Zeta Hydri

{{short description|Star in the constellation Hydrus}}

{{Starbox begin

| name = ζ Hydri

}}

{{Starbox image

|image=

{{Location mark

|image=Hydrus constellation map.svg|alt=|float=center|width=280

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=Zeta Hydri

|x=446|y=484

}}

|caption=Location of ζ Hydri (circled)

}}

{{Starbox observe

| epoch = J2000

| constell = Hydrus

| ra = {{RA|02|45|32.63435}}{{cite journal | arxiv=0708.1752 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | year=2007 | last1=Van Leeuwen | first1=F. | s2cid=18759600 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%2012876 Vizier catalog entry]

| dec = {{DEC|-67|36|59.8268}}

| appmag_v = 4.83{{cite journal | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | title=XHIP: An extended hipparcos compilation | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | s2cid=119257644 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=V/137D/XHIP&HIP=12876 Vizier catalog entry]

}}

{{Starbox character

| class = A2IV

| b-v = +0.06{{cite journal | bibcode=2014JAVSO..42..443M | title=Sloan Magnitudes for the Brightest Stars | journal=The Journal of the American Association of Variable Star Observers | volume=42 | pages=443 | last1=Mallama | first1=A. | year=2014 | issue=2 }}[http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=J/other/JAVSO/42.443/ugriz&HD=017566 Vizier catalog entry]

| u-b = +0.09

}}

{{Starbox astrometry

| radial_v = +3.60{{cite journal | last=Wilson | first=R. E. | year=1953 | title=General Catalogue of Stellar Radial Velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=Carnegie Institution of Washington | bibcode=1953GCRV..C......0W | lccn=54001336 }}

| prop_mo_ra = +66.41

| prop_mo_dec = +43.38

| parallax = 11.47

| p_error = 0.17

| parallax_footnote =

| absmag_v = 0.13

}}

{{Starbox detail

| mass = 2.44{{cite journal | bibcode=1999A&A...352..555A | arxiv=astro-ph/9911002 | title=Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures | journal=Astronomy and Astrophysics | volume=352 | pages=555–562 | last1=Allende Prieto | first1=C. | last2=Lambert | first2=D. L. | year=1999 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=J/A%2bA/352/555/table1&Name=HIP12876 Vizier catalog entry]

| radius = 3.9

| temperature = 9,144{{cite journal | bibcode=2015ApJ...804..146D | doi=10.1088/0004-637X/804/2/146 | arxiv=1501.03154 | title=The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets | journal=The Astrophysical Journal | volume=804 | issue=2 | pages=146 | year=2015 | last1=David | first1=Trevor J. | last2=Hillenbrand | first2=Lynne A. | s2cid=33401607 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=J/ApJ/804/146/table5&HIP=12876 Vizier catalog entry]

| luminosity = 79.55

| rotational_velocity = 116

| gravity = 3.72

}}

{{Starbox catalog

| names = {{odlist | B=ζ Hyi | CPD=−68° 169 | FK5=2191 | HD=17566 | HIP=12876 | HR=837 | SAO=248644 | GC=3354 }}

}}

{{Starbox reference

| Simbad = Zeta+Hydri

}}

{{Starbox end}}

Zeta Hydri, Latinized from ζ Hydri, is a single,{{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=. }} white-hued star in the southern constellation of Hydrus. It is faintly visible to the naked eye with an apparent magnitude of 4.83. This distance to this star can be estimated from its annual parallax shift of 11.47 mas, showing it to be about 284 light years away. It is moving further away from the Sun with a radial velocity of +3.6 km/s.

The spectrum of this star matches a stellar classification of A2 IV, suggesting it is a subgiant star that is in the process of evolving away from the main sequence as the supply of hydrogen at its core becomes exhausted. It has a high rate of spin, showing a projected rotational velocity of 116 km/s. This is giving the star a slight oblate shape with an equatorial bulge that is 5% larger than the polar radius.{{Cite journal | title=Interferometric observations of rapidly rotating stars | year=2012 | last1=Belle | first1=G. T. | journal=The Astronomy and Astrophysics Review | volume=20 | issue=1 | pages=51 | doi=10.1007/s00159-012-0051-2 | bibcode=2012A&ARv..20...51V | arxiv=1204.2572 | s2cid=119273474 }} It has 2.4 times the mass of the Sun and nearly four times the Sun's radius. Zeta Hydri is radiating 80 times the Sun's luminosity into space from its photosphere at an effective temperature of 9,144 K.