Pythagoras, who was an Ionian Greek philosopher and mathematician, first used the term “COSMOS” for the order of the Universe.
Cosmology is the discipline that describes the large scale properties of the universe as a whole.
The distance covered by light in one year is known as “Light Year.” The Velocity of light is 300,000 km/s.
The distance between the Sun and the Earth is known as “Astronomical Unit.” One astronomical unit is (roughly) equal to 149.6 million kilometers.
Wilkinson Microwave Anisotropy Probe (WMAP) is an Explorer Mission of National Aeronautics and Space Administration (NASA). It is launched for the study and measurement of cosmology.
Professor Sir Fred Hoyle, who was an English astronomer, coined the term “Big Bang” to explain a scientific theory on the creation of cosmos.
Galaxy is a huge collection of stellar and interstellar matter, which are bound together by its own gravity in the Space. There are several galaxies in the universe, for example, Milky Way.
The name galaxy where we live is ‘Milky Way.’
The largest galaxy is ‘Andromeda Galaxy.’ It is also the closest to Milky Way. Milky Way is the second largest galaxy.
The radius of Milky Way is about 50,000 light years.
The Solar System is a part of Milky Way.
The Sun takes 225 million light years to complete one circuit.
The collapsed stars, which are immeasurably dense and having huge gravitational force (even light cannot escape rather get absorbed) are known as “Black Holes.”
Quasar is a massive and extremely remote celestial object that keeps emitting remarkably large amounts of energy. Typically, it has a star like image, which can be seen through the telescope.
Constellation is a group of stars being arranged in a pictorial configuration. It was basically observed by the ancient astronomers. For example, Sirius (Canis Major), Canopus (Carina), Turus (Bootes), etc.
Atacama Large Millimeter Array (ALMA) is the British Astronomy center, located at Chajnantor (at an altitude of about 5,000 meters), in the Atacama Desert of northern Chile.
Edwin Hubble, who was an American astronomer, first studied galaxies in detail. Based on Shape, Edwin classified galaxies as Elliptical, Spiral, and Barred Spiral.
At the end of life-cycle, when a star loses its light and the density increases (very high), by this time, it is largely composed of neutrons and hence known as ‘Neutron Star.’
Most likely, the rotating neutron star emits intermittent radio signals, is known as ‘Pulsar.’
A star with low temperature and small mass (glowing feebly) is known as ‘Red Dwarf.’
A star that suddenly increases its brightness (greatly) because of a catastrophic explosion and ejects most of its mass is known as ‘Supernova.’
Satellites (or Moons) are the bodies that keep revolving around their respective planets. For example, Moon revolves around the Earth, etc.
The Sun is the closest star to the Earth (at the distance of about 149,600,000 km).
Located at the distance of about 4.24 light-years, Proxima Centauri is the second closest star to the Earth.
The Sun is made up of extremely hot gasses and its glowing surface is known as the ‘Photosphere.’ The layer immediately above the photosphere is known as ‘Chromosphere’ (sphere of color).
The Chromosphere is 10,000 km thick transparent shell of plasma.
The Outermost layer of the Sun is known as the ‘Corona.’
Temperature of the outer surface is 6, 0000 C and interior temperature is 15, 000,0000 C.
The rotation period of the Sun is 25 days, 9 hours, and 7 minutes.
The traveling speed of the Sun’s Rays is 30,000 m/s.
The time taken by Sun’s Rays to reach the Earth is 8 minutes and 16.6 seconds.
The Sun is largely composed (chemically) of Hydrogen (71%), Helium (26.5%), and some other elements (2.5%).
Sometimes, in the photosphere, some patches of gas, which is cooler that its surrounding (gas) are known as the ‘Sunspots.’
The Planets are the celestial bodies that revolve around the Sun as well as (at the same time) rotate on their imaginary axis.
