main sequence

American  

noun

Astronomy.

1. a narrow band in the Hertzsprung-Russell diagram in which 90 percent of all observed stars are plotted.

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main sequence British  

noun

1. astronomy

   1. a diagonal band on the Hertzsprung Russell diagram containing about 90% of all known stars; stars evolve onto and then off the band during their lifetime

   2. ( as modifier )

      a main-sequence star

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main sequence Scientific  

/ mān /

1. The continuous, generally diagonal line or band in the Hertzsprung-Russell diagram ranging from the upper left to the lower right and representing stars of average size whose luminosities correspond predictably to their surface temperatures. Stars in this grouping maintain a stable nuclear reaction and experience only small fluctuations in luminosity and temperature. Main-sequence stars are believed to be in the stable, middle phase of their development; they are expected to move off the main sequence once the hydrogen in their core is exhausted. At that point, depending on its size, a main-sequence star will become a giant star, a supergiant star, or a white dwarf. The more massive the star, the faster it burns its nuclear fuel and the shorter it remains in the main sequence.

2. See more at Hertzsprung-Russell diagram star

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Etymology

Origin of main sequence

First recorded in 1925–30

Example Sentences

Younger post-main sequence stars had a higher rate of 0.35%, similar to stars still on the main sequence.

From Science Daily • Apr. 4, 2026

Located about 11,000 light years from Earth near the constellation Pupis, Gaia20ehk is a stable "main sequence" star similar to our sun.

From Science Daily • Mar. 11, 2026

EX Hydrae exists in a binary system alongside a normal main sequence star.

From Science Daily • Jan. 8, 2026

The mass of a star determines exactly where it falls on the main sequence.

From Textbooks • Oct. 13, 2016

We now know that Cepheids throb as they do because they are elderly stars that have moved past their "main sequence phase," in the parlance of astronomers, and become red giants.

From "A Short History of Nearly Everything" by Bill Bryson