Universe and Solar System

• Galaxy


  A cluster of billions of stars, planets, asteroids or other bodies in the accompanying planetary system. In between clusters is practically an empty space.
• The Milky Way is a large barred spiral galaxy which our sun and all the planets around are part of it. It is a large group of stars, gas, and dust held together by gravity
• Age of the universe

  13.8 billion years old
• The diameter of the universe is possibly infinite
• How astronomers estimate the age of the universe

  1. Velocity

  2. Distance

  3. Time
• Velocity


  Rate of expansion of the universe
• Distance


  The estimated diameter of the universe
• Time


  Age of the universe
• Singularity


  Refers to an instant where all matter and energy in the universe was concentrated into a single point and that the density and energy of what would become the universe would be arbitrarily very large and infinite
• A singularity is a mathematics concept that has no equivalent in the physical world
• The "bang" should not be taken as an explosion; it is better thought of a simultaneous expansion of space everywhere. The theory does not identify the cause of the "bang."
• Big Bang Theory


  • The prevailing cosmological model for the universe from the earliest known periods trough its subsequent large-scale evolution
  • Postulates that between 13.8 billion years ago the universe expanded from a tiny, dense and hot mass of energy (singularity) to its present size and much cooler state
• Georges Henri Joseph Édouard Lemaitre

  Belgian catholic priest, suggested the big bang theoryon 1927
• Primeval atom hypothesis


  Lemaître's theory that the universe began from a single primordial atom
• Fred Hoyle coined the term "big bang"
• Galaxies appear to be moving away from us at speeds proportional to their distance


  This observation supports the expansion of the universe and suggests that the universe was once compacted
• Redshift


  Indicates that the astronomical body being observed is moving away. The light emitted by the galaxy was shifted to red in the electromagnetic spectrum.

  
• Cosmic microwave background (CMB) radiation


  The remnant radiation leftover from the Big Bang

  
• In 1965, Radioastronomers Arno Penzias and Robert Wilson discovered CMB
• Kuiper belt


  A doughnut-shaped ring of icy objects around the Sun, extending just beyond the orbit of Neptune from about 30 to 55 AU
• Oort cloud


  A spherical layer of icy objects surrounding our Sun, a star, and likely occupies space at a distance between about 2,000 and 100,000 astronomical units (AU) from the Sun
• Dwarf planet


  A celestial body that orbits the sun, has enough mass to assume a nearly round shape, has not cleared the neighborhood around its orbit and is not a moon

  
• Astronomical terms

  • Nebula: Large cloud of interstellar gas and dust
  • Accretion: Process by which dust particles stick together to form larger particles
  • Condensation: Conversion of a vapor or gas to a liquid or solid state
  • Planet: Celestial body moving in an elliptical orbit around a star
  • Planetesimals: Minute planet; body that could or did come together with many others under gravitation to form a planet
  • Protoplanets: Large body of matter in orbit around the sun or a star and thought to be developing into a planet
  • Meteoroid: Small rocky piece of interplanetary matter smaller than a kilometre
• Nebula


  Any large cloud of interstellar gas and dust
• Accretion


  The process by which dust particles stick together to form larger partials (Imagine a snowball thrown through a blizzard. Getting larger as it hits other snowflakes)
• Condensation


  The conversion of a vapor or gas to a liquid or solid state usually caused by reduction of temperature
• Planet


  A celestial body moving in an elliptical orbit around a star

  
• Planetesimals


  A minute planet; a body that could or did come together with many others under gravitation to form a planet
• Protoplanets


  A large body of matter in orbit around the sun or a star and thought to be developing into a planet
• Meteoroid

  Small rocky piece of interplanetary matter that is smaller than a kilometre, if any part of meteoroid survives and enters the Earth it is called meteorite
• Asteroid


  Larger chunks of rocky celestial bodies between the orbits of Mars and Jupiter called the asteroid belt
• Comet


  A celestial body that appears as a fuzzy head surrounding a bright nucleus, that consist of ice, methane, ammonia and dust that often develops tails when near the sun
• Natural satellites


  A celestial body orbiting a planet or minor planet

  
• Rotation

  A celestial body spinning on its axis
• Revolution


  A celestial body going around another object in an orbit or elliptical course
• Galaxy


  An aggregation of stars, stellar remnants, interstellar gas, dust, and other matter
• The solar system is located in the Milky Way galaxy
• The Milky Way is spiral-shaped which part of the so-called Local Group of galaxies, which in turn is part of the Virgo supercluster of galaxies
• Solar system


  The sun together with the group of celestial bodies that are held by its attraction and revolve around it

  
• The solar system comprises the sun, planets, dwarf planets, satellites, asteroids, comets