LuminosityLuminosity is an absolute measure of radiated electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a star, galaxy, or other luminous astronomical object. In SI units, luminosity is measured in joules per second, or watts. In astronomy, the luminosity of the Sun, L☉ is often used as a unit of luminosity.SunStar at the centre of the Solar SystemThe Sun is the star located at the centre of the Solar System. It is a massive sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light and infrared radiation with 10% at ultraviolet energies. It is the main source of energy for life on Earth.
Variable starStar whose brightness fluctuates, as seen from EarthComparison of VLT-SPHERE images of Betelgeuse taken in January 2019 and December 2019, showing the changes in brightness and shape. Betelgeuse is an intrinsically variable star.A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time.
Power (physics)Power is the amount of energy transferred or converted per unit time. In the International System of Units, the unit of power is the watt (symbol W), equal to one joule per second (J/s). Power is a scalar quantity. The output power of a motor is the product of the torque that the motor generates and the angular velocity of its output shaft.
GalaxyA galaxy is a physical system of stars, planetary systems, stellar remnants, substellar objects, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greekgalaxias (γαλαξίας), meaning 'milky', a reference to the Milky Way galaxy that contains the Solar System.
International Astronomical UnionThe International Astronomical Union (IAU; French: Union astronomique internationale, UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and development through global cooperation. It was founded on 28 July 1919 in Brussels, Belgium, and is based in Paris, France.
PhotonElementary particle or quantum of lightA photon (from Ancient Greek φῶς, φωτός (phôs, phōtós) 'light') is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless particles that can only move at one speed, the speed of light measured in a vacuum. The photon belongs to the class of boson particles.
Radiant fluxIn radiometry, radiant flux or radiant power is the radiant energy emitted, reflected, transmitted, or received per unit time, and spectral flux or spectral power is the radiant flux per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength.
AstronomerAn astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers study astronomical objects, such as stars, planets, moons, comets and galaxies, by some combination of observation and the application of astrophysical models. Examples of topics or fields astronomers study include planetary science, solar astronomy, the origin or evolution of stars, or the formation of galaxies.
WattThe watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m⋅s. It is used to quantify the rate of energy transfer. The watt is named in honor of James Watt (1736–1819), an 18th-century Scottishinventor, mechanical engineer, and chemist who in 1776 improved the Newcomen engine with his own steam engine, which became fundamental for the Industrial Revolution.
Absolute magnitudeMeasure of the luminosity of celestial objectsIn astronomy, absolute magnitude (M) is a measure of the luminosity of a celestial object on an inverse logarithmicastronomical magnitude scale; the more luminous (intrinsically bright) an object, the lower its magnitude number.StarLarge self-illuminated object in spaceThe Sun, a G-type main-sequence star, the closest to EarthA star-forming region in the Large Magellanic CloudA star is a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixedpoints of light.*As an Amazon Associate I earn from qualifying purchases.