PH2

PH2, also known as Kepler-86,[1] or KIC 12735740 (2MASS J19190326+5157453), is a G-type star[8][note 1] 1,120 light-years (340 parsecs) distant[4] within the constellation Cygnus.[3] Roughly the size and temperature[6] of the Sun,[10] PH2 gained prominence when it was known to be the host of one of 42 planet candidates detected by the Planet Hunters citizen science project in its second data release.[11] The candidate orbiting around PH2, known as PH2 b, had been determined to have a spurious detection probability of only 0.08%, thus effectively confirming its existence as a planet.[8]

This article is about the star, Planet Hunters 2. For other uses, see Ph2.
PH2 / Kepler-86[1]

Artist's conception of PH2 and its planet, PH2b, viewed from a hypothetical moon of the planet.
Credit: Haven Giguere, Matthew Giguere/Yale
Observation data
Epoch J2000[2]      Equinox J2000[2]
Constellation Cygnus[3]
Right ascension 19h 19m 03.26334s[4]
Declination +51° 57′ 45.4099″[4]
Apparent magnitude (V) 12.699±0.010[5]
Characteristics
Evolutionary stage Main sequence
Spectral type G5V[6][note 1]
Apparent magnitude (J) 11.501±0.023[2]
Apparent magnitude (H) 11.182±0.03[2]
Apparent magnitude (K) 11.116±0.022[2]
Apparent magnitude (B1) 12.34[2]
Apparent magnitude (R1) 12.62[2]
B−V color index 0.072[6]
Astrometry
Radial velocity (Rv)−17.79±1.88[4] km/s
Proper motion (μ) RA: 3.427 mas/yr[4]
Dec.: 16.047 mas/yr[4]
Parallax (π)2.9134 ± 0.0105 mas[4]
Distance1,120 ± 4 ly
(343 ± 1 pc)
Absolute bolometric
magnitude (Mbol)		5.01+0.12
−0.12[7][note 2]
Details[5]
Mass0.958±0.034 M☉
Radius0.961+0.016
−0.015 R☉
Luminosity (bolometric)0.79+0.09
−0.08[8] L☉
Surface gravity (log g)4.45±0.02 cgs
Temperature5711+60
−59 K
Metallicity [Fe/H]−0.03±0.04 dex
Rotation22.6 days
Rotational velocity (v sin i)1.43±0.78[8] km/s
Other designations
PH2, Kepler-86, KOI-3663, KIC 12735740, TIC 416279912, 2MASS J19190326+5157453[9]
Database references
SIMBADdata
KICdata

Located in its parent star's habitable zone, PH2 b (or Kepler-86b[1]) is a Jupiter-size gas giant which could in theory host a natural satellite suitable for hosting life.[11] The report of the confirmed detection of PH2 b was submitted on January 3, 2013.[8] It was discovered by amateur Pole Rafał Herszkowicz using his laptop and access to the Internet project with data from the Kepler space observatory.[12]

History of detection
The Kepler search volume, in the context of the Milky Way Galaxy.

PH2 b was detected, along with 42 other planet candidates, in archival data from Kepler by the Planet Hunters project, in which human volunteers analyze the light curves of Kepler target stars, searching for planetary transit signals which may be missed by computer programs.[8] Previous work by Planet Hunters helped to confirm the existence of PH1b, a Neptune-mass planet within a four-star system.

All of the candidates in the study, including PH2 b, were identified by citizen scientists Abe J. Hoekstra, Thomas Lee Jacobs, Daryll LaCourse, Hans Martin Schwengler, Rafał Herszkowicz and Mike Chopin among others, with the help of Yale University astronomers.[8] In addition to PH2 b itself, twenty other planet candidates were found which are located in the habitable zones of their host stars; however, these have a relatively high probability of spurious detection and may well come from non-planetary sources.[8]

Although the planet's initial detection was made using Kepler data, PH2's stellar spectra, required to rule out background stars or faint companions with planets as sources for the observed transits, were collected using the HIRES instrument at the W. M. Keck Observatory.[8] Results of observations confirmed the existence of PH2 b with "99.9 percent confidence."[8][11]

Planetary system

PH2 is host to one confirmed planet, PH2 b, orbiting with a period of about 282 days, placing it and any possible moons in the habitable zone.[11] The temperature in the upper atmosphere of the planet could range from 185 K (−88 °C; −127 °F) to 303 K (30 °C; 86 °F).[8] A moon of PH2 b would likely have "a rocky core, plus a greenhouse atmosphere of some sort that could have liquid water on its surface" in the words of the researchers, thus further improving its prospects for habitability.[11]

In 2019, the mass of the planet was measured by radial velocity, showing it to be close in mass to Saturn.[5]

The PH2 planetary system[5]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 108.81+29.79
−32.29 M🜨		 0.824+0.019
−0.017		 282.52540+0.00010
−0.00011		 0.280+0.121
−0.133		 89.915+0.020
−0.022°		 9.49±0.16 R🜨

See also

Notes

References
  1. Staff (September 25, 2013). "Congratulations! MT @planethunters: Our 2nd confirmed planet PH2 b has received the alternate Kepler designation of Kepler-86b". inagist/@NASAKepler. Archived from the original on September 27, 2013. Retrieved September 25, 2013.
  2. "Gator Cone Search Result". The Two Micron All Sky Survey at IPAC. NASA/IPAC. Retrieved January 12, 2013.
  3. "VizieR Detailed Page". VizieR. Harvard-Smithsonian Center for Astrophysics. Retrieved January 12, 2013.
  4. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  5. Dubber, Sophie C.; Mortier, Annelies; et al. (December 2019). "Using HARPS-N to characterize the long-period planets in the PH-2 and Kepler-103 systems". Monthly Notices of the Royal Astronomical Society. 490 (4): 5103–5121. arXiv:1910.03518. Bibcode:2019MNRAS.490.5103D. doi:10.1093/mnras/stz2856.
  6. "Kepler Data Search Results". MAST. Space Telescope Science Institute. Retrieved January 12, 2013.
  7. Mamajek, Eric (December 30, 2012). "Basic Astronomical Data for the Sun (BADS)". University of Rochester. Retrieved January 12, 2013.
  8. Wang, Ji; Fischer, Debra A.; et al. (October 2013). "Planet Hunters. V. A Confirmed Jupiter-size Planet in the Habitable Zone and 42 Planet Candidates from the Kepler Archive Data". The Astrophysical Journal. 776 (1): 10. arXiv:1301.0644. Bibcode:2013ApJ...776...10W. doi:10.1088/0004-637X/776/1/10. S2CID 119241051.
  9. "Kepler-86". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 23 April 2023.
  10. Williams, David R. (March 2, 2012). "Sun Fact Sheet". National Aeronautics and Space Administration. Retrieved January 12, 2013.
  11. Howell, Elizabeth (11 January 2013). "Amateur Astronomers Discover 42 Alien Planets". Space.com. Space.com. Retrieved January 12, 2013.
  12. "Polski informatyk Rafał Herszkowicz odkrył nową planete PH2b | Forsal.pl - Giełda, Waluty, Finanse" (in Polish). Forsal. 2013-03-27. Retrieved 2013-07-12.

Footnotes
  1. The stellar temperature is 5629 K, roughly the same as the G2V Sun's 5778 K.
  2. Calculated based on -2.5 log10 of luminosity differences.
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