Population II
Stars observed in galaxies were originally divided into two populations by Walter Baade in the 1940s.
Population II stars are metal poor stars, containing about 0.1% metals. These stars can be found in the spherical portion of the galaxy (the halo and the bulge). Often these stars have tipped and elliptical orbits.
POPULATION II
When we come to study the older populations of the Magellanic Clouds, we look past the brilliant associations with their blue supergiants and HII regions, past the Cepheid variables, ...
Population II: Stars poor in atoms heavier than helium; relatively old stars found in the halo, globular clusters, or the nuclear bulge.
POPULATION II STARS - Relatively old stars found in the halos of galaxies and in globular clusters. Population II stars are metal-poor, with metallicities ranging from ~0.001 to 0.1 that of the Sun (i.e., [Z/H] from -3.0 to -1.0).
Population II
Stars poor in atoms heavier than helium; nearly always relatively old stars found in the halo, globular clusters, or the nuclear bulge.
Position Angle ...
Population II
Older stars, generally formed towards the centre of a galaxy, containing few heavier elements. The brightest of this Population are red giants.
Populations I and II ...
[edit] Population II stars
Population II or metal-poor stars are those with relatively little metal.
Population II stars are much older than Population I stars, contrary to what one might expect from the numbers assigned to them.
Population III stars are stars which have no elements more massive than hydrogen or helium. During Big Bang nucleosynthesis, the only elements that formed aside from hydrogen and helium were trace amounts of lithium.
population II - (n.)
The class of stars with relatively low abundances of heavy elements. These stars are generally found in a spheroidal distribution about the galactic center and throughout the halo, and are relatively old.
Population III - (n.) ...
Population II Stars: Relatively old stars, containing a smaller fraction of metals, found mainly in the halo of the Galaxy and in Globular Clusters.
Population II stars are found in actually two places - away from the disk, in the halo where the globular clusters are, and in the bulge.
The Population II stars inhabit the spheroidal component (the stellar halo and bulge). They are old: ages range from 10 to 13 billion years old, so they have masses less than or equal to 0.8 solar masses.
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These old population II giant stars are mostly found in globular clusters. They are characterised by their short periods, usually about 1.5 hours to a day and have a brightness range of 0.3 to 2 magnitudes. Spectral classes range from A7 to F5.
When these population III stars died in dramatic supernova explosions, the surrounding interstellar medium was enriched with metals which had formed within the stars as they evolved.
Population I stars are young, recently formed stars, whereas population II stars are old and highly evolved. Population II stars are formed early in the history of the galaxy from pure hydrogen with an admixture of primordial helium.
Type I (population II) supernovae can be recognized (and divided into subgroups a,b, and maybe c) based on their spectra and light curves.
Arcturus may be a Population II star and a member of the Milky Way galaxy's thick disk.
We call those stars with very little heavy elements "population II stars" and those with Sun-like heavy element abundances "population I stars".
Almost There for Spotting Population III Stars
(Added 01/16/03) Over half a century ago, the German-American astronomer Walter Baade divided stars into three categories: Population I, Population II, and Population III.
than disk stars (there is a correlation, but there is no absolute connection between these data) * some astronomers have identified an intermediate population of stars, variously called the "metal weak thick disk", the "intermediate population II", ...
Originally thought to be old galactic halo Population II subdwarfs, the two stars are now thought to be younger galactic disk stars, but still considerably older than the Sun, perhaps as much as 8 billion years old.
Sometimes called "Population II Cepheids," they are lower metal, lower mass versions of classical Cepheids with respectively short, intermediate, and longer periods that range to 100 days.
Young metal rich stars are called Population I and old metal poor stars are called Population II. (A possibly helpful mnemonic: II stars are older than I stars because II is bigger than I.) Globular clusters are old clusters of population II stars.
Astronomers often refer to young disk stars as Population I stars and to old halo stars as Population II stars. The idea of two stellar "populations" dates from the 1930s, when the differences between disk and halo stars first became clear.
It contains several million Population II stars, oldest stars to be observed. The stars in the center of the cluster appear so close to each other than the distance between them is believed to be only 0.1 light-years.
This is an odd distinction because the first stars to have populated a given region would now be classified as Population II! ...
This process of being a Helium burning star lasts around 700 000 years and is the Population II stage. The star is now on what it known as the Main Sequence - an escalator that will climb, relatively quickly, to supernova-hood.
Polaris pulsates with 3.97 day period. The luminosity varies by 0.15 magnitude. Polaris is classified as a Population II Cepheid. Stars of this type are about 1.5 magnitudes smaller than Population I Cepheids.
The Distance Scale in the Universe ...
Cepheid variables subdivide into two classes: the classical Cepheid variables, which are population I stars-stars with a high metallicity, and, therefore, of the current generation of stars-and the W Virginis variables, which are population II- stars ...
10, 1773, but he never entered it in his oroginal catalog - however, he published its description and engraving in 1807. It measures about 5,400 ly and apart from population II stars, contains two small dust clouds.
Second generation stars do not just burn hydrogen, they also burn heavier elements, like helium and metals, and were formed from supernova explosions (the debris of exploded population II stars). Our Sun is a seond or third generation star.
RR Lyrae variables can still be employed as distance indicators because their absolute magnitudes tend to be alike. Short-period Cepheids belong to Population II, a class of older stars found in the core and in the halo of the Milky Way Galaxy.
 See also: Population I, Population, Star, Light, Galaxy
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