main sequence


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main sequence

The principal sequence of stars on the Hertzsprung–Russell diagram, running diagonally from upper left (high temperature, high luminosity) to lower right (low temperature, low luminosity) and containing about 90% of all known stars. A star spends most of its life on the main sequence. A newly formed star appears on the main sequence when it first achieves a stable state whereby its core temperature is sufficient for nuclear reactions to begin. It is then at age zero. The positions of the age-zero stars on the H-R diagram are specified by reference to the zero-age main sequence (ZAMS). As hydrogen is converted to helium, changes in chemical composition and stellar structure cause the star's position to shift slightly to the right from its zero-age position.

A star's position on the main sequence depends primarily on its mass, the more massive and thus more luminous stars occurring higher up the sequence. This gives a well-defined mass-luminosity relationship for main-sequence stars. The star's lifetime there also depends on its mass, the more massive stars having much shorter lifetimes: the lifetime is approximately

1010(M /M O )–3 years
where M and M O are the stellar and solar mass. After the star has consumed most of the helium in its core (see stellar evolution) it evolves away from the main sequence: its radius and luminosity increase and it eventually becomes a giant.

main sequence

[′mān ′sē·kwəns]
(astronomy)
The band in the spectrum luminosity diagram which has the great majority of stars; their energy derives from core burning of hydrogen into helium.
References in periodicals archive ?
While the Lingfield Derby Trial victor Main Sequence is generally a 10-1 chance with most bookmakers.
And, while Main Sequence (3-1) still has to prove he is that sort of class, there is no denying the evidence shows the Niarchos family-owned colt is on a steep upward curve.
Main Sequence (3-1) is set to be David Lanigan's first Investec Derby runner after maintaining an unbeaten record of his own in the Betfred Derby Trial.
Now our star has finally made it onto the main sequence and for a typical Sun-like star of around 0.
ECLIPSE AWARD WINNERS Horse of the Year California Chrome 3yo male California Chrome 3yo female Untapable 2yo male American Pharoah 2yo female Take Charge Brandi Older male Main Sequence Older female Close Hatches Male turf Main Sequence Female turf Dayatthespa Male sprinter Work All Week Female sprinter Judy The Beauty Steeplechase horse Demonstrative Jockey Javier Castellano Trainer Todd Pletcher Owner Ken and Sarah Ramsey Apprentice Drayden van Dyke Breeder Ken and Sarah Ramsey
Not beaten far when fourth to Imperial Monarch in the top-level Grand Prix de Paris at Longchamp in July, Main Sequence then lost little in defeat when a neck second to Thought Worth in York's Group 2 Great Voltigeur.
Among his rivals is Aidan O'Brien's 2000 Guineas (G1) and Epsom Derby (G1) sensation Camelot and Main Sequence, the Derby Trials Stakes winner who chased Camelot home in the English blue riband.
SEQUENCE AND VOW ON ROAD TO EPSOM MAIN SEQUENCE is set to be David Lanigan's first Investec Derby runner after maintaining his unbeaten record in the Betfred Derby Trial at Lingfield.
The colour-magnitude diagram (CMD) of a star cluster is a variant of the familiar Herzsprung-Russell diagram (HRD) and provides information about the state of evolution of stars in the cluster in relation to the stellar main sequence.
Tipler's open and flat universe scenario begins with the sun leaving the main sequence of stellar evolution in about a billion years and becoming unreliable as a steady source of energy.
The highlight of the weekend was undoubtedly Main Sequence winning the Breeders' Cup Turf.
He was expected to shine at middle distances, and Camelot duly landed odds of 8-13 in the Derby, tearing away to beat Main Sequence by five lengths, with Thought Worthy back in fourth.