Explore the mysteries of the Universe or Cosmos in this comprehensive study. Delve into the origins, structure, and vastness of space, understanding celestial phenomena and the wonders of the cosmos. Ideal for astronomy enthusiasts and curious minds alike
The Universe or Cosmos: Comprehensive Study
The Universe or Cosmos
The Universe, as we understand it today, consists of millions of galaxies. A galaxy is a vast congregation of stars that are held together by the forces of gravity. Most of the galaxies appear to be scattered in space randomly. But many others remain clustered into groups. The Galaxy in which our Solar System is located is called the Milky Way or 'Akash Ganga', which appears as a river of bright light flowing through the sky and belongs to a cluster of some 24 galaxies called the local group. The Milky Way is made up of over a hundred billion sparkling stars, which, though quite distant from one another seem from the Earth as having been placed close together. The two other nearest galaxies are the Large Magellanic Cloud and the Small Magellanic Cloud. These are named after the famous Portuguese navigator Ferdinand Magellan (1480-1521)), who discovered them. The Universe is infinite, both in time and space. Its age was formerly believed to be between 10-15 billion years. However, in 1999, NASA’s Hubble Space Telescope projects team determined the age of the Universe or cosmos to be 12 billion years. In June 2001, NASA launched the MAP (Microwave Anisotropy probe) to study the cosmic, microwave background radiations in greater detail according to which the exact age of the universe is 13.7 billion years after the theoretical Big Bang. The human concept of the Universe has, however, been different at different times over the long span of the history of localization. The innate human curiousness and tireless pursuit of knowledge have brought about revolutionary changes in our ideas of the cosmos or universe. Conquest of the Moon has now blown off many a myth of the religious testaments. Around the 6th century BC men started inquiring into the mysteries of the Universe in an endeavour to rationally analyze the earthly and the heavenly phenomena. Ancient Greek astronomers and mathematicians came up with the view that the Earth was a perfect motionless sphere, surrounded by eight other crystalline spheres. Ptolemy believed that the Earth is the center of the universe. Copernicus (1473-1543) pointed out that- the sun and stars are motionless, the sun lies at the center of the universe and stars at its circumference, and the earth takes 24 hours to rotate on its axis. These are mentioned in his book ‘De Revulutionibus Orbium Celestium’. Italian astronomer Galileo Galilee (1564-1642) by his newly invented telescope discovered many stars. “British astronomer, Sir William Herschel (1738-1822) in his observation it is said that the Solar System is a small part bigger system called the Galaxy. The Galaxy consists of millions of stars scattered in the sky and a unique pattern of a band of light called the Milky Way”. American astronomer, Edwin Powell Hubble (1889-1953) made the contention that apart from the Milky Way, Large Magellanic Cloud and the Small Magellanic Cloud, there are millions of galaxies in the universe. Space and Outer Space
The Earth and its atmosphere, the Moon, the Sun, and the rest of the Solar System with its other planets and their satellites, and all the stars and galaxies spread over the infinite skies is called space. Outer space refers to the entire space except for the Earth and its atmosphere. Where the Earth’s atmosphere ends outer space begins, and it extends in all directions from above the atmosphere of the Earth. Therefore, different units of measurement, such as the light years and the astronomical unit, have been evolved to measure distances in these spaces, because of their infiniteness.
Members of the Space Family
a. The Sun: It is a shining spherical heavenly body around which the planets rotate. It is one of some 10,000,000 stars that constitute our galaxy. Its average distance from the Earth is 149,597,900 km, its equatorial diameter is 1,392,520 km, and its average density is 1.4 grams per cc. It has its own light and heat.
b. Planets: These revolve around the Sun. A planet with the Sun constitutes the Solar System. These are not self-luminous but shine by radiating the light received from the Sun. Orbits of Planets are elliptical. Their sizes, speeds, and distances from the Sun are dissimilar. The total number of planets in our Solar System is eight. Before 2006, Pluto was considered a planet. But it is no longer a Planet but it is called a dwarf planet. They are; (1) Mercury,(2)Venus, (3) Earth, (4) Mars, (5) Jupiter, (6 )Saturn, (7) Uranus, and (8)Neptune. Mercury lies nearest and Neptune is farthest from the Sun.
c. Satellites: These are secondary bodies that revolve around the planets as planets revolve around the Sun. A satellite is said to have been formed of the matter whirled off from a planet when still in a molten state. The moon is the Earth’s satellite. Venus and Mercury have no Earth’s satellite.
d. Asteroids: These are minor planets whose orbits lie between Jupiter and Mars. These are said to be the fragments of a larger planet disrupted long ago. Their number is estimated to be 30,000 pieces of rocky debris out of which only half are known. Ceres is the largest asteroid and its diameter of 670 km. Most of them are less than 80 km in diameter
e. Meteors: These are small bodies coming from interplanetary space. They become luminous by friction entering the Earth’s atmosphere. These are popularly known as shooting stars.
f. Meteorites: These are the larger meteors that reach the Earth and become meteorites. All meteorites were meteors when in flight.
g. Stars: These are self-luminous bodies, situated at enormous distances from the Solar System. Some of the stars are so distant that it takes millions of years for their light to reach us. There are millions of stars in the Universe.
