145 lines
6.7 KiB
Plaintext
145 lines
6.7 KiB
Plaintext
SUBJECT: HABITABLE PLANETS FILE: UFO2724
|
|
|
|
|
|
|
|
|
|
Date: 01-24-92 20:29
|
|
From: David Galea
|
|
Subj: Habitable Planets, from the January 1992 JBIS.
|
|
|
|
* Originally dated 22 Jan 1992, 9:05
|
|
|
|
From: klaes@mtwain.enet.dec.com (Larry Klaes)
|
|
Organization: Digital Equipment Corporation
|
|
|
|
|
|
The following posting is a summary written by my friend and co-worker,
|
|
Drew LePage, of an article in the January 1992 issue of the JOURNAL OF
|
|
THE BRITISH INTERPLANETARY SOCIETY (JBIS), Volume 45, Number 1. Titled
|
|
"An Estimate of the Prevalence of Biocompatible and Habitable Planets",
|
|
it is authored by M. J. Fogg.
|
|
|
|
-----------------------------------------------------------------------
|
|
|
|
There is a very interesting article in the January 1992 edition of
|
|
the JOURNAL OF THE BRITISH INTERPLANETARY SOCIETY (JBIS) on the
|
|
likelihood of various types of stars having habitable or biocompatible
|
|
planets. A biocompatible planet is one where the long term presence of
|
|
surface liquid water provides environmental conditions suitable for for
|
|
the origin and evolution of life. There are three subsets of
|
|
biocompatible planets:
|
|
|
|
* Juvenile Martian - As the name implies, it is a planet with condition
|
|
similar to those found on Mars early in its life. The planet would
|
|
receive between 27% and 75% of the light we presently receive from the
|
|
Sun and possess plate tectonics or some other geochemical carbon cycle.
|
|
Mars was this type for its first one billion years.
|
|
|
|
* Juvenile Terran - Again as the name implies, this is a planet with
|
|
conditions similar to those found on the early Earth. The planet would
|
|
receive between 75% and 95% of the light we presently receive from the
|
|
Sun and be geologically active. Earth was this type of planet for its
|
|
first four billion years (i.e. during the Precambrian period).
|
|
|
|
* Habitable - This is a planet with Earthlike conditions. The planet
|
|
would receive between 95% and 110% of the light we receive and be
|
|
geologically active.
|
|
|
|
The author of the study collected the results of various studies to
|
|
determine what conditions produce biocompatible and habitable planets,
|
|
the evolution of stars and the effects on planetary environ-ments, the
|
|
likely distribution of planets in other systems, as well as others.
|
|
The results of the author's simulations indicate the following:
|
|
|
|
* Habitable planets can exist around stars with 0.8 to 1.8 times the mass
|
|
of the Sun.
|
|
|
|
* Biocompatible planets can exist around stars with 0.5 to 1.8 times the
|
|
mass of the Sun.
|
|
|
|
* Habitable planets may occur around >3% of the stars between 0.85 and
|
|
1.45 times the mass of the Sun.
|
|
|
|
* Biocompatible planets may occur around >30% of the stars between 0.8
|
|
and 1.25 time the mass of the Sun.
|
|
|
|
If only single stars possess planets:
|
|
|
|
* There would be one habitable planet for every 413 stars.
|
|
|
|
* The mean distance between systems with habitable planets would be 31
|
|
light years.
|
|
|
|
* There would be one biocompatible planet for every 39 stars.
|
|
|
|
* The mean distance between systems with biocompatible planets would be
|
|
14 light years.
|
|
|
|
* There would be about 362 biocompatible (of which 34 would be habitable)
|
|
planets within 100 light years of us.
|
|
|
|
If planets could form in multiple star systems:
|
|
|
|
* There would be one habitable planet for every 196 stars.
|
|
|
|
* The mean distance between systems with habitable planets would be 24
|
|
light years.
|
|
|
|
* There would be one biocompatible planet for every 18 stars.
|
|
|
|
* The mean distance between systems with biocompatible planets would be
|
|
11 light years.
|
|
|
|
* There would be about 763 biocompatible (of which 71 would be habitable)
|
|
planets within 100 light years of us.
|
|
|
|
The author goes further and calculates the probability of the nearer
|
|
stars having biocompatible or habitable planets. Assuming that planets
|
|
can form in multiple star systems the following probabilities were
|
|
calculated:
|
|
|
|
Name Distance (LY) Type Habitable Biocompatible
|
|
|
|
Alpha Centauri A 4.38 G2V 7.8% 44%
|
|
Alpha Centauri B 4.38 K6V 4.4% 38%
|
|
Epsilon Eridani 10.69 K2V 0.6% 34%
|
|
61 Cygni A 11.17 K5V 0.0% 5.8%
|
|
61 Cygni B 11.17 K7V 0.0% 0.3%
|
|
Epsilon Indi 11.21 K5V 0.0% 18%
|
|
Lacille 9352 11.69 M2 0.0% <0.3%
|
|
Tau Ceti 11.95 G8V 1.5% 35%
|
|
Lacille 8760 12.54 M1V 0.0% 1.5%
|
|
Groombridge 1618 15.03 K7 0.0% 2.5%
|
|
70 Ophiuchi A 16.73 K1 4.4% 38%
|
|
70 Ophiuchi B 16.73 K6 0.0% 16%
|
|
36 Ophiuchi A 17.73 K0V 0.0% 28%
|
|
36 Ophiuchi B 17.73 K1V 0.0% 27%
|
|
36 Ophiuchi C 17.73 K5V 0.0% 9.0%
|
|
HR 7703 A 18.43 K3V 0.0% 27%
|
|
Sigma Draconis 18.53 K0V 1.5% 35%
|
|
Delta Pavonis 18.64 G5 5.1% 39%
|
|
Eta Cassiopeiae A 19.19 G0V 3.9% 38%
|
|
Eta Cassiopeiae B 19.19 M0 0.0% 0.7%
|
|
HD 36395 19.19 M1V 0.0% 0.5%
|
|
Wolf 294 19.41 M4 0.0% <0.3%
|
|
+5301320 A 19.65 M0 0.0% 0.6%
|
|
+5301320 B 19.65 M0 0.0% 0.5%
|
|
-45013677 20.6 M0 0.0% <0.3%
|
|
82 Eridani 20.9 G5 4.4% 38%
|
|
Beta Hydri 21.3 G1 7.5% 35%
|
|
HR 8832 21.4 K3 0.0% 23%
|
|
|
|
Assuming that the author's simulations and calculations are correct,
|
|
there could be as many as 5.6 BILLION biocompatible planets in our
|
|
galaxy of which about 500 MILLION are habitable. And, as the above
|
|
table shows, the nearest biocompatible planet could only be 4.38 light
|
|
years away.
|
|
|
|
Drew LePage
|
|
|
|
|
|
|
|
|
|
**********************************************
|
|
* THE U.F.O. BBS - http://www.ufobbs.com/ufo *
|
|
********************************************** |