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Starry sky crossed with the Milky Way and a shooting star Perseid Meteor.jpg
Starry sky crossed with the Milky Way and a shooting star

Starlight is the light emitted by stars. [1] It typically refers to visible electromagnetic radiation from stars other than the Sun observable from Earth during the night time although a component of starlight is observable from the Earth during the daytime.

Light electromagnetic radiation in or near visible spectrum

Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to visible light, which is the visible spectrum that is visible to the human eye and is responsible for the sense of sight. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), or 4.00 × 10−7 to 7.00 × 10−7 m, between the infrared and the ultraviolet. This wavelength means a frequency range of roughly 430–750 terahertz (THz).

Visible spectrum portion of the electromagnetic spectrum that is visible to the human eye

The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 380 to 740 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 430–770 THz.

Electromagnetic radiation form of energy emitted and absorbed by charged particles, which exhibits wave-like behavior as it travels through space

In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.


Sunlight is the term used for the Sun's starlight observed during daytime. During nighttime, albedo describes solar reflections from other Solar System objects including moonlight.

Sunlight portion of the electromagnetic radiation given off by the Sun

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by clouds or reflects off other objects, it is experienced as diffused light. The World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter. Other sources indicate an "Average over the entire earth" of "164 Watts per square meter over a 24 hour day".

Albedo ratio of reflected radiation to incident radiation

Albedo is the measure of the diffuse reflection of solar radiation out of the total solar radiation received by an astronomical body. It is dimensionless and measured on a scale from 0 to 1.

Moonlight light that reaches Earth from the Moon

Moonlight consists of mostly sunlight reflected from the parts of the Moon's surface where the Sun's light strikes.


Observation and measurement of starlight through telescopes is the basis for many fields of astronomy, [2] including photometry and stellar spectroscopy. [3] Hipparchus did not have a telescope or any instrument that could measure apparent brightness accurately, so he simply made estimates with his eyes. He sorted the stars into six brightness categories, which he called magnitudes. [4] He referred to the brightest stars in his catalog as first-magnitudes stars, which were the brightest stars and those so faint he could barely see them were sixth-magnitude stars. [4]

Astronomy natural science that deals with the study of celestial objects

Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets; the phenomena also includes supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, all phenomena that originate outside Earth's atmosphere are within the purview of astronomy. A related but distinct subject is physical cosmology, which is the study of the Universe as a whole.

Hipparchus ancient Greek scholar

Hipparchus of Nicaea was a Greek astronomer, geographer, and mathematician. He is considered the founder of trigonometry but is most famous for his incidental discovery of precession of the equinoxes.

Starlight is also a notable part of personal experience and human culture, impacting a diverse range of pursuits including poetry, [5] astronomy, [2] and military strategy. [6]

Personal experience of a human being is the moment-to-moment experience and sensory awareness of internal and external events or a sum of experiences forming an empirical unity such as a period of life.

Culture societys way of life within anthropology

Culture is the social behavior and norms found in human societies. Culture is considered a central concept in anthropology, encompassing the range of phenomena that are transmitted through social learning in human societies. Cultural universals are found in all human societies; these include expressive forms like art, music, dance, ritual, religion, and technologies like tool usage, cooking, shelter, and clothing. The concept of material culture covers the physical expressions of culture, such as technology, architecture and art, whereas the immaterial aspects of culture such as principles of social organization, mythology, philosophy, literature, and science comprise the intangible cultural heritage of a society.

The United States Army spent millions of dollars in the 1950s and onward to develop a starlight scope, that could amplify starlight, moonlight filtered by clouds, and the fluorescence of rotting vegetation about 50,000 times to allow a person to see in the night. [6] In contrast to previously developed active infrared system such as sniperscope, it was a passive device and did not require additional light emission to see. [6]

United States Army Land warfare branch of the United States Armed Forces

The United States Army (USA) is the land warfare service branch of the United States Armed Forces. It is one of the seven uniformed services of the United States, and is designated as the Army of the United States in the United States Constitution. As the oldest and most senior branch of the U.S. military in order of precedence, the modern U.S. Army has its roots in the Continental Army, which was formed to fight the American Revolutionary War (1775–1783)—before the United States of America was established as a country. After the Revolutionary War, the Congress of the Confederation created the United States Army on 3 June 1784 to replace the disbanded Continental Army. The United States Army considers itself descended from the Continental Army, and dates its institutional inception from the origin of that armed force in 1775.

