HD 164595

HD 164595

Position of star HD 164595 in the constellation Hercules
Observation data Epoch J2000      Equinox J2000
Constellation	Hercules[1]
Right ascension	18^h 00^m 38.894^s[2]
Declination	+29° 34′ 18.92″[2]
Apparent magnitude (V)	7.07[1] + 12.538[3]
Characteristics
Spectral type	G2 V[4] + M2.5 V[5]
B−V color index	0.635±0.005[1]
Astrometry
Radial velocity (Rv)	2.048±0.0007[6] km/s
Proper motion (μ)	RA: −138.982 mas/yr[2] Dec.: 173.502 mas/yr[2]
Parallax (π)	35.402 ± 0.0146 mas[2]
Distance	92.13 ± 0.04 ly (28.25 ± 0.01 pc)
Absolute magnitude (MV)	+4.81[1]
Details
HD 164595 A (primary)
Mass	1.081±0.054[7] M☉
Radius	1.057±0.053[7] R☉
Luminosity	1.023^+0.049 −0.046[8] L☉
Surface gravity (log g)	4.44±0.05[9] cgs
Temperature	5,790±40[9] K
Metallicity [Fe/H]	−0.06[9] dex
Rotational velocity (v sin i)	0.1[8] km/s
Age	4.5[9] Gyr
HD 164595 B (secondary)
Mass	0.455±0.046[3] M☉
Radius	0.464±0.018[3] R☉
Temperature	3,648±21[3] K
Rotation	43.486848 d[10]
Other designations
BD+29 3165, HD 164595, HIP 88194, SAO 85632, PPM 106642, WDS J18006+2934, TYC 2103-1620-1, 2MASS J18003890+2934188[11]
Database references
SIMBAD	data

HD 164595 is a wide binary star^[12] system in the northern constellation of Hercules.^[1] The primary component of this pair hosts an orbiting exoplanet. The system is located at a distance of 92 light years from the Sun based on parallax measurements,^[2] and is drifting further away with a radial velocity of 2.0 km/s.^[6] Although it has an absolute magnitude of +4.81,^[1] at that distance it is too faint to be viewed with the naked eye, having an apparent visual magnitude of 7.07.^[1] The brighter star can be found with binoculars or a small telescope less than a degree to the east-northeast of Xi Herculis.^[13] HD 164595 has a relatively large proper motion, traversing the celestial sphere at an angular rate of 0.222″ yr⁻¹.^[14]

The spectrum of the primary, component A, presents as a G-type main-sequence star with a stellar classification of G2 V.^[4] It is considered an excellent solar twin candidate,^[15][16] although it has a lower logarithm of metallicity ratio, at −0.06 compared with 0.00, and a slightly younger age, at 4.5 versus 4.6 billion years.^[9][17][a] The estimated mass, radius, and luminosity of this star are all similar to the Sun, and the level of magnetic activity in the chromosphere is comparable to solar levels.^[15]

The secondary member, component B, is a magnitude 12.5^[3] star at a projected separation of 2,509±27 AU from the primary.^[12] It is a small red dwarf of spectral class M2.5 V.^[5] Periodic variations in the light curve of this star suggest a rotation period of 43.5 days.^[10]

Planetary system

HD 164595 has one known exoplanet, HD 164595 b, which orbits HD 164595 A every 40 days.^[19][20] It was detected with the radial velocity technique with the SOPHIE echelle spectrograph. Since the inclination of the orbital plane is unknown, only a lower bound on the mass of the object can be determined. The exoplanet has a minimal mass equivalent of 16 Earths.^[19]

The HD 164595 A planetary system^[21]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	>0.0516±0.00856 MJ	0.23	40.00±0.24	0.088^+0.12 −0.066	—	—

Signal observation and SETI

In 2016, HD 164595 briefly attracted media attention after it was reported that a possible SETI signal had been detected from the direction of the star in the previous year. The signal was only heard once and never confirmed by other telescopes, and is thought to have been due to terrestrial interference.

