Classification of stars key terms

luminosity

The total power output of a star, measured in watts (W), representing the energy emitted per unit time.

apparent brightness

The observed brightness of a star as seen from Earth, which decreases with distance and is influenced by the star's luminosity and distance from the observer.

Luminosity

Luminosity: a specific A-Level Physics term for Classification by luminosity. Use it to support use inverse-square relationships for apparent brightness. by linking the named observation, graph, spectrum or measurement to the correct astrophysics conclusion. This definition is intentionally tied to Classification by luminosity, so it is not a generic astronomy label.

Apparent Brightness

The observed brightness of a star as seen from Earth, which decreases with distance according to the inverse-square law.

luminosity

luminosity: a specific A-Level Physics term for Classification by luminosity. Use it to support compare apparent brightness and luminosity. by linking the named observation, graph, spectrum or measurement to the correct astrophysics conclusion. This definition is intentionally tied to Classification by luminosity, so it is not a generic astronomy label.

apparent brightness

The amount of light received from a star per unit area, which decreases with distance from the star.

luminosity

luminosity: a specific A-Level Physics term for Classification by luminosity. Use it to support interpret brightness data for stars. by linking the named observation, graph, spectrum or measurement to the correct astrophysics conclusion. This definition is intentionally tied to Classification by luminosity, so it is not a generic astronomy label.

apparent brightness

The observed brightness of a star as seen from Earth, which diminishes with distance.

apparent magnitude

The brightness of a star as seen from Earth, which can be affected by distance and interstellar material.

absolute magnitude

The intrinsic brightness of a star, defined as the brightness it would have at a standard distance of 10 parsecs from Earth.

distance modulus

The difference between the apparent magnitude and absolute magnitude of a star, used to calculate its distance.

apparent magnitude

A measure of the brightness of a star as seen from Earth, which can vary depending on distance and interstellar material.

parsec

A unit of distance used in astronomy, equal to about 3.26 light-years, defined as the distance at which one astronomical unit subtends an angle of one arcsecond.

parallax angle

The angle formed at a star by the lines of sight from two different positions of the Earth in its orbit, used to measure distances to nearby stars.

magnitude scale

A logarithmic scale used to measure the brightness of celestial objects, where lower numbers indicate brighter objects.

qualitative interpretation

An analysis that describes the characteristics of data without numerical values, focusing on the relative differences in brightness or other properties.

black-body radiation

The theoretical spectrum of electromagnetic radiation emitted by a perfect black body in thermal equilibrium, dependent on its temperature.

Wien's law

A law that describes the relationship between the temperature of a black body and the wavelength at which its emission is maximized, stating that the peak wavelength is inversely proportional to the temperature.

Wien's law

A principle that relates the temperature of a black body to the wavelength at which its emission is maximized, expressed as λ_max = b/T, where b is Wien's displacement constant.

surface temperature

The temperature of a star's surface, which can be estimated using Wien's law based on the peak wavelength of its emitted radiation.

Wien's Law

A principle stating that the peak wavelength of black-body radiation is inversely proportional to the absolute temperature of the body.

Peak Wavelength

The wavelength at which the intensity of radiation emitted by a black body is at its maximum, which varies with temperature.

luminosity

luminosity: a specific A-Level Physics term for Temperature and black-body radiation. Use it to support link radiation output to stellar temperature and radius. by linking the named observation, graph, spectrum or measurement to the correct astrophysics conclusion. This definition is intentionally tied to Temperature and black-body radiation, so it is not a generic astronomy label.

apparent brightness

Astrophysics distinct term: use this keyword only for its own subtopic context. It links the named observation or measurement to a specific A-Level Physics conclusion and should not be merged with nearby brightness, distance, telescope or cosmology vocabulary. Include the relevant graph, spectrum or unit when using it in an exam answer.

Absorption Spectrum

A spectrum that shows dark lines or bands superimposed on a continuous spectrum, indicating the wavelengths of light absorbed by elements in a star's atmosphere.

Element Identification

The process of determining the chemical elements present in a star by analyzing its absorption spectrum and matching the absorption lines to known wavelengths.

Spectral Class

A classification system for stars based on their temperatures and the characteristics of their absorption spectra.

Stellar Temperature

The measure of the thermal energy of a star, which influences its color and spectral characteristics.

Spectra

Spectra are the range of electromagnetic radiation emitted or absorbed by substances, revealing their chemical composition and temperature.

Chemical Evidence

Chemical evidence refers to the identification of elements in stars through their absorption spectra, which indicates the star's composition and temperature.