Exploring the SRAPO Construct

‘Exploring the Construct’ shows what can be done with SRAPO.
(SRAPO is an acronym for Stellar Radii And Planetary Orbits)

As we start, you probably realize,  that in our daily lives we take for granted the individual and combined physical effects of the Earth and the Sun on the our environment, on Earth’s habitats, and on all the life on Earth.
How the star-planet environmental descriptions were derived for this section and how you will define your own theoretical star-planet systems, will be discussed later. In the book that follows,  you’ll be introduced to charts, tables, illustrations and templates which have been included to assist in your discovery. I’ve included mathematical equations, as they were called for, however, the charts and tables have been worked out with scales, thus replacing the need for further calculations.{1}


A star-planet system’s individual or combined parameters have direct physical consequences in determining gravity,  the amount and availability of liquid water, volcanic activity, as well as affecting the atmosphere, climate, seasons, length of year, and intelligent life physiology and morphology.

In order to simplify the star and planetary data and to make learning and visualization more intuitive, I’ve made much of this study ‘relative’. Numerical parameters are usually discussed as being relative to conditions found on Earth, or relative to our Sun; in doing so, I’ve used three symbols, that you’ll encounter:  Š, Ê and AU:

1)  Š, refers to our Sun’s normal condition equaling 1. So, when, star’s  “Diameter  Š =1.3” is given, it means that the star were looking at has a diameter 1.3 times that of our Sun.

2)  Ê, similarly refers to the given condition on planet Earth as equaling 1. Hence, when a planet’s “Mass Ê = 2” is seen in the table, it means the alien planet has a mass of 2 times that of the Earth.

3)  ‘AU’ is the common abbreviation for “astronomical unit”, a distance of about ninety-three million miles, the average distance between Earth and the Sun. For comparison, this distance is taken as AU=1. When  a planet is said to be “0.8 AU” from its parent star, it is only 80% as far away as we are from our Sun, or seen another way, its 20% closer to the heat and light source than we are to ours.

Generally, if a planet is closer to a more luminous star, the planet’s average surface air temperature will be hotter than on Earth. Conversely, if the planet orbits farther from a cool, less luminous star, then it’s average surface temperature will be colder than found on Earth.

If the planet is warmer than Earth, it may not have extensively ice capped polar regions; on the other hand, a cooler planet may have larger, deeper ice caps than Earth.
A large, warmer world would seem generally more humid, while a smaller cool world would have a drier atmosphere.

Let’s take an introductory look at the power of SRAPO by briefly analyzing two dissimilar star-planet systems.

Alien Star-Planet System #1
General description: A small rocky type planet located in the outer ecosphere of large, hot star

