HD 42936#Planetary system
{{Short description|Star in the constellation Mensa}}
{{Starbox begin
| name = HD 42936
}}
{{Starbox image
| image = 250px
| caption = Location of HD 42936 in the night sky. The star is marked within the red diamond.
}}
{{Starbox observe
| constell = Mensa
| dec = {{DEC|-72|30|45.5674}}
}}
{{Starbox character
|component1 = HD 42936A
| type = main sequence star
| u-b =
| v-r =
| r-i =
|component2 = HD 42936B
| type2 = main sequence star
}}
{{Starbox astrometry
| radial_v = {{val|35.64|0.49}}
| prop_mo_ra = −0.716
| prop_mo_dec = −382.755
| parallax = 21.2496
| p_error = 0.1143
}}
{{Starbox orbit
| primary = HD 42936A
| name = HD 42936B
| period_unitless = {{val|506.89|0.01|ul=d}}
| axis_unitless = {{val|1.139|0.004|ul=AU}}
| eccentricity = {{val|0.596|0.001}}
| inclination = {{val|63.89|0.78}}
| node =
| periastron =
| periarg = {{val|158.88|0.03|0.01}}
| k1 = {{val|2.65731|0.00033|0.00002}}
}}
{{Starbox detail
| component1 = HD 42936A
| mass = {{val|0.900|0.009}}
| radius = {{val|0.861|0.005}}
| gravity = {{val|4.266|0.045}}
| luminosity = {{val|0.510|0.003}}
| temperature = {{val|5201|20|fmt=commas}}
| metal_fe = {{val|0.147|0.013}}
| rotation = {{val|21.8|0.5|16.5|ul=days}}
| rotational_velocity = {{val|3.17|0.1}}
| age_gyr = {{val|9.6|0.8}}
| component2 = HD 42936B
| mass_mj2 = {{val|91.90|0.85}}
}}
{{Starbox catalog
| names = DMPP-3, {{odlist|CD = −72°312|CPD = −72°451|GC = 7845|HD = 42936|HIP = 28941|SAO = 256269}}
}}
{{Starbox reference
| Simbad = HD+42936
| NSTED = HD+42936
| ARICNS =
| EPE = HD+42936
}}
{{starbox end}}
HD 42936, also known as DMPP-3, is a star located in the southern circumpolar constellation Mensa. With an apparent magnitude of 9.1, it is too faint to be detected with the naked eye but can be seen with a telescope. The star is relatively close at a distance of about {{convert|153|ly|pc|lk=on|abbr=off}} but is receding with a heliocentric radial velocity of {{val|35.6|ul=km/s}}.
HD 42936 is an early K-type star with the blended luminosity class of a main sequence star and a subgiant. At present it has 87% the mass of the Sun and 91% the radius of the Sun. The object shines at 51% the luminosity of the Sun from its photosphere at an effective temperature of 5,138 K, which gives it an orangish yellow glow. HD 42936 has iron abundance 151% that of the Sun, meaning it is metal enriched despite an age of 10.9 billion years.
HD 42936 has a very low mass companion star in a close orbit, approaching to {{val|0.498|ul=AU}} at periastron.
Planetary system
In 2019, a radial velocity analysis carried out by a team of astronomers led by astronomer John R. Barnes of the Dispersed Matter Planet Project (DMPP) confirmed the existence of a super-Earth in orbit around DMPP-3 A. Planets in close binary star systems such as this are rare.
A follow-up study in 2023 refined the parameters of the planet and companion star, and detected two additional radial velocity signals. One of these could be caused by a second, Earth-mass planet closer to the star, but the other, 800-day signal cannot be caused by an orbiting body because the companion star would make its orbit unstable. The study concludes that the 800-day signal must be caused by stellar activity, but if not for the companion star it could have been considered a likely planet, which has implications for other radial velocity planet detections.
{{OrbitboxPlanet begin
| name = DMPP-3 A
}}
{{OrbitboxPlanet hypothetical
| exoplanet = c
| mass_earth = {{val|1.065|0.173|0.259|p=≥}}
| period = {{val|2.26|0.20|0.10}}
| semimajor = {{val|0.033|0.002|0.0001}}
| eccentricity = 0
}}
{{OrbitboxPlanet
| exoplanet = b
| mass_earth = {{val|2.22|0.50|0.28|p=≥}}
| period = {{val|6.6732|0.0011|0.0003}}
| semimajor = {{val|0.0670|0.0003|0.0002}}
| eccentricity = {{val|0.174|0.032|0.084}}
}}
{{Orbitbox end}}
See also
References
{{Reflist||refs=
{{Cite Gaia DR3|5266148569447305600}}
{{SIMBAD link|HD+42936|HD 42936}}, entry, SIMBAD. Accessed online December 24, 2019.
{{Cite DR2|5266148569447305600}}
{{cite journal |last1=Stevenson |first1=Adam T. |last2=Haswell |first2=Carole A. |display-authors=etal |date=May 2023 |title=DMPP-3: confirmation of short-period S-type planet(s) in a compact eccentric binary star system, and warnings about long-period RV planet detections |journal=Monthly Notices of the Royal Astronomical Society |volume= 523|issue= |pages= 189–207|doi= 10.1093/mnras/stad1441|doi-access=free |arxiv=2305.06263}}
}}
{{Sky|06|06|29.8496258601|-|72|30|45.554148585}}
{{Stars of Mensa}}
{{DEFAULTSORT:HD 42936}}
Category:K-type main-sequence stars
Category:Mensa (constellation)