Sun-like star

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A sun-like star is a star that is similar to the sun in size, luminosity , spectral class or, depending on the context, in other parameters . The fuzzy term is expressed somewhat more precisely in the English technical language by the three attributes solar-type , solar analog and solar twin , whereby these in the above order denote an increasing correspondence between the parameters of a star and those of the sun. The observation of such stars is important for understanding the properties of the sun in comparison to other stars (and vice versa), especially for parameters that are accessible in the case of the sun using measurement methods that cannot be used with other stars.

Solar-type stars

The sun (left) compared to the slightly smaller and less active Tau Ceti (right)

Here are main sequence star with a BV color index listed from 0.48 to 0.80 (Sun: 0.65). (A similar listing based on spectral classes F8V to K2V would correspond to a BV color index between 0.50 and 1.00.)

Such stars usually show a high correlation with regard to their period of rotation, the activity of their chromosphere (e.g. H and K emission lines of calcium ), and the coronary activity (e.g. in the X-ray range). Since such stars are subject to a slowdown in their rotation while they remain on the main sequence, their age can be estimated from the parameters mentioned. In this way, Mamajek and Hillenbrand (2008) estimated the age of 108 such main sequence stars in the spectral class range F8V – K2V at a distance of 16 pc based on their chromospheric activity (H and K emission lines of calcium).

In the table, deviations from the criteria specified for the following list are color-coded.

Selection of solar-type stars in the distance range 50 light years (15.4 pc)
star Coordinates Distance
in LJ 		class Temperature
in K 		Metallicity
in dex 		Note
Right ascension declination
Tau Ceti 01 h 44 m 04.1 s 1844385−15 ° 56 ′ 15 ″ 11.9 G8V 5344 −0.52
40 Eridani A 04 h 15 m 16.3 s 1926090−7 ° 39 ′ 10 ″ 16.5 K1V 5126 −0.31
82 Eridani 03 h 19 m 55.7 s 1569588.8−43 ° 04 ′ 11.2 ″ 19.8 G8V 5338 −0.54
Delta Pavonis 20 h 08 m 43.6 s 1338945−66 ° 10 ′ 55 ″ 19.9 G8IV 5604 +0.33
HR 7722 20 h 15 m 17.4 s 1729841−27 ° 01 ′ 59 ″ 28.8 K0V 5166 −0.04
Gliese 86 A 21025.902 h 10 m 25.9 s 1495075−50 ° 49 ′ 25 ″ 35.2 K1V 5163 −0.24
54 Piscium 00 h 39 m 21.8 s 2211502+ 21 ° 15 ′ 02 ″ 36.1 K0V 5129 +0.19
V538 Aurigae 05 h 41 m 20.3 s 2532851.8+ 53 ° 28 ′ 51.8 ″ 39.9 K1V 3500-5000 −0.20
HD 14412 02 h 18 m 58.5 s 1744355−25 ° 56 ′ 45 ″ 41.3 G5V 5432 −0.46
HR 4587 12 h 00 m 44.3 s 1897354.3−10 ° 26 ′ 45.7 ″ 42.1 G8IV 5538 0.18
HD 172051 18 h 38 m 53.4 s 1789693−21 ° 03 ′ 07 ″ 42.7 G5V 5610 −0.32
72 Herculis 17 h 20 m 39.6 s 2322804+ 32 ° 28 ′ 04 ″ 46.9 G0V 5662 −0.37
HD 196761 20 h 40 m 11.8 s 1765374−23 ° 46 ′ 26 ″ 46.9 G8V 5415 −0.31
Ny² Lupi 15 h 21 m 48.1 s 1518097−48 ° 19 ′ 03 ″ 47.5 G4V 5664 −0.34

Solar analog stars

The stars listed here are photometrically similar to the sun and meet the following criteria:

  • Surface temperature like the sun ± 500 K, i.e. H. about 5200-6300 K.
  • Metallicity 50–200% (± 0.3 dex) compared to the sun, i.e. H. for a protoplanetary disk , a comparable amount of dust for the formation of planets can be assumed as for the sun
  • There are no nearby stellar companions (orbital period 10 days or less). Such companions would cause increased stellar activity.

