The Features of the Observable Universe and Appropriate Units of Distance

The Features of the Observable Universe and Appropriate Units of Distance

Observable Universe:

  • The observable universe is a term that scientists use to describe the part of the Universe that we can currently see from Earth, using the current technology.

  • The observable universe is estimated to be about 93 billion light years in diameter.

  • The absolute limit of the observable universe is marked by the Cosmic Microwave Background radiation. This radiation is the afterglow of the Big Bang and is coming from the most distant parts of the universe that we can currently see.

  • The universe contains galaxies, stars, planets, and other celestial objects such as asteroids and comets.

  • Also encompassed within the observable universe are interstellar and intergalactic mediums, which are simply the matter and energy present in space between the stars (interstellar) and galaxies (intergalactic).

  • The universe is noticeably isotropic and homogenic on a large scale. These properties mean it appears uniform and consistent in all directions when viewed in a large context.

Units of Distance:

  • Astronomical objects are often very distant, hence, larger unites of measurement are required.

  • Astronomical unit (AU) is used to describe distances in the solar system. One astronomical unit is the average distance from the Earth to the Sun, which is approximately 150 million kilometres.

  • Light year (ly) is another unit used in astronomy, it is the distance that light travels in one year. Considering light moves at a speed of approximately 300,000 kilometres per second, one light year is approximately 9.46 trillion kilometres.

  • Parsec (pc) is also used in cosmology. One parsec is the distance at which one astronomical unit subtends an angle of one arcsecond, which is approximately 3.086 × 10^13 kilometres or 3.26 light years.

  • The size and distances in universe are so huge that we also use kilo-parsecs (kpc), Mega-parsecs (Mpc) and Giga-parsecs (Gpc) for convenience.

Remember, while revising these facts about the observable universe and units of distance, try to also understand the concepts behind them. Understanding always comes first, memorising should only act as a support. Best of luck!