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[[Image:Moooghj.jpg|300px|right]]'''Stars''' are extremely large, luminous bodies of gas. They are the most obvious features found in the [[universe]].  They are principally composed of [[hydrogen]] that is undergoing nuclear [[fusion]] to become [[helium]]. Our Sun is the nearest star to Earth, at a distance averaging 93 million miles. The Earth orbits the Sun in a period of approximately 365.25 days, and this defines the [[year]]. The diameter of the Sun, which is a typical star, is about 870,000 miles and its power output is about 10²⁶ watts. The temperature inside the Sun is estimated to be in excess of ten million degrees, and this is hot enough for [[nuclear reactions]] to occur.

[[Image:Moooghj.jpg|300px|right]]'''Stars''' are extremely large, luminous bodies of gas. They are the most obvious features found in the [[universe]].  They are principally composed of [[hydrogen]] that is undergoing nuclear [[fusion]] to become [[helium]]. Our Sun is the nearest star to Earth, at a distance averaging 93 million miles. The Earth orbits the Sun in a period of approximately 365.25 days, and this defines the [[year]]. The diameter of the Sun, which is a typical star, is about 870,000 miles and its power output is about 10²⁶ watts. The temperature inside the Sun is estimated to be in excess of ten million degrees, and this is hot enough for [[nuclear reactions]] to occur.

== Measuring stellar distances ==

 

==Measuring stellar positions==

=== Distances ===

The oldest method of measuring the distance from our solar system to a distant star is the parallax method. To use this method, astronomers measure the right ascension on the sky of the star at two times of the year, half a year apart. The two measurements will differ by a small angle with respect to the most distant stars in that region of the sky. Exactly half this angle is the ''parallax angle'', having symbol ''p''. This is the angle that the star makes with the [[sun]] and the position of the [[earth]] at a right angle with that star.<ref name=Britannica3>"[http://www.britannica.com/eb/article-52809/star Star: Determining stellar distances]." ''Encyclopædia Britannica''. 2008. Encyclopædia Britannica Online. Accessed 21 Apr. 2008</ref> The distance s of the star, in astronomical units (AU), is:

The oldest method of measuring the distance from our solar system to a distant star is the parallax method. To use this method, astronomers measure the right ascension on the sky of the star at two times of the year, half a year apart. The two measurements will differ by a small angle with respect to the most distant stars in that region of the sky. Exactly half this angle is the ''parallax angle'', having symbol ''p''. This is the angle that the star makes with the [[sun]] and the position of the [[earth]] at a right angle with that star.<ref name=Britannica3>"[http://www.britannica.com/eb/article-52809/star Star: Determining stellar distances]." ''Encyclopædia Britannica''. 2008. Encyclopædia Britannica Online. Accessed 21 Apr. 2008</ref> The distance s of the star, in astronomical units (AU), is:

However, the error of measurement of parallax angle is 0.005 arc seconds, and beyond a distance of 100 parsecs, this error becomes significant. 700 stars are near enough to measure their distances directly by using parallax.<ref name=Britannica3/> To measure distances further out than this, astronomers typically use absolute and relative magnitudes, or they apply Hubble's Law to the star's estimated [[redshift]].

However, the error of measurement of parallax angle is 0.005 arc seconds, and beyond a distance of 100 parsecs, this error becomes significant. 700 stars are near enough to measure their distances directly by using parallax.<ref name=Britannica3/> To measure distances further out than this, astronomers typically use absolute and relative magnitudes, or they apply Hubble's Law to the star's estimated [[redshift]].

== Stellar positions and movements ==

=== Positions in sky ===

The most common system for describing the position of a star in the sky is the equatorial system. This system uses two coordinates:

The most common system for describing the position of a star in the sky is the equatorial system. This system uses two coordinates:

# Right ascension on the sky, or the number of hours required for the earth to rotate before an observer can see the star at its highest point in the sky. The zero for right ascension is midnight on the day of the vernal equinox.<ref name=WeissteinRA>Weisstein, Eric W. "[http://scienceworld.wolfram.com/astronomy/RightAscension.html Right Ascension]." ''Eric Weisstein's World of Astronomy'', 2007. Accessed April 21, 2008.</ref>