The table lists those stars in a distance of 50 light years that are not listed in the table below of sun-like stars:

Selection of solar analog stars in a distance of 50 light years
star Coordinates Distance
in LJ 		class Temperature
in K 		Metallicity
in dex 		Note
Right ascension declination
Alpha Centauri A 14 h 39 m 36.5 s 1394998−60 ° 50 ′ 02 ″ 4.37 G2V 5847 +0.24
Alpha Centauri B 14 h 39 m 35.0 s 1394986−60 ° 50 ′ 14 ″ 4.37 K1V 5316 +0.25
70 Ophiuchi A 18 h 05 m 27.3 s 2023000+ 2 ° 30 ′ 00 ″ 16.6 K0V 5314 −0.02
Sigma Draconis 19 h 32 m 21.6 s 2693940+ 69 ° 39 ′ 40 ″ 18.8 K0V 5297 −0.20
Eta Cassiopeiae A 00 h 49 m 06.3 s 2574855+ 57 ° 48 ′ 55 ″ 19.4 G0V 5941 −0.17
107 Piscium 01 h 42 m 29.8 s 2201607+ 20 ° 16 ′ 07 ″ 24.4 K1V 5242 −0.04
Beta Canum Venaticorum 12 h 33 m 44.5 s 2412127+ 41 ° 21 ′ 27 ″ 27.4 G0V 5930 −0.30
61 Virginis 13 h 18 m 24.3 s 1818160−18 ° 18 ′ 40 ″ 27.8 G5V 5558 −0.02
Zeta Tucanae 00 h 20 m 04.3 s 1354771−64 ° 52 ′ 29 ″ 28.0 F9.5V 5956 −0.14
Chi 1 Orionis A 05 h 54 m 23.0 s 2201634+ 20 ° 16 ′ 34 ″ 28.3 G0V 5902 −0.16
Beta Comae Berenices 13 h 11 m 52.4 s 2275241+ 27 ° 52 ′ 41 ″ 29.8 G0V 5970 −0.06
HR 4523 A 11 h 46 m 31.1 s 1596999−40 ° 30 ′ 01 ″ 30.1 G5V 5629 −0.29
61 Ursae Majoris 11 h 41 m 03.0 s 2341206+ 34 ° 12 ′ 06 ″ 31.1 G8V 5483 −0.12
HR 4458 A 11 h 34 m 29.5 s 1675047−32 ° 49 ′ 53 ″ 31.1 K0V 5629 −0.29
HR 511 01 h 47 m 44.8 s 2635109+ 63 ° 51 ′ 09 ″ 32.8 K0V 5333 +0.05
Alpha Mensae 06 h 10 m 14.5 s 1255489−74 ° 45 ′ 11 ″ 33.1 G5V 5594 +0.10
Zeta 1 reticuli 03 h 17 m 46.2 s 1376569−62 ° 34 ′ 31 ″ 39.5 G3-5V 5733 −0.22
Zeta 2 reticuli 03 h 18 m 12.8 s 1376977−62 ° 30 ′ 23 ″ 39.5 G2V 5843 −0.23
55 Cancri 08 h 52 m 35.81 s 2281951+ 28 ° 19 ′ 51 ″ 40.3 G8V 5235 +0.25
HD 69830 08 h 18 m 23.9 s 1876244−12 ° 37 ′ 56 ″ 40.6 K0V 5410 −0.03
HD 10307 01 h 41 m 47.1 s 2423648+ 42 ° 36 ′ 48 ″ 41.2 G1.5V 5848 −0.05
HD 147513 16 h 24 m 01.3 s 1608865−39 ° 11 ′ 35 ″ 42.0 G1V 5858 +0.03
58 Eridani 04 h 47 m 36.3 s 1834396−16 ° 56 ′ 04 ″ 43.3 G3V 5868 +0.02
Ypsilon Andromedae A 01 h 36 m 47.8 s 2412420+ 41 ° 24 ′ 20 ″ 44.0 F8V 6212 +0.13
HD 211415 A 22 h 18 m 15.6 s 1466263−53 ° 37 ′ 37 ″ 44.4 G1-3V 5890 −0.17
47 Ursae Majoris 10 h 59 m 28.0 s 2402549+ 40 ° 25 ′ 49 ″ 45.9 G1V 5954 +0.06
Alpha Fornacis A 03 h 12 m 04.3 s 1714079−28 ° 59 ′ 21 ″ 46.0 F8IV 6275 −0.19
Psi Serpentis A 15 h 44 m 01.8 s 2023055+ 2 ° 30 ′ 55 ″ 47.9 G5V 5636 −0.03
HD 84117 09 h 42 m 14.4 s 1764544−23 ° 54 ′ 56 ″ 48.5 F8V 6167 −0.03
HD 4391 00 h 45 m 45.6 s 1526693−47 ° 33 ′ 07 ″ 48.6 G3V 5878 −0.03
20 Leonis Minoris 10 h 01 m 00.7 s 2315525+ 31 ° 55 ′ 25 ″ 49.1 G3 V 5741 +0.20
Ny Phoenicis 01 h 15 m 11.1 s 1546846−45 ° 31 ′ 54 ″ 49.3 F8V 6140 +0.18
51 pegasi 22 h 57 m 28.0 s 2204608+ 20 ° 46 ′ 08 ″ 50.9 G2.5IVa 5804 +0.20

