Differences between revisions 7 and 8
⇤ ← Revision 7 as of 2016-06-26 15:55:18 →
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Editor: KeithLofstrom
Comment:
← Revision 8 as of 2016-06-26 23:58:20 → ⇥
Size: 3188
Editor: KeithLofstrom
Comment:
Deletions are marked like this. Additions are marked like this.
Line 13: Line 13:
||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 ||		 ||Class || Radius || Mass || Lum || Temp || Example ||
|| || R/R☉ || M/M☉ || L/L☉ || K || ||
Line 22: Line 22:
|| M || L || r || life || vesc || Temp ||
|| M⊙ || L⊙ || AU || GY || km/s || mag || K ||
|| 0.50 || 0.0625 || 0.2500 || 40.0000 || 42.4264 || || 3800. ||
|| 0.55 || 0.0915 || 0.3025 || 30.0526 || 40.4520 || || ||
|| 0.60 || 0.1296 || 0.3600 || 23.1481 || 38.7298 || || ||
|| 0.65 || 0.1785 || 0.4225 || 18.2066 || 37.2104 || || ||
|| 0.70 || 0.2401 || 0.4900 || 14.5773 || 35.8569 || || ||
|| 0.75 || 0.3164 || 0.5625 || 11.8519 || 34.6410 || || 5000. ||
|| 0.80 || 0.4096 || 0.6400 || 9.7656 || 33.5410 || || 5200. ||
|| 0.85 || 0.5220 || 0.7225 || 8.1417 || 32.5396 || || ||
|| 0.90 || 0.6561 || 0.8100 || 6.8587 || 31.6228 || || ||
|| 0.95 || 0.8145 || 0.9025 || 5.8318 || 30.7794 || || ||
|| 1.00 || 1.0000 || 1.0000 || 5.0000 || 30.0000 || G2V || 5780. ||
|| 1.05 || 1.2155 || 1.1025 || 4.3192 || 29.2770 || || ||
|| 1.10 || 1.4641 || 1.2100 || 3.7566 || 28.6039 || G0V || 5920. ||
|| 1.15 || 1.7490 || 1.3225 || 3.2876 || 27.9751 || || ||
|| 1.20 || 2.0736 || 1.4400 || 2.8935 || 27.3861 || || ||
|| 1.25 || 2.4414 || 1.5625 || 2.5600 || 26.8328 || || ||
|| 1.30 || 2.8561 || 1.6900 || 2.2758 || 26.3117 || F5V || 6540. ||
|| 1.35 || 3.3215 || 1.8225 || 2.0322 || 25.8199 || || ||
|| 1.40 || 3.8416 || 1.9600 || 1.8222 || 25.3546 || || ||
Line 23: Line 44:
== 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.		 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

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

R/R☉

M/M☉

L/L☉

K

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

M

L

r

life

vesc

Temp

M⊙

L⊙

AU

GY

km/s

mag

K

0.50

0.0625

0.2500

40.0000

42.4264

3800.

0.55

0.0915

0.3025

30.0526

40.4520

0.60

0.1296

0.3600

23.1481

38.7298

0.65

0.1785

0.4225

18.2066

37.2104

0.70

0.2401

0.4900

14.5773

35.8569

0.75

0.3164

0.5625

11.8519

34.6410

5000.

0.80

0.4096

0.6400

9.7656

33.5410

5200.

0.85

0.5220

0.7225

8.1417

32.5396

0.90

0.6561

0.8100

6.8587

31.6228

0.95

0.8145

0.9025

5.8318

30.7794

1.00

1.0000

1.0000

5.0000

30.0000

G2V

5780.

1.05

1.2155

1.1025

4.3192

29.2770

1.10

1.4641

1.2100

3.7566

28.6039

G0V

5920.

1.15

1.7490

1.3225

3.2876

27.9751

1.20

2.0736

1.4400

2.8935

27.3861

1.25

2.4414

1.5625

2.5600

26.8328

1.30

2.8561

1.6900

2.2758

26.3117

F5V

6540.

1.35

3.3215

1.8225

2.0322

25.8199

1.40

3.8416

1.9600

1.8222

25.3546

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

LongLifeStar (last edited 2016-07-03 07:52:07 by KeithLofstrom)