Pi Herculis

{{Short description|Star in the constellation Hercules}} {{Starbox begin | name = π Herculis }} {{Starbox image | image= {{Location mark |image=Hercules constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=12|mark_link=π Herculis |x=578|y=402 }} |caption=Location of π Herculis (circled in red) }} {{Starbox observe | epoch = J2000.0 | constell = Hercules | ra = {{RA|17|15|02.83424}}<ref name=DR3/> | dec = {{DEC|+36|48|32.9816}}<ref name=DR3/> | appmag_v = +3.15<ref name="MERMILLIOD"/> }} {{Starbox character | class = K3 II<ref name=apj112_362/><ref name=apjss151_2_387/> | b-v = +1.45<ref name="MERMILLIOD"/> | u-b = +1.66<ref name="MERMILLIOD"/> | variable = suspected<ref name=gcvs/> }} {{Starbox astrometry | radial_v = {{val|-25.57|0.20}}<ref name=aaa430_165/> | prop_mo_ra = {{val|-27.402}} | prop_mo_dec = {{val|2.925}} | pm_footnote = <ref name=DR3/> | parallax = 8.8991 | p_error = 0.1323 | parallax_footnote = <ref name=DR3/> | absmag_v = {{val|-2.10|+0.13|-0.12}}<ref name=aj135_3_892/> }} {{Starbox detail | mass = {{val|3.77|0.2}}<ref name=Baines2018/> | radius = {{val|64.02|0.89|0.91}}<ref name=Baines2018/> | gravity = {{val|1.26|0.05}}<ref name=Reffert/> | metal_fe = {{val|0.01|0.1}}<ref name=Reffert/> | luminosity = {{val|1176|67|fmt=commas}}<ref name=Baines2018/> | temperature = {{val|4223|53|fmt=commas}}<ref name=Baines2018/> | rotational_velocity = 6.12<ref name="Hekker & Meléndez"/> | age_myr = {{val|220|40}}<ref name=Baines2018/> }} {{Starbox catalog | names = {{odlist | name=Nüchuang | B=π Her | F=67 Her | BD=+36°2844 | FK5=643 | HD=156283 | HIP=84380 | HR=6418 | SAO=65890}}<ref name="SIMBAD"/> }} {{Starbox reference | Simbad = HD+156283 }} {{Starbox end}}

'''Pi Herculis''', Latinized from π Herculis, formally named '''Nüchuang''',<ref name=IAU-CSN/> is a third-magnitude star in the constellation Hercules. As one of the four stars in the Keystone asterism, specifically representing the northeastern corner, it is one of the constellation's more easily recognized. It has an apparent visual magnitude of +3.2,<ref name="SIMBAD"/> which is visible to the naked eye and makes it one of its brighter members. The Gaia spacecraft mission estimated its distance at roughly 112 parsecs from Earth, or about 367 light years away.<ref name=DR3/> The overall reduction in the star's visual magnitude due to extinction from the intervening cosmic dust is 0.11.<ref name=aaa430_165/>

== Nomenclature == ''Pi Herculis'' (Latinized from π Herculis, abbreviated π Her) is the star's Bayer designation. In Chinese astronomy, this star is part of the asterism Nǚ Chuáng (Woman's Bed, {{lang|zh|女床}}). The IAU Working Group on Star Names adopted the name Nüchuang for this star on 14 May 2026.<ref name=IAU-CSN/>

== Properties == Pi Herculis is a bright giant star with a stellar classification of K3 II.<ref name=apj112_362/><ref name=apjss151_2_387/> P.C. Keenan and R. E. Pitts (1980) graded it as a spectral type K3 IIab<ref name=apjss42_541/> and it is sometimes listed with this alternate classification. The star is enormous compared to the Sun, having a mass that is 4.5 times solar and a radius approximately 60 times depending on which wavelength the star's angular diameter is measured at. Due to limb darkening, all giant and supergiant stars present unique challenges when measuring their photosphere. This orange-hued giant shines with 1,330 times the luminosity of the Sun.<ref name=kaler/> It is a low-amplitude photometric variable star showing a typical change of roughly 0.0054 in magnitude over a 24-hour period.<ref name=apj22130_1_201/>

