Changes

==Properties and Structure==

==Properties and Structure==

The Pi Andromedae system is situated approximately 598.46 [[light year]]s from [[Earth]].<ref name=universeguide/> The [[spectrum]] of the systems suggests the two main stars are [[white dwarf]]s with a [[spectral class]] of B5 and a total [[luminosity]] 2,000 times larger than that of the [[Sun]].<ref name=illinois/> These two stars are thought to be very similar with masses of 4.8 and 5.8 [[solar mass]]es respectively and radii of roughly 4.7 solar radii. One of the stars is known to have a rotation period of less than 8 days, though it is difficult to determine which star as the two are so similar. The two stars [[orbit]] each other in an [[ellipse|elliptical]], taking 143.53 days to complete one orbit with an average distance between them of 1.3&nbsp;[[AU]] (0.005 seconds of arc as viewed from Earth).<ref name=illinois/> The orbit of the stars is fairly [[eccentricity|eccentric]], with the distance between the stars varying from 0.6&nbsp;AU up to 2.1&nbsp;AU, or equivalently an eccentricity of ''e''=0.556.<ref>Eccentricity of the orbit calculated using ''e''=(''a''_max +''a''_min)/(''a''_max+''a''_min)</ref> The plane of the orbit is very nearly alligned along the line of sight to the Earth.

The Pi Andromedae system is situated approximately 598.46 [[light year]]s from [[Earth]].<ref name=universeguide/> The [[spectrum]] of the systems suggests the two main stars are [[white dwarf]]s with a [[spectral class]] of B5 and a total [[luminosity]] 2,000 times larger than that of the [[Sun]].<ref name=illinois/> These two stars are thought to be very similar with masses of 4.8 and 5.8 [[solar mass]]es respectively and radii of roughly 4.7 solar radii. One of the stars is known to have a rotation period of less than 8 days, though it is difficult to determine which star as the two are so similar. The two stars [[orbit]] each other in an [[ellipse|elliptical]], taking 143.53 days to complete one orbit with an average distance between them of 1.3&nbsp;[[AU]] (0.005 seconds of arc as viewed from Earth).<ref name=illinois/> The orbit of the stars is fairly [[eccentric]], with the distance between the stars varying from 0.6&nbsp;AU up to 2.1&nbsp;AU, or equivalently an eccentricity of ''e''=0.556.<ref>Eccentricity of the orbit calculated using ''e''=(''a''_max +''a''_min)/(''a''_max+''a''_min)</ref> The plane of the orbit is very nearly aligned along the line of sight to the Earth.

Further out from the main two stars lies Pi And B, a dwarf star with class A5. The star is significantly fainter than the main two shining at the eight magnitude and is not visible to the unaided eye. It can be found 36 arc-seconds from the main binary pair or 7,200&nbsp;AU.<ref name=illinois/> Further out still is Pi And C, a K type dwarf glowing at the eleventh magnitude roughly 55 second of arc or 11,000&nbsp;AU from the main two. Whether it really is related to the other three is a matter of some debate. Finally there is a possible fifth star, also a K type dwarf but much closer in, at around 40&nbsp;AU. Again whether it is really related to the Pi Andromedae system or merely lies along the same line of sight is unclear.

Further out from the main two stars lies Pi And B, a dwarf star with class A5. The star is significantly fainter than the main two shining at the eight magnitude and is not visible to the unaided eye. It can be found 36 arc-seconds from the main binary pair or 7,200&nbsp;AU.<ref name=illinois/> Further out still is Pi And C, a K type dwarf glowing at the eleventh magnitude roughly 55 second of arc or 11,000&nbsp;AU from the main two. Whether it really is related to the other three is a matter of some debate. Finally there is a possible fifth star, also a K type dwarf but much closer in, at around 40&nbsp;AU. Again whether it is really related to the Pi Andromedae system or merely lies along the same line of sight is unclear.