Solar analog

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Template:Short description Script error: No such module "redirect hatnote".

File:Compare sun tau ceti.png
This illustration compares the somewhat larger and hotter Sun (left) to the relatively inactive star Tau Ceti.

Solar-type stars, solar analogs (also analogues), and solar twins are stars that are particularly similar to the Sun. The stellar classification is a hierarchy with solar twin being most like the Sun followed by solar analog and then solar-type.[1] Observations of these stars are important for understanding better the properties of the Sun in relation to other stars and the habitability of planets.[2]

By similarity to the Sun

Defining the three categories by their similarity to the Sun reflects the evolution of astronomical observational techniques. Originally, solar-type was the closest that similarity to the Sun could be defined. Later, more precise measurement techniques and improved observatories allowed for greater precision of key details like temperature, enabling the creation of a solar analog category for stars that were particularly similar to the Sun. Later still, continued improvements in precision allowed for the creation of a solar-twin category for near-perfect matches.Script error: No such module "Unsubst".

Similarity to the Sun allows for checking derived quantities—such as temperature, which is derived from the color index—against the Sun, the only star whose temperature is confidently known. For stars that are not similar to the Sun, this cross-checking cannot be done.[1]

Solar-type

These stars are broadly similar to the Sun. They are main-sequence stars with a B−V color between 0.48 and 0.80, the Sun having a B−V color of 0.65. Alternatively, a definition based on spectral type can be used, such as F8V through K2V, which would correspond to B−V color of 0.50 to 1.00.[1] This definition fits approximately 10% of stars, so a list of solar-type stars would be quite extensive.[3]

Solar-type stars show highly correlated behavior between their rotation rates and their chromospheric activity (e.g. Calcium H & K line emission) and coronal activity (e.g. X-ray emission)[4] Because solar-type stars spin down during their main-sequence lifetimes due to magnetic braking, these correlations allow rough ages to be derived. Mamajek & Hillenbrand (2008)[5] have estimated the ages for the 108 solar-type (F8V–K2V) main-sequence stars within 52 light-years (16 parsecs) of the Sun based on their chromospheric activity (as measured via Ca, H, and K emission lines).Script error: No such module "Unsubst".

The following table shows a sample of solar-type stars within 50 light years that nearly satisfy the criteria for solar analogs (B−V color between 0.48 and 0.80), based on current measurements (the Sun is listed for comparison):

Sample of solar-type stars
Identifier J2000 coordinates[6] Distance[6]
(ly) 		Stellar
class[6] 		Temperature
(K) 		Metallicity
(dex) 		Age
(Gyr) 		Notes
Right ascension Declination
Sun — — 0.0000158 G2V 5778 +0.00 4.6 [7]
Template:CelestialRefAll Template:RA Template:DEC 4.37 G2V 5790 +0.20 4.4 [8][9][10][11]
Toliman 4.37 K0V 5260 4.4
Template:CelestialRefAll Template:RA Template:DEC 10.4 K2V 5084 -0.13 0.4-0.8
Template:CelestialRefAll Template:RA Template:DEC 11.9 G8V 5344 –0.52 5.8 [12]
Template:CelestialRefAll Template:RA Template:DEC 19.8 G8V 5338 –0.54 6.1 [13]
Template:CelestialRefAll Template:RA Template:DEC 19.9 G8IV 5604 +0.33 ~7 [14]
Template:CelestialRefAll Template:RA Template:DEC 39.9 K1V 5257 −0.20 3.7 [13]
Template:CelestialRefAll Template:RA Template:DEC 41.3 G5V 5432 −0.46 9.6 [13]
Template:CelestialRefAll Template:RA Template:DEC 42.1 G8IV 5538 +0.18 8.5 [13]
Template:CelestialRefAll Template:RA Template:DEC 42.7 G5V 5610 −0.32 4.3 [13]
Template:CelestialRefAll Template:RA Template:DEC 46.9 G0V 5662 −0.37 5 [13]
Template:CelestialRefAll Template:RA Template:DEC 46.9 G8V 5415 −0.31 6.6 [14]
Template:CelestialRefAll Template:RA Template:DEC 47.5 G4V 5664 −0.34 10.3 [14]

