Astronomical units of length Astronomical units of length The angular diameter distance is a distance measure used in astronomy. The angular diameter distance to an object is defined in terms of the objects actual size, , and the angular size of the object as viewed from earth. Astronomical distances are simply so massively huge as to defy the imagination and boggle the mind. For instance, the distance to the nearest star besides the Sun ( Proxima Centauri), is about: ...more on Wikipedia about "Astronomical distance"
The astronomical unit (AU or au or a.u. or sometimes ua) is a unit of distance, approximately equal to the mean distance between Earth and Sun. The currently accepted value of the AU is 149 597 870 691 ± 30 metres (about 150 million kilometres or 93 million miles). ...more on Wikipedia about "Astronomical unit"
Astronomers typically use a number of different length units for different objects. The length unit used is typically determined by two criteria. The distances are closely related to the cosmic distance ladder. ...more on Wikipedia about "Astronomical units of length"
A gigaparsec (one billion parsecs, 1Gpc) is one of the largest distances measures used. One gigaparsec equals 3.261564 billion light years, which is roughly 1/4 the Hubble distance. ...more on Wikipedia about "Gigaparsec"
A light day (also written light-day) is a unit of length. It is defined as the distance light travels in an absolute vacuum in one day (of 86,400 seconds) or 25,902,068,371,200 metres (~26 Tm). ...more on Wikipedia about "Light day"
A light hour (also written light-hour) is a unit of length. It is the distance travelled by light in vacuum in one hour. Based on the current definition of the metre a light-hour is equal to 1,079,252,848,800 metres (~1.08 Tm). ...more on Wikipedia about "Light hour"
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A light minute (also written light-minute) is a unit of length. It is defined as the distance light travels in an absolute vacuum in one minute or 17,987,547,480 metres (~18 Gm). Note that this value is exact, since the metre is actually defined in terms of the light second. ...more on Wikipedia about "Light minute"
A light month (also written light-month) is a unit of length. It is defined as the distance light travels in an absolute vacuum in one full month (thirty days of 86,400 seconds each) or 777,062,051,136,000 metres (~777 Tm). Note that this value is exact, since the metre is actually defined in terms of the speed of light. Nevertheless, since the term "month" can be understood in various ways ( hollow month, average julian month, etc.), use of this unit is not recommended. ...more on Wikipedia about "Light month"
A light second is a unit of length. It is defined as the distance light travels in an absolute vacuum in one second or 299,792,458 metres. Note that this value is considered exact, since the metre is actually (as of 1983) defined in terms of the light second. It is just over 186,282 miles and almost 109 feet. ...more on Wikipedia about "Light second"
A light week (also written light-week) is a unit of length. It is defined as the distance light travels in an absolute vacuum in one week (seven days of 86,400 seconds each) or 181,314,478,598,400 metres (~181 Tm). ...more on Wikipedia about "Light week"
A light year (or light-year, or lightyear), abbreviated ly, is the distance light travels in one year: about 9.461 × 1015 metres (9.461 petametres), or about 5.879 × 1012 (nearly six trillion) miles. More specifically, a light year is defined as the distance that a photon would travel, in free space and infinitely distant from any gravitational or magnetic fields, in one Julian year (365.25 days of 86,400 seconds each). Since the speed of light in a vacuum is exactly 299,792,458 m/s (670,616,629 mph) by the definition of metre, one light year is exactly equal to 9,460,730,472,580,800 m (5,878,625,373,184 mi). ...more on Wikipedia about "Light year"
The megaparsec (abbreviated Mpc) is a unit of distance used in astronomy, equal to one million parsecs. ...more on Wikipedia about "Megaparsec"
The parsec (symbol pc) is a unit of length used in astronomy. It stands for " parallax of one arc second". ...more on Wikipedia about "Parsec"
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A siriometer' is a unit of measurement equal to 1,000,000 Astronomical Units, or about 149,597,870,000,000,000 meters, or about 15.813 light years. ...more on Wikipedia about "Siriometer"
The spat (symbol S), from the Latin Spatium ("Space") is an obsolete unit of distance used in astronomy. It is equal to one billion kilometres (1 Tm or 1012 m). ...more on Wikipedia about "Spat (unit)"
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