SkipCaptcha
1,279
edits
Changes
Jump to navigation
Jump to search
{{Night Sky
| image =
| designation =Alpha Hydrae<br/>α Hydra<br/>30 Hydrae
| rightascension =09<sup>h</sup> 27<sup>m</sup> 35.2427<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Alphard Alphard] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]
{{cite web|url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Alphard|title=Alphard|accessdate=2019-05-03|work=Simbad Astronomical Database|publisher=simbad.u-strasbg.fr}}
</ref><ref name=hip>{{cite journal
|last1=van Leeuwen |first1=F.
|title=Validation of the new Hipparcos reduction
|journal=Astronomy & Astrophysics
|volume=474
|issue=2|page=653-664|date=2007
|doi=10.1051/0004-6361:20078357
|bibcode=2007A&A...474..653V
|ref=harv
}} {{arXiv|0708.1752}}</ref>
| declination =-08° 39′ 30.9583″<ref name=simbad/><ref name=hip/>
| distance =177 ly<ref name=constellation-guide>
{{cite web
|url=https://www.constellation-guide.com/constellation-list/hydra-constellation/
|title=Hydra Constellation
|accessdate=2019-04-11
|publisher=constellation-guide.com
}}
</ref>
| constellation =Hydra
| type =Bright giant star
| dimensions =
| magnitude =Apparent Mag: +1.98<ref name=inthesky>
{{cite web
|url=https://in-the-sky.org/data/object.php?id=TYC5460-1592-1
|title=Alphard (Star)
|accessdate=2019-04-11
|publisher=in-the-sky.org
}}
</ref><br/>Absolute Mag: -1.83<ref name=inthesky/>
| redshift =
| radvelocity =-4.27±0.05 km/s<ref name=simbad/><ref>
{{cite journal
|last1=Jofré |first1=E.
|last2=Petrucci |first2=R.
|last3=Saffe |first3=C.
|last4=Saker |first4=L.
|last5=Artur de la Villarmois |first5=E.
|last6=Chavero |first6=C.
|last7=Gómez |first7=M.
|last8=Mauas |first8=P.
|display-authors=3
|title=Stellar parameters and chemical abundances of 223 evolved stars with and without planets
|journal=Astronomy and Astrophysics
|volume=574
|issue=A50|page=A50|date=2015
|doi=10.1051/0004-6361/201424474
|bibcode=2015A&A...574A..50J
|ref=harv
}} {{arXiv|1410.6422}}
</ref>
| propmotion =R.A.: -15.23 mas/yr<ref name=simbad/><ref name=hip/><br/>Dec.: 34.37 mas/yr<ref name=simbad/><ref name=hip/>
| parallax =18.09±0.18 mas<ref name=simbad/><ref name=hip/>
}}
'''Alphard''' (Alpha Hydrae, α Hydra, Alpha Hya, α Hya) is a [[bright giant star]] in the [[constellation]] of [[Hydra]], the water snake.<ref name=earthsky>
{{cite web
|url=https://earthsky.org/brightest-stars/alphard-the-solitary-one
|title=Alphard is the Snake’s Heart
|accesdate=2019-04-13
|publisher=earthsky.org
|date=2019-03-06
|author=Bruce McClure
}}
</ref> Its name of "Alphard," like many star names, derives from the [[Arabic]] ''al-fard'', meaning "the solitary one."<ref name=constellation-guide/> This comes from the fact it is the only bright star in a constellation of dim ones.<ref name=earthsky/> Arabs also knew the star as the "backbone of the serpent". [[Tycho Brahe]] called the star "Cor Hydrae, or “the heart of the snake.” In [[China]], it is part of the [[asterism]] known only as "Star", and the star is called the "First Star of Star." Its [[Bayer designation]] is ''Alpha Hydra''. Alphard appears on the national flag of [[Brazil]], where it represents or symbolizes the state of Mato Grosso do Sul.<ref name=astronomytrek>
{{cite web
|url=http://www.astronomytrek.com/star-facts-alphard/
|title=Star Facts: Alphard
|accessdate=2019-04-11
|publisher=astronomytrek.com
|author=Peter Christoforou
|date=2018-05-12
}}
</ref>
Alpha Hydra and the rest of the constellation of Hydra can be seen ascending in the east in spring. The 47<sup>th</sup> brightest star in the night sky, it can be seen without [[binoculars]] and appears slightly orange.<ref name=universeguide>
