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Size: 2382
Comment:
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Size: 3339
Comment:
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| Deletions are marked like this. | Additions are marked like this. |
| Line 8: | Line 8: |
|| 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. || |
|| 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).
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.