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| {{Redirect|Weight of the Sun|the song|Tao of the Dead}}
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| [[Image:Rho Cassiopeiae Sol VY Canis Majoris.png|thumb|Size and mass of very large stars: Most massive example, the blue [[Pistol Star]] (150 <math>\begin{smallmatrix}M_\odot\end{smallmatrix}</math>). Others are [[Rho Cassiopeiae]] (40 <math>\begin{smallmatrix}M_\odot\end{smallmatrix}</math>), [[Betelgeuse]] (20 <math>\begin{smallmatrix}M_\odot\end{smallmatrix}</math>), and [[VY Canis Majoris]] (17 <math>\begin{smallmatrix}M_\odot\end{smallmatrix}</math>). (The [[Sun]] (1 <math>\begin{smallmatrix}M_\odot\end{smallmatrix}</math>) which is not visible in this thumbnail is included to illustrate the scale of example stars. Earth's orbit (grey), Jupiter's orbit (red), and Neptune's orbit (blue) are also given.)]]
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| The '''solar mass''' (<math>\begin{smallmatrix}M_\odot\end{smallmatrix}</math>) is a standard [[units of mass|unit of mass]] in [[astronomy]] that is used to indicate the masses of other [[star]]s, as well as [[Star cluster|cluster]]s, [[nebula]]e and [[galaxy|galaxies]]. It is equal to the mass of the [[Sun]], about two [[Names of large numbers|nonillion]] [[kilogram]]s:
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| :<math>M_{\odot}=( 1.98855\ \pm\ 0.00025 )\ \times10^{30}\hbox{ kg}</math><ref>2013 Astronomical Constants http://asa.usno.navy.mil/SecK/2013/Astronomical_Constants_2013.pdf</ref><ref>NIST CODATA http://physics.nist.gov/cgi-bin/cuu/Value?bg</ref>
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| The above mass is about 332,946 times the mass of the [[Earth]] or 1,048 times the mass of [[Jupiter]].
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| Because the Earth follows an [[elliptical orbit]] around the Sun, its solar mass can be computed from the equation for the [[orbital period]] of a small body orbiting a central mass.<ref name=harwit1998/> Based upon the length of the year, the distance from the Earth to the Sun (an [[astronomical unit]] or AU), and the [[gravitational constant]] (''G''), the mass of the Sun is given by:
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| :<math>M_\odot=\frac{4 \pi^2 \times (1\ {\rm AU})^3}{G\times(1\ {\rm year})^2}</math>.
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| The value of the gravitational constant was derived from measurements that were made by [[Henry Cavendish]] in 1798 with a [[torsion balance]]. The value he obtained differs by only 1% from the modern value.<ref>{{cite book
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| | author=Holton, Gerald James; Brush, Stephen G.
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| | title=Physics, the human adventure: from Copernicus to Einstein and beyond
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| | year=2001 | page=137 | edition=3rd
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| | publisher=Rutgers University Press
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| | isbn=0-8135-2908-5 }}</ref> The [[Parallax#Diurnal parallax|diurnal parallax]] of the Sun was accurately measured during the transits of Venus in 1761 and 1769,<ref>{{cite book
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| | author=Pecker, Jean Claude; Kaufman, Susan
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| | title=Understanding the heavens: thirty centuries of astronomical ideas from ancient thinking to modern cosmology | pages=291–291 | publisher=Springer
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| | year=2001 | isbn=3-540-63198-4 }}</ref> yielding a value of 9″ (compared to the present 1976 value of 8.794148″). If we know the value of the diurnal parallax, we can determine the distance to the Sun from the geometry of the Earth.<ref>{{cite book
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| | first=Cesare | last=Barbieri | year=2007
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| | title=Fundamentals of astronomy
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| | pages=132–140 | publisher=CRC Press
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| | isbn=0-7503-0886-9 }}</ref>
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| The first person to estimate the mass of the Sun was [[Isaac Newton]]. In his work ''[[Philosophiæ Naturalis Principia Mathematica|Principia]]'', he estimated that the ratio of the mass of the Earth to the Sun was about 1/28,700. Later he determined that his value was based upon a faulty value for the solar parallax, which he had used to estimate the distance to the Sun (1 AU). He corrected his estimated ratio to 1/169,282 in the third edition of the ''Principia''. The current value for the solar parallax is smaller still, yielding an estimated mass ratio of 1/332,946.<ref>{{cite book
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| | first=David | last=Leverington | year=2003
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| | title=Babylon to Voyager and beyond: a history of planetary astronomy
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| | page=126 | publisher=Cambridge University Press
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| | isbn=0-521-80840-5 }}</ref>
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| As a unit of measurement, the solar mass came into use before the AU and the gravitational constant were precisely measured. This is because the relative mass of another planet in the [[Solar System]] or the combined mass of two [[Binary star#Use in astrophysics|binary stars]] can be calculated in units of Solar mass directly from the orbital radius and orbital period of the planet or stars using Kepler's third law, provided that orbital radius is measured in astronomical units and orbital period is measured in years.