{{cite web
|url=https://www.universeguide.com/star/alphard
|title=Alphard (Alpha Hydrae, 30 Hydrae)
|accessdate=2019-04-11
|publisher=universeguide.com
}}
</ref>
==Properties and structure==
Located 177 [[light year]]s from [[Earth]], Alphard has an [[apparent magnitude]] of +2.0, making it the brightest star in the constellation of [[Hydra]].<ref name=constellation-guide/> It has a [[Stellar Classifications|stellar classification]] of K3 II-III, placing it halfway between an orange [[giant star]] and a [[bright giant star]]. It is thought to have a mass of 3 [[solar mass]es. The star's angular diameter has been measured to be 9.09±0.09 milliarcseconds, corresponding to a radius 50 times larger than that of the [[Sun]].<ref name=revolvy>
{{cite web
|url=https://www.revolvy.com/page/Alphard
|title=Alphard
|accessdate=2019-04-11
|publisher=revolvy.com
}}
</ref><ref>
{{cite journal
|last1=da Silva |first1=L.
|last2=Girardi |first2=L.
|last3=Setiawan |first3=J.
|display-authors=3
|title=Basic physical parameters of a selected sample of evolved stars
|journal=Astronomy and Astrophysics
|volume=458
|issue=2|page=609-623|date=2006
|doi=10.1051/0004-6361:20065105
|bibcode=2006A&A...458..609D
|ref=harv
}} {{arXiv|astro-ph/0608160}}
</ref> The star's surface temperature is estimated at around 4,100 kelvin.<ref name=universeguide/> Alphard is believed to have a luminosity roughly 946 times that of the Sun.<ref name=illinois>
{{cite web
|url=http://stars.astro.illinois.edu/sow/Alphard.html
|title=Alphard
|accessdate=2019-04-11
|publisher=stars.astro.illinois.edu
|author=Jim Kaler
|date=2015-06-16
|work=Stars
}}
</ref> The star has a rotational speed of 1.1 km/s at its equator.<ref name=astronomytrek/>
The star is unusual as its [[spectrum]] suggests it contains a large abundance of [[barium]].<ref name=astronomytrek/><ref>
{{cite journal
|last1=Mennessier |first1=M. O.
|last2=Luri|first2=X.
|last3=Figueras |first3=F.
|display-authors=3
|title=Barium stars, galactic populations and evolution
|journal=Astronomy and Astrophysics
|volume=326
|page=722-730|date=1997
|bibcode=1997A&A...326..722M
|ref=harv
}}
</ref> Barium is often produced through "s process nucleosynthesis." This is common in massive stars with [[white dwarf]] stars as companions, but no such companion has been observed for Alphard. Such stars are sometimes called "barium stars."<ref>
{{cite web
|url=http://www.daviddarling.info/encyclopedia/A/Alphard.html
|title=Alphard (Alpha Hydrae)
|accessdate=2019-04-11
|publisher=daviddarling.info
}}
</ref> The star is also of interest for studying astroseismological events. Multi-periodic oscillations with periods that range from a couple hours to nearly two days.<ref name=revolvy/><ref>
{{cite journal
|last1=Setiawan |first1=J.
|last2=Weise |first2=P.
|last3=Roth |first3=M.
|display-authors=3
|title=Multi-periodic oscillations of alpha Hya
|journal=Memorie della Societa Astronomica Italiana
|volume=77
|page=510–514|date=2006
|bibcode=
|ref=harv
}} {{arXiv|astro-ph/0505184}}
</ref> The short-term oscillations are thought to be similar to those that are caused by stellar pulsations such as those that occur on the [[Sun]], but the exact reason or reasons for the correlation between the variations in the star’s spectral line and radial velocity remains unknown.<ref name=astronomytrek/>
==References==
{{reflist}}
{{stars}}
[[Category:Astronomy]]
[[Category:Stars]]
Created page with " {{Night Sky | image = | designation =Alpha Hydrae<br/>α Hydra<br/>30 Hydrae | rightascension =09<sup>h</sup> 27<sup>m</sup> 35.2427<sup>s</sup><ref name=simba..."