There are four types of stars:- (i) Fixed Stars; (ii) Binary; (iii) Temporary Stars (new stars) and (iv) Variable Stars.
Fixed Stars are also called dog stars which do not appear to alter their relative positions in the sky. Binary stars are groups of two stars revolving around each other under mutual gravitational attraction. Temporary stars are also called novae. These suddenly flare up to greatly increased brightness and fade away after a short time. Variable stars’ brightness changes from time to time.
Dwarfs are small stars, the brightest of them are blue dwarf,s and the dimmest are called red dwarfs. Red Giants are stars that consume their hydrogen at an increasing rate for which they appear reddish.
h. Comets: These are luminous celestial bodies that move around the Solar System in elliptical or hyperbolic orbits. These are usually accompanied by long shining tails. Hyperbolic comets are seen only once and Elliptical comets are periodic and their re-occurrence can be calculated like Halley's Comet.
i. Pulsars: These are highly compact stellar objects, distinct from the stars one sees in the night sky, rotating rapidly and emitting electromagnetic radiation in pulses much in the manner of a lighthouse flashing light. These are thought to be rapidly spinning neutron stars, in which matter in the form of ‘degenerate’ neutron liquid with densities reaching values of 100 million gm per cc.
1 Light Year = 9.4607 X 1012 Km
Astronomical Unit =150 million kilometres. 0 0 0.
The Universe or Cosmos: FAQs
What is the Universe?
The Universe, also known as the cosmos, is a vast and infinite space that contains millions of galaxies, stars, planets, and other celestial bodies. It is believed to be around 13.7 billion years old, according to data from NASA's Microwave Anisotropy Probe.
What are galaxies?
Galaxies are massive systems consisting of stars, stellar remnants, interstellar gas, dust, and dark matter, all bound together by gravity. They can be scattered randomly in space or clustered into groups. Our galaxy, the Milky Way, belongs to a cluster known as the Local Group, which contains about 24 galaxies.
What is the Milky Way?
The Milky Way, also called 'Akash Ganga' in some cultures, is the galaxy that contains our Solar System. It is a spiral galaxy made up of over a hundred billion stars and is part of a cluster known as the Local Group. From Earth, it appears as a bright band of light stretching across the sky.
What are the nearest galaxies to the Milky Way?
The two nearest galaxies to the Milky Way are the Large Magellanic Cloud and the Small Magellanic Cloud. These galaxies were named after the Portuguese navigator Ferdinand Magellan, who discovered them.
How old is the Universe?
The age of the Universe was initially estimated to be between 10-15 billion years. However, with advanced studies and observations, NASA's Hubble Space Telescope team in 1999 and the MAP (Microwave Anisotropy Probe) in 2001 determined the age to be approximately 13.7 billion years.
How did the human understanding of the Universe evolve?
Human understanding of the Universe has evolved significantly over centuries. Ancient Greek astronomers viewed the Earth as the center of the Universe. Later, Copernicus proposed that the Sun, not the Earth, was at the center. Galileo's telescopic discoveries and Herschel's observations further expanded our knowledge. Edwin Hubble's work revealed the existence of millions of galaxies beyond the Milky Way.
What is outer space?
Outer space refers to the vast expanse beyond Earth's atmosphere. It includes all celestial bodies such as the Moon, Sun, planets, stars, and galaxies. It begins where Earth's atmosphere ends and extends infinitely in all directions.
What are the key members of the Solar System?
The Sun: A shining spherical body at the center of the Solar System.
Planets: Eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) revolve around the Sun.
Satellites: Natural bodies that orbit planets, like the Earth's Moon.
Asteroids: Minor planets, primarily found between Mars and Jupiter.
Meteors: Small bodies from space that become luminous upon entering Earth's atmosphere.
Meteorites: Meteors that reach Earth's surface.
Stars: Self-luminous bodies, categorized into various types such as fixed stars, binary stars, temporary stars, and variable stars.
Comets: Celestial bodies with long, glowing tails, moving in elliptical or hyperbolic orbits.
Pulsars: Highly compact, rotating stellar objects emitting electromagnetic radiation in pulses.
What is a light year?
A light year is a unit of distance used in astronomy. It is the distance that light travels in one year, approximately 9.4607 trillion kilometers.
What is an astronomical unit (AU)?
An astronomical unit (AU) is the average distance between the Earth and the Sun, roughly 150 million kilometers. It is commonly used to measure distances within our Solar System. 0 0 0.
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