Fluorescence emission of light by a substance that has absorbed light or other electromagnetic radiation

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. The most striking example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, while the emitted light is in the visible region, which gives the fluorescent substance a distinct color that can be seen only when exposed to UV light. Fluorescent materials cease to glow nearly immediately when the radiation source stops, unlike phosphorescent materials, which continue to emit light for some time after.

Vegetation total of plant formations and plant communities

Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader than the term flora which refers to species composition. Perhaps the closest synonym is plant community, but vegetation can, and often does, refer to a wider range of spatial scales than that term does, including scales as large as the global. Primeval redwood forests, coastal mangrove stands, sphagnum bogs, desert soil crusts, roadside weed patches, wheat fields, cultivated gardens and lawns; all are encompassed by the term vegetation.

The average color of starlight in the observable universe is a shade of yellowish-white that has been given the name Cosmic Latte.

Observable universe A spherical part of the universe which contains all matter that can be observed from the Earth at the present time

The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects has had time to reach Earth since the beginning of the cosmological expansion. There are at least 2 trillion galaxies in the observable universe. Assuming the Universe is isotropic, the distance to the edge of the observable universe is roughly the same in every direction. That is, the observable universe has a spherical volume centered on the observer. Every location in the Universe has its own observable universe, which may or may not overlap with the one centered on Earth.

Starlight spectroscopy, examination of the stellar spectra, was pioneered by Joseph Fraunhofer in 1814. [3] Starlight can be understood to be composed of three main spectra types, continuous spectrum, emission spectrum, and absorption spectrum. [1]

Oldest starlight

One of the oldest stars yet identified (oldest not most distant in this case) was identified in 2014, the star SMSS J031300.362670839.3 was determined to be 6000 light years away but date to 13.8 billion years ago. [7] The starlight shining on Earth would include this star. [7]


Night photography includes photographing subjects that are lit primarily by starlight. [8] Directly taking images of night sky is also a part of astrophotography. [9] Like other photography, it can be used for the pursuit of science and/or leisure. [10] [11] Subjects include nocturnal animals. [9] In many cases starlight photography may also overlap with a need to understand the impact of moonlight. [9]

See also

Related Research Articles

Cygnus (constellation) constellation

Cygnus is a northern constellation lying on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. The swan is one of the most recognizable constellations of the northern summer and autumn, and it features a prominent asterism known as the Northern Cross. Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.

Spectroscopy study of the interaction between matter and electromagnetic radiation

Spectroscopy is the study of the interaction between matter and electromagnetic radiation. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, by a prism. Later the concept was expanded greatly to include any interaction with radiative energy as a function of its wavelength or frequency, predominantly in the electromagnetic spectrum, though matter waves and acoustic waves can also be considered forms of radiative energy; recently, with tremendous difficulty, even gravitational waves have been associated with a spectral signature in the context of LIGO and laser interferometry. Spectroscopic data are often represented by an emission spectrum, a plot of the response of interest as a function of wavelength or frequency.

Astrophotography specialized type of photography for recording images of astronomical objects and large areas of the night sky

Astrophotography is a specialized type of photography for recording photos of astronomical objects, celestial events, and areas of the night sky. The first photograph of an astronomical object was taken in 1840, but it was not until the late 19th century that advances in technology allowed for detailed stellar photography. Besides being able to record the details of extended objects such as the Moon, Sun, and planets, astrophotography has the ability to image objects invisible to the human eye such as dim stars, nebulae, and galaxies. This is done by long time exposure since both film and digital cameras can accumulate and sum light photons over these long periods of time.

Astronomical spectroscopy science of temporal, spatial, and spectral distributions of radiation

Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light and radio, which radiates from stars and other celestial objects. A stellar spectrum can reveal many properties of stars, such as their chemical composition, temperature, density, mass, distance, luminosity, and relative motion using Doppler shift measurements. Spectroscopy is also used to study the physical properties of many other types of celestial objects such as planets, nebulae, galaxies, and active galactic nuclei.

Astrophysics is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the astronomical objects, rather than their positions or motions in space". Among the objects studied are the Sun, other stars, galaxies, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. Because astrophysics is a very broad subject, astrophysicists apply concepts and methods from many disciplines of physics, including mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics.

Observational astronomy part of astronomical science concerned with recording data

Observational astronomy is a division of astronomy that is concerned with recording data about the observable universe, in contrast with theoretical astronomy, which is mainly concerned with calculating the measurable implications of physical models. It is the practice and study of observing celestial objects with the use of telescopes and other astronomical instruments.