•  This system is dominated by a very hot, blue-white star with forty percent more mass and luminosity than our Sun. The heat and light output is such that any existing habitable planet must be in an ecosphere further from the star than we are from the Sun.
•  With our hypothetical planet located 2.1 AU from the star, we  have 67% as much light falling on the top of the atmosphere. Because this is a hot star with a relatively short stable period, we may expect a more turbulent turn over in dominant life forms on the planet.
•  We will now paint a picture of a rather small, dry, cold world. This small terrestrial planet has about half the surface area and half the gravity that we’re use to. Since it has only one fourth the mass, but half the surface area, we would expect there to exist a large dry land area to water ratio. Because there is a reduced amount of light and heat at the top of the atmosphere, the planet tends to be a chilly 37ºF, more than 20ºF cooler than Earth’s average. For comparison, the alien planet is about 2-1/2 times the mass of  Mars; however, because it orbits closer to its parent star, it is considerably more habitable, than what our ‘Rovers’ have found on the ‘red planet’.
•  The cold average planetary surface temperature (APST) would have resulted in the formation of geographically large ice caps, leaving a considerable amount of the planet to exist under cool dry desert conditions.
•  The planet has less oxygen in its relatively thin atmosphere which lends to a reduced oxidation rate and larger lung capacities for the larger mobile life forms.
•  Humidity is low, especially in the areas undergoing late Fall, early Spring and the nine month-long winter.
•  Although the planet is quite cool on average, life’s development may not have been greatly impeded; as relatively clear skies would allow ultra violet rays to easily penetrate into the warmer equatorial regions for easy activation of organic molecules.
•  There would have been less volcanic activity over geologic ages (unless the planet encountered relatively frequent large asteroid and-or comet strikes) and mountain formation would tend to produce some very tall structures. Once formed, mountains would tend to persist due to low burial and erosion rates.
•  The less dense atmosphere produces smaller wind pressure at comparable wind velocities and reduces sound wave propagation.
•  This cool planet would be home to some rather bulky large animal life and a wide variety of moisture conserving plant life.
•  Animals would have developed an efficient means of generating and storing heat at a high rate.
•  A man weighing 150 pounds on Earth would weigh only 78 pounds on this planet. So, what nature withholds in terms of average surface temperature, she makes up for with a low gravity which allows the larger life forms to be bulky and probably tall.
•  Due to the thin atmosphere, the sense of smell and hearing may be reduced while food, predator and mate location may rely more on visual input.
•  The longer day and a light 20% cloud cover allows for larger day and night temperature fluctuations.
•  If we assign a 45° axial inclination to the planet (twice Earth’s tilt), we’d find a great difference in the overall seasonal energy input to each hemisphere. As it is, the planet has a year equal to three of our years, or about 1,129 days, with each season being nine months long.
•  The extended Spring and Summer seasons would favor several successive generations of ‘grasses’, followed by a long, bitter cold, dormant winter period. ‘Trees’ (meaning, their counterparts) could easily exist along flood basins and in lower latitudes. Mid latitudes would consist of grasses, cold desert vegetation which would give way to a geographically, very large tundra.
•  Massive melting in the Summer polar region would produce interesting  liquid water movement patterns and undoubtedly affect a major portion of the planet’s life forms. North-south migration across the equatorial region might be expected of tall, long limbed quadrupeds, as they moved between late Fall in one hemisphere and  Spring in the other.
•  An intelligent, tool using, upright alien, on this low gravity planet might stand and average of seven or more feet tall. Cold temperatures would favor a stocky build which provides greater internal mass for heat generation and a smaller surface area for heat loss.
• A large frame would fit in well with a large chest which would house the expanded lung  capacity needed for breathing the thinner air.
•  Also, low gravity on this cool grassy world would tend to favor tall creatures with a greater lung capacity for long distance running or migration.
•  Due to overall cool temperatures, the day and night temperature fluctuation and the  extreme season lengths, higher life forms would probably have developed warm-blooded adaptations.
•  Nearly cloudless skies and a lighter, less dense atmosphere, would allow a large amount of UV to penetrate to the surface, this damaging radiation might be blocked by the aliens having developed dark pigmentation or maintenance of a fur coat.
•  Cool average surface temperatures, the long cold brittle winters and a generally dusty environment would favor hairy-furry bodies with a long nasal passage to prewarm and  remove dust from inhaled air. These ‘people’ would probably also have a larger, more powerful heart for delivering warmed blood and a thinner oxygen supply to peripheral organs and extremities.

Alien Star-Planet System #2
General description: A large planet located near the inner ecosphere of star slightly hotter than the Sun.

•  This system is dominated by a hot white star with a slightly grater mass than the Sun, but with 22% greater luminosity. Under such luminosity conditions a terrestrial type planet could be somewhat closer and yet a good deal further from its Sun than we are from Sol and still fall within the habitable ecosphere boundaries. For this example, I have placed the planet 0.8 AU or 78 million miles from its parent star. The planet is therefore 20% closer to a star with 22% more luminosity that the Sun, resulting in 74% more light falling on the top of the atmosphere.
•  This relatively hot star has a slightly shorter stable period than the Sun so we might expect a bit faster turnover in dominant life forms (should we consider changes driven by stellar effects alone)
•  We will now paint a picture of a large, hot wet world with an essentially continuous cloud cover of 88%. This planet has twice the water producing mass yet only 42% more surface area than Earth, which points to a large water to land ratio.

