Earth

terrestrialworldGlobal
The standard astronomical symbol of Earth consists of a cross circumscribed by a circle, representing the four corners of the world. Human cultures have developed many views of the planet. Earth is sometimes personified as a deity. In many cultures it is a mother goddess that is also the primary fertility deity, and by the mid-20th century, the Gaia Principle compared Earth's environments and life as a single self-regulating organism leading to broad stabilization of the conditions of habitability. Creation myths in many religions involve the creation of Earth by a supernatural deity or deities.

Orion (constellation)

OrionOrion constellationconstellation of Orion
By extending the line of the Belt southeastward, Sirius (α CMa) can be found; northwestward, Aldebaran (α Tau). A line eastward across the two shoulders indicates the direction of Procyon (α CMi). A line from Rigel through Betelgeuse points to Castor and Pollux (α Gem and β Gem). Additionally, Rigel is part of the Winter Circle asterism. Sirius and Procyon, which may be located from Orion by following imaginary lines (see map), also are points in both the Winter Triangle and the Circle. Orion's seven brightest stars form a distinctive hourglass-shaped asterism, or pattern, in the night sky.

Astrometry

astrometricastrometricalastrometrist
He made the first measurement of stellar parallax: 0.3 arcsec for the binary star 61 Cygni. Being very difficult to measure, only about 60 stellar parallaxes had been obtained by the end of the 19th century, mostly by use of the filar micrometer. Astrographs using astronomical photographic plates sped the process in the early 20th century. Automated plate-measuring machines and more sophisticated computer technology of the 1960s allowed more efficient compilation of star catalogues. In the 1980s, charge-coupled devices (CCDs) replaced photographic plates and reduced optical uncertainties to one milliarcsecond.

John Herschel

Sir John HerschelJohnHerschel
This was to be a completion as well as extension of the survey of the northern heavens undertaken initially by his father William Herschel. He arrived in Cape Town on 15 January 1834 and set up a private 21 ft telescope at Feldhausen at Claremont, a suburb of Cape Town. Amongst his other observations during this time was that of the return of Comet Halley. Herschel collaborated with Thomas Maclear, the Astronomer Royal at the Cape of Good Hope and the members of the two families became close friends. During this time, he also witnessed the Great Eruption of Eta Carinae (December, 1837).

Procyon

Procyon Aα CMiCanis minor
Procyon is the eighth-brightest star in the night sky, culminating at midnight on January 14. It forms one of the three vertices of the Winter Triangle asterism, in combination with Sirius and Betelgeuse. The prime period for evening viewing of Procyon is in late winter in the northern hemisphere. It has a color index of 0.42, and its hue has been described as having a faint yellow tinge to it. Procyon is a binary star system with a bright primary component, Procyon A, having an apparent magnitude of 0.34, and a faint companion, Procyon B, at magnitude 10.7. The pair orbit each other with a period of 40.82 years along an elliptical orbit with an eccentricity of 0.407.

Table of stars with Bayer designations

This table lists those stars or other objects which have Bayer designations by the constellation in which those stars or objects lie. The name given is that of the article if it does not reflect the Bayer designation (e.g. Aldebaran instead of Alpha Tauri). Abbreviations are used in other cases.

Vega

2828constellation of VegaWhānui
Vega, also designated Alpha Lyrae (α Lyrae, abbreviated Alpha Lyr or α Lyr), is the brightest star in the constellation of Lyra, the fifth-brightest star in the night sky, and the second-brightest star in the northern celestial hemisphere, after Arcturus. It is relatively close at only 25 light-years from the Sun, and, together with Arcturus and Sirius, one of the most luminous stars in the Sun's neighborhood. Vega has been extensively studied by astronomers, leading it to be termed “arguably the next most important star in the sky after the Sun”. Vega was the northern pole star around 12,000 BC and will be so again around the year 13,727, when the declination will be +86°14'.

Parallax

solar parallaxmotion parallaxtrigonometric parallax
The first successful measurements of stellar parallax were made by Friedrich Bessel in 1838 for the star 61 Cygni using a heliometer. Stellar parallax remains the standard for calibrating other measurement methods. Accurate calculations of distance based on stellar parallax require a measurement of the distance from the Earth to the Sun, now based on radar reflection off the surfaces of planets. The angles involved in these calculations are very small and thus difficult to measure. The nearest star to the Sun (and thus the star with the largest parallax), Proxima Centauri, has a parallax of 0.7687 ± 0.0003 arcsec.

