Astrophysical X-ray source

X-ray sourceX-ray sourcesdiffuse cosmic X-ray background
The cluster is filled with a vast cloud of 50 MK gas that radiates strongly in X rays. Chandra observed that the central galaxy is a strong, complex source of X rays. Hot X-ray emitting gas pervades the galaxy cluster MS 0735.6+7421 in Camelopardus. Two vast cavities – each 600,000 lyrs in diameter appear on opposite sides of a large galaxy at the center of the cluster. These cavities are filled with a two-sided, elongated, magnetized bubble of extremely high-energy electrons that emit radio waves. The X-ray landmark NGC 4151, an intermediate spiral Seyfert galaxy has a massive black hole in its core. A Chandra X-ray image of Sirius A and B shows Sirius B to be more luminous than Sirius A.

J band (infrared)

J bandJJ-band
In infrared astronomy, the J band refers to an atmospheric transmission window (1.1 to 1.4 um) centred on 1.25 micrometres (in the near-infrared). Betelgeuse is the brightest near-IR source in the sky with a J band magnitude of −2.99. The next brightest stars in the J band are Antares (−2.7), R Doradus (−2.6), Arcturus (−2.2), and Aldebaran (−2.1). In the J band Sirius is the 9th brightest star.

VY Canis Majoris

This demonstrates that LBVs, such as Eta Carinae, are not the only progenitors of SNe IIn or HN, but it stressed the requirement that these types of supernovae increased episodic mass loss just prior to the explosion. For a star as massive as VY CMa, the remnant would be likely a black hole rather than a neutron star. * Remote Sensing Tutorial Page A-5 archive VLT image of the surroundings of VY Canis Majoris seen with SPHERE Astronomers Map a Hypergiant Star's Massive Outbursts, HubbleSite NewsCenter, 2007-01-08. "What is the Biggest Star in the Universe?", Fraser Cain, Universe Today, published 2008-04-06, updated 13 May 2013.


Saturn's atmosphereplanetringed planet
NASA previously requested for plans to be put forward for a mission to Saturn that included an atmospheric entry probe and possible investigations into the habitability and possible discovery of life on Saturn's moons Titan and Enceladus. Saturn is the most distant of the five planets easily visible to the naked eye from Earth, the other four being Mercury, Venus, Mars and Jupiter. (Uranus and occasionally 4 Vesta are visible to the naked eye in dark skies.) Saturn appears to the naked eye in the night sky as a bright, yellowish point of light. The mean apparent magnitude of Saturn is 0.46 with a standard deviation of 0.34.

Nevil Maskelyne

MaskelyneReverend Dr Nevil MaskelyneMaskelyne, Nevil
From Maskelyne's observations Charles Hutton deduced a density for the earth 4.5 times that of water (the modern value is 5.515). Maskelyne’s first contribution to astronomical literature was A Proposal for Discovering the Annual Parallax of Sirius, published in 1760. Subsequent contributions to the Transactions contained his observations of the transits of Venus (1761 and 1769), on the tides at Saint Helena (1762), and on various astronomical phenomena at Saint Helena (1764) and at Barbados (1764).

Christiaan Huygens

HuygensHuygens, ChristiaanChristiaen Huygens
Christiaan Huygens (Hugenius; 14 April 1629 – 8 July 1695) was a Dutch physicist, mathematician, astronomer and inventor, who is widely regarded as one of the greatest scientists of all time and a major figure in the scientific revolution. In physics, Huygens made groundbreaking contributions in optics and mechanics, while as an astronomer he is chiefly known for his studies of the rings of Saturn and the discovery of its moon Titan. As an inventor, he improved the design of the telescope with the invention of the Huygenian eyepiece.

Martin Schwarzschild

Schwarzschild was renowned as a teacher and held major leadership positions in several scientific societies. In the 1980s, Schwarzschild applied his numerical skills to building models for triaxial galaxies. Dr. Schwarzschild was the Eugene Higgins Professor Emeritus of Astronomy at Princeton University, where he spent most of his professional life. *Asteroid 4463 Marschwarzschild Karl Schwarzschild Medal (1959). Henry Norris Russell Lectureship (1960). Henry Draper Medal of the National Academy of Sciences (1960). Eddington Medal (1963). Bruce Medal (1965). Rittenhouse Medal (1966). Gold Medal of the Royal Astronomical Society (1969). Brouwer Award (1992).