{{Night Sky
| image =
| designation =Alpha Hydrae<br/>α Hydra<br/>30 Hydrae
| rightascension =09<sup>h</sup> 27<sup>m</sup> 35.2427<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Alphard Alphard] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]
{{cite web|url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Alphard|title=Alphard|accessdate=2019-05-03|work=Simbad Astronomical Database|publisher=simbad.u-strasbg.fr}}
</ref><ref name=hip>{{cite journal
|last1=van Leeuwen |first1=F.
|title=Validation of the new Hipparcos reduction
|journal=Astronomy & Astrophysics
|volume=474
|issue=2|page=653-664|date=2007
|doi=10.1051/0004-6361:20078357
|bibcode=2007A&A...474..653V
|ref=harv
}} {{arXiv|0708.1752}}</ref>
| declination =-08° 39′ 30.9583″<ref name=simbad/><ref name=hip/>
| distance =177 ly<ref name=constellation-guide>
{{cite web
|url=https://www.constellation-guide.com/constellation-list/hydra-constellation/
|title=Hydra Constellation
|accessdate=2019-04-11
|publisher=constellation-guide.com
}}
</ref>
| constellation =Hydra
| type =Bright giant star
| dimensions =
| magnitude =Apparent Mag: +1.98<ref name=inthesky>
{{cite web
|url=https://in-the-sky.org/data/object.php?id=TYC5460-1592-1
|title=Alphard (Star)
|accessdate=2019-04-11
|publisher=in-the-sky.org
}}
</ref><br/>Absolute Mag: -1.83<ref name=inthesky/>
| redshift =
| radvelocity =-4.27±0.05 km/s<ref name=simbad/><ref>
{{cite journal
|last1=Jofré |first1=E.
|last2=Petrucci |first2=R.
|last3=Saffe |first3=C.
|last4=Saker |first4=L.
|last5=Artur de la Villarmois |first5=E.
|last6=Chavero |first6=C.
|last7=Gómez |first7=M.
|last8=Mauas |first8=P.
|display-authors=3
|title=Stellar parameters and chemical abundances of 223 evolved stars with and without planets
|journal=Astronomy and Astrophysics
|volume=574
|issue=A50|page=A50|date=2015
|doi=10.1051/0004-6361/201424474
|bibcode=2015A&A...574A..50J
|ref=harv
}} {{arXiv|1410.6422}}
</ref>
| propmotion =R.A.: -15.23 mas/yr<ref name=simbad/><ref name=hip/><br/>Dec.: 34.37 mas/yr<ref name=simbad/><ref name=hip/>
| parallax =18.09±0.18 mas<ref name=simbad/><ref name=hip/>
}}
'''Alphard''' (Alpha Hydrae, α Hydra, Alpha Hya, α Hya) is a [[bright giant star]] in the [[constellation]] of [[Hydra]], the water snake.<ref name=earthsky>
{{cite web
|url=https://earthsky.org/brightest-stars/alphard-the-solitary-one
|title=Alphard is the Snake’s Heart
|accesdate=2019-04-13
|publisher=earthsky.org
|date=2019-03-06
|author=Bruce McClure
}}
</ref> Its name of "Alphard," like many star names, derives from the [[Arabic]] ''al-fard'', meaning "the solitary one."<ref name=constellation-guide/> This comes from the fact it is the only bright star in a constellation of dim ones.<ref name=earthsky/> Arabs also knew the star as the "backbone of the serpent". [[Tycho Brahe]] called the star "Cor Hydrae, or “the heart of the snake.” In [[China]], it is part of the [[asterism]] known only as "Star", and the star is called the "First Star of Star." Its [[Bayer designation]] is ''Alpha Hydra''. Alphard appears on the national flag of [[Brazil]], where it represents or symbolizes the state of Mato Grosso do Sul.<ref name=astronomytrek>
{{cite web
|url=http://www.astronomytrek.com/star-facts-alphard/
|title=Star Facts: Alphard
|accessdate=2019-04-11
|publisher=astronomytrek.com
|author=Peter Christoforou
|date=2018-05-12
}}
</ref>
Alpha Hydra and the rest of the constellation of Hydra can be seen ascending in the east in spring. The 47<sup>th</sup> brightest star in the night sky, it can be seen without [[binoculars]] and appears slightly orange.<ref name=universeguide>