On 15 May 2015, a brief, single radio signal at 11 GHz (2.7 cm wavelength)^[22] was observed in the direction of HD 164595 by a team led by N. N. Bursov^[23] involving Claudio Maccone at the RATAN-600 radio observatory. The signal may have been caused by terrestrial radio-frequency interference or gravitational lensing from a more distant source.^[24][25] It was observed only once (for two seconds), by a single team, at a single telescope, giving it a Rio Scale^[26] score of 1 (insignificant) or 2 (low). Discussions in the media from 29 August 2016 onwards featured speculation that the signal could be caused by an isotropic beacon from a Type II civilization.^[27]

The senior astronomer of the SETI Institute, Seth Shostak, stated that confirmation by another telescope is required.^[28] Astronomer Nicholas Suntzeff of Texas A&M University stated that the signal is in a military frequency band, and that it could have been a satellite downlink, implying that some such systems may be kept secret and therefore would be unknown to SETI scientists.^[22]

SETI and METI studies followed with the Allen Telescope Array and the Boquete Optical SETI Observatory.^[29][28] Also, scientists at Berkeley SETI Research Center at the University of California, Berkeley observed HD 164595 using the Green Bank Telescope as part of the Breakthrough Listen program. No signal was detected at the position and frequency of the transient reported by the RATAN group.^[30][31]

The Special Astrophysical Observatory of the Russian Academy of Sciences has since released an official statement that the signal is of a "most probable terrestrial origin".^[32]

See also

• Arecibo message, a three-minute-long message sent into space
• HD 162826
• Tabby's Star (KIC 8462852)
• Wow! signal, possible alien radio signal

Footnotes

1. An exact solar twin would be a G2V star with a 5778 K temperature, be 4.6 billion years old, with the correct metallicity and a 0.1% solar luminosity variation.^[18][17]