Solar analog

These stars are photometrically similar to the Sun, having the following qualities:[1]

  • Temperature within 500 K from that of the Sun (5278 to 6278 K)
  • Metallicity of 50–200% (± 0.3 dex) of that of the Sun, meaning the star's protoplanetary disk would have had similar amounts of dust from which planets could form
  • No close companion (orbital period of ten days or less), because such a companion stimulates stellar activity

Solar analogs not meeting the stricter solar twin criteria include, within 50 light years and in order of increasing distance (The Sun is listed for comparison.):

Identifier J2000 coordinates[6] Distance[6]
(ly) 		Stellar
class[6] 		Temperature
(K) 		Metallicity
(dex) 		Age
(Gyr) 		Notes
Right ascension Declination
Sun — — 0.0000158 G2V 5,778 +0.00 4.6 [7]
Template:CelestialRefAll Template:RA Template:DEC 18.8 G9–K0 V 5,297 −0.20 4.7 [15]
Template:CelestialRefAll Template:RA Template:DEC 27.4 G0V 5,930 −0.30 6.0 [13]
Template:CelestialRefAll Template:RA Template:DEC 27.8 G5V 5,558 −0.02 6.3 [14]
Template:CelestialRefAll Template:RA Template:DEC 28.0 F9.5V 5,956 −0.14 2.5 [12]
Template:CelestialRefAll Template:RA Template:DEC 29.8 G0V 5,970 −0.06 2.0 [13]
Template:CelestialRefAll Template:RA Template:DEC 31.1 G8V 5,483 −0.12 1.0 [13]
Template:CelestialRefAll Template:RA Template:DEC 32.8 K0V 5,333 +0.05 3.0 [13]
Template:CelestialRefAll Template:RA Template:DEC 33.1 G5V 5,594 +0.10 5.4 [12]
Template:CelestialRefAll Template:RA Template:DEC 40.6 K0V 5,410 −0.03 10.6 [12]
Template:CelestialRefAll Template:RA Template:DEC 41.2 G1.5V 5,848 −0.05 7.0 [13]
Template:CelestialRefAll Template:RA Template:DEC 42.0 G1V 5,858 +0.03 0.4 [14]
Template:CelestialRefAll Template:RA Template:DEC 43.3 G3V 5,868 +0.02 0.6 [12]
Template:CelestialRefAll Template:RA Template:DEC 45.9 G1V 5,954 +0.06 6.0 [12]
Template:CelestialRefAll Template:RA Template:Dec 47.8 G5V 5,683 0.04 3.2 [16]
Template:CelestialRefAll Template:RA Template:DEC 48.5 F8V 6,167 −0.03 3.1 [12]
Template:CelestialRefAll Template:RA Template:DEC 48.6 G3V 5,878 −0.03 1.2 [12]
Template:CelestialRefAll Template:RA Template:DEC 49.1 G3V 5,741 +0.20 6.5 [13]
Template:CelestialRefAll Template:RA Template:DEC 49.3 F8V 6,140 +0.18 5.7 [12]
Template:CelestialRefAll Template:RA Template:DEC 50.9 G2.5IVa 5,804 +0.20 7.0 [12]

Solar twin

To date no solar twin that exactly matches the Sun has been found.[17] However, there are some stars that come very close to being identical to the Sun, and are such considered solar twins by members of the astronomical community. An exact solar twin would be a G2V star with a 5,778 K surface temperature, be 4.6 billion years old, with the correct metallicity and a 0.1% solar luminosity variation.[17] Stars with an age of 4.6 billion years are at the most stable state. Proper metallicity, radius, chemical composition, rotation, magnetic activity, and size are also very important to low luminosity variation.[18][19][20][21]

File:Morgan-Keenan spectral classification.svg
Morgan-Keenan spectral classification of stars. Most common star type in the universe are M-dwarfs, 76%. The Sun is a 4.6 billion year-old G-class (G2V) star and is more massive than 95% of all stars. Only 7.6% are G-class stars

The stars below are more similar to the Sun and having the following qualities:[1]