List of brightest stars and other record stars

This is a list of the brightest stars together with record holders of other categories with many details in compact form that can be compared. The brightest stars are completely listed until apparent magnitude of 2 including Polaris. Some record holders, like the nearest star, the largest star, the most luminous star of the Milky Way etc. are added to the list. The main purpose for this list is the possibility to compare stars of different categories, like to compare the most luminous known star R136a1 with the brightest star of our sky Sirius, which is not possible with the existing lists in Lists of stars. For multiple values from different sources the average value is displayed.

Absolute magnitude

bolometric magnitudeabsolute magnitude (H)absolute visual magnitude
An object's absolute bolometric magnitude represents its total luminosity over all wavelengths, rather than in a single filter band, as expressed on a logarithmic magnitude scale. To convert from an absolute magnitude in a specific filter band to absolute bolometric magnitude, a bolometric correction is applied. For Solar System bodies that shine in reflected light, a different definition of absolute magnitude (H) is used, based on a standard reference distance of one astronomical unit. In stellar and galactic astronomy, the standard distance is 10 parsecs (about 32.616 light-years, 308.57 petameters or 308.57 trillion kilometres).

Table of stars with Flamsteed designations

If the star has a Greek-letter Bayer designation this is used in preference except where such designation contains an extra attached number; for example, "Rho-1 Cancri" is less common than "55 Cancri". List of constellations. Table of stars with Bayer designations.

Supernova

supernovaesupernovastype II supernova
A number of close or well known stars have been identified as possible core collapse supernova candidates: the red supergiants Antares and Betelgeuse; the yellow hypergiant Rho Cassiopeiae; the luminous blue variable Eta Carinae that has already produced a supernova impostor; and the brightest component, a Wolf–Rayet star, in the Regor or Gamma Velorum system, Others have gained notoriety as possible, although not very likely, progenitors for a gamma-ray burst; for example WR 104. Identification of candidates for a Type Ia supernova is much more speculative. Any binary with an accreting white dwarf might produce a supernova although the exact mechanism and timescale is still debated.

Timeline of the far future

far future40,000 yearsfar-future
Current data suggest that the universe has a flat geometry (or very close to flat), and thus will not collapse in on itself after a finite time, and the infinite future allows for the occurrence of a number of massively improbable events, such as the formation of Boltzmann brains. The timelines displayed here cover events from the beginning of the 11th millennium to the furthest reaches of future time. A number of alternative future events are listed to account for questions still unresolved, such as whether humans will become extinct, whether protons decay, and whether the earth survives when the sun expands to become a red giant.

Proper motion

proper motionsproper-motionhigh proper motion star
Measurements were made of the radial motion of objects in that galaxy moving directly toward and away from us, and assuming this same motion to apply to objects with only a proper motion, the observed proper motion predicts a distance to the galaxy of 7.2 Mpc. Proper motion was suspected by early astronomers (according to Macrobius, AD 400) but a proof was not provided until 1718 by Edmund Halley, who noticed that Sirius, Arcturus and Aldebaran were over half a degree away from the positions charted by the ancient Greek astronomer Hipparchus roughly 1850 years earlier.

Variable star

variablevariable starsvariability
Society for Popular Astronomy – Variable Star Section.

Star system

multiple star systemmultiple systemstriple star
The orbits of the stars are oriented in such a way that all three stars eclipse each other. Capella, a pair of giant stars orbited by a pair of red dwarfs, around 42 light years away from the Solar System. It has an apparent magnitude of around −0.47, making Capella one of the brightest stars in the night sky. 4 Centauri. Mizar is often said to have been the first binary star discovered when it was observed in 1650 by Giovanni Battista Riccioli, p. 1 but it was probably observed earlier, by Benedetto Castelli and Galileo. Later, spectroscopy of its components Mizar A and B revealed that they are both binary stars themselves. HD 98800.

Egyptian astronomy

EgyptianEgyptian astronomersEgyptians
Astronomy played a considerable part in religious matters for fixing the dates of festivals and determining the hours of the night. The titles of several temple books are preserved recording the movements and phases of the sun, moon and stars. The rising of Sirius (Egyptian: Sopdet, Greek: Sothis) at the beginning of the inundation was a particularly important point to fix in the yearly calendar. One of the most important Egyptian astronomical texts was the Book of Nut, going back to the Middle Kingdom or earlier. The death of a king had a strong connection to the stars for Ancient Egyptians. They believed once a king was deceased, their soul would rise to the heavens and become a star.