== Radial velocity variations == Low-amplitude radial velocity variations with a period of 613 days in the bright giant have suggested the possible presence of a substellar companion. If this is really due to a low-mass object, such a companion would be as small as 0.027 solar masses (27 times the mass of Jupiter, probably a brown dwarf) and 3 astronomical units away from the bright primary. A substellar companion is only one of several hypotheses to explain the star's behaviour. Most likely the cause of the variation is weak pulsation of the star's atmosphere.<ref name=kaler/>

With a luminosity more than 1,000 times that of the Sun, an orbit where a planet could be habitable would be located 37 AU away from Pi Herculis—in Solar System terms, halfway between Neptune's and Pluto's orbits. On the other hand, a putative companion would orbit in a scorching region and would be as hot as a planet would at 0.08 AU around a Sun-like star. In any case it's likely that it would soon be swallowed up by the expanding giant.<ref name="HATZES"/>

==See also== * Pi2 Ursae Majoris * Beta Ophiuchi

==References== <references> <ref name=DR3>{{Cite DR3|1339952869195300608}}</ref>

<ref name=Reffert>{{Cite journal |last=Reffert |first=Sabine |last2=Bergmann |first2=Christoph |last3=Quirrenbach |first3=Andreas |last4=Trifonov |first4=Trifon |last5=Künstler |first5=Andreas |date=2015-02-01 |title=Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity |bibcode=2015A&A...574A.116R |journal=Astronomy and Astrophysics |volume=574 |pages=A116 |doi=10.1051/0004-6361/201322360 |issn=0004-6361|arxiv=1412.4634 }}</ref>

<ref name=gcvs>{{citation | last1=Samus | first1=N. N. | last2=Kazarovets | first2=E. V. | last3=Durlevich | first3=O. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | display-authors=1 | title=General Catalogue of Variable Stars | version=GCVS 5.1 | journal=Astronomy Reports | year=2017 | volume=61 | issue=1 | pages=80–88 | doi=10.1134/S1063772917010085 | bibcode=2017ARep...61...80S | s2cid=125853869 }}</ref>

<ref name=Baines2018>{{citation | title=Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer | last1=Baines | first1=Ellyn K. | last2=Armstrong | first2=J. Thomas | last3=Schmitt | first3=Henrique R. | last4=Zavala | first4=R. T. | last5=Benson | first5=James A. | last6=Hutter | first6=Donald J. | last7=Tycner | first7=Christopher | last8=Belle | first8=Gerard T. van | display-authors=1 | journal=The Astronomical Journal | volume=155 | at=30 | year=2018 | issue=1 | postscript=. | arxiv=1712.08109 | bibcode=2018AJ....155...30B | doi=10.3847/1538-3881/aa9d8b | s2cid=119427037 | doi-access=free }}</ref>

<ref name=aaa430_165>{{citation | display-authors=1 | last1=Famaey | first1=B. | last2=Jorissen | first2=A. | last3=Luri | first3=X. | last4=Mayor | first4=M. | last5=Udry | first5=S. | last6=Dejonghe | first6=H. | last7=Turon | first7=C. | title=Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters | journal=Astronomy and Astrophysics | volume=430 | pages=165–186 |date=January 2005 | doi=10.1051/0004-6361:20041272 | bibcode=2005A&A...430..165F |arxiv = astro-ph/0409579 | s2cid=17804304 }}</ref>

<ref name=apjss151_2_387>{{citation | display-authors=1 | last1=Ivanov | first1=Valentin D. | last2=Rieke | first2=Marcia J. | last3=Engelbracht | first3=Charles W. | last4=Alonso-Herrero | first4=Almudena | last5=Rieke | first5=George H. | last6=Luhman | first6=Kevin L. | title=A Medium-Resolution Near-Infrared Spectral Library of Late-Type Stars. I | journal=The Astrophysical Journal Supplement Series | volume=151 | issue=2 | pages=387–397 |date=April 2004 | doi=10.1086/381752 | bibcode=2004ApJS..151..387I |arxiv = astro-ph/0311596 | s2cid=55537399 }}</ref>

