclei overcomes the force of gravity, and the core recoils out from the heart of the star in a shock wave, which we see as a supernova explosion.
As the shock encounters material in the star's outer layers, the material is heated, fusing to form new elements and radioactive isotopes. While many of the more common elements are made through nuclear fusion in the cores of stars, it takes the unstable conditions of the supernova explosion to form many of the heavier elements. The shock wave propels this material out into space. The material that is exploded away from the star is now known as a supernova remnant.
The hot material, the radioactive isotopes, as well as the leftover core of the exploded star, produce X-rays and gamma-rays.
Questions: Where is Earth located in the Universe ?
Answer: universe—-Virgo supercluster galaxy (54 cluster of galaxies) —— spiral Milky Way galaxy( contains billions of stars) ——— located 30,000light years away from Milky Way galaxy centre( Sagittarius A*) ——solar system———3rd planet from Sun (Earth). —located from 150million km from sun also called 1 astronomical unit.
Solar system,planets and other objects
The sun along with its eight planets, asteroids and comets comprise the 'solar system'. The planets are divided into inner or terrestrial planets which have higher densities e.g. Mercury, Venus, Earth and Mars and outer planets which have lower densities e.g. Jupiter, Saturn, Uranus and Neptune.
The Sun
• The sun is in the center of the solar • It is made up of extremely hot gases particularly hydrogen. The sun is 109 times bigger than the earth and weighs 2 × 1027 tonnes.
• The sun is about 150 million km away from the earth. The light from the sun reaches earth in about 8 minutes.
• The glowing surface of the sun is called 'Photosphere'. Above the 'Photosphere' is red coloured 'Chromosphere'. Beyond the Chromosphere is the 'Corona', visible during eclipses.
• The temperature of the photosphere is about 6000°C and that of the Chromosphere is about 32400°C, and that of the corona about 2,700,000°C. The core of the sun has a temperature about 15 million degrees Kelvin. But that tremen- dous heat is not felt so much by us be- cause despite being our nearest star, it is far away from us.
• It takes 250 million years to complete
one revolution round its centre. This period is called 'Cosmic year'.
• Sun spots' are dark patches notched on the surface of the sun. They appear dark because they are cooler i.e. they have a
temperature of about 1500°C.
• The 'Aurora Borealis' or northern lights
are multicoloured lights that sweep across the sky in waves and are visible in the arctic region. The 'Aurora Australis' or southern lights are similarly visible near the Antarctica region.
The Moon
• The moon is the only satellite of the earth.
• Its size is approximately one-fourth that of the earth. It has a diameter of 3475 km.
• Its orbit is elliptical. The maximum distance (apogee) of the moon from the earth is 406,000 km and the minimum distance (perigee) is 364,000 km.
• 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.
• The bright parts of the moon are moun- tains whereas the dark patches are lowlying plains.
Asteroids
Asteroids are a series of very small planets or fragments of planets lying between the orbit of Mars and that of Jupiter. They number about
45,000. 'Ceres' whose length is about 1000km is the largest one. They revolve around the sun in the same way as the planets.
Meteors and Meteorites
The meteors are the remains of comets which are scattered in the interplanetary space of the solar system. On contact with the earth's atmosphere, they burn due to friction. Those which completely burn out into ash are called meteors or 'shooting star.' Those which do not burn completely and strike the earth in the form of rocks are called 'meteorites'.
Planetary System
There are eight planets in our solar system. They are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Earlier, Pluto was considered as a planet. But recently it has lost this status. All the eight planets of the solar system move around the sun in fixed paths. These paths are elongated. They are called orbits. A new planet 2003 UB 313 has been discovered recently in our solar system. It is bigger than Pluto and farthest from the Sun.
A. Mercury
1. Mercury is the smallest and the nearest planet to the Sun.
2. It takes only about 88 days to complete one round along its orbit.
3. It has no atmosphere and no satellite.
4. Its days are scorching hot and nights are frigid.
B. Venus
1. Venus is considered as 'Earth's-twin' because its size and shape are very much similar to that of the earth.
2. It is also called the 'morning' or 'evening star'.
3. It is probably the hottest planet because its atmosphere contains 90-95% of carbon dioxide. The day and night temperatures are almost the same.
