en>Conquerist: math according to WP:MSM

2012-11-21T23:21:27Z

math according to WP:MSM

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{{Starbox begin
| name=Pi Hydrae
}}
{{Starbox image
| image =
<div style="position: relative">[[File:Hydra IAU.svg|250px|alt=Diagram showing star positions and boundaries of the Hydra constellation and its surroundings]]
<div style="position: absolute; left: 16.8%; top: 59.7%;">[[File:Cercle rouge 100%.svg|12px]]</div>
</div>
| caption=Location of π Hydra (circled)
}}
{{Starbox observe
| epoch = J2000
| ra = {{RA|14|06|22.29749}}<ref name=aaa474_2_653/>
| dec = {{DEC|–26|40|56.5024}}<ref name=aaa474_2_653/>
| appmag_v = 3.25<ref name=scfs/>
| constell = [[Hydra (constellation)|Hydra]]
}}
{{Starbox character
| class = K1 III–IV<ref name=aj132_1_161/>
| b-v = +1.120<ref name=mnras172_667/>
| u-b = +1.040<ref name=mnras172_667/>
| variable =
}}
{{Starbox astrometry
| radial_v = +26.7<ref name=scfs/>
| prop_mo_ra = +43.70<ref name=aaa474_2_653/>
| prop_mo_dec = −141.18<ref name=aaa474_2_653/>
| parallax = 32.30
| p_error = 0.16
| parallax_footnote = <ref name=aaa474_2_653/>
| absmag_v = 0.79<ref name=aaa454_3_943/>
}}
{{Starbox detail
| mass = 1.76<ref name=aaa454_3_943/> to 2.45<ref name=aaa190_1_148/>
| radius = 12–13<ref name=lang2006/>
| luminosity =
| temperature = 4,670<ref name=aaa475_3_1003/>
| metal_fe = 0.04<ref name=ajss75_579/>
| rotation =
| rotational_velocity = 2.25<ref name=aaa475_3_1003/>
| gravity = 2.65<ref name=aaa475_3_1003/>
| age =
}}
{{Starbox catalog
| names = Markeb, 49 Hydrae, [[Henry Draper catalogue|HD]] 123123, [[Harvard Revised catalogue|HR]] 5287, SAO 182244, [[FK5]] 519, [[Cape Photographic Durchmusterung|CPD]]−26 5170, [[Hipparcos catalogue|HIP]] 68895.<ref name=SIMBAD/>
}}
{{Starbox end}}
'''Pi Hydrae''' (π Hya, π Hydrae) is a [[star]] in the [[constellation]] [[Hydra (constellation)|Hydra]] with an [[apparent visual magnitude]] of 3.3,<ref name=scfs/> making it visible to the naked eye. [[Parallax]] measurements put this star at a distance of about {{Convert|101|ly|pc|abbr=off|lk=on}} from the Earth.

The [[spectrum]] of this star shows it to have a [[stellar classification]] of K1 III-IV,<ref name=aj132_1_161/> with the [[luminosity class]] of 'III-IV' suggesting it is in an [[stellar evolution|evolutionary]] transition stage somewhere between a [[subgiant star|subgiant]] and a [[giant star]]. It has a low [[stellar rotation|projected rotational velocity]] of 2.25 km s<sup>–1</sup>.<ref name=aaa475_3_1003/> Pi Hydrae is radiating energy from its outer envelope with an [[effective temperature]] of 4,670 K,<ref name=aaa475_3_1003/> giving it the orange hue of a K-type star.<ref name=csiro/>

Pi Hydrae is a type of giant known as a [[cyanogen]]-weak star, which means that its spectrum displays weak [[absorption line]]s of CN<sup>–</sup> relative to the [[metallicity]]. (The last is a term astronomers use when describing the abundance of elements other than hydrogen and helium.) Otherwise, it appears to be a normal star of its evolutionary class, having undergone first [[dredge-up]] of [[nuclear fusion]] by-products onto its surface layers.<ref name=ajss75_579/> The measured [[angular diameter]] of this star, after correction for [[limb darkening]], is {{nowrap|3.76 ± 0.04 [[milliarcsecond|mas]]}}.<ref name=aaa431_773/> At its estimated distance, this yields a physical size of about 12–13 times the [[Solar radius|radius of the Sun]].<ref name=lang2006/> It has an estimated mass of 2.45 times the [[solar mass|mass of the Sun]].<ref name=aaa190_1_148/>

== References ==
{{Reflist|30em|refs=

<ref name=aaa474_2_653>{{citation | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 }}</ref>

<ref name=ajss75_579>{{citation | last1=Luck | first1=R. Earle | title=Chemical abundances for cyanogen-weak giants | journal=Astrophysical Journal Supplement Series | volume=75 | pages=579–610 |date=February 1991 | doi=10.1086/191542 | bibcode=1991ApJS...75..579L }}</ref>