<ref name="SIMBAD">{{cite simbad | title=* pi. Her | access-date=2010-11-15 }}</ref>

<ref name="MERMILLIOD">{{cite journal | last1=Mermilliod | first1=J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV Data | year=1986 | publisher=SIMBAD | bibcode=1986EgUBV........0M }}</ref>

<ref name="Hekker & Meléndez">{{cite journal | 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 | year=2007 | bibcode=2007A&A...475.1003H | doi=10.1051/0004-6361:20078233 | arxiv=0709.1145 | s2cid=10436552 }}</ref>

<ref name="HATZES">{{cite journal | last1=Hatzes | first1=Artie P. | last2=Cochran | first2=William D. | title=Long-period, low-amplitude radial velocity variations in the K giant star pi Herculis: rotation, substellar companion or non-radial pulsations? | journal=Monthly Notices of the Royal Astronomical Society | volume=304 | issue=1 | pages=109–118 |date=March 1999 | doi=10.1046/j.1365-8711.1999.02288.x | bibcode=1999MNRAS.304..109H | doi-access=free }}</ref>

<ref name=apjss42_541>{{citation | last1=Keenan | first1=P. C. | last2=Pitts | first2=R. E. | title=Revised MK spectral types for G, K, and M stars | journal=Astrophysical Journal Supplement Series | volume=42 | pages=541–563 |date=April 1980 | doi=10.1086/190662 | bibcode=1980ApJS...42..541K | doi-access=free }}</ref>

<ref name=apj112_362>{{citation | last1=Morgan | first1=W. W. | last2=Roman | first2=Nancy G. | title=Revised Standards for Supergiants on the System of the Yerkes Spectral Atlas | journal=Astrophysical Journal | volume=112 | pages=362–364 |date=November 1950 | doi=10.1086/145351 | bibcode=1950ApJ...112..362M }}</ref>

<ref name=apj22130_1_201>{{citation | display-authors=1 | last1=Henry | first1=Gregory W. | last2=Fekel | first2=Francis C. | last3=Henry | first3=Stephen M. | last4=Hall | first4=Douglas S. | title=Photometric Variability in a Sample of 187 G and K Giants | journal=The Astrophysical Journal Supplement Series | volume=130 | issue=1 | pages=201–225 |date=September 2000 | doi=10.1086/317346 | bibcode=2000ApJS..130..201H | citeseerx=10.1.1.40.8526 | s2cid=17160805 }}</ref>

<ref name=kaler>{{citation | first1=James B. | last1=Kaler | title=Pi Herculis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/piher.html | access-date=2012-03-13 }}</ref>

<ref name=aj135_3_892>{{citation | display-authors=1 | last1=Carney | first1=Bruce W. | last2=Gray | first2=David F. | last3=Yong | first3=David | last4=Latham | first4=David W. | last5=Manset | first5=Nadine | last6=Zelman | first6=Rachel | last7=Laird | first7=John B. | title=Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars | journal=The Astronomical Journal | volume=135 | issue=3 | pages=892–906 |date=March 2008 | doi=10.1088/0004-6256/135/3/892 | bibcode=2008AJ....135..892C |arxiv = 0711.4984 | s2cid=2756572 }}</ref>

<ref name=IAU-CSN>{{cite web |title=IAU Catalog of Star Names |url=https://exopla.net/star-names/modern-iau-star-names/ |access-date=18 May 2026}}</ref> </references>

== External links == * http://stars.astro.illinois.edu/sow/piher.html * http://www.dibonsmith.com/her_p.htm

Herculis, Pi Herculis, 067 156283 084380 6418 Category:Hercules (constellation) Category:K-type bright giants Category:Hypothetical planetary systems BD+36 2844 Category:Suspected variables Nüchuang