Kaj Aage Gunnar Strand

Kaj Strand
Kaj Aage Gunnar Strand (27 February 1907 – 31 October 2000) was a Danish astronomer who worked in Denmark and the United States. He was Scientific Director of the U.S. Naval Observatory from 1963 to 1977. He specialized in astrometry, especially work on double stars and stellar distances. Kaj Strand was born February 27, 1907 in Hellerup, Denmark, on the outskirts of Copenhagen. He entered the University of Copenhagen in 1926, majored in astronomy, and graduated in 1931 with Magister (Master's) and Candidate Magister degrees.

Peter van de Kamp

Piet van de Kampvan de Kamp, Petervan de Kamp
Van de Kamp never admitted that his claim was in error and continued to publish papers about a planetary system around Barnard's Star into the 1980s, while modern radial velocity curves place a limit on the planets much smaller than claimed by Van de Kamp. Recent evidence suggests that there is, indeed, a planet orbiting Barnard's Star, albeit of much lower mass than Van de Kamp could have detected. From the 1940s on Van de Kamp and his staff made similar claims of planetary systems around the nearby stars Lalande 21185, 61 Cygni, and many others, based on the same flawed photographic plates. All of these claims have been refuted.


lunarthe moonLuna
Understanding of the Moon's cycles was an early development of astronomy: by the 5th century BC, Babylonian astronomers had recorded the 18-year Saros cycle of lunar eclipses, and Indian astronomers had described the Moon's monthly elongation. The Chinese astronomer Shi Shen (fl. 4th century BC) gave instructions for predicting solar and lunar eclipses. Later, the physical form of the Moon and the cause of moonlight became understood. The ancient Greek philosopher Anaxagoras (d. 428 BC) reasoned that the Sun and Moon were both giant spherical rocks, and that the latter reflected the light of the former.


In the system of Greek numerals, it has a value of 1. It was derived from the Phoenician and Hebrew letter aleph - an ox or leader. Letters that arose from alpha include the Latin A and the Cyrillic letter А. In English, the noun "alpha" is used as a synonym for "beginning", or "first" (in a series), reflecting its Greek roots. In Ancient Greek, alpha was pronounced and could be either phonemically long ([aː]) or short ([a]). Where there is ambiguity, long and short alpha are sometimes written with a macron and breve today: Ᾱᾱ, Ᾰᾰ. In Modern Greek, vowel length has been lost, and all instances of alpha simply represent.

Astronomical object

celestial bodiescelestial bodycelestial object
An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms object and body are often used interchangeably. However, an astronomical body or celestial body is a single, tightly bound, contiguous entity, while an astronomical or celestial object is a complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures. Examples of astronomical objects include planetary systems, star clusters, nebulae, and galaxies, while asteroids, moons, planets, and stars are astronomical bodies.

Observational astronomy

astronomical observationobservationsobservational
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. As a science, the study of astronomy is somewhat hindered in that direct experiments with the properties of the distant universe are not possible. However, this is partly compensated by the fact that astronomers have a vast number of visible examples of stellar phenomena that can be examined.

Orbital period

periodsynodic periodsynodic
Opposition (astronomy). List of periodic comets.

Interstellar medium

interstellar gasinterstellarinterstellar matter
For example, collisional excitation of the n = 2 level of hydrogen will release a Ly-α photon upon de-excitation. In molecular clouds, excitation of rotational lines of CO is important. Once a molecule is excited, it eventually returns to a lower energy state, emitting a photon which can leave the region, cooling the cloud. Radio waves from ≈10 kHz (very low frequency) to ≈300 GHz (extremely high frequency) propagate differently in interstellar space than on the Earth's surface. There are many sources of interference and signal distortion that do not exist on Earth. A great deal of radio astronomy depends on compensating for the different propagation effects to uncover the desired signal.


astrolabesthat instrumentland astrolabes
Many astronomical clocks use an astrolabe-style display, such as the famous clock at Prague, adopting a stereographic projection (see below) of the ecliptic plane. In recent times, astrolabe watches have become popular. For example, Swiss watchmaker Dr. Ludwig Oechslin designed and built an astrolabe wristwatch in conjunction with Ulysse Nardin in 1985. Dutch watchmaker Christaan van der Klauuw also manufactures astrolabe watches today. An astrolabe consists of a disk, called the mater (mother), which is deep enough to hold one or more flat plates called tympans, or climates.

John Flamsteed

FlamsteedSir John FlamsteedFlamsteed, John
He was responsible for several of the earliest recorded sightings of the planet Uranus, which he mistook for a star and catalogued as '34 Tauri'. The first of these was in December 1690, which remains the earliest known sighting of Uranus by an astronomer. On 16 August 1680 Flamsteed catalogued a star, 3 Cassiopeiae, that later astronomers were unable to corroborate.

