View source for Astronomy:HD 96700

{{Short description|Star in the constellation Hydra}}
{{Starbox begin}}
{{Starbox observe
 | epoch = J2000.0
 | constell = [[Astronomy:Hydra (constellation)|Hydra]]
 | ra = {{RA|11|07|54.427}}<ref name=GaiaEDR3/>
 | dec = {{DEC|−30|10|28.45}}<ref name=GaiaEDR3/>
 | appmag_v = 6.51<ref name=aa552_A64/>
}}
{{Starbox character
 | class = G0&nbsp;V<ref name=aj132_1_161/>
 | b-v = 0.606<ref name=aa552_A64/>
 | u-b =
 | variable =
}}
{{Starbox astrometry
 | radial_v = 12.839{{±|0.0105}}<ref name=aa552_A64/>
 | prop_mo_ra = {{val|−505.371}}
 | prop_mo_dec = {{val|−132.293}}
 | pm_footnote = <ref name=GaiaEDR3/>
 | parallax = 39.3975
 | p_error = 0.0208
 | parallax_footnote = <ref name=GaiaEDR3/>
 | absmag_v =
}}
{{Starbox detail
 | mass = 0.96<ref name=aa556_A150/>
 | radius = 0.96 or 1.1<ref name=cadars/>
 | luminosity =
 | gravity = 4.36<ref name=aj132_1_161/>
 | temperature = 5,879<ref name=aj132_1_161/>
 | metal_fe = −0.14<ref name=aj132_1_161/>
 | rotation =
 | rotational_velocity =
 | age_gyr = 11.9<ref name=cgssn09/>
}}
{{Starbox catalog
 | names = {{odlist | CD=−29° 8875 | GJ=412.2 | HD=96700 | HIP=54400 | HR=4328 | SAO=179558 }}<ref name=SIMBAD/>
}}
{{Starbox reference
 | Simbad = HD+96700
}}
{{Starbox end}}

'''HD 96700''' is the ''Henry Draper Catalogue'' designation for a star in the equatorial [[Astronomy:Constellation|constellation]] of [[Astronomy:Hydra (constellation)|Hydra]]. It has an [[Astronomy:Apparent visual magnitude|apparent visual magnitude]] of 6.51,<ref name=aa552_A64/> which puts it below the limit that can be seen with the naked eye by a typical observer.<ref name=Weaver1947/> (According to the [[Astronomy:Bortle scale|Bortle scale]], it is possible for some observers to see it from dark rural skies.) Based upon [[Astronomy:Stellar parallax|parallax]] measurements, this star is around 83&nbsp;[[Light year|light year]]s away from the [[Astronomy:Sun|Sun]].<ref name=GaiaEDR3/> It is drifting further away with a [[Astronomy:Radial velocity|radial velocity]] of 12.8&nbsp;km/s.<ref name=aa552_A64/>

This is considered a high [[Astronomy:Proper motion|proper motion]] star, shifting its position across the [[Celestial sphere|celestial sphere]] at a rate of 0.52 [[Arc second|arc second]]s per year, along a [[Astronomy:Position angle|position angle]] of 255.21°.<ref name=apjss141_1_187/> It is a member of the [[Astronomy:Thin disk|thin disk]] population of stars and is orbiting the [[Galactic Center|galactic core]] at a mean galactocentric distance of {{Convert|7.17|kpc|kly|abbr=on|lk=on|order=flip}} with an [[Astronomy:Orbital eccentricity|orbital eccentricity]] 0.16. The inclination of its galactic orbit carries it no more than {{Convert|290|pc|ly|abbr=on|lk=off|order=flip}} away from the [[Astronomy:Galactic plane|galactic plane]].<ref name=aa394_927/>

