Changes

==Properties and Structure==

==Properties and Structure==

The star is situated 5,930.24 [[light year]]s away, though some sources suggest it is closer at around only 2,400&nbsp;ly.<ref name=universeguide/><ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/constellation-list/cepheus-constellation/|title=Cepheus Constellation|accessdate=December 28, 2019|publisher=constellation-guide.com}}</ref> The star is a class M bright supergiant with a [[spectral class]] of M2Ia and one of the largest stars ever observed. The radius of Mu Cephei is 1,650 times greater than the [[Sun]], meaning it is roughly 7.7 times larger than the [[orbit]] of the [[Earth]] around the Sun.<ref name=constellation-guide/> Mu Cephei has a mass of 19 [[solar mass]]es and a [[luminosity]] of 600,000 solar luminosities.<ref name=universetoday/> This high luminosity means it is not only one of the brightest stars visible in the night sky but also the [[Milky Way|galaxy]]. The star is believed to have a surface temperature of 3,690±50 kelvin.<ref>{{cite web|url=https://freestarcharts.com/mu-cephei|title=Mu Cephei - Herschel's Garnet Star|accessdate=December 28, 2019|publisher=freestarcharts.com}}</ref>

The star is situated 5,930.24 [[light year]]s away, though some sources suggest it is closer at around only 2,400&nbsp;ly.<ref name=universeguide/><ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/constellation-list/cepheus-constellation/|title=Cepheus Constellation|accessdate=December 28, 2019|publisher=constellation-guide.com}}</ref> The star is a class M bright supergiant with a [[spectral type|spectral class]] of M2Ia and one of the largest stars ever observed. The radius of Mu Cephei is 1,650 times greater than the [[Sun]], meaning it is roughly 7.7 times larger than the [[orbit]] of the [[Earth]] around the Sun.<ref name=constellation-guide/> Mu Cephei has a mass of 19 [[solar mass]]es and a [[luminosity]] of 600,000 solar luminosities.<ref name=universetoday/> This high luminosity means it is not only one of the brightest stars visible in the night sky but also the [[Milky Way|galaxy]]. The star is believed to have a surface temperature of 3,690±50 kelvin.<ref>{{cite web|url=https://freestarcharts.com/mu-cephei|title=Mu Cephei - Herschel's Garnet Star|accessdate=December 28, 2019|publisher=freestarcharts.com}}</ref>

The star deep red color is partly due to a cloud of interstellar dust located in between the star and Earth.<ref name=illinois>{{cite web|url=http://stars.astro.illinois.edu/sow/garnet.html|title=Garnet star|accessdate=December 28, 2019|work=Stars|author=Jim Kaler|date=September 20, 2017}}</ref> The dust absorbs bluer light more strongly than redder light, meaning there is  light that reaches us on Earth than blue, and so the star appears red. If the dust was not present, the star would appear significantly brighter with an apparent magnitude of +1.97 rather than the observed +4.23.<ref name=illinois/> The red color is also due to the star itself emitting more light in the red region of the spectrum than the blue. A third factor is the Purkinje effect, an optical illusion where the longer someone looks a red star, the brighter it appears to become.

The star deep red color is partly due to a cloud of interstellar dust located in between the star and Earth.<ref name=illinois>{{cite web|url=http://stars.astro.illinois.edu/sow/garnet.html|title=Garnet star|accessdate=December 28, 2019|work=Stars|author=Jim Kaler|date=September 20, 2017}}</ref> The dust absorbs bluer light more strongly than redder light, meaning there is  light that reaches us on Earth than blue, and so the star appears red. If the dust was not present, the star would appear significantly brighter with an apparent magnitude of +1.97 rather than the observed +4.23.<ref name=illinois/> The red color is also due to the star itself emitting more light in the red region of the spectrum than the blue. A third factor is the Purkinje effect, an optical illusion where the longer someone looks a red star, the brighter it appears to become.

As a [[variable star]], its [[apparent magnitude]] varies from a minimum of +4.142 to a maximum of +3.622 and it varies in a semi-regular cycle.<ref name=universeguide/> Mu Cephei varies over a 755&nbsp;day (2.5&nbsp;year) cycle on average though other cycles ranging from 100&nbsp;days to 12.8&nbsp;years are known.<ref name=universetoday/> It is classified as a Semiregular late-M type variable star. It was the first of this type of variable star to be discovered.<ref name=constellation-guide/>

As a [[variable star]], its [[apparent magnitude]] varies from a minimum of +4.142 to a maximum of +3.622 and it varies in a semi-regular cycle.<ref name=universeguide/> Mu Cephei varies over a 755&nbsp;day (2.5&nbsp;year) cycle on average though other cycles ranging from 100&nbsp;days to 12.8&nbsp;years are known.<ref name=universetoday/> It is classified as a Semiregular late-M type variable star. It was the first of this type of variable star to be discovered.<ref name=constellation-guide/>

Mu Cephei is known to produce a strong [[stellar wind]] and is enclosed in a dusty shell that envelopes the star up to a distance of 15,000 [[Astronomical units]].<ref name=illinois/> This shell contributes to some of the reddening.

Mu Cephei is known to produce a strong [[stellar wind]] and is enclosed in a dusty shell that envelopes the star up to a distance of 15,000 [[Astronomical unit|Astronomical units]].<ref name=illinois/> This shell contributes to some of the reddening.

==References==

==References==