Main Sequence A Type Stars - Habitable Simulation

The A-Type Stars are bright Main Sequence Stars on The H-R Diagram. They are the second most common stars seen in the night sky. They are subdivided from A0 to A9. 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 5500 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:

Roche limit - below it, a star's gravity would tear apart any planet;
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.
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.
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.

Further parameters:

Extended habitable zone (for Sol 0.223 to 31.6 AU): After applying all these constrains, one can determine the extended Habitable Zone, where greenhouse gasses or anti-greenhouse technology can bring temperature within acceptable boundaries, plants have enough red and blue light and toxic UV radiation is within acceptable limits.
Earth-like planet orbit: The distance of a Habitable Zone Planet or Earth-Like Planet (for Sol, 1 AU) is where a planet can exist without greenhouse gasses or anti greenhouse technology. It is listed if it fits within the extended habitable zone.
Tidal index: The star's tidal force on a planet in the extended habitable zone.
Orbital period: the orbital period of a star within the extended habitable zone.
Angular size: the size of the star as viewed from a planet in the habitable zone (Sol from Earth: 9.34). To see yourself how large a star would be as seen from a planet, draw a circle with the listed size in millimetres and look at it from a distance of one metre.

A0 Star[]

Main parameters:

Temperature: 9700
Mass: 2.18
Radius: 2.193
Bolometric magnitude: 0.78
Visual magnitude: 0.99

Spectral parameters:

Main light spectra: 327 (blue)

Solar constant: 22.8
Infrared light: 9.31
Red light: 16.14
Visible light: 21.0
Blue light: 40.0
Ultraviolet light: 911
Far UV light: 1.17*10^12

Habitable zone, based on light emissions:

Solar constant = 20: 1.067 AU
Solar constant = 1: 4.77 AU
Solar constant = 1/1000: 150.8 AU
Minimum red light: 127.1 AU
Minimum blue light: 178.8 AU
Maximum near UV light: 3.02 AU
Maximum far UV light: 1.083 AU
Roche limit: 0.00017 AU

Further parameters:

Extended habitable zone: 3.02 - 127.1 AU
Earth-like planet orbit: 4.77 AU
Tidal index: 0.0001350 - 0.239
Orbit period (days): 1297 - 354000 (3.6 - 970 years)
Angular size: 0.16 to 6.79.

An A0 star offers a wide habitable zone. An Earth-like planet would orbit just where the far UV radiation becomes too strong for Earth-like life to survive. A0 stars have a wide habitable area that can support many outer planets.

A1 Star[]

Main parameters:

Temperature: 9300
Mass: 2.05
Radius: 2.136
Bolometric magnitude: 1.02
Visual magnitude: 1.16

Spectral parameters:

Main light spectra: 342 (blue)

Solar constant: 19.02
Infrared light: 8.39
Red light: 14.09
Visible light: 18.02
Blue light: 26.8
Ultraviolet light: 620
Far UV light: 2.11*10^11

Habitable zone, based on light emissions:

Solar constant = 20: 0.975 AU
Solar constant = 1: 4.36 AU
Solar constant = 1/1000: 137.9 AU
Minimum red light: 118.7 AU
Minimum blue light: 163.6 AU
Maximum near UV light: 2.49 AU
Maximum far UV light: 0.459 AU
Roche limit: 0.00016 AU

Further parameters:

Extended habitable zone: 2.49 - 118.7 AU
Earth-like planet orbit: 4.36 AU
Tidal index: 0.0001455 - 0.331
Orbit period (days): 1002 - 330000 (2.7 - 903 years)
Orbital period for Earth-like planet: 2322 (6.4 years)
Angular size: 0.17 to 8.02
Angular size for Earth-like planet: 4.58.

An A1 star offers a wide habitable zone and can host an Earth-like planet. There are plenty of orbits available for outer planets that can be terraformed. Inner planets are exposed to high doses of UV radiation beyond what Earth-like organisms can tolerate. An Earth-like planet will still experience huge doses of UV radiation. Settlers will need sunscreen while out in the daylight.

