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Main Sequence B Type Stars - Habitable Simulation

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The B-Type Stars are bright Main Sequence Stars on The H-R Diagram. Despite being rare, because of their brightness, they are the most common stars seen in the night sky. They are subdivided from B0 to B9. 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.

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.

B0 Star[]

Main parameters:

  • Temperature: 31400
  • Mass: 17.7
  • Radius: 7.6
  • Bolometric magnitude: -6.89
  • Visual magnitude: -3.9

Spectral parameters:

Main light spectra: 101 (ultraviolet)

  • Solar constant: 9270
  • Infrared light: 416
  • Red light: 1169
  • Visible light: 1890
  • Blue light: 4100
  • Ultraviolet light: 2510000
  • Far UV light: 5.53*10^24

Habitable zone, based on light emissions:

  • Solar constant = 20: 21.5 AU
  • Solar constant = 1: 96.3 AU
  • Solar constant = 1/1000: 3040 AU
  • Minimum red light: 1081 AU
  • Minimum blue light: 2024 AU
  • Maximum near UV light: 158.4 AU
  • Maximum far UV light: 2350000 AU
  • Roche limit: 0.00045 AU

The far ultraviolet light is very bright around B0 stars, sterilising all life within what otherwise would be a habitable zone. So, even if habitable temperature can be maintained as far as 3040 AU and there is enough light for plants as far as 1081 AU, terraforming is impossible without a powerful UV shield.

B1 Star[]

Main parameters:

  • Temperature: 26000
  • Mass: 11.0
  • Radius: 5.61
  • Bolometric magnitude: -5.58
  • Visual magnitude: -3

Spectral parameters:

Main light spectra: 122 (ultraviolet)

  • Solar constant: 2870
  • Infrared light: 185.2
  • Red light: 500
  • Visible light: 794
  • Blue light: 1674
  • Ultraviolet light: 801000
  • Far UV light: 2.53*10^23

Habitable zone, based on light emissions:

  • Solar constant = 20: 11.97 AU
  • Solar constant = 1: 53.5 AU
  • Solar constant = 1/1000: 1693 AU
  • Minimum red light: 707 AU
  • Minimum blue light: 1294 AU
  • Maximum near UV light: 89.5 AU
  • Maximum far UV light: 502000 AU
  • Roche limit: 0.00037 AU

The far ultraviolet light is very bright around B1 stars, sterilising all life within what otherwise would be a habitable zone. So, even if habitable temperature can be maintained as far as 1693 AU and there is enough light for plants as far as 707 AU, terraforming is impossible without a powerful UV shield.

B2 Star[]

Main parameters:

  • Temperature: 20600
  • Mass: 7.3
  • Radius: 4.6
  • Bolometric magnitude: -3.83
  • Visual magnitude: -1.8

Spectral parameters:

Main light spectra: 154 (ultraviolet)

  • Solar constant: 959
  • Infrared light: 96.8
  • Red light: 245
  • Visible light: 378
  • Blue light: 762
  • Ultraviolet light: 245000
  • Far UV light: 3.88*10^21

Habitable zone, based on light emissions:

  • Solar constant = 20: 6.92 AU
  • Solar constant = 1: 31.0 AU
  • Solar constant = 1/1000: 979 AU
  • Minimum red light: 495 AU
  • Minimum blue light: 873 AU
  • Maximum near UV light: 49.5 AU
  • Maximum far UV light: 62300 AU
  • Roche limit: 0.00031 AU

The far ultraviolet light is very bright around B2 stars, sterilising all life within what otherwise would be a habitable zone. So, even if habitable temperature can be maintained as far as 979 AU and there is enough light for plants as far as 495 AU, terraforming is impossible without a powerful UV shield.

B3 Star[]

Main parameters:

  • Temperature: 17000
  • Mass: 5.4
  • Radius: 3.61
  • Bolometric magnitude: -2.74
  • Visual magnitude: -1.2

Spectral parameters:

Main light spectra: 187 (ultraviolet)

  • Solar constant: 332
  • Infrared light: 48.2
  • Red light: 114.0
  • Visible light: 170.9
  • Blue light: 328
  • Ultraviolet light: 68900
  • Far UV light: 5.08*10^19

Habitable zone, based on light emissions:

  • Solar constant = 20: 4.07 AU
  • Solar constant = 1: 18.22 AU
  • Solar constant = 1/1000: 576 AU
  • Minimum red light: 338 AU
  • Minimum blue light: 573 AU
  • Maximum near UV light: 26.3 AU
  • Maximum far UV light: 7130 AU
  • Roche limit: 0.00026 AU

Around B3 stars, the environment is scorched with UV radiation, sterilizing all life. Still, it is questionable if some sort of bacteria would be able to survive at 600 AU from the star. On such a planet, greenhouse gasses would maintain the required temperature, but light would be too dim for most plants. Far UV radiation would be very strong, but still manageable for certain microorganisms. On the other hand, given the ionizing effect of far UV radiation, greenhouse gasses might suffer photodisintegration.

