HD 7924
{{short description|Star in the constellation Cassiopeia}}
{{Starbox begin}}
{{Starbox image
| image = 250px
| caption = Position of star HD 7924 in the constellation Cassiopeia
}}
{{Starbox observe
| epoch = J2000.0
| constell = Cassiopeia
}}
{{Starbox character
| type = main sequence
| appmag_1_passband = B
| appmag_2_passband = J
| appmag_3_passband = H
| appmag_4_passband = K
| u-b =
| variable =
}}
{{Starbox astrometry
| radial_v = {{Val|−22.70|0.15}}
| prop_mo_ra = {{val|−34.643|0.041}}
| prop_mo_dec = {{val|−32.660|0.038}}
| parallax = 58.8216
| p_error = 0.0249
}}
{{Starbox detail
| mass = {{Val|0.81|0.01}}
| radius = {{Val|0.74|0.01}}
| gravity = {{Val|4.6|0.01}}
| luminosity = {{Val|0.364|0.001}}
| temperature = {{Val|5216|13|fmt=commas}}
| metal_fe = {{Val|−0.15|0.03}}
| age_gyr = {{Val|3.0|1.8}}
}}
{{Starbox catalog
| names = {{odlist | HD=7924 | HIP=6379 | BD=+75°58 | SAO=4386 | GCRV=766 | GJ=56.5 | GSC=04494-01396 | 2MASS=J01215911+7642372 | PPM=4675 | TYC=4494-1346-1 | Wo=9054 }}
}}
{{Starbox reference
| Simbad = HD+7924
| NSTED = HD 7924
| ARICNS = 00118
| EPE = HD+7924
}}
{{Starbox end}}
HD 7924 is a single star located 55.5 light years away from the Sun in the northern constellation of Cassiopeia, near the northern constellation border with Cepheus. It has an orange hue and is only visible by means of binoculars or a telescope due to a low apparent visual magnitude of 7.167. The star is drifting closer to the Sun with a radial velocity of –22.7 km/s, and is expected to approach to within {{Convert|2.8391|pc|ly|1|disp=out|abbr=off}} in around 711,700 years.
This is a K-type main-sequence star with a stellar classification of K0.5V. Low-level chromospheric activity has been detected, with the star showing spots and an activity cycle. The star is about three billion years old and is spinning with a projected rotational velocity of just 0.9 km/s. It has 81% of the mass of the Sun and 74% of the Sun's radius. The metal content is about seven-tenths as much as the Sun. It is radiating 36.4% of the luminosity of the Sun from its photosphere at an effective temperature of 5,216 K.
Planetary system
In 2009, a super-Earth exoplanet was found in orbit around the star. In 2015, two more planets were discovered, and the mass of the original planet was revised downwards slightly. It is possible that planets c and d are in the 8:5 mean motion resonance. All of the planets lie below the star's habitable zone.
{{OrbitboxPlanet begin
}}
{{OrbitboxPlanet
| exoplanet = b
| mass_earth = ≥ {{Val|8.68|0.52}}
| period = {{Val|5.39792|0.00025}}
| semimajor = {{Val|0.05664|0.00068}}
| eccentricity = 0.058 {{±|0.056|0.040}}
}}
{{OrbitboxPlanet
| exoplanet = c
| mass_earth = ≥ {{Val|7.86|0.72}}
| period = {{Val|15.299|0.0033}}
| semimajor = {{Val|0.1134|0.0014}}
| eccentricity = 0.098 {{±|0.096|0.069}}
}}
{{OrbitboxPlanet
| exoplanet = d
| mass_earth = ≥ {{Val|6.44|0.79}}
| period = {{Val|24.451|0.016}}
| semimajor = {{Val|0.1551|0.0019}}
| eccentricity = 0.21 {{±|0.13|0.12}}
}}
{{Orbitbox end}}
See also
References
{{Reflist|refs=
{{cite simbad | title=HD 7924 | access-date=2019-11-07}}
{{Cite Gaia DR2|560130775546153344}}
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| title=2MASS All Sky Catalog of point sources
| bibcode=2003tmc..book.....C }}
| title=Stellar diameters and temperatures - V. 11 newly characterized exoplanet host stars
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| doi=10.1093/mnras/stt2360 | doi-access=free }}
| first=Robert | last=Sanders | date=April 28, 2015
| work=Berkeley News | publisher=UC Berkeley
| title=Robotic telescope discovers three super-Earth planetary neighbors
| url=http://newscenter.berkeley.edu/2015/04/28/robotic-telescope-discovers-three-super-earth-planetary-neighbors/
| access-date=2019-11-07 }}
| title=Revising the ages of planet-hosting stars
| url=http://www.aanda.org/articles/aa/full_html/2015/03/aa24951-14/aa24951-14.html
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| display-authors=1 | journal=Astronomy and Astrophysics
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| arxiv=1411.4302 | bibcode=2015A&A...575A..18B
| doi=10.1051/0004-6361/201424951 | s2cid=54555839
}}
| title=Three Super-Earths Orbiting HD 7924
| last1=Fulton | first1=Benjamin J. | last2=Weiss | first2=Lauren M.
| last3=Sinukoff | first3=Evan | last4=Isaacson | first4=Howard
| last5=Howard | first5=Andrew W. | last6=Marcy | first6=Geoffrey W.
| last7=Henry | first7=Gregory W. | last8=Holden | first8=Bradford P.
| last9=Kibrick | first9=Robert I. | display-authors=1
| journal=The Astrophysical Journal
| volume=805 | issue=2 | pages=175 | year=2015
| arxiv=1504.06629 | bibcode=2015ApJ...805..175F
| doi=10.1088/0004-637X/805/2/175 | s2cid=7969255 }}
| title=The NASA-UC Eta-Earth Program. I. A Super-Earth Orbiting HD 7924
| last1=Howard | first1=Andrew W. | last2=Johnson | first2=John Asher
| last3=Marcy | first3=Geoffrey W. | last4=Fischer | first4=Debra A.
| last5=Wright | first5=Jason T. | last6=Henry | first6=Gregory W.
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| journal=The Astrophysical Journal
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| arxiv=0901.4394 | bibcode=2009ApJ...696...75H
| doi=10.1088/0004-637X/696/1/75 | s2cid=1415310 }}
| title=Resolving Close Encounters: Stability in the HD 5319 and HD 7924 Planetary Systems
| last=Kane | first=Stephen R.
| journal=The Astrophysical Journal
| volume=799 | issue=1 | at=105 | year=2016
| arxiv=1411.5374 | bibcode=2016ApJ...830..105K
| doi=10.3847/0004-637X/830/2/105 | s2cid=118542104 | doi-access=free }}
}}
{{Stars of Cassiopeia}}
{{Sky|01|21|59.1153|+|76|42|37.024|54.85}}
Category:K-type main-sequence stars
Category:Planetary systems with three confirmed planets