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Astronomy & Space vocabulary · Stars & Stellar Evolution

Main sequence

Meaning in astronomy & space, with examples

nounAdvanced term

In astronomy & space, main sequence means: The long, stable stage of a star's life when it fuses hydrogen into helium in its core. On a chart of star brightness against temperature, these stars form a diagonal band.

In Turkish: anakol

How it is used

Used in astronomy courses together with the Hertzsprung–Russell (H–R) diagram. A star is 'on the main sequence' or 'leaves the main sequence'. About 90% of stars, including the Sun, are main-sequence stars.

Example sentences

  1. The Sun has been on the main sequence for about 4.6 billion years.

  2. Massive stars leave the main sequence much sooner than small ones.

Common collocations

  • main-sequence star
  • on the main sequence
  • leave the main sequence
  • main-sequence lifetime
  • starA huge ball of hot gas, mainly hydrogen and helium, that produces light and heat through nuclear reactions in its core. The Sun is the nearest star to Earth.
  • nuclear fusionA reaction in which light atomic nuclei, such as hydrogen, join to form heavier ones, such as helium, releasing a huge amount of energy. It powers the Sun and other stars.
  • red giantA large, cool and very bright star in a late stage of its life. It forms when a star like the Sun uses up the hydrogen in its core and its outer layers swell.
  • white dwarfThe small, very dense and hot core left behind when a Sun-like star dies. It is about the size of Earth but has a mass comparable to the Sun's.
  • SunThe star at the centre of our solar system. Its gravity holds the planets in their orbits, and its light and heat make life on Earth possible.

More terms: Stars & Stellar Evolution

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