Algol paradox
Encyclopedia
In stellar astronomy, the Algol paradox is an apparently paradox
ical situation when elements of a binary star
seem to evolve in discord with the established theories of stellar evolution
. A fundamental feature of these theories is that the rate of evolution of stars
depends on the mass of the star: The greater the mass of the star, the faster this evolution, and the more quickly it leaves the main-sequence, entering either a subgiant or giant
phase.
In the case of Algol and other binary stars we can observe something completely different: The less massive star is already a subgiant, and the star with much greater mass is still on the main-sequence. Initially, this seems paradoxical as the partner stars of the binary are thought to have formed at approximately the same time and so should have similar ages. Thus the more massive star, rather than the less massive one, should have left the main sequence.
The paradox is resolved by the fact that in many binary stars, there can be a flow of material between the two stars, disturbing the normal process of stellar evolution. As the flow progresses, the evolutionary stage of the stars will advance, even as the relative masses change. Eventually, the originally more massive star will reach the next stage in its evolution despite having lost much of its mass to its companion.
Paradox
Similar to Circular reasoning, A paradox is a seemingly true statement or group of statements that lead to a contradiction or a situation which seems to defy logic or intuition...
ical situation when elements of a binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
seem to evolve in discord with the established theories of stellar evolution
Stellar evolution
Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years to trillions of years .Stellar evolution is not studied by observing the life of a single...
. A fundamental feature of these theories is that the rate of evolution of stars
Stellar evolution
Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years to trillions of years .Stellar evolution is not studied by observing the life of a single...
depends on the mass of the star: The greater the mass of the star, the faster this evolution, and the more quickly it leaves the main-sequence, entering either a subgiant or giant
Giant star
A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Stars still more luminous than giants are...
phase.
In the case of Algol and other binary stars we can observe something completely different: The less massive star is already a subgiant, and the star with much greater mass is still on the main-sequence. Initially, this seems paradoxical as the partner stars of the binary are thought to have formed at approximately the same time and so should have similar ages. Thus the more massive star, rather than the less massive one, should have left the main sequence.
The paradox is resolved by the fact that in many binary stars, there can be a flow of material between the two stars, disturbing the normal process of stellar evolution. As the flow progresses, the evolutionary stage of the stars will advance, even as the relative masses change. Eventually, the originally more massive star will reach the next stage in its evolution despite having lost much of its mass to its companion.