Stellar System Generator, Part 2

Copyright RMF Runyan © 2011

Edited by Aaron Smalley for The Guild Companion

"Before you even consider the type of system, one should first decide the age of the system's primary. This will help to determine the classes of companion stars, if any."

Editor's Note: The following is the second chapter of the documentation provided by the author. The previous installment, combined with this and the following three installments (five in all) are intended to provide background information as to the science and reasoning behind the application that RMF Runyan has put together. Once we publish the last installment (tentatively planned for December of 2011), we will also provide the entire documentation in the form of a pdf, which will include all of these article installments as well as a table of contents. In the meantime we are also publishing the "SSG Users Guide" put togehter by RMF Runyan which includes a link to download the application that he is developing. He is continuing to work on the application to improve it and create more functionality within it, and as such he is looking for comments and suggestions from users, which can be posted on the appropriate forums at We will release each updated and improved version of the application through the end of the series of articles in December of this year.

Chapter 2: System Types

As with galaxies, stellar systems come in various types: solitary, binary, trinary, and multiples. They also come in three broad categories: giant, major, and minor. The category is based on the primary star if it is not a solitary system. If minor systems are included, then solitary types form the greatest majority, almost 75% of all stellar systems. You should remember that multiple star systems are more massive and tend to have younger stars. It should also be noted that multiple systems of more than three stars tend to be unstable and will probably break apart in the very near future (when considering star life, this could be in 1 to 200 million years). Most multiple systems will only be binary or trinary. However there have been systems found to have as many as eight stars orbiting a common barycenter. We have not found any with more than eight stars excepting open clusters.

Stellar Age

Before you even consider the type of system, one should first decide the age of the system's primary. This will help to determine the classes of companion stars, if any.


These stars are invariably O and B class stars (blue-stars), and the supergiants (0, Ia, Ib, and II luminosity class stars). O class stars and supergiants rarely live longer than 10 to 15 million years before dying in a supernova. B class stars can live for as long as 1 billion years, but usually end with a supernova also. In fact, the supernova witnessed in 2003 (I can no longer find the news report) by the Hubble telescope was from what was thought to be a stable B class star. Originally, it was thought that only the supergiants and W, O, and WO class stars were the only ones that end in supernova. Now, some scientists are beginning to think that perhaps stars as cold as the A class may be able to supernova. They are sure nothing at or below an F class can supernova since they are such long-lived and stable stars.

SSG does not generate systems for the supergiants and blue-stars since they are severely depleted of gas, it being blown out of the system by the brutal radiation these stars blast. These stars can even blow away gas and dust from neighboring systems and clouds within the star-breeding areas. These stars are also the reason for non-Jovian systems. These stars also tend to be very unstable. For our purposes, Newborn stars will usually only be surrounded by massive asteroid fields which are still trying to form into planets but are severely hampered by the immense radiation blasting outwards from these stars. Also, these stars can tend to "burp" several times before they actually go supernova. The image below shows the most recent mass ejection (burp) of the star Eta Carinae in the Carina Nebula. Eta Carinae is believed to be a WO class star. For scale, those lobes have a combined diameter greater than the size of our system (about 10 billion miles).

The Doomed Star Eta Carinae, burped about 150 years ago


Young stars are less than a billion years old and are generally stable in terms of mass during this period in the star's life. Young stars are generally B and A class stars. If a B class star can live longer than 500 million years without going supernova, then it is probably stable enough to continue progressing into a normal Main Sequence lifetime. Young stars will usually still be too young to have a planetary system conducive for life. But then again, there is no reason why a young star cannot have life. Although it took 4.5 billion years for us to evolve, there is no reason why life could not evolve faster. It seems that once the right chemicals are present for life to exist, it seems to explode with fervor. For instance, look at Cambrian Explosion of life here on Earth. Another article here . If the young star is in a particularly vacuous area of the galaxy, life could evolve faster without the constant bombardment of extinction level event meteor impacts. In fact, such a system would probably have very few planets, perhaps one or two terrestrials and a prime Jovian, with the prime Jovian and star having swept away most of the other matter. Thus, in just half a billion years, a planet could have evolved rudimentary intelligent life. At least the planet could be habitable for colonization.


These are the middle-aged stars of the F, G, and K class, and some A class stars. They are usually at least 2 billion years old and can be as old as 7 billion. Planetary orbits are usually very stable during this period of a star's life and the immense impact bombardment during the newborn and young stages has practically ceased. Not to say an extinction level impact may never happen, just highly unlikely. Once a star reaches about 8 to 12 billion years old, it will go through the red-giant stage, devouring or burning the inner planets. At the end of this red-giant stage of about 100 to 300 million years, the outer layers of the star will be expelled in a nova event as the core collapses into a white dwarf. Then the star will be a white dwarf for the next 15 to 25 billion years before cooling down to its final stage as a black dwarf (not to be confused with black hole). Any F, G, or K class star that is old is on the verge going into its red-giant stage.