Solar twins

The stars listed here fully or predominantly correspond to the following narrow criteria (deviations in the table marked in color):

  • Surface temperature like the sun ± 50 K, i.e. H. about 5720-5830 K.
  • Metallicity 89 to 112% (± 0.053 dex) compared to the sun, i.e. H. for a protoplanetary disk , a similar amount of dust can be assumed for the formation of planets as for the sun.
  • The star does not belong to a multiple star system .
  • The stellar age corresponds to that of the Sun ± 1 billion years, i.e. H. about 3.5-5.6 x 10 9 years.
Selection of well-known solar twins
star Coordinates Distance
in LJ 		class Temperature
in K 		Metallicity
in dex 		Age
in 10 9 years 		Note
Right ascension declination
Sun - - 0.00 G2V 5778 +0.00 4.6
18 Scorpii 16 h 15 m 37.3 s 1917794−8 ° 22 ′ 06 ″ 45.1 G2Va 5835 +0.04 4.2
HD 44594 06 h 20 m 06.1 s 1515571−48 ° 44 ′ 29 ″ 84 G3V 5840 +0.15 4.1
HD 195034 20 h 28 m 11.8 s 2220744+ 22 ° 07 ′ 44 ″ 92 G5 5760 −0.04 5.1
HD 138573 15 h 32 m 43.7 s 2105806+ 10 ° 58 ′ 06 ″ 101 G5IV-V 5710 −0.03 7.8
HD 142093 15 h 52 m 00.6 s 2151409+ 15 ° 14 ′ 09 ″ 103 G2V 5841 −0.15 5.0
HD 98618 11 h 21 m 29.1 s 2582904+ 58 ° 29 ′ 04 ″ 126 G5V 5851 +0.03 4.7
HD 143436 16 h 00 m 18.8 s 2000813+ 0 ° 08 ′ 13 ″ 141 G0 5768 +0.00 3.8
HD 129357 14 h 41 m 22.4 s 2290332+ 29 ° 03 ′ 32 ″ 154 G2V 5749 −0.02 8.2
HD 133600 15 h 05 m 13.2 s 2061724+ 6 ° 17 ′ 24 ″ 171 G0 5808 +0.02 6.3
HD 101364 11 h 40 m 28.5 s 2690031+ 69 ° 00 ′ 31 ″ 217 G5V 5783 +0.01 5.4
HD 197027 20 h 41 m 45.6 s 1728743−27 ° 12 ′ 57 ″ 255 G3V 5723 -0.01 8.2

Solar siblings

A solar sibling ( sibling of the sun ) is understood to mean a star that has the same chemical composition as the sun and thus possibly formed in the same star cluster. The only candidate so far is HD 162826 . Since the asterisk is slightly larger than the sun, he departs for example in the spectral class F8 V more of the sun from the Solar twins .