A2 Star[]

Main parameters:

Temperature: 8800
Mass: 1.98
Radius: 2.117
Bolometric magnitude: 1.28
Visual magnitude: 1.35

Spectral parameters:

Main light spectra: 361 (blue)

Solar constant: 185.83
Infrared light: 7.71
Red light: 12.36
Visible light: 15.47
Blue light: 22.2
Ultraviolet light: 385
Far UV light: 2.10*10^10

Habitable zone, based on light emissions:

Solar constant = 20: 0.890 AU
Solar constant = 1: 3.98 AU
Solar constant = 1/1000: 125.8 AU
Minimum red light: 111.2 AU
Minimum blue light: 149.0 AU
Maximum near UV light: 1.963 AU
Maximum far UV light: 0.145 AU
Roche limit: 0.00016 AU

Further parameters:

Extended habitable zone: 1.963 - 111.2 AU
Earth-like planet orbit: 3.98 AU
Tidal index: 0.0001603 - 0.514
Tidal index for Earth-like planet: 0.1251
Orbit period (days): 713 - 304000 (2.0 - 832 years)
Orbital period for Earth-like planet: 2060 (5.6 years)
Angular size: 0.18 to 10.08
Angular size for Earth-like planet: 4.97.

There is a wide habitable zone around an A2 star, with possible orbits for Earth-like planets. While not many inner planets can theoretically be terraformed, there are plenty of orbits for outer planets.

A3 Star[]

Main parameters:

Temperature: 8600
Mass: 1.86
Radius: 1.861
Bolometric magnitude: 1.66
Visual magnitude: 1.7

Spectral parameters:

Main light spectra: 369 (blue)

Solar constant: 11.42
Infrared light: 5.79
Red light: 9.10
Visible light: 11.28
Blue light: 15.95
Ultraviolet light: 244
Far UV light: 6040000000

Habitable zone, based on light emissions:

Solar constant = 20: 0.756 AU
Solar constant = 1: 3.38 AU
Solar constant = 1/1000: 106.9 AU
Minimum red light: 95.4 AU
Minimum blue light: 126.3 AU
Maximum near UV light: 1.563 AU
Maximum far UV light: 0.0777 AU
Roche limit: 0.00015 AU

Further parameters:

Extended habitable zone: 1.563 - 95.4 AU
Earth-like planet orbit: 3.38 AU
Tidal index: 0.000204 - 0761
Tidal index for Earth-like planet: 0.163
Orbit period (days): 523 - 248000 (1.4 - 679 years)
Orbital period for Earth-like planet: 1663 (4.6 years)
Angular size: 0.18 to 11.13
Angular size for Earth-like planet: 5.15.

A3 stars can host Earth-like planets (even if exposed to high doses of UV radiation) and can host terraformable inner and outer planets. The inner limiting factor is near UV radiation and the outer limiting factor is the red light. A mid-outer planet would experience acceptable levels of radiation and still will receive significant amounts of light.

A4 Star[]

Main parameters:

Temperature: 8250
Mass: 1.93
Radius: 1.794
Bolometric magnitude: 1.92
Visual magnitude: 1.94

Spectral parameters:

Main light spectra: 385 (blue)

Solar constant: 9.37
Infrared light: 5.11
Red light: 7.74
Visible light: 9.43
Blue light: 12.95
Ultraviolet light: 156.8
Far UV light: 884000000

Habitable zone, based on light emissions:

Solar constant = 20: 0.684 AU
Solar constant = 1: 3.06 AU
Solar constant = 1/1000: 96.8 AU
Minimum red light: 88.0 AU
Minimum blue light: 113.8 AU
Maximum near UV light: 1.252 AU
Maximum far UV light: 0.0298 AU
Roche limit: 0.00016 AU

Further parameters:

Extended habitable zone: 1.252 - 88.0 AU
Earth-like planet orbit: 3.06 AU
Tidal index: 0.000249 - 1.231
Tidal index for Earth-like planet: 0.206
Orbit period (days): 368 - 217000 (1.0 - 594 years)
Orbital period for Earth-like planet: 1407 (3.9 years)
Angular size: 0.19 to 13.39
Angular size for Earth-like planet: 5.48.