HD 96700 is a G-type main sequence star with a [[Astronomy:Stellar classification|stellar classification]] of G0&nbsp;V.<ref name=aj132_1_161/> It has a slightly lower mass than the Sun<ref name=aa556_A150/> and a lower [[Astronomy:Metallicity|metallicity]].<ref name=aj132_1_161/> The estimated size is similar to the Sun, ranging from 96% to 110% depending on the method used.<ref name=cadars/> The [[Astronomy:Effective temperature|effective temperature]] of the star's [[Astronomy:Stellar atmosphere|outer atmosphere]] is 5,879&nbsp;K,<ref name=aj132_1_161/> giving it the yellow-hued glow of a G-type star.<ref name=csiro/> It appears to be much older than the Sun, with age estimates ranging up to 11.9 billion years.<ref name=cgssn09/>

A 2015 survey ruled out the existence of any additional stellar companions at projected distances from 7 to 209 [[Astronomy:Astronomical unit|astronomical unit]]s.<ref name=Mugrauer_Ginski_2015/>

==Planetary system==
Two planetary companions have been discovered by the [[Astronomy:High Accuracy Radial Velocity Planet Searcher|HARPS]] instrument, which measures variations in the star's [[Astronomy:Radial velocity|radial velocity]] that are presumed to be caused by gravitational perturbations from orbiting objects. The innermost planet, HD 96700 b, is orbiting close to the star at a distance of roughly 0.08&nbsp;AU with a brief [[Astronomy:Orbital period|orbital period]] of 8.13 days. It has at least nine times the mass of the Earth, and so may be a [[Astronomy:Neptune|Neptune]]-like planet. But until astronomers can determine the [[Astronomy:Orbital inclination|orbital inclination]] or directly image the planet, there is no way to know for certain its actual mass.<ref name=HARPS2011/>

The second companion, HD 96700 c, is orbiting at roughly the same distance as [[Astronomy:Mercury (planet)|Mercury]] from the Sun, with a semimajor axis of 0.42&nbsp;AU and a period of around 103 days. It may have a relatively high [[Astronomy:Orbital eccentricity|eccentricity]] of 0.4. This object has at least 13 times the mass of the Earth.<ref name=HARPS2011/> A 2017 study found that HD 96700 b does not [[Astronomy:Astronomical transit|transit]] its host star.<ref name=Gillon2017/> The existence of both planets was confirmed in 2021, and an additional planetary companion orbiting between them was found.<ref name=Unger2021/>

{{OrbitboxPlanet begin
 | name = HD 96700
 | table_ref = <ref name=Unger2021/>
}}
{{OrbitboxPlanet
 | exoplanet = b
 | mass_earth = {{val|8.9|0.4|p=≥}}
 | period = {{val|8.1245|0.0006}}
 | semimajor = {{val|0.0777|0.0013}}
 | eccentricity = <0.138
}}
{{OrbitboxPlanet
 | exoplanet = c
 | mass_earth = {{val|3.5|0.4|p=≥}}
 | period = {{val|19.88|0.01}}
 | semimajor = {{val|0.141|0.002}}
 | eccentricity = <0.293
}}
{{OrbitboxPlanet
 | exoplanet = d
 | mass_earth = {{val|12.7|1.0|p=≥}}
 | period = {{val|103.5|0.1}}
 | semimajor = {{val|0.424|0.007}}
 | eccentricity = {{val|0.27|0.08}}
}}
{{Orbitbox end}}

== References ==
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<ref name=Gillon2017>{{citation
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<ref name=SIMBAD>{{cite simbad
 | title=HD 96700
 | access-date=2015-12-07
}}</ref>

}}
{{Stars of Hydra|state=collapsed}}

{{DEFAULTSORT:HD 96700}}
<!-- Properties -->
[[Category:G-type main-sequence stars]]
[[Category:Exoplanets detected by radial velocity]]
<!-- Location/catalogues -->
[[Category:Hydra (constellation)]]
[[Category:Bright Star Catalogue objects|4328]]
[[Category:Durchmusterung objects|CD-29 08875]]
[[Category:Gliese and GJ objects|0412.2]]
[[Category:Henry Draper Catalogue objects|96700]]
[[Category:Hipparcos objects|054400]]

{{Sourceattribution|HD 96700}}