Astrology

astrologerastrologicalastrologers
Major astronomers including Tycho Brahe, Johannes Kepler and Galileo practised as court astrologers. Astrological references appear in literature in the works of poets such as Dante Alighieri and Geoffrey Chaucer, and of playwrights such as Christopher Marlowe and William Shakespeare. Throughout most of its history, astrology was considered a scholarly tradition. It was accepted in political and academic contexts, and was connected with other studies, such as astronomy, alchemy, meteorology, and medicine. At the end of the 17th century, new scientific concepts in astronomy and physics (such as heliocentrism and Newtonian mechanics) called astrology into question.

Planetarium

planetariaplanetarium experienceoptical-mechanical projector
A planetarium (plural planetaria or planetariums) is a theatre built primarily for presenting educational and entertaining shows about astronomy and the night sky, or for training in celestial navigation. A dominant feature of most planetaria is the large dome-shaped projection screen onto which scenes of stars, planets, and other celestial objects can be made to appear and move realistically to simulate the complex 'motions of the heavens'. The celestial scenes can be created using a wide variety of technologies, for example precision-engineered 'star balls' that combine optical and electro-mechanical technology, slide projector, video and fulldome projector systems, and lasers.

History of astronomy

astronomyhistorian of astronomyEuropean influence
Astronomy played a considerable part in religious matters for fixing the dates of festivals and determining the hours of the night. The titles of several temple books are preserved recording the movements and phases of the sun, moon and stars. The rising of Sirius (Egyptian: Sopdet, Greek: Sothis) at the beginning of the inundation was a particularly important point to fix in the yearly calendar. Writing in the Roman era, Clement of Alexandria gives some idea of the importance of astronomical observations to the sacred rites: And after the Singer advances the Astrologer, with a horologium in his hand, and a palm, the symbols of astrology.

Mercury (planet)

Mercuryplanet MercuryMercurio
The Maya may have represented Mercury as an owl (or possibly four owls; two for the morning aspect and two for the evening) that served as a messenger to the underworld. In medieval Islamic astronomy, the Andalusian astronomer Abū Ishāq Ibrāhīm al-Zarqālī in the 11th century described the deferent of Mercury's geocentric orbit as being oval, like an egg or a pignon, although this insight did not influence his astronomical theory or his astronomical calculations. In the 12th century, Ibn Bajjah observed "two planets as black spots on the face of the Sun", which was later suggested as the transit of Mercury and/or Venus by the Maragha astronomer Qotb al-Din Shirazi in the 13th century.

Johann Bayer

Bayer Johann BayerBayer, Johann
The Uranometria introduced a new system of star designation which has become known as the Bayer designation. Bayer's atlas included twelve new constellations invented a few years earlier to fill in the far south of the night sky, which was unknown to ancient Greece and Rome. The crater Bayer on the Moon is named after him. * Full digital facsimile, Linda Hall Library Julius Schiller. Bayer designation.

Hydrogen

HH 2 hydrogen gas
They are the source of the important 21 cm hydrogen line in astronomy at 1420 MHz. Hydrogen has three naturally occurring isotopes, denoted, and. Other, highly unstable nuclei ( to ) have been synthesized in the laboratory but not observed in nature. Hydrogen is the only element that has different names for its isotopes in common use today. During the early study of radioactivity, various heavy radioactive isotopes were given their own names, but such names are no longer used, except for deuterium and tritium.

Aldebaran

Alpha Tauribrightest starAldeberan
Past this radius, the modest outflow of the stellar wind itself declines in temperature to about 7,500 K at a distance of 1 Astronomical Unit (AU)−the distance of the Earth from the Sun. The wind continues to expand until it reaches the termination shock boundary with the hot, ionized interstellar medium that dominates the Local Bubble, forming a roughly spherical astrosphere with a radius of around 1,000 AU, centered on Aldebaran. Aldebaran is one of the easiest stars to find in the night sky, partly due to its brightness and partly due to its spatial relation to one of the more noticeable asterisms in the sky.

Kelvin

KkelvinsmK
Colour temperature is based upon the principle that a black body radiator emits light whose colour depends on the temperature of the radiator. Black bodies with temperatures below about 4000 K appear reddish, whereas those above about 7500 K appear bluish. Colour temperature is important in the fields of image projection and photography, where a colour temperature of approximately 5600 K is required to match "daylight" film emulsions. In astronomy, the stellar classification of stars and their place on the Hertzsprung–Russell diagram are based, in part, upon their surface temperature, known as effective temperature.