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Main Sequence O Type Stars - Habitable Simulation

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The O-Type Stars are the brightest of all Main Sequence Stars on The H-R Diagram. They are very rare and extremely bright. They are subdivided from O0 to O9. This article is based on data available from [www.pas.rochester.edu/~emamajek/EEM_dwarf_UBVIJHK_colors_Teff.txt here]. Additional parameters are calculated using the black body radiation formulas available at Math And Terraforming.

Please note that no main-sequence O0, O1 and O2 stars have been discovered yet. In our current universe, stars cannot form above a certain mass. This was not the case of the early Universe, where Primordial Stars are theorized to be far larger and more massive then what we have today. I calculated the parameters for these three subcategories by extending the table available [www.pas.rochester.edu/~emamajek/EEM_dwarf_UBVIJHK_colors_Teff.txt here].

It is very important to remember that stars don't behave exactly as shown in the table. Each star has its own variations. Also, my calculations are based on the black body radiation formulas and they do not include flares and the Stellar Wind.

For each star model, parameters are compared to our own sun, Sol.

This article is dedicated for sci-fi writers, to have a better and close-up idea if a planet around a certain star can indeed be terraformed or not and at what cost. Please don't take it as a scientific work, it is just a simulation made with values that are much more easy to understand then dedicated scientific papers.

About the values[]

For all stars, the following parameters are calculated:

Main parameters:

  • Temperature (in degrees K, for our Sun, Sol it is 5778 K).
  • Mass: given in Solar masses
  • Radius: given in Solar radii
  • Bolometric Magnitude: includes all star's radiation, for Sol it is 4.81.
  • Visual magnitude: includes only visual light, for Sol it is 4.81.

Spectral parameters:

Main light spectra (for Sol, it is 577 nm). It helps us see if most light is emitted in red, blue, infrared or ultraviolet spectra.

  • Solar Constant - total energy output of the star: (Sol = 1)
  • Infrared light: (Sol = 1)
  • Red light: (Sol = 1)
  • Visible light: (Sol = 1)
  • Blue light: (Sol = 1)
  • Ultraviolet light: (Sol = 1)
  • Far UV light: (Sol = 1)

Habitable zone, based on light emissions:

Calculating the habitable zone, one must include four parameters:

  1. Roche limit - below it, a star's gravity would tear apart any planet;
  2. Solar constant - depends on distance from the star. For Earth, it is 1. Using Greenhouse Gases, it is possible to terraform a planet with a solar constant of 1/1000. By using Anti-Greenhouse Technology, it might be possible to terraform a planet with a solar constant of 20.
  3. Light spectra - Plants on New Worlds need both red and blue light, which must be at least 1/1000 of what is on Earth. If either red or blue light fall below this limit, plants will not survive.
  4. Toxic radiation include UV (especially far UV), X, gamma rays and ionized particle from the Stellar Wind. If toxic radiation is over 100 times higher then on Earth, Earth-like life is seriously threatened and atmosphere becomes too ionized and might be blown into space.

O0 Star[]

Main parameters:

  • Temperature: 52000
  • Mass: 139
  • Radius: 17.4
  • Bolometric magnitude: -11.3
  • Visual magnitude: -6.7

Spectral parameters:

Main light spectra: 61 (mid UV)

  • Solar constant: 221000
  • Infrared light: 3700
  • Red light: 11210
  • Visible light: 18730
  • Blue light: 42700
  • Ultraviolet light: 40300000
  • Far UV light: 3.29*10^27

Habitable zone, based on light emissions:

  • Solar constant = 20: 105 AU
  • Solar constant = 1: 470 AU
  • Solar constant = 1/1000: 14860 AU
  • Minimum red light: 3350 AU
  • Minimum blue light: 6540 AU
  • Maximum near UV light: 635 AU
  • Maximum far UV light: 57300000 AU
  • Roche limit: 0.0013 AU

As one can see, plants that need red light cannot live beyond 3350 AU, where red light is too dim. On the other hand, UV radiation is very high.

