Science

• Stars


  Massive, luminous balls of hot gas (plasma), which are held together by gravity
• Alpha Centauri is 4.3 light years away, this is approximately 41,000,000,000,000 km away
• All the energy in a star is produced in its center or core, by nuclear fusion
• Life Cycle of a Star

  1. Stars are formed in clouds of gas and dust, known as nebulae

  2. Nuclear reactions at the center (or core) of stars provides enough energy to make them shine brightly for many years

  3. The lifetime of star depends on its size, Very large massive stars burn their fuel much faster than smaller stars and may only last a few hundred thousand years
• Light of a star


  Tells its distance from Earth
• Light-year


  The distance that light travels in 1 year
• 1 light-year is equivalent to 9.66 * 10 ^ 12 * km
• Classes of stars according to color

  • 7 classes
  • As temperature increases, the color gets darker
• Conventional Color

  Peak of stellar spectrum
• Actual Apparent Color


  Colors that an observer sees, which is lighter than the conventional color description
• Blue has the biggest amplitude
• Size of star

  Inverse proportional to its life
• Supernova


  1. Massive star explodes

  2. Dust clears, leaving behind a very dense star known as a neutron star, these can often be rapidly spinning and are known pulsars

  3. If the star which explodes is especially large, it can even form a black hole
• Magnitude


  Describes how bright the star is
• Apparent Magnitude


  Stars brightness as observed from the earth measured using a scale from -1.0 to 10. The lower the value of the scale, the brightness the object is.
• Absolute Magnitude


  Measures how bright the star is
• Stars are massive, bright ball of very hot gas made up mostly of hydrogen and helium
• Stars get so hot by burning hydrogen into helium in a process called nuclear fusion
• Life Cycle of a Star

  1. Nebula

  2. Main Sequence Star

  3. Red Giant/Red Supergiant

  4. White Dwarf

  5. Supernova

  6. Neutron Star or Black Hole
• Nebula


  Birthplace of stars, a massive cloud of dust and gas in space
• Average star

  Mass is 0.5 to 8 times that of Earth's sun
• Massive star


  Mass is 8 times the size of the sun
• Main Sequence Star


  Star that continues to burn energy and glow for billions of years, until it runs out of hydrogen
• White Dwarf


  What is left when stars like our sun have exhausted all of their fuel, fades and changes color as it cools
• Supernova


  Larger star with more mass will go on making nuclear reactions, getting hotter and expanding until it explodes, throwing hot gas into space
• Neutron Star


  Remnant of a supernova explosion
• Black Hole


  Remnant of a supernova explosion of an especially large star
• Mass


  Quantity of matter or the form of matter that holds or clings together in one body
• Light Year


  The distance light travels in one year
• Apparent Brightness


  How bright a star appears from the Earth
• Luminosity


  The intrinsic brightness of a celestial object
• Brightness


  The quality or state of giving out or reflecting light
• Astronomers


  Scientists who study the stars, planets, and other natural objects in space