These are usually M class stars nearing the end of their fusion fuel reserves. Most of these stars are largely composed of heavier elements such as carbon, silicon, and iron. The M class star will rarely go nova, instead fading away into a less dense form of the black dwarf, known as the black cinder. Note: Black Cinder is mine own terminology.


Not much can be said for these. They are the remains of supernova (neutron stars or black hole), nova (white dwarf), or black cinder. Although a remnant may still have planets orbiting it, none will be able to harbor life without some form of life support. Consult the table below if you wish to determine the age of your system randomly.

Random generation of system age.
Star Type Age Determination
Supergiant Always newborn
Class O Main Sequence Always newborn
Class B Main Sequence 01-11 = newborn; 12-00 = young
Class A Main Sequence 01-04 = newborn; 05-98 = young; 99-00 = mature
Class F Main Sequence 01-34 = young; 35-00 = mature
Class G Main Sequence 01-08 = young; 09-97 = mature; 98-00 = old
Class K Main Sequence 01-03 = young; 04-97 = mature; -00 = old
Class M Red Dwarf Always mature or old
Class D White Dwarf Always remnant
Neutron Star Always remnant


Basically, self-explanatory. This is a single star which may or may not have planets.


This is two stars which orbit around a common center of mass between the two stars. For a binary system to have habitable planets, it must be a circular system instead of an elliptical system. The elliptical form of a binary system is usually too unstable for inner planets to form close enough to also support life. In an elliptical binary system, most planets in stable orbits will be too far away to be conducive for life.

Determining the barycenter of a binary system is fairly simple. Each star of a binary system orbits at a distance proportional to its percentage of mass of the total mass of the two stars. First figure out the percentage amount of the total mass, then subtract that from 100%. This is the percentage distance of the entire distance between the two stars. Also see this Wikipedia page for some barycenter animation examples.

Example: A binary system is composed of an F class star and an M class star. The F class star has a mass of 1.5 Sol Units while the M class star has a mass of 0.5 Sol Units. The total mass is 2.0 Sol units. (Sol Unit = 1.98892e30 kilograms.) The F class star has 75% of the total mass. This means the barycenter will be 25% of the total distance between the two stars. If the total distance between the two stars is 4 AUs, this means the barycenter is 1 AU from the F class star and 3 AUs from the M class star. See the image below for visual representation.

Barycenter of a Binary System
Binary Star Separation
Roll Result
01-09 2d8 million kilometer separation. Roll d100 again, on a 96+, the system is a contact system binary with a separation <= one stellar diameter. The stars share their stellar atmosphere. This creates brutally intense radiation and particle winds rendering the system inhospitable to life. Shielded bases may exist though.
10-18 d12 10 AU separation.
19-36 d20 AU separation.
37-64 2d6 10 AU separation.
65-82 d12 100 AU separation.
83-91 d12 1000 AU separation.
92-00 d6 10,000 AU separation.


Trinary systems are usually a binary system orbiting with another solitary. For some nice, simple animations (up to quaternary systems), see this page Determining the barycenter of a trinary system is a two step process. First, the two most massive stars will be orbiting each other like in a binary system. Once you find this barycenter, treat the two stars as if a single star to determine the barycenter with the third star. See the image below for visual representation.

Barycenters of a Trinary System
Trinary and Quaternary Separation Sub-Pair Separation
01-14 2d8 million kilometer separation. Roll d100 again, on a 96+, the system is a contact system binary with a separation <= one stellar diameter. The stars share their stellar atmosphere. This creates brutally intense radiation and particle winds rendering the system inhospitable to life. In fact, this may cause the third star to be "pushed" out of the system unless the orbit is stable. Shielded bases may exist though.
15-29 d12/10 AU separation
29-58 d20 AU separation
59-00 2d6 10 AU separation
Secondary Separation in Trinary/Quaternary System
Roll Result
01-50 d12 100 AU separation
51-83 d12 1000 AU separation
84-00 d6 10,000 AU separation


Quaternary systems are usually a double binary system. You will have to calculate the barycenter for the two individual binaries, and then calculate the third barycenter for these two binaries. I would suggest not having any system greater than a trinary due to the complexity of having to calculate multiple barycenters for quinary, senary, septenary, and octonary systems. Besides, any system with more than three stars will probably pump out so much radiation as to have planets that are nothing more than burnt cinders. Or, they would have to be too far away to be nothing more than a large ice-ball, or Jovian type planets.

Companion Stars

First, look in Chapter 3: Stellar Primaries >> Spectral Class, Spectral Level, and Luminosity Class, and determine these parameters for the primary star. This will determine the maximum class for the companion stars. Supergiant Systems below refers to Spectral Class O stars and Luminosity Class 0, Ia, Ib, II, and III stars. Major Systems below refers to Spectral B, A, F, G, and K stars and Luminosity Class IV and V stars. Minor Systems is all others.