Similarity to the sun according to the friendliness of possible planets

The sun-likeness of a star is sometimes also described in terms of the possibility of being orbited by a planet in the habitable zone that is earth-like and potentially life-friendly in a similar way to the earth. The following parameters can be taken into account:

  • The star is a main sequence star that is at least 3 billion years old. This corresponds to an upper limit for the mass of approx. 1.5 solar masses, corresponding to an earliest spectral class F5V. Such stars can reach an absolute brightness of up to 2.5 M at the end of their main sequence existence (8.55 times the solar brightness).
  • The star is not a variable star . Ideally, a variability of less than 1% is assumed, practical is a limit of 3% according to the accuracy of the available data. In multiple star systems with a highly eccentric orbit of a companion star, the resulting variable radiation intensity in the habitable zone must also be taken into account.
  • The habitable zone must be dynamically stable. For Earth-like planets in multiple star systems with three or more stars, the probability that their orbits are stable in the long term is low (while in double systems orbits around one of the partners (S-type) or around a close pair of stars as a whole (P-type) can be stable ). Also eccentric Jupiter can change the orbits of planets in the habitable zone.

An example of such a star is HD 70642 .

See also

literature

Individual evidence

  1. ^ A b c D. R. Soderblom, JR King: Solar-Type Stars: Basic Information on Their Classification and Characterization . In: Solar Analogs: Characteristics and Optimum Candidates . 1998. Retrieved February 26, 2008.
  2. ↑ EE Mamajek, LA Hillenbrand: Improved Age Estimation for Solar-Type Dwarfs Using Activity rotation Diagnostics . In: Astrophysical Journal . 687, No. 2, 2008, p. 1264. arxiv : 0807.1686 . bibcode : 2008ApJ ... 687.1264M . doi : 10.1086 / 591785 .
  3. ↑ a b c d e f g h i SIMBAD Astronomical Database . In: SIMBAD . Center de Données astronomiques de Strasbourg. Retrieved January 14, 2009.
  4. ↑ a b c d e f g h i j k l m n o p q N. C. Santos, G. Israelian, S. Randich, RJ García López, R. Rebolo: Beryllium anomalies in solar-type field stars . In: Astronomy and Astrophysics . 425, No. 3, October 2004, pp. 1013-1027. arxiv : astro-ph / 0408109 . bibcode : 2004A & A ... 425.1013S . doi : 10.1051 / 0004-6361: 20040510 .
  5. ↑ a b c d e f g h i j k l m n o p J. Holmberg, B. Nordstrom, J. Andersen: The Geneva-Copenhagen survey of the solar neighborhood. III. Improved distances, ages, and kinematics . In: Astronomy and Astrophysics . 501, No. 3, July 2009, pp. 941-947. arxiv : 0811.3982 . bibcode : 2009A & A ... 501..941H . doi : 10.1051 / 0004-6361 / 200811191 . See Vizier catalog V / 130 .
  6. ↑ a b c d e f g h S. G. Sousa, NC Santos, M. Mayor, S. Udry, L. Casagrande, G. Israelian, F. Pepe, D. Queloz and others. a .: Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe / H] and the frequency of exo-Neptunes . In: Astronomy and Astrophysics . 487, No. 1, August 2008, pp. 373-381. arxiv : 0805.4826 . bibcode : 2008A & A ... 487..373S . doi : 10.1051 / 0004-6361: 200809698 . See VizieR catalog J / A + A / 487/373 .
  7. ^ A b G. F. Porto de Mello, W. Lyra, GR Keller: The Alpha Centauri binary system. Atmospheric parameters and element abundances . In: Astronomy and Astrophysics . 488, No. 2, September 2008, pp. 653-666. arxiv : 0804.3712 . bibcode : 2008A & A ... 488..653P . doi : 10.1051 / 0004-6361: 200810031 .
