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Size: 2075
Comment:
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Size: 4153
Comment:
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| Deletions are marked like this. | Additions are marked like this. |
| Line 7: | Line 7: |
| || M || L || r || life || vesc || Wp || || M⊙ || L⊙ || AU || GY || km/s || mag || || 0.50 || 0.0625 || 0.2500 || 40.0000 || 42.4264 || M1V || || 0.55 || 0.0915 || 0.3025 || 30.0526 || 40.4520 || || || 0.60 || 0.1296 || 0.3600 || 23.1481 || 38.7298 || M0V || || 0.65 || 0.1785 || 0.4225 || 18.2066 || 37.2104 || || || 0.70 || 0.2401 || 0.4900 || 14.5773 || 35.8569 || K5V || || 0.75 || 0.3164 || 0.5625 || 11.8519 || 34.6410 || K3V || est. || || 0.80 || 0.4096 || 0.6400 || 9.7656 || 33.5410 || K2V || est. || || 0.85 || 0.5220 || 0.7225 || 8.1417 || 32.5396 || G9V || || 0.90 || 0.6561 || 0.8100 || 6.8587 || 31.6228 || G7V || || 0.95 || 0.8145 || 0.9025 || 5.8318 || 30.7794 || G6V || || 1.00 || 1.0000 || 1.0000 || 5.0000 || 30.0000 || G4V || || 1.05 || 1.2155 || 1.1025 || 4.3192 || 29.2770 || G3V || || 1.10 || 1.4641 || 1.2100 || 3.7566 || 28.6039 || G1V || || 1.15 || 1.7490 || 1.3225 || 3.2876 || 27.9751 || F9V || est. || || 1.20 || 2.0736 || 1.4400 || 2.8935 || 27.3861 || F7V || est. || || 1.25 || 2.4414 || 1.5625 || 2.5600 || 26.8328 || F6V || est. || || 1.30 || 2.8561 || 1.6900 || 2.2758 || 26.3117 || F4V || est. || || 1.35 || 3.3215 || 1.8225 || 2.0322 || 25.8199 || F3V || est. || || 1.40 || 3.8416 || 1.9600 || 1.8222 || 25.3546 || F1V || est. || |
'''NOTE''' the "lifetime" should be scaled (somehow) to the amount of photosynthesis-friendly red light compared to the amount of life-scrambling thermal infrared. Life decays with thermal energy, and builds from red photons (blue is used by terrestrial photosynthesis, but probably is not necessary). '''NOTE 2''' Other photosynthetic systems may be more optimal, using different colors of light. == not so good table == ||Class || Radius || Mass || Lum || Temp || Example || || B || V || R || H || Planet || vesc || || || R/R☉ || M/M☉ || L/L☉ || K || || GY || 445 || 551 || 658 || 1630 || AU || km/s || || F0 || 1.3 || 1.7 || 6 || 7,240 || Gamma Virginis || || F5 || 1.2 || 1.3 || 2.5 || 6,540 || Eta Arietis || || G0 || 1.05 || 1.10 || 1.26 || 5,920 || Beta Comae Berenices || || G2 || 1.00 || 1.00 || 1.00 || 5,780 || Sun || || G5 || 0.93 || 0.93 || 0.79 || 5,610 || Alpha Mensae || || K0 || 0.85 || 0.78 || 0.40 || 5,240 || 70 Ophiuchi A || == not so good table == || M || L || r || life || vesc || Wp || Temp || B || V || G || R || H || || M⊙ || L⊙ || AU || GY || km/s || mag || K || 445 || 551 || || 658 || 1630 || || 0.50 || 0.0625 || 0.2500 || 40.0000 || 42.4264 || M1V || || || || || || || || 0.55 || 0.0915 || 0.3025 || 30.0526 || 40.4520 || || || || || || || || || 0.60 || 0.1296 || 0.3600 || 23.1481 || 38.7298 || M0V || || || || || || || || 0.65 || 0.1785 || 0.4225 || 18.2066 || 37.2104 || || || || || || || || || 0.70 || 0.2401 || 0.4900 || 14.5773 || 35.8569 || K5V || || || || || || || || 0.75 || 0.3164 || 0.5625 || 11.8519 || 34.6410 || K3V || || || || || || || || 0.80 || 0.4096 || 0.6400 || 9.7656 || 33.5410 || K2V || || || || || || || || 0.85 || 0.5220 || 0.7225 || 8.1417 || 32.5396 || G9V || || || || || || || || 0.90 || 0.6561 || 0.8100 || 6.8587 || 31.6228 || G7V || || || || || || || || 0.95 || 0.8145 || 0.9025 || 5.8318 || 30.7794 || G6V || || || || || || || || 1.00 || 1.0000 || 1.0000 || 5.0000 || 30.0000 || G2V || || || || || || || || 1.05 || 1.2155 || 1.1025 || 4.3192 || 29.2770 || G3V || || || || || || || || 1.10 || 1.4641 || 1.2100 || 3.7566 || 28.6039 || G1V || || || || || || || || 1.15 || 1.7490 || 1.3225 || 3.2876 || 27.9751 || F9V || 6130 || || || || || || || 1.20 || 2.0736 || 1.4400 || 2.8935 || 27.3861 || F7V || || || || || || || || 1.25 || 2.4414 || 1.5625 || 2.5600 || 26.8328 || F6V || 6520 || || || || || || 25 Cancri || || 1.30 || 2.8561 || 1.6900 || 2.2758 || 26.3117 || F4V || || || || || || || || || 1.35 || 3.3215 || 1.8225 || 2.0322 || 25.8199 || F3V || 6740 || 14.2 || 13.3 || || 13.1 || 11.7 || COROT-3 || || 1.40 || 3.8416 || 1.9600 || 1.8222 || 25.3546 || F1V || || || || || || || |
Long Life Star
The heating Sun will make the (unmodified) Earth uninhabitable in less than a billion years. How long would a lower mass star last, and for a closer planet with the same illumination as earth, what would the system escape velocity be?