References

1. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
2. 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.
3. Mann, Andrew W.; et al. (May 2015). "How to Constrain Your M Dwarf: Measuring Effective Temperature, Bolometric Luminosity, Mass, and Radius". The Astrophysical Journal. 804 (1): 38. arXiv:1501.01635. Bibcode:2015ApJ...804...64M. doi:10.1088/0004-637X/804/1/64. S2CID 19269312. 64.
4. Harlan, E. A.; Taylor, D. C. (1970). "Erratum: MK classifications for F- and G-type stars. II [Astron. J., Vol. 75, p. 165 - 166 (1970)]". The Astronomical Journal. 75: 507–508. Bibcode:1970AJ.....75..507H. doi:10.1086/110986.
5. Alonso-Floriano, F. J.; et al. (May 2015). "CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS". Astronomy & Astrophysics. 577: 19. arXiv:1502.07580. Bibcode:2015A&A...577A.128A. doi:10.1051/0004-6361/201525803. S2CID 53135130. A128.
6. Soubiran, C.; et al. (2018). "Gaia Data Release 2. The catalogue of radial velocity standard stars". Astronomy and Astrophysics. 616: A7. arXiv:1804.09370. Bibcode:2018A&A...616A...7S. doi:10.1051/0004-6361/201832795. S2CID 52952408.
7. Kervella, Pierre; et al. (March 2019), "Stellar and substellar companions of nearby stars from Gaia DR2. Binarity from proper motion anomaly", Astronomy & Astrophysics, 623: 23, arXiv:1811.08902, Bibcode:2019A&A...623A..72K, doi:10.1051/0004-6361/201834371, S2CID 119491061, A72.
8. Brewer, John M.; et al. (26 August 2016). "Spectral Properties of Cool Stars: Extended Abundance Analysis of 1,617 Planet-search Stars". The Astrophysical Journal Supplement Series. 225 (2): 32. arXiv:1606.07929. Bibcode:2016ApJS..225...32B. doi:10.3847/0067-0049/225/2/32. ISSN 0067-0049. S2CID 118507965.
9. Porto de Mello, G. F.; et al. (March 2014). "A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun; I. Atmospheric parameters and color similarity to the Sun". Astronomy and Astrophysics. 563: A52. arXiv:1312.7571. Bibcode:2014A&A...563A..52P. doi:10.1051/0004-6361/201322277. S2CID 119111150.
10. Hartman, J. D.; et al. (May 2011). "A Photometric Variability Survey of Field K and M Dwarf Stars with HATNet". The Astronomical Journal. 141 (5): 166. arXiv:0907.2924. Bibcode:2011AJ....141..166H. doi:10.1088/0004-6256/141/5/166. 166.
11. "HD 164595". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 28 December 2023.
12. Montes, D.; et al. (September 2018). "Calibrating the metallicity of M dwarfs in wide physical binaries with F-, G-, and K-primaries - I: High-resolution spectroscopy with HERMES: stellar parameters, abundances, and kinematics". Monthly Notices of the Royal Astronomical Society. 479 (1): 1332–1382. arXiv:1805.05394. Bibcode:2018MNRAS.479.1332M. doi:10.1093/mnras/sty1295. S2CID 119260219.
13. Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. Vol. 3. Sky Publishing Corporation and the European Space Agency. p. 1177. ISBN 0-933346-84-0.
14. Lépine, Sébastien; Shara, Michael M. (March 2005). "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)". The Astronomical Journal. 129 (3): 1483–1522. arXiv:astro-ph/0412070. Bibcode:2005AJ....129.1483L. doi:10.1086/427854. S2CID 2603568.
15. Porto de Mello, G. F.; et al. (March 2014). "A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun; I. Atmospheric parameters and color similarity to the Sun". Astronomy and Astrophysics. 563: A52. arXiv:1312.7571. Bibcode:2014A&A...563A..52P. doi:10.1051/0004-6361/201322277. S2CID 119111150.
16. Mahdi, D.; et al. (March 2016). "Solar twins in the ELODIE archive". Astronomy & Astrophysics. 587: A131. arXiv:1601.01599. Bibcode:2016A&A...587A.131M. doi:10.1051/0004-6361/201527472. S2CID 119205608.
17. Williams, D. R. (2004). "Sun Fact Sheet". NASA. Retrieved 23 June 2009.
18. "Solar Variability and Terrestrial Climate - NASA Science". NASA. Retrieved 8 January 2013.
19. "HD 164595 b Confirmed Planet Overview Page". NASA. Retrieved 31 August 2016.
20. Courcol, Bastien; et al. (1 September 2015). "The SOPHIE search for northern extrasolar planets". Astronomy & Astrophysics. 581: A38. arXiv:1506.07144. Bibcode:2015A&A...581A..38C. doi:10.1051/0004-6361/201526329. ISSN 0004-6361. S2CID 119181352.
21. HD 164595 b on exoplanet.eu
22. Berger, Eric (29 August 2016). "Ars Technica". Ars Technica. Retrieved 29 August 2016.
23. Gilster, Paul (27 August 2016). "An Interesting SETI Candidate in Hercules". Centauri Dreams. Retrieved 29 August 2016.
24. Bursov, N.; et al. (2016). "SETI observations on the RATAN-600 telescope in 2015 and detection of a strong signal in the direction of HD 164595". IAA SETI Permanent Committee. Guadalajara, Mexico.
25. "Mystery radio signal may be from distant star system — or a military transmitter". KurzweilAI. 29 August 2016. Retrieved 31 August 2016.
26. "Rio scale calculator". AV Sport. Archived from the original on 2 September 2016. Retrieved 29 August 2016.
27. Seemangal, Robin (29 August 2016). "Not a Drill: SETI Is Investigating a Possible Extraterrestrial Signal From Deep Space". Observer. Retrieved 29 August 2016.
28. "They're not saying it's aliens, but signal traced to sunlike star sparks SETI interest". GeekWire. 29 August 2016. Retrieved 29 December 2023.
29. "'Leaked' space signal report has SETI groups scrambling". SFGate. 29 August 2016. Retrieved 29 December 2023.
30. "Preliminary analysis of star HD 164595" (PDF). University of Berkeley. Retrieved 29 December 2023.
31. Croft, Steve; et al. "Breakthrough Listen Follow-up of a Transient Signal from the RATAN-600 Telescope in the Direction of HD 164595" (PDF). University of Berkeley. Retrieved 29 December 2023.
32. "Monitoring of the continuum of SETI candidates with RATAN-600 (SAO RAS official comment)". Sternberg Astronomical Institute. Retrieved 29 December 2023.