•  Such a world might contain several Australia size continents and many strings of islands rising from submerged planetary mountain chains.
•  There is a lot more sun light arriving at the top of the atmosphere, but much of this is reflected back into space by the planets expansive cloud cover.
•  Light penetrating the clouds to reach the surface would transform into long wave heat radiation, which becomes trapped and elevates temperatures via the green house effect. Light input, plus the green house effect would create an average surface air temperature (APST) in the neighborhood of 135ºF.
•  The hot, humid atmosphere would also contain a lot of oxygen leading to an accelerated oxidation rate and the necessity of smaller lung capacities for the larger, mobile land life forms.
•  The planet’s atmospheric density would provide greater wind pressure when compared to similar wind speeds on Earth, at the same time favor sound propagation.
•  The planets larger mass would provide more volcanic activity than we are used to, but volcanic effluents dispensed into the atmosphere would precipitate out faster.
•  The increased gravity would result in smaller mountain heights, while heavy frequent precipitation would enhance the burial rate and increase erosion. Subduction and other crustal movements beneath the seas would make tidal waves more common on this planet  than on ours.
•  This wet, hot and humid world would be home to rather small, sinuous dry land animal life and a variety of succulent and tropical like vegetation.
•  Animal life would have developed efficient means of getting rid of internal heat, since the  high temperatures found across much of the planet threaten the integrity of complex organic molecules with disruption.
The fast rate of planetary rotation helps reduce the day and night temperature differences, while a continuous cloud cover helps depress day temperatures and elevate night temperatures• 

•  If we assign the planet with 0° degree of axial inclination, then there is no tilt and therefore no seasons. In place of seasons, we create thermal zones. The hottest zone being on either side of the equator with moderating temperatures found as one proceeds toward either polar region.
•  Warm blooded, intelligent life would be found more frequently in the ‘cooler’ higher latitudes.
•  Due to the higher gravity and temperatures, our hypothetical intelligent alien would stand about four feet tall with a thin frame, supported by strong bones and powerful muscles. He would carry little if any fat. •  Due to the dense atmosphere, his sense of smell and particularly hearing, would be enhanced.
•  Ear flap projections might not be necessary around the aural tract.
•  A smaller heart and thinner blood would carry oxygen to body cells and to heat dissipating organic networks.
•  His eyes might be located a bit more peripherally than ours and he may have no nasal passage projection, or ‘nose’. Air could be taken in through one or more nasal apertures.
•  Temperature and humidity would favor a hairless, smooth body.
•  Although the planets extensive cloud cover would tend to shield animal life, the occasional clear day would result in severe sunburn, for this, at least a yellow-gray level of protective pigmentation would be required by skin cells. The alien would possibly appear a mid shade color.
•  On this alien world, life could easily develop and thrive in the higher latitudes where more temperate climates  are found.
•  With the existence of islands and small continents, even a hot wet world could develop intelligent, tool using, technically advanced life forms.

Such a world might sound hot and terrible to us, but to a creature born into that world with its genetic adaptations, the planet would be as comfortable in places, as Earth is to us. This intelligent life form, would find our planet uncomfortably cold and dry. The alien might not survive for long in the searing heat of his planet’s equatorial region, but how long would we survive, isolated, in either our own polar regions, or on the Anza-Borrego Desert, without shade and water?


1. The calculations were done with slide rule, in a time before home computers, and at a time when expensive personal scientific calculators were just showing up in specialty retail stores-in the period that can now be thought of as ‘digital prehistory’.


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Filed under SRAPO (Stellar Radii and Planetary Orbits), __ Exploring the SRAPO Construct

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