Beta Orionisβ Ori (Rigel)β Orionis
In the southern hemisphere, Rigel is the first bright star of Orion visible as the constellation rises. The star is a vertex of the "Winter Hexagon", an asterism that includes Aldebaran, Capella, Pollux, Procyon, and Sirius. Rigel is a prominent equatorial navigation star, being easily located and readily visible in all the world's oceans (the exception is the area within 8° of the North Pole). Rigel's spectral type is a defining point of the classification sequence for supergiants.


Procyon BProcyon ACanis minor
Procyon is the brightest object in the constellation of Canis Minor and usually the eighth-brightest star in the night sky with a visual apparent magnitude of 0.34. It has the Bayer designation α Canis Minoris, which is Latinised to Alpha Canis Minoris, and abbreviated α CMi or Alpha CMi, respectively. As determined by the European Space Agency Hipparcos astrometry satellite, this system lies at a distance of just 11.46 ly, and is therefore one of Earth's nearest stellar neighbours. A binary star system, Procyon consists of a white-hued main-sequence star of spectral type F5 IV–V, designated component A, in orbit with a faint white dwarf companion of spectral type DQZ, named Procyon B.

International Astronomical Union

IAUWorking Group for Planetary System NomenclatureInternational Astronomical Union (IAU)
List of proper names of stars. Planetary nomenclature. XXVIth General Assembly 2006. XXVIIth General Assembly 2009. XXVIIIth General Assembly 2012. XXIXth General Assembly 2015. XXXth General Assembly 2018.

Babylonian star catalogues

Babylonian zodiacearliest known star cataloguesMUL
Babylonian astronomy collated earlier observations and divinations into sets of Babylonian star catalogues, during and after the Kassite rule over Babylonia. These star catalogues, written in cuneiform script, contained lists of constellations, individual stars, and planets. The constellations were probably collected from various other sources. The earliest catalogue, Three Stars Each, mentions stars of Akkad, of Amurru, of Elam and others. Various sources have theorized a Sumerian origin for these Babylonian constellations, but an Elamite origin has also been proposed.


HipparchosHipparchus of NicaeaHipparchus of Nicea
Hipparchus wrote a commentary on the Arateia – his only preserved work – which contains many stellar positions and times for rising, culmination, and setting of the constellations, and these are likely to have been based on his own measurements. Hipparchus made his measurements with an armillary sphere, and obtained the positions of at least 850 stars. It is disputed which coordinate system(s) he used. Ptolemy's catalog in the Almagest, which is derived from Hipparchus's catalog, is given in ecliptic coordinates.

Johann Bayer

Bayer Johann BayerBayer, Johann
Bayer is most famous for his star atlas Uranometria Omnium Asterismorum ("Uranometry of all the asterisms"), which was first published in 1603 in Augsburg and dedicated to two prominent local citizens. This was the first atlas to cover the entire celestial sphere. It was based upon the work of Tycho Brahe and may have borrowed from Alessandro Piccolomini's 1540 star atlas, De le stelle fisse ("Of the fixed stars"), although Bayer included an additional 1,000 stars. The Uranometria introduced a new system of star designation which has become known as the Bayer designation.


lunarthe MoonLuna
The Moon is exceptionally large relative to Earth: Its diameter is more than a quarter and its mass is 1/81 of Earth's. It is the largest moon in the Solar System relative to the size of its planet, though Charon is larger relative to the dwarf planet Pluto, at 1/9 Pluto's mass. The Earth and the Moon's barycentre, their common center of mass, is located 1700 km (about a quarter of Earth's radius) beneath Earth's surface. The Earth revolves around the Earth-Moon barycentre once a sidereal month, with 1/81 the speed of the Moon, or about 12.5 m per second. This motion is superimposed on the much larger revolution of the Earth around the Sun at a speed of about 30 km per second.


galaxiesgalacticgalactic nuclei
The current era of star formation is expected to continue for up to one hundred billion years, and then the "stellar age" will wind down after about ten trillion to one hundred trillion years (10 13 –10 14 years), as the smallest, longest-lived stars in our universe, tiny red dwarfs, begin to fade. At the end of the stellar age, galaxies will be composed of compact objects: brown dwarfs, white dwarfs that are cooling or cold ("black dwarfs"), neutron stars, and black holes. Eventually, as a result of gravitational relaxation, all stars will either fall into central supermassive black holes or be flung into intergalactic space as a result of collisions.

