{{short description|Star in the constellation Grus}} {{Starbox begin}} {{Starbox image | image = {{Location mark |image=Grus constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=η Gruis |x=408|y=970 }} | caption = Location of η Gruis (circled in red) }} {{Starbox observe | epoch = J2000.0 | equinox = J2000.0 (ICRS) | constell = Grus<ref name=Anderson2012/> | ra = {{RA|22|45|37.88194}}<ref name=dr3/> | dec = {{DEC|−53|30|00.4315}}<ref name=dr3/> | appmag_v = 4.85<ref name=Johnson1966/> }} {{Starbox character | type = red giant branch<ref name=dr3/> | class = {{nowrap|K2 III CNIV}}<ref name=houk1979/> | b-v = +1.18<ref name=Johnson1966/> | u-b = +1.17<ref name=Johnson1966/> | variable = }} {{Starbox astrometry | radial_v = {{Val|+27.8|2.8}}<ref name=Gontcharov2006/> | prop_mo_ra = +30.717<ref name=dr3/> | prop_mo_dec = +17.334<ref name=dr3/> | parallax = 7.2136 | p_error = 0.1013 | parallax_footnote = <ref name=dr3/> | absmag_v = −0.68<ref name=Anderson2012/> }} {{Starbox detail | source = | mass = 4.4<ref name=dr3/> | radius = 33<ref name=dr3/> | luminosity = 355<ref name=dr3/> | temperature = 4,491<ref name=dr3/> | gravity = 1.52<ref name=dr3/> | metal_fe = | rotational_velocity = 3.3<ref name=demedeiros2014/> | age_gyr = }} {{Starbox catalog | names = {{odlist | B=η Gru | CPD=−54°10123 | FK5=3821 | HD=215369 | HIP=112374 | HR=8655 | SAO=247570 | WDS=J22456-5330A }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = eta+Gru }} {{Starbox end}}

'''Eta Gruis''', Latinized from '''η Gruis''', is a solitary<ref name=Eggleton2008/> star in the southern constellation of Grus. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.85.<ref name=Johnson1966/> Based upon an annual parallax shift of {{Val|7.2|ul=mas}} as seen from the Earth, the system is located about 452&nbsp;light years from the Sun. The star is drifting further away with a radial velocity of +28&nbsp;km/s.

This object is an evolved K-type giant star with a stellar classification of {{nowrap|K2 III CNIV}},<ref name=houk1979/> where the suffix notation indicates this is an intermediate CN star. It is a periodic microvariable with an amplitude of 0.0055 magnitude and a frequency of 0.36118 cycles per day.<ref name=koen2002/> With the supply of hydrogen exhausted at its core, the star has expanded and cooled, now having 33 times the Sun's girth. It is radiating 355 times the luminosity of the Sun from its swollen photosphere at an effective temperature of {{val|4,491|ul=K}}.<ref name=dr3/>

Eta Gruis has a magnitude 11.5 visual companion located at an angular separation of {{Val|25.6|ul=arcsecond}} along a position angle of 187°, as of 2012.<ref name=WDSC2014/>

==References== <references>

<ref name=dr3>{{cite Gaia DR3|6507189711902334080}}</ref>

<ref name=Anderson2012>{{cite XHIP|112374}}</ref>

<ref name=demedeiros2014>{{cite journal |bibcode=2014A&A...561A.126D |title=A catalog of rotational and radial velocities for evolved stars. V. Southern stars |last1=De Medeiros |first1=J. R. |last2=Alves |first2=S. |last3=Udry |first3=S. |last4=Andersen |first4=J. |last5=Nordström |first5=B. |last6=Mayor |first6=M. |journal=Astronomy and Astrophysics |date=2014 |volume=561 |pages=A126 |doi=10.1051/0004-6361/201220762 |arxiv=1312.3474 }}</ref>

<ref name=koen2002>{{citation | title=New periodic variables from the Hipparcos epoch photometry | last1=Koen | first1=Chris | last2=Eyer | first2=Laurent | journal=Monthly Notices of the Royal Astronomical Society | volume=331 | pages=45–59 | year=2002 | issue=1 | doi=10.1046/j.1365-8711.2002.05150.x | doi-access=free | bibcode=2002MNRAS.331...45K | arxiv=astro-ph/0112194 | s2cid=10505995 | postscript=. }}</ref>

<ref name=Gontcharov2006>{{citation | last1=Gontcharov | first1=G. A. | title=Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system | journal=Astronomy Letters | postscript=. | volume=32| issue=11| pages=759–771| date=November 2006 | doi = 10.1134/S1063773706110065| bibcode=2006AstL...32..759G |arxiv = 1606.08053 | s2cid=119231169 }}</ref>

<ref name=Eggleton2008>{{citation | last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A. | title=A catalogue of multiplicity among bright stellar systems | journal=Monthly Notices of the Royal Astronomical Society | volume=389 | issue=2 | pages=869–879 | date=September 2008 | bibcode=2008MNRAS.389..869E | doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | arxiv=0806.2878 | s2cid=14878976 | postscript=. }}</ref>

<ref name=Johnson1966>{{citation | display-authors=1 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | year=1966 | page=99 | bibcode=1966CoLPL...4...99J | postscript=. }}</ref>

<ref name=houk1979>{{citation | last1=Houk | first1=Nancy | last2=Cowley | first2=A. P. | title=Michigan catalogue of two-dimensional spectral types for the HD stars | publication-place=Ann Arbor, Michigan | postscript=. | publisher=Dept. of Astronomy, University of Michigan | year=1979 | volume=1 | bibcode=1978mcts.book.....H }}</ref>

<ref name=SIMBAD>{{cite simbad | title=eta Gru | access-date=2017-06-28 }}</ref>

<ref name=WDSC2014>{{citation | postscript=. | display-authors=1 | last1=Mason | first1=B. D. | last2=Wycoff | first2=G. L. | last3=Hartkopf | first3=W. I. | last4=Douglass | first4=G. G. | last5=Worley | first5=C. E. | title=The Washington Visual Double Star Catalog | journal=The Astronomical Journal | year=2014 | volume=122 | issue=6 | page=3466 | bibcode=2001AJ....122.3466M | doi=10.1086/323920 | doi-access=free }}</ref>

</references>

{{Stars of Grus|state=collapsed}}

Category:K-type giants Category:Grus (constellation) Gruis, Eta PD-54 10123 215369 112374 8655 Gruis, 061