Star count
From Wikipedia, the free encyclopedia
Star counts are census counts of stars[1] and the statistical and geometrical methods used to correct the corresponding data for bias.[citation needed] The surveys are most often made of nearby stars in the Milky Way galaxy.[citation needed]
The total number of stars counted in a particular direction depends on the location and density of stars, the luminosity function, and the absorption.[2] Star count programs can therefore collect data that bounds or determines these values.[2]
One of the interests of astronomy is to determine how many stars there are of each of several types that stars can be categorized into, and how these stars are distributed in space.
When performing star counts, astronomers consider many different categories that have been created to classify a few stars that have been well studied. One of the hopes of studying the results of star counts is to discover new categories. Different counts typically seek to categorize stars for only a few of the qualities listed below, and determine how common each considered quality is and how stars of that kind are distributed.
- Temperature: In astronomy, temperature is usually shown using the letter codes O B A F G K M running from 'blue' (type O, actually bluish white) through white (type F) to 'red' (type M, actually ruddy orange). Types L and T are used for brown dwarfs, whose 'colors' are in the infrared.
- Size: Size is usually designated by Roman numerals I (supergiants) through V (dwarfs).
- Age: Stars are usually grouped into Population I (young) and Population II (old).
- Location: In the Milky Way galaxy the groups are described as thin disk, thick disk, central bulge, and halo.
- Multiplicity: Most stars are members of double star, or triple star, or even double-double star systems. Our own sun appears to be unusual for not having a companion star.
There are many finer subdivisions in all of the above categories.
