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Concept of Universe and its divisions Goutam Das Department of Geography Balurghat College
What is universe? • The universe is everything. It includes all of space, and all the matter and energy that space contains. It even includes time itself and, of course, it includes you.
Continue............ • Earth and the Moon are part of the universe, as are the other planets and their many dozens of moons. Along with asteroids and comets, the planets orbit the Sun. • The Sun is one among hundreds of billions of stars in the Milky Way galaxy, and most of those stars have their own planets, known as exoplanets.
What is Galaxy? • A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems.A galaxy is held together by gravity. Our galaxy, the Milky Way, also has a super massive black hole in the middle. When you look up at stars in the night sky, you're seeing other stars in the Milky Way.
Continue............ All in all, Hubble reveals an estimated 100 billion galaxies in the universe or so, but this number is likely to increase to about 200 billion as telescope technology in space improves
Continue............ • Andromeda is the closest big galaxy to the Milky Way and is expected to collide with the Milky Way around 4.5 billion years from now.
What is Solar System? • Our solar system consists of our star, the Sun, and everything bound to it by gravity – the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; dwarf planets such as Pluto; dozens of moons; and millions of asteroids, comets, and meteoroids.
The Sun takes about 230 million years to complete one revolution around the center of the Milky Way galaxy. This is known as a galactic year or cosmic year.
Continue............ • Our planetary system is the only one officially called “solar system,” but scientists estimate that there may be tens of billions of solar systems in our galaxy, perhaps even as many as 100 billion. That's just how many we've found so far. There are likely to be many more planetary systems out there waiting to be discovered!
What is Stars? • A star is any massive self-luminous celestial body of gas that shines by radiation derived from its internal energy sources. Of the tens of billions of trillions of stars in the observable universe, only a very small percentage are visible to the naked eye.
What is Sun? • The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its.
What is Planet? • According to the IAU(International Astronomical Union, 2006),a planet is an object that • orbitsastar • has sufficient self-gravity to make it round • has a mass below the minimum mass to triggernuclear fusion • has cleared the neighborhood around its orbit. • A dwarfplanet (such asPluto) fulfills allthese definitions except 4 • Planetsshineby reflectedlight • Planetsmayberocky,icy, or gaseous in composition.
Terrestrial Planets Ice Giants Jovian (Gas) Giants
Continue............ • In general, planets can be classified into three categories based on what they are made of. • Terrestrial planets are those planets like Earth, Mercury, Venus, and Mars that have a core of metal surrounded by rock. • Jovian planets (also called Gas Giant) are those planets like Jupiter and Saturn that consist predominantly of hydrogen and helium. • Ice giants are planets such as Uranus and Neptune that consist largely of water ice, methane (CH4) ice, and ammonia (NH3) ice, and have rocky cores.
Often, the ice giant planets Uranus and Neptune are grouped with Jupiter and Saturn as gas giants; however, Uranus and Neptune are very different from Jupiter and Saturn.
What is Asteroids? • An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are metallic or rocky bodies with no atmosphere.
Continue............ • Most of them are located in the main asteroid belt – a region between the orbits of Mars and Jupiter. Some asteroids go in front of and behind Jupiter.
What is Comets? • Comets are cosmic snowballs of frozen gases, rock, and dust that orbit the Sun. When frozen, they are the size of a small town. • when passing close to the Sun, warms and begins to release gases, a process that is called out gassing. This produces a visible atmosphere or coma, and sometimes also a tail.
Always try to relate your theoretical knowledge to the field evidence….. Thank You
