alpha Hydri

{{Starbox image

| image =

{{Location mark

| image=Hydrus IAU.svg

| float=center | width=240 | position=right

| mark=Red circle.svg | mark_width=10 | mark_link=α Hyi

| x%=58.4 | y%=25.4

}}

| caption=Location of α Hydri (circled)

}}

{{Starbox observe

| epoch = J2000.0

| constell = Hydrus

| ra = {{RA|01|58|46.19467}}

| dec = {{DEC|−61|34|11.4948}}

| appmag_v = +2.90

}}

{{ Starbox character

| class = F0 IV

| variable =

| b-v = +0.290

| u-b = +0.189

}}

{{ Starbox astrometry

| radial_v = +7

| prop_mo_ra = +263.66

| prop_mo_dec = +26.77

| parallax = 45.43

| p_error = 0.44

| parallax_footnote =

| absmag_v = +1.153

}}

{{ Starbox detail

| source =

| mass = 2.0

| radius = {{val|3.040|0.058}}

| luminosity = {{val|21.00|0.75}}

| temperature = {{val|7087|47|fmt=commas}}

| age_myr = 810

| metal_fe = {{val|0.07|0.10}}

| gravity = {{val|3.67|0.20}}

| rotational_velocity = 118

}}

{{ Starbox catalog

| names = {{odlist | B=α Hyi | GJ=83 | CD=−62°71 | HD 12311 | HIP=9236 | HR=591 | SAO=248474 }}

}}

{{Starbox reference

| Simbad=alf+Hyi

}}

Alpha Hydri, Latinized from α Hydri, is the second brightest star in the southern circumpolar constellation of Hydrus. It is readily visible to the naked eye in locations south of 28°N with an apparent visual magnitude of +2.9. It is sometimes informally known as the Head of Hydrus. This should not be confused with Alpha Hydrae (Alphard) in the constellation Hydra. Alpha Hydri is one of only three stars in the constellation Hydrus that are above the fourth visual magnitude. This star can be readily located as it lies to the south and east of the prominent star Achernar in the constellation Eridanus.

Based upon parallax measurements from the Hipparcos mission, Alpha Hydri is located at a distance of about {{Convert|71.8|ly|pc|abbr=off|lk=on}} from Earth. This subgiant star is three times larger and twice as massive as the Sun, with a stellar classification of F0 IV. It is about 810 million years old and is radiating 21 times the Sun's luminosity from its outer atmosphere at an effective temperature of 7,087 K. Alpha Hydri emits X-rays similar to Altair. The space velocity components of this star are [U, V, W] = {{nowrap|[−14, −14, -2] km/s}}.{{cite book

| author=Gliese, W. | title=Catalogue of Nearby Stars

| date=1969 | location=Karlsruhe }}

Naming

In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, {{lang|zh|蛇首}} ({{lang|zh-Latn|Shé Shǒu}}), meaning Snake's Head, refers to an asterism consisting of α Hydri and β Reticuli. Consequently, α Hydri itself is known as {{lang|zh|蛇首一}} ({{lang|zh-Latn|Shé Shǒu yī}}, {{langx|en|the First Star of Snake's Head}}.){{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0607/ap060727.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 27 日] {{Webarchive|url=https://web.archive.org/web/20110522003318/http://aeea.nmns.edu.tw/2006/0607/ap060727.html |date=2011-05-22 }}

References

{{reflist|refs=

{{cite journal

| title=Precision angular diameters for 16 southern stars with VLTI/PIONIER

| display-authors=1 | last1=Rains | first1=Adam D.

| last2=Ireland | first2=Michael J. | last3=White | first3=Timothy R.

| last4=Casagrande | first4=Luca | last5=Karovicova | first5=I.

| journal=Monthly Notices of the Royal Astronomical Society

| volume=493 | issue=2 | pages=2377–2394 | date=April 2020

| arxiv=2004.02343 | bibcode=2020MNRAS.493.2377R

| doi=10.1093/mnras/staa282 | doi-access=free | s2cid=214802418 }}

{{cite journal | 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 | s2cid=18759600 }}

{{cite journal | author=Gutierrez-Moreno, Adelina | title=A System of photometric standards | journal=Publications of the Department of Astronomy University of Chile | publisher=Publicaciones Universidad de Chile, Department de Astronomy | volume=1 | pages=1–17 | date=1966 | bibcode=1966PDAUC...1....1G |display-authors=etal}}

{{cite journal | last=Wilson | first=R. E. | date=1953 | title=General Catalogue of Stellar Radial Velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=Carnegie Institute of Washington D.C. | bibcode=1953GCRV..C......0W }}

{{citation | last1=Malagnini | first1=M. L. | last2=Morossi | first2=C. | title=Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars | journal=Astronomy and Astrophysics Supplement Series | volume=85 | issue=3 | pages=1015–1019 |date=November 1990 | bibcode=1990A&AS...85.1015M }}

{{cite web | title=LTT 1059 | work=SIMBAD | publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=LTT+1059 | accessdate=2009-10-13 }}

{{cite journal | author=Lachaume, R. | title=Age determinations of main-sequence stars: combining different methods | journal=Astronomy and Astrophysics | volume=348 | pages=897–909 |date=August 1999 | bibcode=1999A&A...348..897L | url=http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999A%26A...348..897L&link_type=ARTICLE&db_key=AST&high= | accessdate=2009-10-13 |display-authors=etal}}

{{ cite journal |doi=10.1086/162986 | last1=Schmitt | first1=J. H. M. M. | last2=Golub | first2=L. | last3=Harnden | first3=F. R. Jr. | last4=Maxson | first4=C. W. | last5=Rosner | first5=R. | last6=Vaiana | first6=G. S. | title=An Einstein Observatory X-ray survey of main-sequence stars with shallow convection zones | journal=Astrophysical Journal |date=March 1985 | volume=290 | issue=Part 1 | pages=307–20 | bibcode=1985ApJ...290..307S | doi-access=free }}

{{cite book | first=Patrick | last=Moore | date=2005 | title=The observer's year: 366 nights of the universe | url=https://archive.org/details/observersyearnig00moor | url-access=limited | page=[https://archive.org/details/observersyearnig00moor/page/n149 4] | edition=2nd | publisher=Springer | isbn=1-85233-884-9 }}

{{cite book | first=Richard Hinckley | last=Allen | date=1963 | page=[https://archive.org/details/starnamestheirlo00alle/page/377 377] | title=Star Names, Their Lore and Meaning | publisher=Dover | location=New York | isbn=0-486-21079-0 | url-access=registration | url=https://archive.org/details/starnamestheirlo00alle/page/377 }}

}}

Category:F-type subgiants

Category:Hydrus

Hydri, Alpha

Category:Durchmusterung objects