  8. ↑ Luca Casagrande, Chris Flynn, Laura Portinari, Leo Girardi, Raul Jimenez: The helium abundance and ΔY / ΔZ in lower main-sequence stars . In: Monthly Notices of the Royal Astronomical Society . 382, No. 4, December 2007, pp. 1516-1540. arxiv : astro-ph / 0703766 . bibcode : 2007MNRAS.382.1516C . doi : 10.1111 / j.1365-2966.2007.12512.x .
  9. ↑ Tabetha S. Boyajian, Harold A. McAlister, Ellyn K. Baines, Douglas R. Gies, Todd Henry, Wei ‐ Chun Jao, David o'Brien, Deepak Raghavan and others. a .: Angular Diameters of the G Subdwarf μ Cassiopeiae A and the K Dwarfs σ Draconis and HR 511 from Interferometric Measurements with the CHARA Array . In: The Astrophysical Journal . 683, No. 1, August 2008, pp. 424-432. arxiv : 0804.2719 . bibcode : 2008ApJ ... 683..424B . doi : 10.1086 / 589554 .
  10. ^ A b A. Jeff Valenti, A. Debra Fischer: Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs . In: The Astrophysical Journal Supplement Series . 159, No. 1, July 2005, pp. 141-166. bibcode : 2005ApJS..159..141V . doi : 10.1086 / 430500 . See VizieR catalog J / ApJS / 159/141 .
  11. ↑ VV Kovtyukh, C. Soubiran, SI Belik, NI Gorlova: High precision effective temperatures for 181 FK dwarfs from line-depth ratios . In: Astronomy and Astrophysics . 411, No. 3, 2003, pp. 559-564. arxiv : astro-ph / 0308429 . bibcode : 2003A & A ... 411..559K . doi : 10.1051 / 0004-6361: 20031378 .
  12. ^ DR Williams: Sun Fact Sheet . NASA . 2004. Retrieved June 23, 2009.
  13. ↑ a b c d Jorge Meléndez, Iván Ramírez: HIP 56948: A Solar Twin with a Low Lithium Abundance . In: The Astrophysical Journal . 669, No. 2, November 2007, pp. L89-L92. arxiv : 0709.4290 . bibcode : 2007ApJ ... 669L..89M . doi : 10.1086 / 523942 .
  14. ↑ SG Sousa, J. Fernandes, G. Israelian, NC Santos: Higher depletion of lithium in planet host stars: no age and mass effect . In: Astronomy and Astrophysics . 512, March 2010, p. L5. arxiv : 1003.0405 . bibcode : 2010A & A ... 512L ... 5S . doi : 10.1051 / 0004-6361 / 201014125 .
  15. ↑ Y. Takeda, A. Tajitsu: high-dispersion Spectroscopic Study of Solar Twins: HIP 56948, HIP 79672, and HIP 100963 . In: Publications of the Astronomical Society of Japan . 61, 2009, p. 471. arxiv : 0901.2509 . bibcode : 2009PASJ ... 61..471T .
  16. ↑ a b c d Jeremy R. King, Ann M. Boesgaard, Simon C. Schuler: Keck HIRES Spectroscopy of Four Candidate Solar Twins . In: The Astronomical Journal . 130, No. 5, November 2005, pp. 2318-2325. arxiv : astro-ph / 0508004 . bibcode : 2005AJ .... 130.2318K . doi : 10.1086 / 452640 .
  17. ^ Vázquez, M .; Pallé, E .; Rodríguez, P. Montañés: Is Our Environment Special? . In: The Earth as a Distant Planet: A Rosetta Stone for the Search of Earth-Like Worlds  (= Astronomy and Astrophysics Library). Springer New York, 2010, ISBN 978-1-4419-1683-9 , pp. 391-418, doi : 10.1007 / 978-1-4419-1684-6 . See table 9.1.
  18. ↑ Monroe, TR: High Precision abundances of the Old solar twin HIP 102152: Insights on Li depletion from the Oldest Sun . In: The Astrophysical Journal Letters . 774, No. 2, 2013, p. 22. arxiv : 1308.5744 . bibcode : 2013ApJ ... 774L..32M . doi : 10.1088 / 2041-8205 / 774/2 / L32 .
  19. ↑ a b c d M. C. Turnbull, JC Tarter: Target Selection for SETI. I. A Catalog of Nearby Habitable Stellar Systems . In: The Astrophysical Journal Supplement Series . 145, 2002, p. 181. arxiv : astro-ph / 0210675 . bibcode : 2003ApJS..145..181T . doi : 10.1086 / 345779 .
  20. ↑ Solar system 'twin' found . In: BBC News , July 3, 2003.