Universe and Units use by astronauts

What is Universe?

The Universe is everything we can touch, feel, sense, measure or detect. It includes living things, planets, stars, galaxies, dust clouds, light, and even time. Before the birth of the Universe, time, space and matter did not exist.  

The Universe have uncountable stars and millions of galaxies The space between the stars and galaxies is largely empty. However, even places far from stars and planets contain scattered particles of dust or a few hydrogen atoms per cubic centimeter. Space is also filled with radiation (e.g. light and heat), magnetic fields and high energy particles . 

The universe is very huge, we can imagine by this if we take modern fighter jet , we take million of years to reach only nearest star of our sun or by traveling with the speed of light(which is 300000km per sec)it will take time 100000 light years to cross only milky way galaxy 

Units Used In astronomy

Astronomical Unit-

Distances in the solar system are often measured in astronomical units (abbreviated AU). An astronomical unit is the average distance between the Earth and the Sun

1 AU = 1.496 x 108 km = 93 million miles

Light-years-

To measure the distances between stars, astronomers often use light-years (abbreviated ly). A light-year is the distance that light travels in a vacuum in one year 

1 ly = 9.5 x 1012 km = 63,240 AU 

Parsecs-

Many astronomers prefer to use parsecs (abbreviated pc) to measure distance to stars. This is because its definition is closely related to a method of measuring the distances between stars. A parsec is the distance at which 1 AU subtends an angle of 1 arcsec. 

1 pc = 3.09 x 1013 km = 3.26 ly 

 

 

 

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