O1 Star[]

Main parameters:

  • Temperature: 49600
  • Mass: 132
  • Radius: 16.6
  • Bolometric magnitude: -10.8
  • Visual magnitude: -6.4

Spectral parameters:

Main light spectra: 64 (mid UV)

  • Solar constant: 173400
  • Infrared light: 3190
  • Red light: 9630
  • Visible light: 16040
  • Blue light: 36500
  • Ultraviolet light: 33300000
  • Far UV light: 2.089*10^27

Habitable zone, based on light emissions:

  • Solar constant = 20: 93.1 AU
  • Solar constant = 1: 416 AU
  • Solar constant = 1/1000: 13170 AU
  • Minimum red light: 3100 AU
  • Minimum blue light: 6040 AU
  • Maximum near UV light: 577 AU
  • Maximum far UV light: 45700000 AU
  • Roche limit: 0.0012 AU

As one can see, plants that need red light cannot live beyond 3100 AU, where red light is too dim. On the other hand, UV radiation is very high.

O2 Star[]

Main parameters:

  • Temperature: 47200
  • Mass: 126
  • Radius: 15.8
  • Bolometric magnitude: -10.3
  • Visual magnitude: -6.1

Spectral parameters:

Main light spectra: 67 (mid UV)

  • Solar constant: 135000
  • Infrared light: 2750
  • Red light: 8230
  • Visible light: 13700
  • Blue light: 31000
  • Ultraviolet light: 27400000
  • Far UV light: 1.29*10^27

Habitable zone, based on light emissions:

  • Solar constant = 20: 82.3 AU
  • Solar constant = 1: 368 AU
  • Solar constant = 1/1000: 11600 AU
  • Minimum red light: 2870 AU
  • Minimum blue light: 5570 AU
  • Maximum near UV light: 523 AU
  • Maximum far UV light: 35900000 AU
  • Roche limit: 0.0012 AU

As one can see, plants that need red light cannot live beyond 2870 AU, where red light is too dim. On the other hand, UV radiation is very high.

O3 Star[]

Main parameters:

  • Temperature: 44900
  • Mass: 120
  • Radius: 15.0
  • Bolometric magnitude: -9.81
  • Visual magnitude: -5.8

Spectral parameters:

Main light spectra: 71 (mid UV)

  • Solar constant: 106000
  • Infrared light: 2360
  • Red light: 7030
  • Visible light: 11700
  • Blue light: 26300
  • Ultraviolet light: 22400000
  • Far UV light: 7.78*10^26

Habitable zone, based on light emissions:

  • Solar constant = 20: 78.7 AU
  • Solar constant = 1: 325 AU
  • Solar constant = 1/1000: 10200 AU
  • Minimum red light: 2650 AU
  • Minimum blue light: 5130 AU
  • Maximum near UV light: 474 AU
  • Maximum far UV light: 27900000 AU
  • Roche limit: 0.0012 AU

As one can see, plants that need red light cannot live beyond 2650 AU, where red light is too dim. On the other hand, UV radiation is very high.

O4 Star[]

Main parameters:

  • Temperature: 42900
  • Mass: 85.3
  • Radius: 13.43
  • Bolometric magnitude: -9.4
  • Visual magnitude: -5.5

Spectral parameters:

Main light spectra: 74 (mid UV)

  • Solar constant: 73800
  • Infrared light: 1803
  • Red light: 5340
  • Visible light: 8830
  • Blue light: 19820
  • Ultraviolet light: 16340000
  • Far UV light: 4.23*10^26

Habitable zone, based on light emissions:

  • Solar constant = 20: 60.8 AU
  • Solar constant = 1: 272 AU
  • Solar constant = 1/1000: 8590 AU
  • Minimum red light: 2310 AU
  • Minimum blue light: 4450 AU
  • Maximum near UV light: 404 AU
  • Maximum far UV light: 20600000 AU
  • Roche limit: 0.0010 AU

As one can see, plants that need red light cannot live beyond 2310 AU, where red light is too dim. On the other hand, UV radiation is very high.

O5 Star[]

Main parameters:

  • Temperature: 41400
  • Mass: 60
  • Radius: 12.0
  • Bolometric magnitude: -9.11
  • Visual magnitude: -5.35

Spectral parameters:

Main light spectra: 77 (mid UV)

  • Solar constant: 53000
  • Infrared light: 1387
  • Red light: 4090
  • Visible light: 6740
  • Blue light: 15080
  • Ultraviolet light: 12090000
  • Far UV light: 2.46*10^26

Habitable zone, based on light emissions:

  • Solar constant = 20: 51.5 AU
  • Solar constant = 1: 230 AU
  • Solar constant = 1/1000: 7280 AU
  • Minimum red light: 2020 AU
  • Minimum blue light: 3880 AU
  • Maximum near UV light: 348 AU
  • Maximum far UV light: 15690000 AU
  • Roche limit: 0.00087 AU

As one can see, plants that need red light cannot live beyond 2020 AU, where red light is too dim. On the other hand, UV radiation is very high.