{{cite web
|url=https://www.universeguide.com/star/alphard
|title=Alphard (Alpha Hydrae, 30 Hydrae)
|accessdate=2019-04-11
|publisher=universeguide.com
}}
</ref>
==Properties and structure==
Located 177 [[light year]]s from [[Earth]], Alphard has an [[apparent magnitude]] of +2.0, making it the brightest star in the constellation of [[Hydra]].<ref name=constellation-guide/> It has a [[Stellar Classifications|stellar classification]] of K3 II-III, placing it halfway between an orange [[giant star]] and a [[bright giant star]]. It is thought to have a mass of 3 [[solar mass]es. The star's angular diameter has been measured to be 9.09±0.09 milliarcseconds, corresponding to a radius 50 times larger than that of the [[Sun]].<ref name=revolvy>
{{cite web
|url=https://www.revolvy.com/page/Alphard
|title=Alphard
|accessdate=2019-04-11
|publisher=revolvy.com
}}
</ref><ref>
{{cite journal
|last1=da Silva |first1=L.
|last2=Girardi |first2=L.
|last3=Setiawan |first3=J.
|display-authors=3
|title=Basic physical parameters of a selected sample of evolved stars
|journal=Astronomy and Astrophysics
|volume=458
|issue=2|page=609-623|date=2006
|doi=10.1051/0004-6361:20065105
|bibcode=2006A&A...458..609D
|ref=harv
}} {{arXiv|astro-ph/0608160}}
</ref> The star's surface temperature is estimated at around 4,100 kelvin.<ref name=universeguide/> Alphard is believed to have a luminosity roughly 946 times that of the Sun.<ref name=illinois>
{{cite web
|url=http://stars.astro.illinois.edu/sow/Alphard.html
|title=Alphard
|accessdate=2019-04-11
|publisher=stars.astro.illinois.edu
|author=Jim Kaler
|date=2015-06-16
|work=Stars
}}
</ref> The star has a rotational speed of 1.1 km/s at its equator.<ref name=astronomytrek/>
The star is unusual as its [[spectrum]] suggests it contains a large abundance of [[barium]].<ref name=astronomytrek/><ref>
{{cite journal
|last1=Mennessier |first1=M. O.
|last2=Luri|first2=X.
|last3=Figueras |first3=F.
|display-authors=3
|title=Barium stars, galactic populations and evolution
|journal=Astronomy and Astrophysics
|volume=326
|page=722-730|date=1997
|bibcode=1997A&A...326..722M
|ref=harv
}}
</ref> Barium is often produced through "s process nucleosynthesis." This is common in massive stars with [[white dwarf]] stars as companions, but no such companion has been observed for Alphard. Such stars are sometimes called "barium stars."<ref>
{{cite web
|url=http://www.daviddarling.info/encyclopedia/A/Alphard.html
|title=Alphard (Alpha Hydrae)
|accessdate=2019-04-11
|publisher=daviddarling.info
}}
</ref> The star is also of interest for studying astroseismological events. Multi-periodic oscillations with periods that range from a couple hours to nearly two days.<ref name=revolvy/><ref>
{{cite journal
|last1=Setiawan |first1=J.
|last2=Weise |first2=P.
|last3=Roth |first3=M.
|display-authors=3
|title=Multi-periodic oscillations of alpha Hya
|journal=Memorie della Societa Astronomica Italiana
|volume=77
|page=510–514|date=2006
|bibcode=
|ref=harv
}} {{arXiv|astro-ph/0505184}}
</ref> The short-term oscillations are thought to be similar to those that are caused by stellar pulsations such as those that occur on the [[Sun]], but the exact reason or reasons for the correlation between the variations in the star’s spectral line and radial velocity remains unknown.<ref name=astronomytrek/>
==References==
{{reflist}}
{{stars}}
[[Category:Astronomy]]
[[Category:Stars]]