White dwarf

white dwarfswhite dwarf starcentral star
Astronomy Picture of the Day. NGC 2440: Cocoon of a New White Dwarf 2010 February 21. Dust and the Helix Nebula 2009 December 31. The Helix Nebula from La Silla Observatory 2009 March 3. IC 4406: A Seemingly Square Nebula 2008 July 27. A Nearby Supernova in Spiral Galaxy M100 2006 March 7. Astronomy Picture of the Day: White Dwarf Star Spiral 2005 June 1.

Cosmic dust

interstellar dustdustspace dust
Cosmic dust contains some complex organic compounds (amorphous organic solids with a mixed aromatic–aliphatic structure) that could be created naturally, and rapidly, by stars. A smaller fraction of dust in space is "stardust" consisting of larger refractory minerals that condensed as matter left by stars. Interstellar dust particles were collected by the Stardust spacecraft and samples were returned to Earth in 2006. Cosmic dust was once solely an annoyance to astronomers, as it obscures objects they wish to observe. When infrared astronomy began, the dust particles were observed to be significant and vital components of astrophysical processes.


In astronomy, declination (abbreviated dec; symbol δ) is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the celestial equator, along the hour circle passing through the point in question. The root of the word declination (Latin, declinatio) means "a bending away" or "a bending down". It comes from the same root as the words incline ("bend toward") and recline ("bend backward"). In some 18th and 19th century astronomical texts, declination is given as North Pole Distance (N.P.D.), which is equivalent to 90 - (declination).

Radio astronomy

radio astronomerradioradioastronomy
Sullivan, III, Cosmic Noise: A History of Early Radio Astronomy. Cambridge University Press, 2009. Woodruff T. Sullivan, III, Classics in Radio Astronomy. Reidel Publishing Company, Dordrecht, 1982. National Radio Astronomy Observatory. The History of Radio Astronomy * Reber Radio Telescope - National Park Services. Radio Telescope Developed - a brief history from NASA Goddard Space Flight Center. Society of Amateur Radio Astronomers. Visualization of Radio Telescope Data Using Google Earth. A general reference for radio spectrum allocations, including radio astronomy. Improving Radio Astronomy Images by Array Processing.


In astronomy, metallicity is used to describe the abundance of elements present in an object that are heavier than hydrogen or helium. Most of the physical matter in the Universe is in the form of hydrogen and helium, so astronomers use the word "metals" as a convenient short term for "all elements except hydrogen and helium". This usage is distinct from the usual physical definition of a solid metal. For example, stars and nebulae with relatively high abundances of carbon, nitrogen, oxygen, and neon are called "metal-rich" in astrophysical terms, even though those elements are non-metals in chemistry.


BoorongBoorong peopleWotjobaluk
A reanalysis of Stanbridge's material has recently led to the hypothesis that the Wergaia had registered the massive flaring or 'great eruption' of η Carinae, which they identified as collowgullouric war (a female crow and wife of war (Canopus)), and did so sometimes after 1837, and had incorporated it into their ethnoastronomical system. A few examples illustrate the intimate correlation they established between the movements of celestial bodies and the cycles of natural phenomena in their native habitat. The northern rise of Arcturus, known as Marpeankuurk signaled that it was time to harvest the larvae of a species of Carpenter ant, the wood ant are ready to be harvested.

Doppler effect

Dopplerdoppler shiftDoppler shifts
The use of the Doppler effect for light in astronomy depends on our knowledge that the spectra of stars are not homogeneous. They exhibit absorption lines at well defined frequencies that are correlated with the energies required to excite electrons in various elements from one level to another. The Doppler effect is recognizable in the fact that the absorption lines are not always at the frequencies that are obtained from the spectrum of a stationary light source. Since blue light has a higher frequency than red light, the spectral lines of an approaching astronomical light source exhibit a blueshift and those of a receding astronomical light source exhibit a redshift.

Mount Wilson Observatory

Mount WilsonMt. WilsonMount Wilson Obs.
In 1919 the 100 inch Hooker telescope was equipped with a special attachment, a 20-foot optical astronomical interferometer developed by Albert A. Michelson and Francis G. Pease. It was attached to the end of the 100 inch telescope and used the telescope as a guiding platform to maintain alignment with the stars being studied. By December 1920, Michelson and Pease were able to use the equipment to determine the precise diameter of a star, the red giant Betelgeuse, the first time the angular size of a star had ever been measured. In the next year, Michelson and Pease measured the diameters of 6 more red giants before reaching the resolution limit of the 20 foot beam interferometer.