Alnilam estrella supergeganta blava

Alnilam, also designated ε Orionis, and 46 Orionis, is a large blue supergiant star some 2,000 light-years distant in the constellation of Orion. It is estimated to be 275,000 to 832,000 times as luminous as the Sun, and 30–64.5 times as massive.

Sloan Digital Sky Survey multi-spectral imaging and spectroscopic redshift survey

The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project was named after the Alfred P. Sloan Foundation, which contributed significant funding.

Margaret Lindsay Huggins astronomer

Margaret Lindsay, Lady Huggins , born Margaret Lindsay Murray, was an Irish-English scientific investigator and astronomer. With her husband William Huggins she was a pioneer in the field of spectroscopy and co-authored the Atlas of Representative Stellar Spectra (1899).

Magnitude (astronomy) logarithmic measure of the brightness of a celestial object, in astronomy

In astronomy, magnitude is a unitless measure of the brightness of an object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths. An imprecise but systematic determination of the magnitude of objects was introduced in ancient times by Hipparchus.

40 Aurigae is a binary star in the constellation Auriga. Its apparent magnitude is 5.345, meaning it can just barely be seen with the naked eye. Based on parallax estimates made by the Hipparcos spacecraft, the system is located some 340 light-years away.

Westerlund 1

Westerlund 1 is a compact young super star cluster in the Milky Way galaxy, about 3.5–5 kpc away from Earth. It is one of the most massive young star clusters in the Milky Way, and was discovered by Bengt Westerlund in 1961 but remained largely unstudied for many years due to high interstellar absorption in its direction. In the future, it will probably evolve into a globular cluster.

14 Eridani is a star in the Eridanus constellation. It has an apparent visual magnitude of 6.143 and is moving closer to the Sun with a radial velocity of around −5 km/s. The measured annual parallax shift is 29.26 mas, which provides an estimated distance of about 111 light years. Proper motion studies indicate that this is an astrometric binary. The visible component has a stellar classification of F5 V Fe−0.7 CH−0.5, which indicates it has the spectrum of an F-type main-sequence star with underabundances of iron and methylidyne. The system has been detected as a source of X-ray emission.

HD 37974 star

HD 37974 a variable B[e] hypergiant in the Large Magellanic Cloud. It is surrounded by an unexpected dust disk.

Radio Objects with Continuous Optical Spectra, is a group of about 80 astrophysical objects characterized by optical spectra anomalously devoid of emission or absorption features, which makes it impossible to determine their distances and locations in relation to our galaxy. They are considered to be a subclass of blazars, and are similar in their spectral characteristics to DC-dwarfs and single stellar-mass black holes.

28 Cygni is a single star in the northern constellation of Cygnus. It is a faint blue-white hued star but visible to the naked eye with an apparent visual magnitude of 4.93. The distance to 28 Cyg, as estimated from its annual parallax shift of 5.3 mas, is around 620 light years. It has an absolute magnitude of −2.56, which means that if the star were just 10 parsecs away it would be brighter than Sirius, the brightest star in the night sky.

74 Orionis is a class F5V star in the constellation Orion. Its apparent magnitude is 5.04 and it is approximately 62.8 light years away based on parallax.


  1. 1 2 Keith Robinson – Starlight: An Introduction to Stellar Physics for Amateurs (2009) – Page 38-40 (Google Books Link)
  2. 1 2 Macpherson, Hector (1911). The romance of modern astronomy. p. 191.
  3. 1 2 J. B. Hearnshaw – The analysis of starlight: one hundred and fifty years of astronomical spectroscopy (1990) – Page 51 (Google Books link)
  4. 1 2 Astronomy. Rice University. 2016. p. 761. ISBN   1938168283- via Open Stax.
  5. Wells Hawks Skinner – Studies in literature and composition for high schools, normal schools, and ... (1897) – Page 102 (Google eBook link)
  6. 1 2 3 Popular Mechanics – Jan 1969 – "How the Army Learned to See in the Dark" by Mort Schultz (Google Books link)
  7. 1 2 "Ancient Star May Be Oldest in Known Universe".
  8. Rowell, Tony (2 April 2018). "Sierra Starlight: The Astrophotography of Tony Rowell". Heyday via Google Books.
  9. 1 2 3 Ray, Sidney (23 October 2015). "Scientific Photography and Applied Imaging". CRC Press via Google Books.
  10. Ray, Sidney (2015-10-23). Scientific Photography and Applied Imaging. CRC Press. ISBN   9781136094385.
  11. Ray, Sidney (2015-10-23). Scientific Photography and Applied Imaging. CRC Press. ISBN   9781136094385.