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Sketch of Hertzsprung–Russell diagram of a globular cluster, showing blue stragglers. A blue straggler is a type of star that is more luminous and bluer than expected. . Typically identified in a stellar cluster, they have a higher effective temperature than the main sequence turnoff point for the cluster, where ordinary stars begin to evolve towards the red gi
Below there are lists the nearest stars separated by spectral type. The scope of the list is still restricted to the main sequence spectral types: M , K , F , G , A , B and O . It may be later expanded to other types, such as S , D or C .
Gagea villosa, common name hairy star of Bethlehem, [2] is a Eurasian and North African plant species in the lily family. Gagea villosa is found in Europe, North Africa and Western Asia. Its range extends from Spain and Morocco east to Russia and Iran, and as far north as Sweden. [1] It was first described to science by Bieberstein in 1808. [3] [2]
It is prominent in many galactic open clusters, and it is also noticeable in many intermediate-age globular clusters and in nearby field stars (e.g. the Hipparcos stars). The red clump giants are cool horizontal branch stars, stars originally similar to the Sun which have undergone a helium flash and are now fusing helium in their cores.
Each star follows an evolutionary track across this diagram. If this track takes the star through a region containing an intrinsic variable type, then its physical properties can cause it to become a variable star. An example of this is the instability strip, a region of the H-R diagram that includes Delta Scuti, RR Lyrae and Cepheid variables. [7]
Disc of debris around an F-type star, HD 181327. [1] An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K. [2] Tables VII and VIII.
These diagrams enable the assessment of nucleosynthesis channels and galactic evolution in samples of stars as a first-order approximation. They are among the most commonly used tools for Galactic population analysis of the Milky Way. The diagrams use abundance ratios normalised to the Sun, (placing the Sun at (0,0) in the diagram).
K-type main-sequence stars are about three to four times as abundant as G-type main-sequence stars, making planet searches easier. [17] K-type stars emit less total ultraviolet and other ionizing radiation than G-type stars like the Sun (which can damage DNA and thus hamper the emergence of nucleic acid based life). In fact, many peak in the red.