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Derek Haselden - Astronomical Glossary
Category: Meteorology and astronomy > Astronomy
Date & country: 05/11/2007, UK
Words: 797


The Scorpion
The constellation Scorpius. Genitive name: Scorpii. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

The Sculptor
The constellation Sculptor. Genitive name: Sculptoris. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

The Sea-Goat
The constellation Capricornus. Genitive name: Capricorni. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Serpent
The constellation Serpens. Genitive name: Serpentis. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Serpent-Holder
The constellation Ophiuchus. Genitive name: Ophiuchi. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Sextant
The constellation Sextans. Genitive name: Sextantis. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Shield
The constellation Scutum. Genitive name: Scuti. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Small Water-Snake Hydri
The constellation Hydrus. Genitive name: Hyi. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

The Smaller Lion
The constellation Leo Minor. Genitive name: Leonis Minoris. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Southern Crown
The constellation Corona Australis. Genitive name: Coronae Australis. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

The Southern Fish
The constellation Pisces Australis. Genitive name: Piscis Australis. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Stern
The constellation Puppis. Genitive name: Puppis. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

The Swan
The constellation Cygnus. Genitive name: Cygni. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Table (Mountain)
The constellation Mensa. Genitive name: Mensae. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

The Telescope
The constellation Telescopium. Genitive name: Telescopii. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

The Toucan
The constellation Tucana. Genitive name: Tucanae. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

The Triangle
The constellation Triangulum. Genitive name: Trianguli. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Twins
The constellation Gemini. Genitive name: Geminorium. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Unicorn
The constellation Monoceros. Genitive name: Monocerotis. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Virgin
The constellation Virgo. Genitive name: Virginis. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Water Bearer
The constellation Aquarius. Genitive name: Aquarii. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Water-Snake
The constellation Hydra. Genitive name: Hydrae. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Whale
The constellation Cetus. Genitive name: Ceti. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

The Wolf
The constellation Lupus. Genitive name: Lupi. Visibility: Parts visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Thebe
Satellite of the planet Jupiter. See TABLE 7. JUPITER - SATELLITE DATA

Themis
One of the `minor planets` of our solar system. Discovered by De Gasparis on 5 Apr 1853. Diameter in km: 228. More data in TABLE 13. THE MINOR PLANETS

Themisto
Satellite of the planet Jupiter. See TABLE 7. JUPITER - SATELLITE DATA

Thetis
One of the `minor planets` of our solar system. Discovered by Luther on 17 Apr 1852. Diameter in km: 98. More data in TABLE 13. THE MINOR PLANETS

Thrym
Satellite of the planet Saturn. See TABLE 8. SATURN - SATELLITE DATA

Thyone
Satellite of the planet Jupiter. See TABLE 7. JUPITER - SATELLITE DATA

Titan
Satellite of the planet Saturn. See TABLE 8. SATURN - SATELLITE DATA

Titania
Satellite of the planet Uranus. See TABLE 9. URANUS - SATELLITE DATA

Topocentric
Meaning: As seen from the surface of the Earth. Most celestial co-ordinates used are topocentric.

TrA
The constellation Triangulum Australis The Southern Triangle Trianguli Australis. Genitive name: 110. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Transit
(1). The passage of a body across the observer's meridian. (2). The passage of Mercury or Venus across the face of the Sun.

Trianguli
The constellation Triangulum. English name: The Triangle. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Triangulum
English name: The Triangle. Genitive name: Trianguli. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Trinculo
Satellite of the planet Uranus. See TABLE 9. URANUS - SATELLITE DATA

Triton
Satellite of the planet Neptune. See TABLE 10. NEPTUNE - SATELLITE DATA

Troposphere
The lowest layer of the Earth's atmosphere, lying at an average height of up to 11km (6.5 miles). Above the troposphere lies the stratosphere, above that the ionosphere, above that the exosphere. In the troposphere the temperature drops steadily except for localised layers of temperture inversion.

Tsuchinshan 1
A comet in our solar system with an orbital period of 6.67years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Tsuchinshan 2
A comet in our solar system with an orbital period of 6.82years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Tucana
English name: The Toucan. Genitive name: Tucanae. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Tucanae
The constellation Tucana. English name: The Toucan. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Tuttle
A comet in our solar system with an orbital period of 13.5years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Tuttle-Giacobini-Kresak
A comet in our solar system with an orbital period of 5.46years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Twilight
By astronomical definition, the state of the sky when the Sun is below the horizon but by no more than 18 degrees.