B4 Star[]

Main parameters:

  • Temperature: 16400
  • Mass: 5.1
  • Radius: 3.46
  • Bolometric magnitude: -2.49
  • Visual magnitude: -1.0

Spectral parameters:

Main light spectra: 194 (ultraviolet)

  • Solar constant: 274
  • Infrared light: 42.6
  • Red light: 99.2
  • Visible light: 147.7
  • Blue light: 281
  • Ultraviolet light: 53800
  • Far UV light: 2.08*10^19

Habitable zone, based on light emissions:

  • Solar constant = 20: 3.70 AU
  • Solar constant = 1: 16.55 AU
  • Solar constant = 1/1000: 523 AU
  • Minimum red light: 315 AU
  • Minimum blue light: 530 AU
  • Maximum near UV light: 23.2 AU
  • Maximum far UV light: 4570 AU
  • Roche limit: 0.00026 AU

Around B4 stars, the environment is scorched with UV radiation, sterilizing all life. Still, it is questionable if some sort of bacteria would be able to survive at 550 AU from the star. On such a planet, greenhouse gasses would maintain the required temperature, but light would be too dim for most plants. Far UV radiation would be very strong, but still manageable for certain microorganisms. On the other hand, given the ionizing effect of far UV radiation, greenhouse gasses might suffer photodisintegration.

B5 Star[]

Main parameters:

  • Temperature: 15700
  • Mass: 4.7
  • Radius: 3.36
  • Bolometric magnitude: -2.19
  • Visual magnitude: -0.85

Spectral parameters:

Main light spectra: 202 (ultraviolet)

  • Solar constant: 227
  • Infrared light: 38.2
  • Red light: 87.5
  • Visible light: 129.2
  • Blue light: 242
  • Ultraviolet light: 41300
  • Far UV light: 7.10*10^18

Habitable zone, based on light emissions:

  • Solar constant = 20: 3.37 AU
  • Solar constant = 1: 15.05 AU
  • Solar constant = 1/1000: 476 AU
  • Minimum red light: 296 AU
  • Minimum blue light: 492 AU
  • Maximum near UV light: 20.3 AU
  • Maximum far UV light: 2660 AU
  • Roche limit: 0.00025 AU

Around B5 stars, the environment is scorched with UV radiation, sterilizing all life. It is interesting that blue light is so intense that at the end of thermal habitable zone (492 compared to 476 AU) it is strong enough to support life. On the other hand, red light is too dim at that distance. Even that far, the far UV radiation is too strong for most Earth-like plants. Some bacteria and algae would still survive.

B6 Star[]

Main parameters:

  • Temperature: 14500
  • Mass: 4.3
  • Radius: 3.27
  • Bolometric magnitude: -1.68
  • Visual magnitude: -0.55

Spectral parameters:

Main light spectra: 219 (ultraviolet)

  • Solar constant: 169.0
  • Infrared light: 33.1
  • Red light: 73.1
  • Visible light: 106.2
  • Blue light: 194.1
  • Ultraviolet light: 26300
  • Far UV light: 9.33*10^17

Habitable zone, based on light emissions:

  • Solar constant = 20: 2.91 AU
  • Solar constant = 1: 13.00 AU
  • Solar constant = 1/1000: 411 AU
  • Minimum red light: 270 AU
  • Minimum blue light: 441 AU
  • Maximum near UV light: 16.21 AU
  • Maximum far UV light: 966 AU
  • Roche limit: 0.00023 AU

Around B6 stars, the environment is scorched with UV radiation, sterilizing all life. It is interesting that blue light is so intense that at the end of thermal habitable zone (441 compared with 411 AU) it is strong enough to support life. On the other hand, red light is too dim at that distance. Even that far, the far UV radiation is too strong for most Earth-like plants. Some bacteria and algae would still survive.

