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 ?
Main Sequence Ventures co-led Morse Micros seed round and were keen to co-lead again, with partner Mike Nicholls stating: Since funding their seed round in 2017, the team has outperformed on both product delivery and customer business development.
In that sense, SBK's definition of the main sequence's end is about 6.5 billion years from now, after the Sun is left with a significantly hydrogen-depleted core and has begun to move fairly rapidly to lower temperatures, becoming a "subgiant" star.
depending on mass, main sequence stars--what I should be in a man's
"But to make the trips a reality, one needs to have horses like Main Sequence," Maragh added.
Since defeating 2012 Derby runner-up Main Sequence in the Brigadier Gerard Stakes at Sandown in May, William Haggas' colt has been beaten by just two horses - Al Kazeem twice and Declaration Of War - when making the podium in the Prince of Wales's Stakes (second) and Coral-Eclipse (third).
I like Main Sequence at 10-1 to take on the favourite, but my best bet is an each way bet on Cavaliero at 50-1, ridden by the glamorous Hayley Turner.
Paired talks on theory and observation review the current status of solar abundances, main sequence stars, massive stars close to the main sequence, red giant branch, asymptotic giant branch stars, binaries, and nucleosynthesis.
The more massive a star, the brighter it is, the more rapidly it consumes its nuclear fuel, and the shorter its life on the main sequence (see 1914).
Such stars, perhaps only a million or so years old and comparable in mass to the sun, are too young to have core temperatures high enough to fuse hydrogen into helium and thus have not yet entered the main sequence of stellar evolution.
Acting Minister for Industry, Innovation and Science, Senator the Hon Michaelia Cash, said the launch of Main Sequence Ventures is an important step to ensure we can further harness Australian innovation to create new enterprises and the jobs of tomorrow.
IN A dreadful period Stateside for news of equine illness and injury, North America's champion older horse Main Sequence became the third star to make unwanted headlines when it was announced he has been retired because of a tendon problem.
Most stars fall on a diagonal line--the main sequence --from upper left to lower right.