Twilight is the time between dawn and sunrise or between sunset and dusk, during which sunlight scattering in the upper atmosphere illuminates the lower atmosphere, and the surface of the earth is neither completely lit nor completely dark. The sun itself is not directly visible because it is below the horizon. Owing to the distinctive quality of the ambient light at this time, twilight has long been popular with photographers and painters, who refer to it as the "blue hour", after the French expression l'heure bleue. Twilight is technically defined as the periods between sunset and sunrise during which there is natural light provided by the upper atmosphere, which receives direct sunlight and scatters part of it towards the earth's surface.

The collateral adjective for twilight is crepuscular; it is most frequently encountered when applied to certain insects, fishes and mammals that are most active during that time.

Twilight is defined according to the solar elevation angle Failed to parse (Missing texvc executable; please see math/README to configure.): \theta_\mathrm{s} , which is the position of the geometric center of the sun relative to the horizon. There are three established and widely accepted subcategories of twilight: civil twilight (brightest), nautical twilight, and astronomical twilight (darkest).

Kristen Jaymes Stewart (born April 9, 1990) is an American actress. She is best known for playing Bella Swan in The Twilight Saga. She has starred in other films, including Panic Room (2002), Zathura (2005), In the Land of Women (2007), The Messengers (2007), Adventureland (2009), The Runaways (2010), and Snow White and the Huntsman. She will star in upcoming films in 2012: On the Road and The Twilight Saga: Breaking Dawn – Part 2.

Stewart was born and raised in Los Angeles, California. Her father, John Stewart, is a stage manager and television producer who has worked for Fox. Her mother, Jules Mann-Stewart, is a script supervisor originally from Maroochydore, Queensland, Australia. She has an older brother, Cameron Stewart, and an adopted brother, Taylor. Stewart attended school until the seventh grade and then continued her education by correspondence. She has since completed high school.

Her whole family all worked behind the camera and Stewart thought she would become a writer/director, but never considered being an actor. "I never wanted to be the center of attention – I wasn't that 'I want to be famous, I want to be an actor' kid. I never sought out acting, but I always practiced my autograph because I love pens. I'd write my name on everything." Stewart's acting career began at the age of eight, after an agent saw her perform in her elementary school's Christmas play. After a year of auditioning, Stewart's first role was a small nonspeaking part in the Disney Channel original film The Thirteenth Year. Then, she had another part in the film The Flintstones in Viva Rock Vegas as the "ring toss girl". She subsequently appeared in the independent film The Safety of Objects, in which she played the tomboy daughter of a troubled single mother (Patricia Clarkson). Stewart also played a tomboy in the film Panic Room, playing the diabetic daughter of a divorced mother (Jodie Foster). She was nominated for a Young Artist Award for her performance.