  • Temperature within 50 K from that of the Sun (5728 to 5828 K)Template:Efn (within 10 K of sun (5768–5788 K)).
  • Metallicity of 89–112% (± 0.05 dex) of that of the Sun, meaning the star's proplyd would have had almost exactly the same amount of dust for planetary formation
  • No stellar companion, because the Sun itself is a solitary star
  • An age within 1 billion years from that of the Sun (3.6 to 5.6 Ga)

Other Sun parameters:[22]


The following are the known stars that come closest to satisfying the criteria for a solar twin. The Sun is listed for comparison. Highlighted boxes are out of range for a solar twin. The star may have been noted as solar twin in the past, but are more of a solar analog.

Identifier J2000 coordinates[6] Distance[6]
(ly) 		Stellar
class[6] 		Temperature
(K) 		Metallicity
(dex) 		Age
(Gyr) 		Notes
Right ascension Declination
Sun — — 0.0000158 G2V 5,778 +0.00 4.6 [7]
Template:CelestialRefAll Template:RA Template:DEC 45.1 G2Va 5,433 −0.03 2.9 [24][25]
Template:CelestialRefAll Template:RA Template:DEC 88 G2 5,750 −0.04 6.2 [25]
Template:CelestialRefAll Template:RA Template:DEC 91 G2 5,810 −0.06 4.5 [25]
Template:CelestialRefAll Template:RA Template:DEC 92 G5 5,760 −0.04 2.9 [26]
Template:CelestialRefAll Template:RA Template:DEC 98 G3 5,730 −0.10 6.1 [25]
Template:CelestialRefAll Template:RA Template:DEC 99 G5IV–V 5,757 +0.00 7.1 [27]
Template:CelestialRefAll Template:RA Template:DEC 124 G2 5,701 −0.075 8.1 [28]
Template:CelestialRefAll Template:RA Template:DEC 135 G4V 5,759 −0.02 2.3 [25]
Template:CelestialRefAll Template:RA Template:DEC 141 G0 5,768 +0.00 3.8 (±2.9) [29]
Template:CelestialRefAll Template:RA Template:DEC 154 G2V 5,749 −0.02 8.2 [29]
Template:CelestialRefAll Template:RA Template:DEC 171 G0 5,808 +0.02 6.3 [24]
Template:CelestialRefAll Template:RA Template:DEC 184 G3 5,675 +0.00 4.5 [30]
Template:CelestialRefAll Template:RA Template:DEC 190 G5V 5,760 –0.059 4.1 [31]
Template:CelestialRefAll Template:RA Template:DEC 208 G5V 5,795 +0.02 7.1 [24][32]
Template:CelestialRefAll Template:RA Template:DEC 250 G3V 5,723 −0.013 8.2 [33]
Template:CelestialRefAll Template:RA Template:DEC 1400 G2V 5,757 +0.21 6.0 [34]
Template:CelestialRefAll Template:RA Template:DEC 2934 G5V 5,780 +0.023 ~ 4.2 (± 1.6) [35]

Some other stars are sometimes mentioned as solar-twin candidates such as: Beta Canum Venaticorum; however it has too low metallicities (−0.21) for solar twin. 16 Cygni B is sometimes noted as twin, but is part of a triple star system and is very old for a solar twin at 6.8 Ga.

By potential habitability

Another way of defining solar twin is as a "habstar"—a star with qualities believed to be particularly hospitable to a life-hosting planet. Qualities considered include variability, mass, age, metallicity, and close companions.[36]Template:Efn

  • At least 0.5–1 billion years old
  • On the main sequence
  • Non-variable
  • Capable of harboring terrestrial planets
  • Support a dynamically stable habitable zone
  • 0–1 non-wide stellar companion stars.