A4 stars have large extended habitable zones. They can host Earth-like planets (even if baked in UV radiation). Their light is good for supporting plant life. Terraformed planets will experience long seasons as their orbit period is long.

A5 Star[]

Main parameters:

Temperature: 8100
Mass: 1.88
Radius: 1.785
Bolometric magnitude: 2.01
Visual magnitude: 2.01

Spectral parameters:

Main light spectra: 392 (blue)

Solar constant: 8.78
Infrared light: 4.94
Red light: 7.36
Visible light: 8.89
Blue light: 12.05
Ultraviolet light: 131.2
Far UV light: 377000000

Habitable zone, based on light emissions:

Solar constant = 20: 0.662 AU
Solar constant = 1: 2.96 AU
Solar constant = 1/1000: 93.7 AU
Minimum red light: 85.8 AU
Minimum blue light: 109.8 AU
Maximum near UV light: 1.146 AU
Maximum far UV light: 0.01942 AU
Roche limit: 0.00016 AU

Further parameters:

Extended habitable zone: 1.146 - 85.8 AU
Earth-like planet orbit: 2.96 AU
Tidal index: 0.000256 - 1.433
Tidal index for Earth-like planet: 0.214
Orbit period (days): 326 - 211000 (0.9 - 578 years)
Orbital period for Earth-like planet: 1358 (3.7 years)
Angular size: 0.19 to 14.56
Angular size for Earth-like planet: 5.63.

A5 stars have large extended habitable zones. They can host Earth-like planets (even if baked in UV radiation). Their light is good for supporting plant life. Terraformed planets will experience long seasons as their orbit period is long.

A6 Star[]

Main parameters:

Temperature: 7910
Mass: 1.83
Radius: 1.775
Bolometric magnitude: 2.05
Visual magnitude: 2.12

Spectral parameters:

Main light spectra: 401 (blue)

Solar constant: 8.08
Infrared light: 4.75
Red light: 6.90
Visible light: 8.25
Blue light: 10.99
Ultraviolet light: 103.9
Far UV light: 122800000

Habitable zone, based on light emissions:

Solar constant = 20: 0.654 AU
Solar constant = 1: 2.84 AU
Solar constant = 1/1000: 89.9 AU
Minimum red light: 83.1 AU
Minimum blue light: 104.9 AU
Maximum near UV light: 1.019 AU
Maximum far UV light: 0.01108 AU
Roche limit: 0.00015 AU

Further parameters:

Extended habitable zone: 1.019 - 83.1 AU
Earth-like planet orbit: 2.84 AU
Tidal index: 0.000265 - 1.761
Tidal index for Earth-like planet: 0.226
Orbit period (days): 278 - 204000 (0.8 - 559 years)
Orbital period for Earth-like planet: 1293 (3.5 years)
Angular size: 0.20 to 16.27
Angular size for Earth-like planet: 5.83.

A6 stars have large extended habitable zones. They can host Earth-like planets (even if baked in UV radiation). Their light is good for supporting plant life. Terraformed planets will experience long seasons as their orbit period is long.

A7 Star[]

Main parameters:

Temperature: 7760
Mass: 1.77
Radius: 1.75
Bolometric magnitude: 2.21
Visual magnitude: 2.23

Spectral parameters:

Main light spectra: 409 (blue)

Solar constant: 7.82
Infrared light: 4.50
Red light: 6.43
Visible light: 7.62
Blue light: 10.00
Ultraviolet light: 84.1
Far UV light: 47800000

Habitable zone, based on light emissions:

Solar constant = 20: 0.609 AU
Solar constant = 1: 2.72 AU
Solar constant = 1/1000: 86.1 AU
Minimum red light: 80.2 AU
Minimum blue light: 100.0 AU
Maximum near UV light: 0.917 AU
Maximum far UV light: 0.00691 AU
Roche limit: 0.00015 AU

Further parameters:

Extended habitable zone: 0.917 - 80.2 AU
Earth-like planet orbit: 2.72 AU
Tidal index: 0.000275 - 2.10
Tidal index for Earth-like planet: 0.239
Orbit period (days): 241 - 197000 (0.7 - 539 years)
Orbital period for Earth-like planet: 1233 (3.4 years)
Angular size: 0.20 to 17.83
Angular size for Earth-like planet: 6.00.