<ref name=aj132_1_161>{{citation | display-authors=1 | last1=Gray | first1=R. O. | last2=Corbally | first2=C. J. | last3=Garrison | first3=R. F. | last4=McFadden | first4=M. T. | last5=Bubar | first5=E. J. | last6=McGahee | first6=C. E. | last7=O'Donoghue | first7=A. A. | last8=Knox | first8=E. R. | title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample | journal=The Astronomical Journal | volume=132 | issue=1 | pages=161–170 |date=July 2006 | doi=10.1086/504637 | bibcode=2006AJ....132..161G |arxiv = astro-ph/0603770 }}</ref>

<ref name=scfs>{{citation | display-authors=1 | title=Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions | last1=Wielen | first1=R. | last2=Schwan | first2=H. | last3=Dettbarn | first3=C. | last4=Lenhardt | first4=H. | last5=Jahreiß | first5=H. | last6=Jährling | first6=R. | publisher=Astronomisches Rechen-Institut Heidelberg | issue=35 | year=1999 | bibcode=1999VeARI..35....1W }}</ref>

<ref name=mnras172_667>{{citation | last1=Jennens | first1=P. A. | last2=Helfer | first2=H. L. | title=A new photometric metal abundance and luminosity calibration for field G and K giants. | journal=Monthly Notices of the Royal Astronomical Society | volume=172 | pages=667–679 |date=September 1975 | bibcode=1975MNRAS.172..667J }}</ref>

<ref name=aaa475_3_1003>{{citation | last1=Hekker | first1=S. | last2=Meléndez | first2=J. | title=Precise radial velocities of giant stars. III. Spectroscopic stellar parameters | journal=Astronomy and Astrophysics | volume=475 | issue=3 | pages=1003–1009 |date=December 2007 | doi=10.1051/0004-6361:20078233 | bibcode=2007A&A...475.1003H |arxiv = 0709.1145 }}</ref>

<ref name=aaa431_773>{{citation | last1=Richichi | pages=A. | last2=Percheron | first2=I. | last3=Khristoforova | first3=M. | title=CHARM2: An updated Catalog of High Angular Resolution Measurements | journal=Astronomy and Astrophysics | volume=431 | pages=773–777 |date=February 2005 | doi=10.1051/0004-6361:20042039 | bibcode=2005A&A...431..773R }}</ref>

<ref name=lang2006>{{citation | first1=Kenneth R. | last1=Lang | title=Astrophysical formulae | volume=1 | series=Astronomy and astrophysics library | edition=3 | publisher=Birkhäuser | year=2006 | isbn=3-540-29692-1 | url=http://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41 }}. The radius (R<sub>*</sub>) is given by:
:<math>\begin{align} 2\cdot R_*
& = \frac{(10^{-3}\cdot 31\cdot 3.76)\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\
& \approx 25.1\cdot R_{\bigodot}
\end{align}</math></ref>

<ref name=SIMBAD>{{citation | title=49 Hya -- Star | work=SIMBAD | publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Pi+Hydrae | accessdate=2012-01-16 }}</ref>

<ref name=csiro>{{citation | title=The Colour of Stars | date=December 21, 2004 | work=Australia Telescope, Outreach and Education | publisher=Commonwealth Scientific and Industrial Research Organisation | url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | accessdate=2012-01-16 }}</ref>

<ref name=aaa190_1_148>{{citation | last1=Edvardsson | first1=B. | title=Spectroscopic surface gravities and chemical compositions for 8 nearby single sub-giants | journal=Astronomy and Astrophysics | volume=190 | issue=1-2 | pages=148–166 |date=January 1988 | bibcode=1988A&A...190..148E }}</ref>

<ref name=aaa454_3_943>{{citation | display-authors=1 | last1=Hekker | first1=S. | last2=Reffert | first2=S. | last3=Quirrenbach | first3=A. | last4=Mitchell | first4=D. S. | last5=Fischer | first5=D. A. | last6=Marcy | first6=G. W. | last7=Butler | first7=R. P. | title=Precise radial velocities of giant stars. I. Stable stars | journal=Astronomy and Astrophysics | volume=454 | issue=3 | pages=943–949 |date=August 2006 | doi=10.1051/0004-6361:20064946 | bibcode=2006A&A...454..943H |arxiv = astro-ph/0604502 }}</ref>

}}

==External links==
*{{citation | first1=James B. | last1=Kaler | title=PI HYA (Pi Hydrae) | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/pihya.html | accessdate=2012-01-16 }}

{{Stars of Hydra}}
[[Category:Bayer objects|Hydrae, Pi]]
[[Category:Hydra (constellation)]]

Horizontal eccentricity - Revision history

en>Conquerist: math according to WP:MSM