# Right ascension on the sky, or the number of hours required for the earth to rotate before an observer can see the star at its highest point in the sky. The zero for right ascension is midnight on the day of the vernal equinox.<ref name=WeissteinRA>Weisstein, Eric W. "[http://scienceworld.wolfram.com/astronomy/RightAscension.html Right Ascension]." ''Eric Weisstein's World of Astronomy'', 2007. Accessed April 21, 2008.</ref>

# Declination, or the north-south angle between the star and the celestial equator.<ref name=WeissteinD>Weisstein, Eric W. "[http://scienceworld.wolfram.com/astronomy/Declination.html Declination]." ''Eric Weisstein's World of Astronomy'', 2007. Accessed April 21, 2008.</ref>

# Declination, or the north-south angle between the star and the celestial equator.<ref name=WeissteinD>Weisstein, Eric W. "[http://scienceworld.wolfram.com/astronomy/Declination.html Declination]." ''Eric Weisstein's World of Astronomy'', 2007. Accessed April 21, 2008.</ref>

All stars move, but the most distant stars are considered "fixed" because their motion would be undetectable. The ''proper motion'' (symbol m) of any star is the angular velocity of its position across the sky. This describes the motion at right angles to the line of sight of the observer. To convert this to actual ''tangential velocity'', multiply the tangent of this angular velocity by the star's distance.

All stars move, but the most distant stars are considered "fixed" because their motion would be undetectable. The ''proper motion'' (symbol m) of any star is the angular velocity of its position across the sky. This describes the motion at right angles to the line of sight of the observer. To convert this to actual ''tangential velocity'', multiply the tangent of this angular velocity by the star's distance.

Rarely, this cycle branches into a somewhat different cycle involving [[fluorine]], and that second cycle is thought to branch again in some of the most massive stars.

Rarely, this cycle branches into a somewhat different cycle involving [[fluorine]], and that second cycle is thought to branch again in some of the most massive stars.

== Young Earth Creationism View ==

=== Young Earth Creationism View ===

[[Young earth creationism|Young earth creationist]] scientists assert that [[materialism|materialistic]] explanations of the origin of stars are errant and contra-evidence and reports of stars forming are invalid. <ref>http://www.icr.org/article/403/</ref><ref>http://www.answersingenesis.org/creation/v18/i2/stars.asp</ref><ref>http://www.creationscience.com/onlinebook/AstroPhysicalSciences21.html</ref><ref>http://www.answersingenesis.org/Docs/399.asp#55</ref><ref>http://www.answersingenesis.org/creation/v19/i1/feedback.asp</ref>  In addition, creationists cite the secular scientific literature in order to make the case that materialist explanations of star formation are inadequate:

[[Young earth creationism|Young earth creationist]] scientists assert that [[materialism|materialistic]] explanations of the origin of stars are errant and contra-evidence and reports of stars forming are invalid. <ref>http://www.icr.org/article/403/</ref><ref>http://www.answersingenesis.org/creation/v18/i2/stars.asp</ref><ref>http://www.creationscience.com/onlinebook/AstroPhysicalSciences21.html</ref><ref>http://www.answersingenesis.org/Docs/399.asp#55</ref><ref>http://www.answersingenesis.org/creation/v19/i1/feedback.asp</ref>  In addition, creationists cite the secular scientific literature in order to make the case that materialist explanations of star formation are inadequate:

==Old Universe View of Stars==

===Old Universe View===

A team of astronomers from the University of Texas at Austin McDonald Observatory recently estimated the age of one of the oldest stars in the Milky Way, HE 1523-0901, at 13.2 billion years. They used radioactive decay dating techniques. This star is close to the estimated age of the universe, 13.7 billion years.  

A team of astronomers from the University of Texas at Austin McDonald Observatory recently estimated the age of one of the oldest stars in the Milky Way, HE 1523-0901, at 13.2 billion years. They used radioactive decay dating techniques. This star is close to the estimated age of the universe, 13.7 billion years.  

The team hopes to gain new experimental data and important clues about the hypothesized creation and evolution of the chemical elements shortly after the Big Bang. <ref> http://www.astronomy.com/asy/default.aspx?c=a&id=5533 </ref>

The team hopes to gain new experimental data and important clues about the hypothesized creation and evolution of the chemical elements shortly after the Big Bang. <ref> http://www.astronomy.com/asy/default.aspx?c=a&id=5533 </ref>

==References==

==References==