|
Search over 100 encyclopedias and dictionaries: |
Research categories | Follow us on Twitter |
Research categories
View all topics in the newsView all reference sources at Encyclopedia.com |
|||
astronomical unit
astronomical unit (AU) A unit of length, formerly the mean distance of the Earth from the Sun, but now defined more technically, as below. In the original definition of the AU by C. F.Gauss, the Earth's mean distance from the Sun (i.e. the semimajor axis of the Earth's orbit) was given by the precise form of Kepler's third law as found by Newton:n2a3 = k2 (m + mE),
where n is the Earth's mean motion (in radians per day), a is the semimajor axis of the Earth's orbit (in AU), m and mE are the masses of the Sun and Earth respectively (in solar masses), and k is the Gaussian gravitational constant. The astronomical unit is now defined as the distance from the Sun of a massless particle moving in a circular orbit around the Sun with an orbital period of one Gaussian year of 2π/k ephemeris days. The Earth's mean distance from the Sun is 1.000 000 031 AU, where 1 AU × 149 597 870 km. |
|
|
Cite this article
"astronomical unit." A Dictionary of Astronomy. 1997. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. "astronomical unit." A Dictionary of Astronomy. 1997. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O80-astronomicalunit.html "astronomical unit." A Dictionary of Astronomy. 1997. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-astronomicalunit.html |
|
astronomical unit
astronomical unit (AU), mean distance between the earth and sun; one AU is c.92,960,000 mi (149,604,970 km). The astronomical unit is the principal unit of measurement within the solar system, e.g., Mercury is just over 1/3 AU and Pluto is about 39 AU from the sun. |
|
|
Cite this article
"astronomical unit." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. "astronomical unit." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1E1-astronomU.html "astronomical unit." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-astronomU.html |
|
astronomical unit
astronomical unit (AU) Mean distance between the Earth and the Sun, used as a fundamental unit of distance, particularly for distances in the Solar System. It is equal to 149.598 million km (92.956 million mi).
|
|
|
Cite this article
"astronomical unit." World Encyclopedia. 2005. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. "astronomical unit." World Encyclopedia. 2005. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O142-astronomicalunit.html "astronomical unit." World Encyclopedia. 2005. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-astronomicalunit.html |
|
astronomical unit
|
|
|
Cite this article
AILSA ALLABY and MICHAEL ALLABY. "astronomical unit." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "astronomical unit." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O13-astronomicalunit.html AILSA ALLABY and MICHAEL ALLABY. "astronomical unit." A Dictionary of Earth Sciences. 1999. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-astronomicalunit.html |
|
Search over 100 encyclopedias and dictionaries:
HighBeam™ Research, Inc. © Copyright 2012. All rights reserved.
The Encyclopedia.com advertising network includes:
