Horizontal Branch stars
This is a phase of stellar evolution undergone by intermediate-mass stars, i.e. those with masses 0.8 M⊙ < < 8 M⊙, a range which encompasses the majority of stars in the Galaxy, including our Sun.
Horizontal Branch Star - A star which is undergoing helium fusion in its core and hydrogen fusion in a shell surrounding the core ...
Horizontal Branch Star
A metal-poor star, similar in mass to the Sun, that fuses helium into carbon and oxygen at its core. Such stars range in color from blue to yellow. RR Lyrae stars are horizontal-branch stars.
Horizontal branch stars are characterized by helium core burning and hydrogen burning in a shell surrounding the core.
2. What element makes up the core of a massive star just before it goes supernova?
Iron.
horizontal branch stars (NASA Thesaurus) Horizontal strips of stars on the Hertzsprung-Russell diagram of globular clusters to the left of the red giant branch.
An isolated galaxy which does not belong to any cluster of galaxies. The ratio of galaxies in clusters to field galaxies is about 23:1. [H76]
Field Horizontal Branch Stars ...
RR LYRAE STAR - Variable, horizontal branch stars with periods ranging from a few hours to 2 days, and optical brightnesses that typically vary between 0.3 and 2 magnitudes.
Considering the substantial changes that take place when a star runs out of hydrogen in its core, one can see how it should be easy to distinguish between main sequence stars and red giants and horizontal branch stars.
Horizontal branch stars are powered by helium fusion (aka the triple-alpha reaction) in the core and hydrogen fusion in a shell surrounding the core.
The Sun will become a horizontal branch star, burning helium in its core in a stable fashion much like it burns hydrogen today. The helium-fusing stage will last only 100 million years.
Aside from the additional hydrogen-burning layer, a horizontal branch star is somewhat like a zero-age main sequence star in that it will continue to evolve until it exhausts its supply of helium.
The star will now become a Horizontal Branch Star, for as the core expands, it cools and the energy generation in the hydrogen burning shell will drop; so the luminosity decreases, the star will shrink, and the surface temperature rise.
These are stars which are normally found only in globular clusters which are much older than NGC 6791. Unlike a typical globular cluster, however, NGC 6791 contains simultaneously both red and very blue horizontal branch stars, ...
extrasolar planets, detection
extrasolar planets, searches
extreme horizontal branch star (EHB star)
extreme Population I star
extremely large telescope
extrinsic variable
eye relief
eyepiece
Eyes, The (NGC 4435 and 4438) ...
 See also: Horizontal Branch, Sun, Star, Luminosity, Horizon
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