A7 stars have large extended habitable zones. They can host Earth-like planets (even if baked in UV radiation). Their light is good for supporting plant life. Terraformed planets will experience long seasons as their orbit period is long.

A8 Star[]

Main parameters:

Temperature: 7590
Mass: 1.81
Radius: 1.747
Bolometric magnitude: 2.34
Visual magnitude: 2.32

Spectral parameters:

Main light spectra: 419 (blue)

Solar constant: 6.92
Infrared light: 4.36
Red light: 6.09
Visible light: 7.14
Blue light: 9.22
Ultraviolet light: 67.5
Far UV light: 16150000

Habitable zone, based on light emissions:

Solar constant = 20: 0.588 AU
Solar constant = 1: 2.63 AU
Solar constant = 1/1000: 83.2 AU
Minimum red light: 78.0 AU
Minimum blue light: 96.0 AU
Maximum near UV light: 0.822 AU
Maximum far UV light: 0.00402 AU
Roche limit: 0.00015 AU

Further parameters:

Extended habitable zone: 0.822 - 78.0 AU
Earth-like planet orbit: 2.63 AU
Tidal index: 0.000297 - 2.68
Tidal index for Earth-like planet: 0.262
Orbit period (days): 302 - 187100 (0.8 - 512 years)
Orbital period for Earth-like planet: 1157 (3.2 years)
Angular size: 0.21 to 19.87
Angular size for Earth-like planet: 6.21.

A8 stars have large extended habitable zones. They can host Earth-like planets (even if baked in UV radiation). Their light is good for supporting plant life. Terraformed planets will experience long seasons as their orbit period is long. Inner planets will have an year comparable with the length of an Earth year and will experience some slowdown in their rotation period caused by star's tidal force.

A9 Star[]

Main parameters:

Temperature: 7400
Mass: 1.75
Radius: 1.740
Bolometric magnitude: 2.45
Visual magnitude: 2.43

Spectral parameters:

Main light spectra: 429 (blue)

Solar constant: 6.41
Infrared light: 4.23
Red light: 5.74
Visible light: 6.65
Blue light: 8.41
Ultraviolet light: 52.4
Far UV light: 4550000

Habitable zone, based on light emissions:

Solar constant = 20: 0.566 AU
Solar constant = 1: 2.53 AU
Solar constant = 1/1000: 0.1 AU
Minimum red light: 75.8 AU
Minimum blue light: 91.7 AU
Maximum near UV light: 0.724 AU
Maximum far UV light: 0.00213 AU
Roche limit: 0.00015 AU

Further parameters:

Extended habitable zone: 0.724 - 75.8 AU
Earth-like planet orbit: 2.53 AU
Tidal index: 0.000305 - 3.34
Tidal index for Earth-like planet: 0.273
Orbit period (days): 169.9 - 182100 (0.5 - 499 years)
Orbital period for Earth-like planet: 1112 (3.0 years)
Angular size: 0.22 to 22.6
Angular size for Earth-like planet: 6.45.

A9 stars have large extended habitable zones. They can host Earth-like planets (even if baked in UV radiation). Their light is good for supporting plant life. Terraformed planets will experience long seasons as their orbit period is long. Inner planets will have an year comparable with the length of an Earth year and will experience some slowdown in their rotation period caused by star's tidal force.

Conclusion[]

A stars have enough red light to support life on their outer planets close to the area where the solar constant falls to 1/1000. They have enough blue light to sustain plant life even beyond. Most of them can support an Earth-like planet within the heart of the habitable zone. These star emit strong doses of UV radiation. Inner planets are, in most cases, too irradiated to be suitable for terraforming. Planets would experience long seasons as their rotation period is long.

Main Sequence A Type Stars - Habitable Simulation

Contents

About the values[]

A0 Star[]

A1 Star[]

A2 Star[]

A3 Star[]

A4 Star[]

A5 Star[]

A6 Star[]

A7 Star[]

A8 Star[]

A9 Star[]

Conclusion[]

See Also[]