4. The atmospheric pressure is 100 times that of the earth.
5. There is no satellite.
C. The Earth
1. The earth is the third nearest planet to the Sun.
2. In size, it is the fifth largest planet.
3. It is slightly flattened at the poles. That is why its shape is described as a Geoid.
4. From the outer space, the earth appears blue because its two-thirds surface is covered by water. It is, therefore, called a blue planet.
D. Mars
1. It is marked with dormant volcanoes and deep chasms where once water flowed.
2. It has a thin atmosphere comprising of Nitrogen and Argon.
3. Beneath its atmosphere, Mars is barren,covered with pink soil and boulder. Because of this it is known as 'red planet'.
4. It has two satellites namely 'Phobos' and 'Demos'.
5. The highest mountain here is Nix Olympia which is three times higher than Mount Everest.
6. Recent explorations have thrown light on the possibility of existence of life here.
E. Jupiter
1. It is the largest planet of the solar system.
2. Its atmosphere contains hydrogen, helium, methane and ammonia.
3. It contains two and a half times the mass of all the other planets combined.
4. It reflects more than three times the energy it receives from the sun.
5. It has the great red spot which is an
enormous eddy in the turbulent cloud cover. It also contains dusty rings and volcanoes.
6. It has 79 satellites like Ganymede, Aayo,Europa, Callisto etc. second after Saturn.
F. Saturn
1. It is the second largest planet of the solar system.
2. It has a celebrated rings composed of thousands of rippling, spiraling bands of icy rock and dust just 200 feet thick and 270,000 km in diameter.
3. It has largest number of known satellites after addition of 20 new moons now it has total 82 moon. Among them Titan, Phobe, Tethys and Mimas are important.
4. Its moon, Titan has nitrogen atmosphere and hydrocarbons, the necessity of life but no life exists.
G. Uranus
1. It is the only planet that lies on its side.
Hence, one pole or the other faces the sun as it orbits.
2. It is one of the coldest planets because of having an average temperature of -223?C.
3. Its atmosphere is made of mainly hydrogen. The landscape is barren and there is frozen methane cloud.
4. There are 9 dark compact rings around the planet and a corkscrew shaped magnetic field.
5. It has 15 satellites; prominent ones are
Aerial, Ambrial, Titania, Miranda etc. 6. It rotates north to south.
H. Neptune
1. It is the most distant planet from the sun.
2. There are five rings of Neptune. The outer ring seems to be studded with icy moonlets while the inner ring appears narrow and nearly solid.
3. It has 8 satellites like Titron, Merid, N-1,N-2, N-3 etc.
4. Its atmosphere mostly contains hydrocarbon compounds. The atmosphere appear blue, with quickly changing white icy methane clouds often suspended high above an apparent surface.
Pluto from Planet to Plutoid
Pluto, demoted from planet status in 2006, got a consolation prize - it and other dwarf planets like it will be called plutoids. Plutoids are celestial bodies in orbit around the Sun at a distance greater than that of Neptune that have sufficient mass for their hydrostatic equilibrium (near-
spherical) shape. The two known plutoids are Pluto and Eris. It is expected that more plutoids will be named as science progresses and new discoveries are made.
New Definition of planets, dwarf planet and Plutoid ?
The most recent definition of a planet was adopted by the International Astronomical Union in 2006. It says a planet must do three things:
It must orbit a star (in our cosmic neighborhood, the Sun).
It must be big enough to have enough gravity to force it into a spherical shape.
It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun.
The IAU therefore resolves that planets and other bodies, except satellites, in our Solar System be defined into three distinct categories in the following way: in 2006
A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.—eight planets
A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
—- 5 dwarf planets are being defined as below in picture:
All other objects,except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
In 2008 plutoid is being defined as a sub category of dwarf planet. Pluto and eris are transneptunian objects.
Note the interplanetary missions of NASA, ESA , JAPAN ,ISRO and china.
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