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Helium Flash

Astronomy  Helium  Helium-3

The helium flash is correctly named, because unlike most phases of stellar evolution, the flash itself occurs over a matter of minutes rather than millions of years.


Helium Flash
The onset of runaway helium burning under degenerate conditions. The helium flash occurs in the hydrogen-exhausted core of a star in the red-giant phase of evolution.

helium flash
The nearly explosive beginning of helium burning in the dense core of a red giant star.
Herbig-Haro objects
Small, luminous nebulae associated with the end points of jets emanating from young stars.

HELIUM FLASH

The explosive start of nuclear reactions converting helium into carbon in the core of an aging star.

Helium Flash
The explosive ignition of helium burning that takes place in some giant stars.
Herbig-Haro Object ...

~ - The explosive consumption of helium in the core of a star when helium fusion begins in a degenerate gas in which pressure doesn't rise as energy is produced and temperature increases ...

THE ~
For stars comparable in mass to the Sun, there is a major complication when helium fusion begins.

~ An explosive event in the post-main-sequence evolution of a low-mass star. When helium fusion begins in a dense stellar core, the burning is explosive in nature.

~ - (n.)
A rapid burst of nuclear reactions in the degenerate core of a moderate-mass star in the hydrogen shell-burning phase. The flash occurs when the core temperature reaches a sufficiently high temperature to trigger the triple-alpha reaction.
Hertz (Hz) - (n.) ...

~: In certain low-mass stars when they become red giants their cores are supported by electron-degeneracy pressure.

No ~, but steady Helium fusion
Planetary Nebula
Carbon/Oxygen rich White Dwarf ...

After the helium flash one is left with a star in a new equilibrium: a core burning helium into carbon and a surrounding hydrogen-burning shell. Such a star now settles in for a period as a horizontal branch star.

~ The sudden onset of helium core fusion (or "burning") in post-main sequence stars is called the ~.

~ Somewhat sudden and rapid ignition of helium in the electron-degenerate core of a star, after which the star settles down to fusing helium quietly into carbon.

~ in low-mass red giant stars, the onset of the fusing of helium in the core can be very rapid, almost explosive. hertz (Hz): unit of frequency. One hertz = 1 wave peak/second. Hertzsprung-Russell diagram (H-R diagram) a plot of stellar luminosity vs.

* In some cases, depending on the star's mass, the helium core will be squeezed enough to suddenly ignite in what's called the "helium flash". This expels as much energy as 100,000,000 Suns. But the flash is brief, and the released energy does not disturb the outer layers of the star.

The stage when a star fuses helium into carbon and oxygen. All stars born with more than half a solar mass eventually burn helium. [C95]
Helium Flash ...

Red Giant - Helium Flash
As the Helium core of the star contracts, nuclear reactions continue in a shell surrounding the core.

At this point the density and temperature will become so high that the fusion of helium into carbon will begin, leading to a helium flash; the Sun will shrink from around 250 to 11 times its present (main sequence) radius.

When the temperature and pressure in the core become sufficient to ignite helium fusion in the core, a helium flash will occur if the core is largely supported by electron degeneracy pressure; in more massive stars, whose core is not overwhelmingly supported by electron degeneracy pressure, ...

Medium-mass stars ( ) exhaust hydrogen in their cores, fuse hydrogen in their shells, become giant stars, undergo helium flash, fuse helium in their shells around a carbon-oxygen core. Because temperatures are not high enough to fuse carbon, the core continues to contract and the envelope expands.

The commencement of this helium fusion in the stellar core is known as the helium flash and causes the temperature to increase while the radius decreases, thus the luminosity remains constant.

begun life as a hot class B dwarf some 100 million years ago, and having begun its evolution as a giant only 13 million years ago, the star seems now to be entering a phase in which deep helium- and hydrogen-fusing shells alternately turn on and off, the former violently, leading to a "helium flash" ...

See also: See also: What is the meaning of Helium, Star, Sun, Astro, Main Sequence?

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