Fixed stars

fixed starfixedstars
However, fixed stars do have parallax, which is a change in apparent position caused by the orbital motion of the Earth. This effect was small enough not to be accurately measured until the 19th century. It can be used to find the distance to nearby stars. This motion is only apparent; it is the Earth that moves. The fixed stars exhibit real motion as well, however. This motion may be viewed as having components that consist in part of motion of the galaxy to which the star belongs, in part of rotation of that galaxy, and in part of motion peculiar to the star itself within its galaxy.


luminousbolometric luminosityluminosities
Some such as the UBV or Johnson system are defined against photometric standard stars, while others such as the AB system are defined in terms of a spectral flux density. A star's luminosity can be determined from two stellar characteristics: size and effective temperature. The former is typically represented in terms of solar radii, R ⊙, while the latter is represented in kelvins, but in most cases neither can be measured directly. To determine a star's radius, two other metrics are needed: the star's angular diameter and its distance from Earth.

Celestial pole

North Celestial Polesouth celestial polecelestial north pole
In about 5,500 years, the pole will have moved near the position of the star Alderamin (Alpha Cephei), and in 12,000 years, Vega (Alpha Lyrae) will become the "North Star", though it will be about six degrees from the true north celestial pole. To find Polaris, from a point in the Northern Hemisphere, face north and locate the Big Dipper (Plough) and Little Dipper asterisms. Looking at the "cup" part of the Big Dipper, imagine that the two stars at the outside edge of the cup form a line pointing upward out of the cup. This line points directly at the star at the tip of the Little Dipper's handle. That star is Polaris, the North Star.

Open cluster

open star clusterstar clusteropen clusters
The most massive stars have begun to evolve away from the main sequence and are becoming red giants; the position of the turn-off from the main sequence can be used to estimate the age of the cluster. Because the stars in an open cluster are all at roughly the same distance from Earth, and were born at roughly the same time from the same raw material, the differences in apparent brightness among cluster members is due only to their mass. This makes open clusters very useful in the study of stellar evolution, because when comparing one star to another, many of the variable parameters are fixed.


Between the stars lies the interstellar medium, a region of sparse matter. In the densest regions, molecular clouds of molecular hydrogen and other elements create star-forming regions. These begin as a compact pre-stellar core or dark nebulae, which concentrate and collapse (in volumes determined by the Jeans length) to form compact protostars. As the more massive stars appear, they transform the cloud into an H II region (ionized atomic hydrogen) of glowing gas and plasma. The stellar wind and supernova explosions from these stars eventually cause the cloud to disperse, often leaving behind one or more young open clusters of stars.


Stars and Planets Guide, Collins, London. ISBN: 978-0-00-725120-9. Princeton University Press, Princeton. ISBN: 978-0-691-13556-4. The Javanese people of Indonesia call this constellation Banyakangrem ("the brooded swan") or Kalapa Doyong ("leaning coconut tree") due to the shape similarity. In Hawaii, Scorpius is known as the demigod Maui's Fishhook or Ka Makau Nui o Māui (meaning the Big Fishhook of Māui) and the name of fishhook was Manaiakalani. Scorpius was divided into two asterisms which were used by Bugis sailors for navigation. The northern part of Scorpius (α, β, γ or σ Lib, δ, ε, ζ, μ, σ and τ Scorpii) was called bintoéng lambarué, meaning "skate stars".

Brocchi's Cluster

CoathangerCollinder 399
The asterism is best seen in July–August and north of 20° north latitude it is displayed upside down (as in the picture top right of this page) when it is at its highest point. South of this latitude it is shown upright as the 'hanger' is south of the line of 6 stars. The asterism and its immediate surroundings are a useful gauge for determining the faintest stars visible in a small telescope as there are a wide range of stellar magnitudes within the cluster easily viewed in one small location of the sky. The following is a list of the 10 stars commonly included as members of the Coathanger, organized by right ascension.


1603Uranometria atlasUranometria Omnium Asterismorum
Bayer took the southern star positions and constellation names for the 49th plate from the catalog of Dutch navigator Pieter Dirkszoon Keyser, who corrected the older observations of Amerigo Vespucci and Andrea Corsali, as well as the report of Pedro de Medina. Uranometria contains many more stars than did any previous star atlas, though the exact number is disputed as not all stars on the charts are labeled. Each of the constellations' stars are overlain on an engraved image of the subject of the constellation. For reasons unknown, many of the human constellations are engraved as figures seen from behind whereas they had traditionally been rendered as facing the Earth.

Australian Aboriginal astronomy

Aboriginal AstronomyKungkarungkaraSeven Sisters
Aboriginal calendars tend differ from European calendars: many groups in northern Australia use a calendar with six seasons, and some groups mark the seasons by the stars which are visible during them. For the Pitjantjatjara, for example, the rising of the Pleiades at dawn (in May) marks the start of winter. Many stories exist where the heliacal rising or setting of stars or constellations are used to tell Aboriginal Australians when it is time to move to a new place and/or look for a new food source. The Boorong people in Victoria know that when the Malleefowl constellation (Lyra) disappears in October, to "sit with the Sun", it is time to start gathering her eggs on Earth.

