Definition of Astronomy:

Astronomy is the study of the sun, moon, stars, planets, comets, gas, asteroids, galaxies, dust, and other non-Earthly bodies and their phenomena. It uses mathematics, physics, and chemistry to explain their origin and evolution.

It is the oldest of the natural science and its origins in the religious, mythological, cosmological, calendrical, and astrological. In Europe, it was not separated at the time of the Copernican revolution starting in 1543.


In between the 12th to 18th centuries, many institutions like churches support the study of astronomy.

In early history, people identified celestial objects with god and spirits. So is believed that the first astronomers were priests. Calendars of the world have set by the observations of the sun and moon.


A leap year is a calendar year that adds one more day with the common year. The Earth takes 365.2422 days for orbiting around the Sun and this year is called a common year. But when it takes 366 days for orbiting around the Sun then the year is called a leap year. The extra day is 29th February which comes every 4th year and this year becomes a leap year. In ancient times there were many calendars for describing the leap year.

Algorithm to determine whether is a leap year or not is:

if (the year is divisible by 4) then (it is a leap year)

else if (the year is divisible by 100) then (it is a common year)

else if(the year is divisible by 400) then( it is a leap year)

else (it is a common year)

There were many calendars to describe how leap year comes such as a revised Julian calendar, Chinese calendar, Hebrew calendar, Islamic calendar, Solar Hijri calendar etc.


A time zone is a region on the Earth that observes a uniform standard time for legal, social, and commercial purposes. They are based on the boundaries of the countries or lines of longitudes. Greenwich Mean Time (GMT) is the mean solar time in Greenwich, London considered at a longitude of zero degrees. 


GMT and Universal Coordinated Time (UTC) reflect the same time. GMT is a time zone while UTC is a standard time that is used for civil time and time zones worldwide. 

Most of the time zones on Earth are offset from UTC by a whole number of hours. Generally, time zones are defined as + or - an integer number of hours in relation to UTC, for example, UTC-05:00, UTC+08:00, and so on. 

The GMT was established in England in the 1675s.


A solstice is an event when the Earth orbits around the Sun at its tropic of cancer or tropic of Capricorn plane. In other ways, at this event, the Sun appears to reach its most northerly or southerly excursion relative to the Earth’s equator. Two solstices occur every year on around June 21 and December 21.

On June 21 we experience a long day and in December we experience a short day. 

The day of the solstice is either hemisphere has either the most sunlight of the year (summer solstice) or the least sunlight of the year (winter solstice) for any place on the Earth.


Asteroids are small rocky objects that orbit around the Sun. It is also called a minor planet formed from the formation of the solar system about 4.6 billion years ago. The current known asteroids count is 796,786. 

Most asteroids can be found in the asteroid belt which is between the orbit of Mars and Jupiter. The largest asteroid found in the asteroid belt is Ceres with a diameter of 945km. The total mass of all asteroids is less than that of Earth’s Moon.

The shape of the asteroids is irregular such as a spherical, cubic, prismatic, cylindrical, and another type. 

Composition: -   The three composition classes of asteroids are C-, S- and M types. The C- type (chondrite) asteroids consist of clay and silicate rocks and are dark in appearance. The S-type asteroids made of silicate materials and nickel-iron. And S-type asteroids are metallic made of nickel-iron. 


When meteoroids enter the Earth’s atmosphere then it called meteors. We also say it a shooting star. So meteoroids are made of space rocks and its size is in the range of grains from dust to a small asteroid. This term is only used when they are in space. Most are pieces of other large bodies that have been broken or blasted off. Some come from comets some come from asteroids and others come from other planets or even from the moon. 

So when meteoroids enter Earth’s atmosphere or other planets atmosphere with high speed and burn up then they called meteors. If meteoroids survive through the atmosphere and hit the ground of the planet then they called meteorites.

Sometimes meteors appear brighter than Venus called fireballs.


Scientists estimate that about 48.5 tons of meteoritic material fall on the Earth every day.


Several meteors per hour can be seen at any night. When we watch lots of meteors then they called a meteor shower. 

In ancient times, civilization from Mesopotamia, Greece, Persia, India, China, Egypt, and Central America observed the sky and gave ideas about the universe. 

During the Renaissance, proposed a heliocentric modal of the solar system. After that Galileo Galilei defended this idea and observe the universe by the first telescope. Johannes Kepler explained the motion of the planets around the Sun by his three Kepler's law. After that Sir Isaac Newton describes the motion of the planet around the Sun by gravitational law.

Jupiter’s massive gravity and close encounter of Mars or other objects change their path and get out of the asteroid belt and hit other objects or planets. Scientists continuously monitor Earth-crossing asteroids whose paths intersect Earth’s orbit. Many asteroids hit the Earth and many incidents involved by hitting the asteroids. 

In 1908s one asteroid hit the Earth surface in Siberia, Russia. Again in February 1947, another large bolide impacted the Earth in Russia.