Ultraviolet
Electromagnetic radiation with a wavelength shorter than visible light but longer than X-rays.

Umbra
(1). The darkest part of the shadow cast by Earth into space. (2). The darker portion of a sunspot.

Umbriel
Satellite of the planet Uranus. See TABLE 9. URANUS - SATELLITE DATA

Universal Time (UT, UTC)
Co-ordinated Universal Time. The time standard by which Greenwich Mean Time became known as for scientific purposes in 1928. UTC is the time given by broadcast time since 1972. The time-scale is widely known as Greenwich Mean Time but astronomically speaking the term GMT is no longer used.

Urania
One of the `minor planets` of our solar system. Discovered by Hind on 22 Jul 1854. Diameter in km: 94. More data in TABLE 13. THE MINOR PLANETS

Uranus
SOLAR SYSTEM - PLANETARY ORBITAL DATA
Average dist.from Sun (AU) - 19.191
Min. distance from Sun (AU) - 18.286
Max. distance from Sun (AU) - 20.096
Eccentricity of orbit - 0.047
Inclination to ecliptic(°) - 0.77
SOLAR SYSTEM - PLANETARY PERIODS AND MOTIONS
Sidereal period (days or years) - 84.017 y
Mean orbital velocity(km/sec.) - 6.84
Sidereal period of axial rotation - 17.240 h (R)
Inclination of equator to ecliptic(°) - 97.86
SOLAR SYSTEM - PLANETARY PHYSICAL DATA
Equatorial dia.(km) - 51 118
Polar dia.(km) - 49 946
Mass (Earth=1) - 14.50
Volume (Earth=1) - 63.0
Oblateness (Earth=1) - 0.023
Surface gravity (Water=1) - 0.889
Density - 1.30

Ursa Major
English name: The Great Bear. Genitive name: Ursae Majoris. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Ursa Minor
English name: The Little Bear. Genitive name: Ursae Minoris. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Ursae Majoris
The constellation Ursa Major. English name: The Great Bear. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Ursae Minoris
The constellation Ursa Minor. English name: The Little Bear. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Ursids
Meteor shower. Most active day is Dec.22. Weak shower.

Vaisala 1
A comet in our solar system with an orbital period of 10.9years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Van Biesbroeck
A comet in our solar system with an orbital period of 12.4years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Variable stars
A star that varies in brightness over a period of time. There are many types of variable stars, some vary over hundreds of days while other display minute variation over a matter of minutes. Another demarkation of variable stars is extrinsic, and intrinsic. Extrinsic variable are not true variables, their fluctuations are caused by eclipse events as in an eclipsing variable. Intrinsic variable are true variables. Their fluctuations are due to physical processes taking place in the stars themselves.

Vela
English name: The Sails. Genitive name: Velorum. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Velorum
The constellation Vela. English name: The Sails. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Venus
SOLAR SYSTEM - PLANETARY ORBITAL DATA
Average dist.from Sun (AU) - 0.723
Min. distance from Sun (AU) - 0.718
Max. distance from Sun (AU) - 0.728
Eccentricity of orbit - 0.007
Inclination to ecliptic(°) - 3.39
SOLAR SYSTEM - PLANETARY PERIODS AND MOTIONS
Sidereal period (days or years) - 224.701 d
Mean orbital velocity(km/sec.) - 35.02
Sidereal period of axial rotation - 243.019 d (R)
Inclination of equator to ecliptic(°) - 177.36
SOLAR SYSTEM - PLANETARY PHYSICAL DATA
Equatorial dia.(km) - 12 104
Polar dia.(km) - 12 104
Mass (Earth=1) - 0.82
Volume (Earth=1) - 0.86
Oblateness (Earth=1) - 0
Surface gravity (Water=1) - 0.907
Density - 5.24

Vesta
One of the `minor planets` of our solar system. Discovered by Olbers on 29 Mar 1807. Diameter in km: 576. More data in TABLE 13. THE MINOR PLANETS

Victoria
One of the `minor planets` of our solar system. Discovered by Hind on 13 Sep 1850. Diameter in km: 136. More data in TABLE 13. THE MINOR PLANETS

Virginia
One of the `minor planets` of our solar system. Discovered by Ferguson on 4 Oct 1857. Diameter in km: ±88. More data in TABLE 13. THE MINOR PLANETS

Virginids
Meteor shower. Most active day is Apr.10. 2 most prominent radiants of several in Virgo, active Mar. to Apr. Slow, long paths.