B7 Star[]

Main parameters:

  • Temperature: 14000
  • Mass: 3.92
  • Radius: 2.94
  • Bolometric magnitude: -1.45
  • Visual magnitude: -0.40

Spectral parameters:

Main light spectra: 227 (ultraviolet)

  • Solar constant: 123.0
  • Infrared light: 25.7
  • Red light: 55.8
  • Visible light: 80.5
  • Blue light: 145.3
  • Ultraviolet light: 17650
  • Far UV light: 3.00*10^17

Habitable zone, based on light emissions:

  • Solar constant = 20: 2.48 AU
  • Solar constant = 1: 11.09 AU
  • Solar constant = 1/1000: 351 AU
  • Minimum red light: 236 AU
  • Minimum blue light: 381 AU
  • Maximum near UV light: 13.28 AU
  • Maximum far UV light: 547 AU
  • Roche limit: 0.00022 AU

Around B7 stars, greenhouse and anti-greenhouse technology could make a planet habitable between 2.48 and 351 AU. However, plants would not have enough red light beyond 236 AU and under 547 AU far UV radiation is too strong. Still, it could be possible for some algae and bacteria to survive around 200-300 AU, on a planet protected with a thick layer of greenhouse gasses.

B8 Star[]

Main parameters:

  • Temperature: 12300
  • Mass: 3.38
  • Radius: 2.86
  • Bolometric magnitude: -0.73
  • Visual magnitude: 0.00

Spectral parameters:

Main light spectra: 258 (near ultraviolet)

  • Solar constant: 78.9
  • Infrared light: 21.0
  • Red light: 42.5
  • Visible light: 59.4
  • Blue light: 101.9
  • Ultraviolet light: 7950
  • Far UV light: 7.02*10^15

Habitable zone, based on light emissions:

  • Solar constant = 20: 1.986 AU
  • Solar constant = 1: 8.88 AU
  • Solar constant = 1/1000: 281 AU
  • Minimum red light: 206 AU
  • Minimum blue light: 319 AU
  • Maximum near UV light: 8.92 AU
  • Maximum far UV light: 83.8 AU
  • Roche limit: 0.00021 AU

Habitable zone parameters:

  • Inner habitable zone: 83.8 AU
  • Earth-like planet orbit: 8.88 AU
  • Outer habitable zone: 206.2 AU
  • Tidal index in habitable zone (Earth = 1): 0.0000795 - 0.000482
  • Orbital period in habitable zone: 152000 - 588000 days (416 - 1610 years)
  • Angular Size in habitable zone: 0.130 - 0.319 (Sun from Earth = 9.34)

Around B8 stars, some sort of habitable zone appears possible. Even if an Earth-Like Planet would be expected at 9 AU, because of strong far UV radiation, habitability is possible only among outer planets, between 83.8 and 206.2 AU. That far, plants have enough light to survive, even if they are bombarded by massive doses of radiation. Any planet would experience very long seasons.

B9 Star[]

Main parameters:

  • Temperature: 10700
  • Mass: 2.75
  • Radius: 2.49
  • Bolometric magnitude: 0.08
  • Visual magnitude: 0.5

Spectral parameters:

Main light spectra: 297 (near ultraviolet)

  • Solar constant: 39.4
  • Infrared light: 13.49
  • Red light: 25.1
  • Visible light: 33.7
  • Blue light: 54.2
  • Ultraviolet light: 2420
  • Far UV light: 5.59*10^13

Habitable zone, based on light emissions:

  • Solar constant = 20: 1.403 AU
  • Solar constant = 1: 6.27 AU
  • Solar constant = 1/1000: 198.4 AU
  • Minimum red light: 158.4 AU
  • Minimum blue light: 233 AU
  • Maximum near UV light: 4.92 AU
  • Maximum far UV light: 7.48 AU
  • Roche limit: 0.00019 AU

B9 stars offer the first truly habitable zone, where Earth-like life can exist. Let's take a closer look at it:

  • Earth-like temperatures: 6.27 AU
  • Habitable zone borders: 7.48 - 158.4 AU
  • Tidal index (Earth = 1): 0.0001095 - 0.0492
  • Orbital period in days: 4500 - 439000 (12.3 to 1202 years)
  • Angular size (Sun from Earth = 9.34): 0.147 - 3.11

A terraformed planet around a B9 star will be mostly an Outer Planet. There will be a strong far UV radiation, which will force organisms to adapt. At the inner edge of the habitable zone, conditions will be like on Mars, while at the outer edge, it will be like on the moons of Uranus.

Conclusion[]

B - type stars are at the outer edge of habitable stars. Despite their extreme brightness, which cause apparent large habitable zones to exist, these stars emit deadly amounts of far UV radiation. Still, some outer planets can be, in certain cases, terraformed. For stars brighter then B5, life is basically out of question. For stars classified as B5 to B7, some algae and bacteria might survive, but certainly humans will not be able to survive without a radiation protection gear. It is interesting that B8 and B9 stars can offer a habitable zone for humans, even if not actually a friendly one.

See Also[]

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