The requirement that the star remain on the main sequence for at least 0.5–1 Ga sets an upper limit of approximately 2.2–3.4 solar masses, corresponding to a hottest spectral type of A0-B7V. Such stars can be 100x as bright as the Sun.[36][37] Tardigrade-like life (due to the UV flux) could potentially survive on planets orbiting stars as hot as B1V, with a mass of 10 M☉, and a temperature of 25,000 K, a main-sequence lifetime of about 20 million years.Template:Efn

Non-variability is ideally defined as variability of less than 1%, but 3% is the practical limit due to limits in available data. Variation in irradiance in a star's habitable zone due to a companion star with an eccentric orbit is also a concern.[19][20][36][21]

Terrestrial planets in multiple star systems, those containing three or more stars, are not likely to have stable orbits in the long term. Stable orbits in binary systems take one of two forms: S-Type (satellite or circumstellar) orbits around one of the stars, and P-Type (planetary or circumbinary) orbits around the entire binary pair. Eccentric Jupiters may also disrupt the orbits of planets in habitable zones.[36]

Metallicity of at least 40% solar ([Fe/H] = −0.4) is required for the formation of an Earth-like terrestrial planet. High metallicity strongly correlates to the formation of hot Jupiters, but these are not absolute bars to life, as some gas giants end up orbiting within the habitable zone themselves, and could potentially host Earth-like moons.[36]

One example of such a star is Template:CelestialRefAll, a G5V, at temperature of 5533 K, but is much younger than the Sun, at 1.9 billion years old.[38]

Another such example would be HIP 11915, which has a planetary system containing a Jupiter-like planet orbiting at a similar distance that the planet Jupiter does in the Solar System.[39] To strengthen the similarities, the star is class G5V, has a temperature of 5750 K, has a Sun-like mass and radius, and is only 500 million years younger than the Sun. As such, the habitable zone would extend in the same area as the zone in the Solar System, around 1 AU. This would allow an Earth-like planet to exist around 1 AU.[40]

See also

Footnotes

Template:Notelist

References

Template:Reflist

Further reading

  • Script error: No such module "Citation/CS1".
  • Script error: No such module "Citation/CS1".
  • Script error: No such module "Citation/CS1".
  • Script error: No such module "Citation/CS1".
  • Script error: No such module "Citation/CS1".
  1. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named soderblum_king1998
  2. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lowell
  3. ↑ Script error: No such module "citation/CS1".
  4. ↑ Script error: No such module "Citation/CS1".
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named apj687_1264
  6. ↑ a b c d e f g h i Cite error: Invalid <ref> tag; no text was provided for refs named SIMBAD
  7. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named nssdc
  8. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named AlphaCentauriA1
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named AlphaCentauriA2
  10. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named AlphaCentauriA3
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named AlphaCentauriA4
  12. ↑ a b c d e f g h i j Cite error: Invalid <ref> tag; no text was provided for refs named aaa425
  13. ↑ a b c d e f g h i j k l Cite error: Invalid <ref> tag; no text was provided for refs named geneva3
  14. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named aaa487
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named apj683_1
  16. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aaa587
  17. ↑ a b Script error: No such module "citation/CS1".
  18. ↑ Script error: No such module "Citation/CS1".
  19. ↑ a b Script error: No such module "citation/CS1".
  20. ↑ a b Script error: No such module "citation/CS1".
  21. ↑ a b Script error: No such module "citation/CS1".
  22. ↑ Script error: No such module "Citation/CS1".
  23. ↑ Bjarne Rosenkilde Jørgensen, “The G Dwarf Problem: Analysis of a New Data Set,” Astronomy & Astrophysics 363, November 2000, 947
  24. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named apj669_2
  25. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named aaa563_A52
  26. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Takeda2009
  27. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Mahdi2016
  28. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named arxiv.org1
  29. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named apj130_5
  30. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aaa619
  31. ↑ Script error: No such module "Citation/CS1".
  32. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named vazquez_et_al_2010
  33. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Monroe2013
  34. ↑ Script error: No such module "citation/CS1".
  35. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named M67-1194
  36. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named Turnbull2002
  37. ↑ Script error: No such module "citation/CS1".
  38. ↑ Script error: No such module "citation/CS1".
  39. ↑ Script error: No such module "citation/CS1".
  40. ↑ Script error: No such module "citation/CS1".
Retrieved from "http://debianws.lexgopc.com/wiki143/index.php?title=Solar_analog&oldid=1454894"