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| The mass of the Sun has decreased since the time it formed. This has occurred through two processes in nearly equal amounts. First, in the [[Solar core|Sun's core]] hydrogen is converted into helium by [[nuclear fusion]], in particular the [[Proton–proton chain reaction|pp chain]], and this reaction converts some mass into energy in the form of gamma ray photons. Most of this energy eventually [[Solar luminosity|radiates away]] from the Sun. Second, high energy protons and electrons in the atmosphere of the Sun are ejected directly into outer space as a [[solar wind]].
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| The original mass of the Sun at the time it reached the [[main sequence]] remains uncertain. The early Sun had much higher mass loss rates than at present, so it may have lost anywhere from 1–7% of its natal mass over the course of its main sequence lifetime.<ref name=apj583_2_1024/> The Sun gains a very small mass through the impact of [[asteroids]] and [[comets]]; however the Sun already holds 99.86% of the Solar System's total mass, so these impacts cannot offset the mass lost by radiation and ejection.
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| ==Related units==
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| One solar mass, ''M''<sub>☉</sub>, can be converted to related units:
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| * 27,068,510 [[Lunar mass]] (''M''<sub>L</sub>)
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| * 332,946 [[Earth mass]] (''M''<sub>⊕</sub>)
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| * 1,047.56 [[Jupiter mass]] (''M''<sub>J</sub>)
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| It is also frequently useful in [[general relativity]] to express mass in units of length or time.
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| :<math>M_\odot \frac{G}{c^2} \approx 1.48~\mathrm{km};\ \ M_\odot \frac{G}{c^3} \approx 4.93~ \mathrm{\mu s}</math>
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| ==See also==
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| {{Col-begin}}
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| {{Col-1-of-2}}
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| * [[Chandrasekhar limit]]
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| * [[Gaussian gravitational constant]]
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| {{Col-2-of-2}}
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| {{Portal|Star}}
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| * [[Orders of magnitude (mass)]]
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| * [[Sun|The Sun]]
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| * [[Sungrazing comet]]
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| {{Col-end}}
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| ==References==
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| {{Reflist|30em|refs=
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| <ref name=harwit1998>{{citation | first1=Martin | last1=Harwit | year=1998 | title=Astrophysical concepts | series=Astronomy and astrophysics library | edition=3 | publisher=Springer | isbn=0-387-94943-7 | pages=72, 75 | url=http://books.google.com/books?id=trAAgqWZVlkC&pg=PA72 }}</ref>
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| <ref name=apj583_2_1024>{{citation | last1=Sackmann | first1=I.-Juliana | last2=Boothroyd | first2=Arnold I. | title=Our Sun. V. A Bright Young Sun Consistent with Helioseismology and Warm Temperatures on Ancient Earth and Mars | journal=The Astrophysical Journal | volume=583 | issue=2 | pages=1024–1039 |date=February 2003 | doi=10.1086/345408 | bibcode=2003ApJ...583.1024S |arxiv = astro-ph/0210128 }}</ref>
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| }}
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| ==Further reading==
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| * {{cite journal | author = I.-J. Sackmann, A. I. Boothroyd | title=Our Sun. V. A Bright Young Sun Consistent with Helioseismology and Warm Temperatures on Ancient Earth and Mars | journal=The Astrophysical Journal | year=2003 | volume=583 | issue=2 | pages=1024–1039 | bibcode=2003ApJ...583.1024S | doi=10.1086/345408 |arxiv = astro-ph/0210128 }}
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| {{Star}}
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| {{DEFAULTSORT:Solar Mass}}
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| [[Category:Units of mass]]
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| [[Category:Units of measurement in astronomy|Mass]]
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| [[Category:Sun]]
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Got nothing to say about me really.
Enjoying to be a part of wmflabs.org.
I just wish Im useful at all
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