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In astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band.

Light curves can be periodic, as in the case of eclipsing binaries, cepheid variable
Cepheid variable

A Cepheid variable or Cepheid is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of Radial pulsations and absolute luminosity....
s and other variables, or aperiodic, like the light curve of a nova
Nova

A nova is a cataclysmic nuclear explosion caused by the Accretion of hydrogen onto the surface of a white dwarf star. Novae are not to be confused with Type Ia supernovae, or another form of stellar explosion first announced by Caltech in May 2007, Luminous Red Novae....
, a cataclysmic variable star
Cataclysmic variable star

Cataclysmic variable stars are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state. They were initially called novae, from the Latin 'new', since ones with an outburst brightness visible to the naked eye and a quiescent brightness invisible appeared as new stars in the sky....
 or a supernova
Supernova

A supernova is a Astronomy#Stellar astronomy explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months....
.

The study of the light curve, together with other observations, can yield considerable information about the physical process that produces it or constrain the physical theories about it.

lanetology, a light curve can be used to estimate the rotation period of a minor planet
Minor planet

An asteroid group or minor planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid....
 or moon
Natural satellite

A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. Technically, the term natural satellite could refer to a planet orbiting a star, or a dwarf galaxy orbiting a major galaxy, but it is normally synonymous with moon and used to identify non-artificial satellites...
.






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In astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band.

Light curves can be periodic, as in the case of eclipsing binaries, cepheid variable
Cepheid variable

A Cepheid variable or Cepheid is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of Radial pulsations and absolute luminosity....
s and other variables, or aperiodic, like the light curve of a nova
Nova

A nova is a cataclysmic nuclear explosion caused by the Accretion of hydrogen onto the surface of a white dwarf star. Novae are not to be confused with Type Ia supernovae, or another form of stellar explosion first announced by Caltech in May 2007, Luminous Red Novae....
, a cataclysmic variable star
Cataclysmic variable star

Cataclysmic variable stars are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state. They were initially called novae, from the Latin 'new', since ones with an outburst brightness visible to the naked eye and a quiescent brightness invisible appeared as new stars in the sky....
 or a supernova
Supernova

A supernova is a Astronomy#Stellar astronomy explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months....
.

The study of the light curve, together with other observations, can yield considerable information about the physical process that produces it or constrain the physical theories about it.

Planetology

In planetology, a light curve can be used to estimate the rotation period of a minor planet
Minor planet

An asteroid group or minor planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid....
 or moon
Natural satellite

A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. Technically, the term natural satellite could refer to a planet orbiting a star, or a dwarf galaxy orbiting a major galaxy, but it is normally synonymous with moon and used to identify non-artificial satellites...
. From the Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
 there is often no way to resolve a small object in our Solar System
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
, even in the most powerful of telescope
Telescope

A telescope is an instrument designed for the observation of remote objects by the collection of electromagnetic radiation. The first known practically functioning telescopes were invented in the Netherlands at the beginning of the 17th century....
s, since the apparent angular size of the object is smaller than one pixel in the detector. Thus, astronomers measure the amount of light produced by an object as a function of time (the light curve). Looking for peaks in the light curve can produce estimates of the rotation rate of the object, assuming that there are parts of the object that are brighter or darker than average. In this case, there is sometimes aliasing
Aliasing

In statistics, signal processing, computer graphics and related disciplines, aliasing refers to an effect that causes different continuous signals to become indistinguishable when sampling ....
, where it is unclear whether there is one or two light curve peaks per rotation period. For example, an asteroid light curve is a light curve of an asteroid, caused by the fact that asteroids are generally non-uniform in shape. This light curve can be used to determine an asteroid's spin rate.

Botany

In botany
Botany

Botany, plant science, phytology, or plant biology is a branch of biology and is the Scientific method of plant life and development....
, a light curve shows the photosynthetic response of leaf tissue or algal communities to varying light intensities. The shape of the curve illustrates the principle of limiting factor
Limiting factor

A limiting factor or limiting resource is a factor that controls a process, such as organism growth or species population, size, or distribution....
s; in low light levels, the rate of photosynthesis is limited by the concentration of chlorophyll
Chlorophyll

Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. Its name is derived from Greek language: ?????? and f????? ....
 and the efficiency of the light-dependent reactions, but in higher light levels it is limited by the efficiency of RuBisCo
RuBisCO

Ribulose-1,5-bisphosphate carboxylase/oxygenase, most commonly known by the shorter name RuBisCO, is an enzyme that is used in the Calvin cycle to catalyze the first major step of carbon fixation, a process by which the atoms of atmospheric carbon dioxide are made available to organisms in the form of fuel molecules such as sucrose....
 and the availability of carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
. The point on the curve where these two differing slopes meet is called the light saturation point and is where the light-dependent reactions are producing more ATP
Adenosine triphosphate

This article is about the chemical used by cells as an energy carrier. For other uses, see ATP .Adenosine-5'-triphosphate is a multifunctional nucleotide, and plays an important role in cell biology as a coenzyme that is the "molecule unit of currency" of intracellular energy transfer....
 and NADPH than can be utilized by the light-independent reaction
Light-independent reaction

Photosynthesis, the light-independent reactions, are chemical reactions that convert carbon dioxide and other Chemical compounds into glucose. They occur in the stroma, the fluid filled area of a chloroplast outside of the thylakoid membranes....
s. Since photosynthesis is also limited by ambient carbon dioxide levels, light curves are often repeated at several different constant carbon dioxide concentrations.

External links

  • can plot light curves for thousands of variable stars
  • by NASA's Imagine the Universe