Star Names

Richard Hinckley AllenStar Names: Their Lore and MeaningR. H. Allen
There is no direct modern equivalent, although Ian Ridpath deals with traditional Greek and Roman constellation mythology, while Short Guide to Modern Star Names by Paul Kunitzsch and Tim Smart (Otto Harrassowitz, 1986) is an authoritative source on the origin of star names. *History of the constellations * Allen's Star Names at LacusCurtius


Southern CrossSouthern Cross constellationCrux Australis
Crux is a constellation centred on four stars in the southern sky in a bright portion of the Milky Way. It is among the most easily distinguished constellations as its hallmark (asterism) stars each have an apparent visual magnitude brighter than +2.8, even though it is the smallest of all 88 modern constellations. Its name is Latin for cross, and it is dominated by a cross-shaped or kite-like asterism that is commonly known as the Southern Cross. Predominating the constellation is the first-magnitude blue-white star of α Crucis (Acrux), its brightest and most southerly member.

Ancient Greek astronomy

Greek astronomyGreek astronomerastronomy
the constellation Boötes. the star cluster Hyades. the constellation Orion. the star cluster Pleiades. Sirius, the Dog Star. the constellation Ursa Major. 1) Moon. 2) Mercury. 3) Venus. 4) Sun. 5) Mars. 6) Jupiter. 7) Saturn. 8) Fixed stars. Aglaonice. Anaxagoras. Archimedes. Archytas. Aristaeus. Aristarchus. Aristyllus. Conon of Samos. Democritus. Empedocles. Heraclides Ponticus. Hicetas. Hippocrates of Chios. Macrobius. Martianus Capella. Menelaus of Alexandria (Menelaus theorem). Meton of Athens. Parmenides. Porphyry. Posidonius. Proclus. Thales. Theodosius of Bithynia. Antikythera mechanism. Greek mathematics. History of astronomy. Babylonian influence on Greek astronomy.

United States

In soccer, the country hosted the 1994 FIFA World Cup, the men's national soccer team qualified for ten World Cups and the women's team has won the FIFA Women's World Cup four times; Major League Soccer is the sport's highest league in the United States (featuring 21 American and 3 Canadian teams). The market for professional sports in the United States is roughly $69 billion, roughly 50% larger than that of all of Europe, the Middle East, and Africa combined.

Circumpolar constellation

circumpolarcircumpolar starsconstellation which takes in the southern pole
In astronomy, a circumpolar constellation is a constellation (group of stars) that never sets below the horizon, as viewed from a location on Earth. Due to Earth's rotation and axial tilt with respect to the Sun, the stars and constellations can be divided into two categories. Those stars and constellations that never rise or set are called circumpolar. The rest are divided into seasonal stars and constellations. The stars and constellations that are circumpolar depends on the observer's latitude. In the Northern Hemisphere, certain stars and constellations will always be visible in the northern circumpolar sky.

Gamma Pegasi

γ PegAlgenibγ
Gamma Pegasi (γ Pegasi, abbreviated Gamma Peg or γ Peg), formally named Algenib, is a star in the constellation of Pegasus, located at the southeast corner of the asterism known as the Great Square. The average apparent visual magnitude of +2.84 puts this at fourth place among the brightest stars in the constellation. The distance to this star has been measured using the parallax technique, yielding a value of roughly 390 ly with a margin of error of 5%. Gamma Pegasi is the star's Bayer designation. Although it also had the traditional name Algenib, this name was also used for Alpha Persei.

Alpha Pegasi

α PegMarkabα
Alpha Pegasi (α Pegasi, abbreviated Alpha Peg, α Peg), formally named Markab, is the third-brightest star in the constellation of Pegasus and one of the four stars in the asterism known as the Great Square of Pegasus. α Pegasi (Latinised to Alpha Pegasi) is the star's Bayer designation. It bore the traditional name Markab (or Marchab), which derived from an Arabic word مركب markab "the saddle of the horse", or is mistranscription of Mankib, which itself comes from an Arabic phrase منكب الفرس Mankib al-Faras "(the Star of) the Shoulder (of the Constellation) of the Horse" for Beta Pegasi.


α VirAzimechAlaezel
In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Spica for this star. It is now so entered in the IAU Catalog of Star Names. In Chinese, 角宿 (Jiǎo Xiù), meaning Horn (asterism), refers to an asterism consisting of Spica and ζ Virginis. Consequently, the Chinese name for Spica is 角宿一 (Jiǎo Xiù yī, the First Star of Horn). In Hindu astronomy, Spica corresponds to the Nakshatra Chitrā.