In the mass range near the suns ( 0.5 M⊙ < M < 2.0 M⊙), the luminosity is approximately L/L⊙ = (M/M⊙)⁴ . Assuming a 5 billion year lifetime for Earth, and an escape velocity of 30 km/s, what is the orbit radius in AU and the escape velocity for an "earthlike" planet?
NOTE the "lifetime" should be scaled (somehow) to the amount of photosynthesis-friendly red light compared to the amount of life-scrambling thermal infrared. Life decays with thermal energy, and builds from red photons (blue is used by terrestrial photosynthesis, but probably is not necessary).
NOTE 2 Other photosynthetic systems may be more optimal, using different colors of light.
not so good table
Class |
Radius |
Mass |
Lum |
Temp |
Example |
|
B |
V |
R |
H |
Planet |
vesc |
|
R/R☉ |
M/M☉ |
L/L☉ |
K |
|
GY |
445 |
551 |
658 |
1630 |
AU |
km/s |
|| F0 || 1.3 || 1.7 || 6 || 7,240 || Gamma Virginis ||
F5 |
1.2 |
1.3 |
2.5 |
6,540 |
Eta Arietis |
G0 |
1.05 |
1.10 |
1.26 |
5,920 |
Beta Comae Berenices |
G2 |
1.00 |
1.00 |
1.00 |
5,780 |
Sun |
G5 |
0.93 |
0.93 |
0.79 |
5,610 |
Alpha Mensae |
K0 |
0.85 |
0.78 |
0.40 |
5,240 |
70 Ophiuchi A |
not so good table
M |
L |
r |
life |
vesc |
Wp |
Temp |
B |
V |
G |
R |
H |
|
M⊙ |
L⊙ |
AU |
GY |
km/s |
mag |
K |
445 |
551 |
|
658 |
1630 |
|
0.50 |
0.0625 |
0.2500 |
40.0000 |
42.4264 |
M1V |
|
|
|
|
|
|
|
0.55 |
0.0915 |
0.3025 |
30.0526 |
40.4520 |
|
|
|
|
|
|
|
|
0.60 |
0.1296 |
0.3600 |
23.1481 |
38.7298 |
M0V |
|
|
|
|
|
|
|
0.65 |
0.1785 |
0.4225 |
18.2066 |
37.2104 |
|
|
|
|
|
|
|
|
0.70 |
0.2401 |
0.4900 |
14.5773 |
35.8569 |
K5V |
|
|
|
|
|
|
|
0.75 |
0.3164 |
0.5625 |
11.8519 |
34.6410 |
K3V |
|
|
|
|
|
|
|
0.80 |
0.4096 |
0.6400 |
9.7656 |
33.5410 |
K2V |
|
|
|
|
|
|
|
0.85 |
0.5220 |
0.7225 |
8.1417 |
32.5396 |
G9V |
|
|
|
|
|
|
|
0.90 |
0.6561 |
0.8100 |
6.8587 |
31.6228 |
G7V |
|
|
|
|
|
|
|
0.95 |
0.8145 |
0.9025 |
5.8318 |
30.7794 |
G6V |
|
|
|
|
|
|
|
1.00 |
1.0000 |
1.0000 |
5.0000 |
30.0000 |
G2V |
|
|
|
|
|
|
|
1.05 |
1.2155 |
1.1025 |
4.3192 |
29.2770 |
G3V |
|
|
|
|
|
|
|
1.10 |
1.4641 |
1.2100 |
3.7566 |
28.6039 |
G1V |
|
|
|
|
|
|
|
1.15 |
1.7490 |
1.3225 |
3.2876 |
27.9751 |
F9V |
6130 |
|
|
|
|
|
|
1.20 |
2.0736 |
1.4400 |
2.8935 |
27.3861 |
F7V |
|
|
|
|
|
|
|
1.25 |
2.4414 |
1.5625 |
2.5600 |
26.8328 |
F6V |
6520 |
|
|
|
|
|
25 Cancri |
1.30 |
2.8561 |
1.6900 |
2.2758 |
26.3117 |
F4V |
|
|
|
|
|
|
|
1.35 |
3.3215 |
1.8225 |
2.0322 |
25.8199 |
F3V |
6740 |
14.2 |
13.3 |
|
13.1 |
11.7 |
COROT-3 |
1.40 |
3.8416 |
1.9600 |
1.8222 |
25.3546 |
F1V |
|
|
|
|
|
|
Twice the escape energy for a star lasting 8 times as long. A "perfect" star system for star-faring life might be a K5, with 3 times the lifetime and 20% more escape velocity.