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18947847. LC Class. PZ7.L9673 Nu 1989. Number the Stars is a work of historical fiction by the American author Lois Lowry about the escape of a family of Jews from Copenhagen, Denmark, during World War II. The story revolves around ten-year-old Annemarie Johansen, who lives with her mother, father, and sister Kirsti in Copenhagen in 1943.
Representative lifetimes of stars as a function of their masses The change in size with time of a Sun-like star Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right Chart of stellar evolution
Stellar classification. In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines.
Hertzsprung–Russell diagram. An observational Hertzsprung–Russell diagram with 22,000 stars plotted from the Hipparcos Catalogue and 1,000 from the Gliese Catalogue of nearby stars. Stars tend to fall only into certain regions of the diagram. The most prominent is the diagonal, going from the upper-left (hot and bright) to the lower-right ...
Since the lifespan of such stars is greater than the current age of the universe (13.8 billion years), no stars under about 0.85 M ☉ [81] are expected to have moved off the main sequence. Besides mass, the elements heavier than helium can play a significant role in the evolution of stars.
In addition, knowing the age of one member of a star system can help determine the age of that system. In a star system, stars almost always form at the same time as each other, and given the age of one star, the age of all of the others can be known. [14] However, this method does not work for galaxies. These units are much larger, and are not ...
The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A direct distance measurement of an astronomical object is possible only for those objects that are "close enough" (within about a thousand parsecs) to Earth.
Star count. Star counts are bookkeeping surveys of stars and the statistical and geometrical methods used to correct the survey data for bias. The surveys are most often made of nearby stars in the Milky Way galaxy. One of the interests of astronomy is to determine how many stars there are of each of several types that stars can be categorized ...