O6 Star[]

Main parameters:

  • Temperature: 39500
  • Mass: 43.7
  • Radius: 10.7
  • Bolometric magnitude: -8.67
  • Visual magnitude: -5.10

Spectral parameters:

Main light spectra: 80 (mid UV)

  • Solar constant: 36600
  • Infrared light: 1052
  • Red light: 3080
  • Visible light: 5060
  • Blue light: 11270
  • Ultraviolet light: 8690000
  • Far UV light: 1.27*10^26

Habitable zone, based on light emissions:

  • Solar constant = 20: 42.8 AU
  • Solar constant = 1: 191.4 AU
  • Solar constant = 1/1000: 6050 AU
  • Minimum red light: 1754 AU
  • Minimum blue light: 3360 AU
  • Maximum near UV light: 295 AU
  • Maximum far UV light: 11260000 AU
  • Roche limit: 0.00075 AU

As one can see, plants that need red light cannot live beyond 1754 AU, where red light is too dim. On the other hand, UV radiation is very high.

O7 Star[]

Main parameters:

  • Temperature: 37100
  • Mass: 30.9
  • Radius: 9.52
  • Bolometric magnitude: -8.21
  • Visual magnitude: -4.80

Spectral parameters:

Main light spectra: 86 (mid UV)

  • Solar constant: 24000
  • Infrared light: 778
  • Red light: 2250
  • Visible light: 3690
  • Blue light: 8170
  • Ultraviolet light: 5950000
  • Far UV light: 5.42*10^25

Habitable zone, based on light emissions:

  • Solar constant = 20: 34.6 AU
  • Solar constant = 1: 154.9 AU
  • Solar constant = 1/1000: 4900 AU
  • Minimum red light: 1501 AU
  • Minimum blue light: 2860 AU
  • Maximum near UV light: 244 AU
  • Maximum far UV light: 7360000 AU
  • Roche limit: 0.00063 AU

As one can see, plants that need red light cannot live beyond 1501 AU, where red light is too dim. On the other hand, UV radiation is very high.

O8 Star[]

Main parameters:

  • Temperature: 35100
  • Mass: 23
  • Radius: 8.5
  • Bolometric magnitude: -7.74
  • Visual magnitude: -4.50

Spectral parameters:

Main light spectra: 90 (mid UV)

  • Solar constant: 16200
  • Infrared light: 585
  • Red light: 1680
  • Visible light: 2740
  • Blue light: 6020
  • Ultraviolet light: 4160000
  • Far UV light: 2.43*10^25

Habitable zone, based on light emissions:

  • Solar constant = 20: 28.5 AU
  • Solar constant = 1: 127.2 AU
  • Solar constant = 1/1000: 4020 AU
  • Minimum red light: 1296 AU
  • Minimum blue light: 2450 AU
  • Maximum near UV light: 204 AU
  • Maximum far UV light: 4930000 AU
  • Roche limit: 0.00054 AU

As one can see, plants that need red light cannot live beyond 1296 AU, where red light is too dim. On the other hand, UV radiation is very high.

O9 Star[]

Main parameters:

  • Temperature: 33300
  • Mass: 19.63
  • Radius: 7.51
  • Bolometric magnitude: -7.31
  • Visual magnitude: -4.2

Spectral parameters:

Main light spectra: 95 (mid UV)

  • Solar constant: 10800
  • Infrared light: 432
  • Red light: 1229
  • Visible light: 1996
  • Blue light: 4360
  • Ultraviolet light: 2850000
  • Far UV light: 1.07*10^25

Habitable zone, based on light emissions:

  • Solar constant = 20: 23.2 AU
  • Solar constant = 1: 103.9 AU
  • Solar constant = 1/1000: 3290 AU
  • Minimum red light: 1108 AU
  • Minimum blue light: 2090 AU
  • Maximum near UV light: 168.8 AU
  • Maximum far UV light: 3260000 AU
  • Roche limit: 0.00050 AU

As one can see, plants that need red light cannot live beyond 1108 AU, where red light is too dim. On the other hand, UV radiation is very high.

Conclusion[]

O - type stars are not habitable for chlorophyll type plants and Earth animals. The ultraviolet radiation is far too strong to allow this type of life to exist. Purple or orange plants may or may not survive. What is worse is that these stars emit strong doses of far UV, which is extremely poisonous for Earth-like life and has a strong ionizing effect on whatever atmospheres hosted planets might have.

See Also[]

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