Virginis
The constellation Virgo. English name: The Virgin. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Virgo
English name: The Virgin. Genitive name: Virginis. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Visual (or Apparent) magnitude
The apparent brightness of a celestial object. The lower the magnitude, the less bright the object. Thus, the Sun has an apparent magnitude of -27; the Moon up to -12; Venus up to -4; the brightest stars -1; the faintest stars visible to the naked-eye +6, the faintest objects yet detected about +30. For mainly historical reasons the magnitude scale has the peculiar attribute of having brighter objects at negative values and vice-versa. (See also Absolute magnitude and Magnitude.)

Volans
English name: The Flying Fish. Genitive name: Volantis. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Volantis
The constellation Volans. English name: The Flying Fish. Visibility: Never visible from the UK. See TABLE 20: THE CONSTELLATIONS.

Volume
The amount of space occupied by a body or fluid.

Vulpecula
English name: The Fox. Genitive name: Vulpeculae. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Vulpeculae
The constellation Vulpecula. English name: The Fox. Visibility: Visible from the UK See TABLE 20: THE CONSTELLATIONS.

Wavelength
The distance between a given point on one wave to the same point on the next wave.

Weight
The 'heaviness' of an object, the amount of attraction between two or more masses. Weight is often measured in Kilogrammes but the proper (SI) unit of weight is the Newton. Weight is not the same as mass which is a measure of how much matter or inertia an object has. Weight on the other hand is dependant on two or more masses and is a measure of the force of gravity acting on those two objects. For example, an astronaut will experience weightlessness in space because he is distant (though not entirely free) from the Earth's gravitational influence. His mass however will still be the same as it would be on Earth. He is just as massive as he was before - but he weighs little or nothing!

West-Kohoutek-Ikemura
A comet in our solar system with an orbital period of 6.12years. More data in TABLE 14. NOTABLE PERIODIC COMETS

White dwarf
A very small, dense star that has used up its nuclear energy. Stars of this kind are at the end of their evolution.

Wild 1
A comet in our solar system with an orbital period of 13.3years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Wild 2
A comet in our solar system with an orbital period of 6.17years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Wild 3
A comet in our solar system with an orbital period of 6.91years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Wirtanen
A comet in our solar system with an orbital period of 5.50years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Wolf
A comet in our solar system with an orbital period of 8.25years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Wolf-Harrington
A comet in our solar system with an orbital period of 6.57years. More data in TABLE 14. NOTABLE PERIODIC COMETS

Wolf-Rayet stars
Stars that are very hot and are surrounded by an expanding gaseous envelope. They appear greenish-white in colour and their spectra show distinctive bright emmision lines.

X-rays
Electromagnetic radiation with a wavelength shorter than ultraviolet light but longer than gamma rays.

Year, anomalistic
The period for successive perihelion passages of the Earth, a little less than 5 minutes longer than the sidereal year.

Year, calendar
The mean length of the year according to the Gregorian calendar, 365 days, 5 hours, 49 minutes and 12 seconds.

Year, sidereal
The period taken by the Earth to complete one orbit of the Sun, 365.26 days.

Year, tropical
The period taken for successive passages of the Sun across the Vernal Equinox, 365.24 days.

Ymir
Satellite of the planet Saturn. See TABLE 8. SATURN - SATELLITE DATA

Zenith
The point on the celestial sphere that lies directly overhead an observer, exactly 90 degrees away from every part of the observer's horizon.

Zenith distance
The angular distance of an object from the zenith.

Zodiac
The band of constellations through which the Sun travels each year. The Zodiac is actually a band across the sky, 8 degrees either side of the ecliptic. With the exception of Pluto, all the planets and the Sun and Moon will be found within the Zodiac.

Zodiacal light
A cone of light stretching from the horizon along the ecliptic. It is only seen during good sky conditions when the Sun is a few degrees below the horizon. It is caused by fine, thinly spread interplanetary material lying close to the plane of the solar system.