A Be star is a B-type star with prominent emission lines of hydrogen in its spectrum. The designation is combined by the spectral class, B, and the lowercase e denoting emission in the spectral classification system. Line emission from other atomic ions might be present as well, but is typically much weaker. Other observational characteristics include optical linear polarization and often infrared radiation that is much stronger than in ordinary B-class stars, called infrared excess. As the Be nature is transient, Be stars might exhibit a normal B-type spectrum at times, and hitherto normal B stars may become Be stars.

While most Be stars are on the main sequence, the identifier actually refers to a heterogeneous group of objects including pre main sequence stars, supergiant stars, protoplanetary nebulae, and others. They may be subclassed into B[e] supergiants (notation sgB[e]), Herbig Be stars, compact planetary nebula B[e], symbiotic B[e], and a catch-all "unclear" category.

The first star recognized as a Be star was Gamma Cassiopeiae, observed 1866 by Angelo Secchi, the first star ever observed with emission lines. With the understanding of the processes of emission line formation in the early 20th century it became clear that these lines must come from the circumstellar environment, not from the star itself. Nowadays, all the observational characteristics are explained with a gaseous disk that is formed of material ejected from the star. The infrared excess and the polarization result from the scattering of stellar light in the disk, while the line emission is formed by re-processing stellar ultraviolet light in the gaseous disc.

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth. Other stars are visible from Earth during the night, when they are not obscured by atmospheric phenomena, appearing as a multitude of fixed luminous points because of their immense distance. Historically, the most prominent stars on the celestial sphere were grouped together into constellations and asterisms, and the brightest stars gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations.

For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen in its core releasing energy that traverses the star's interior and then radiates into outer space. Almost all naturally occurring elements heavier than helium were created by stars, either via stellar nucleosynthesis during their lifetimes or by supernova nucleosynthesis when stars explode. Astronomers can determine the mass, age, chemical composition and many other properties of a star by observing its spectrum, luminosity and motion through space. The total mass of a star is the principal determinant in its evolution and eventual fate. Other characteristics of a star are determined by its evolutionary history, including diameter, rotation, movement and temperature. A plot of the temperature of many stars against their luminosities, known as a Hertzsprung–Russell diagram (H–R diagram), allows the age and evolutionary state of a star to be determined.

Tyra Lynn Banks (born December 4, 1973). is an American model, media personality, actress, occasional singer, author and businesswoman. She first became famous as a model, appearing twice on the cover of the Sports Illustrated Swimsuit Issue and working for Victoria's Secret as one of their original Angels. Banks is the creator and host of the UPN/The CW reality television show America's Next Top Model, co-creator of True Beauty, and host of her own talk show, The Tyra Banks Show.

Tyra Banks was born in Inglewood, California. She is the daughter of Caroline (née London; now London-Johnson), a medical photographer, and Donald Banks, a computer consultant. She has a brother, Devin, who is five years older. In 1980, when Banks was 6 years old, her parents divorced. Banks attended John Burroughs Middle School and graduated in 1991 from Immaculate Heart High School in Los Angeles. Tyra Banks is one of four African Americans and seven women to have repeatedly ranked among the world's most influential people by Time magazine.