Supergiant System Major System Minor System
01-20 Solitary 01-50 Solitary 01-75 Solitary
21-50 Binary 51-85 Binary 76-95 Binary
51-75 Trinary 86-97 Trinary 96-00 Trinary
76-95 Quaternary 98-00 Quaternary
96-00 Quinary +; roll d4+4 for number
Modifiers for Companion Stars
Spectral Class Modifiers Luminosity Class Modifiers
Spectral Class Hottest Companion Class Allowable Modifier to Spectral Class Roll Luminosity Class Modifier to Luminosity Class Roll
O O +0 Hypergiant (0) +1
B B +0 Luminous Supergiant (Ia) +2
A A +1 Supergiant (Ib) +3
F F +4 Bright Giant (II) +5
G G +12 Giant (III) +10
K K +24 Subgiant (IV) +20
M M +24 Main Sequence (V) +30
Dwarf (VI) +90

Once you determine the primary's companion, use the secondary star to determine the modifiers for the tertiary star, and then use the tertiary to determine the quaternary star, and so on, until you have determined all the stars.

Unusual Objects

Many unusual objects exist out there in the universe. If you are an adherent to hard science, these include black holes, black dwarfs, planetary nebula, supernova remnants, neutron stars, quasars. But if you like pseudo-science, these can include temporal rifts, quantum singularity, dimensional rift, cosmic string, quantum filament, wormhole, transwarp conduit, gravimetric expulsor (opposite of a black hole), etc. In the SSG, I stick with the hard science objects. For the pseudo-science objects, you are on your own. Although I did come up with the idea "gravimetric expulsor," I have never expounded on it.


Nebulae come in three different types: emission, reflection, and dark. Emission nebulae are nebula which have a star or stars inside and are often newly formed stars. These stars excite the nebula dust and gas with the emission of their UV radiation. This is the same way that neon arc tubes work. Although they appear very colorful in Hubble photos, this is due to the very long exposure times taken in varying spectrums (red, green, blue, NIR, X-ray, etc.) and then combined. To our naked eyes, they would actually appear to be milky and colorless.

Reflection and dark nebula are virtually the same. The only difference depends upon the locations of any nearby stars, the nebula, and the observer. If the nebula is between the star and observer, then it is a dark nebula. If the star is between the nebula and observer, then it is a reflection nebula.

Although nebula can be quite large, spanning an average of 30 to 35 parsecs (97.85 to 114.16 light years), the concentration of dust and gas is still sparse enough to allow astrogation in safety. However, there can be pockets that are dense enough to present hazards to astrogation.

"Mystic Mountain" in Carina Nebula
"Pillars of Creation" in Eagle Nebula

Planetary Nebulae

These nebulae have nothing to do with planets and are not even nebula, despite their name. These are actually the outer layers of a main sequence star that has gone nova after going through its red-giant stage. These layers expand outward from the star like an enlarging bubble. They will also tend to glow like an emission nebula since the star's core, now a white dwarf, continues to shine. Planetary nebula are not much denser than the vacuum of space thus, do not present any particular hazard to space travel. Planetary nebulae rarely get larger than a half parsec and only last for a few tens of thousands of years.

"Eskimo" Nebula
"Glowing Eye" Nebula,
sometimes called "The Eye of God"

Supernova Remnant

While similar in mechanics as planetary nebula, they are blown outward at a much greater velocity. These can be up to two parsecs in size and, like planetary nebulae, also last for only a few tens of thousands of years.

Supernova Remnant at star WR124
The most famous supernova remnant:
Crab Nebula (in 1054 AD)

Neutron Stars

These are the remaining core of a star that has gone supernova. In a supernova, the star's core collapses suddenly, in a matter of a few minutes, and ignites the fuel that appears in between the outer layer and core. This explosion is tremendously powerful both blasting the outer layers away and further imploding the collapse of the core. Unlike main sequence stars that nova and become white dwarfs, these are from O, B, and possibly A spectral class stars and the supergiants. With a much greater mass, the core of these stars will continue to collapse beyond the white dwarf star into a degenerate mass composed of neutrons and quarks. The rebound effect of this collapse causes the explosion to be much greater than the explosion itself. It is theorized that this blast can propel the matter of the outer layers at velocities approaching 75% to 85% the speed of light. The remaining neutron star will rotate several times a second, some as much as a few thousand times a second. Neutron stars will possess immense magnetic fields, often in excess of a million gauss. Magnetic fields this powerful are strong enough to actually distort the shape of atoms and pull molecules apart into what is called a "magnetic soup." A neutron star is so dense that one teaspoon (5 milliliters) of its material would have a mass over 5.5e12 kg, about 900 times the mass of the Great Pyramid of Giza (Wikipedia) . Neutron stars also emit powerful radio beacons from their magnetic poles and are seen as "pulsars" from Earth.

Artist's conception of a neutron star with visible magnetic streamers

Black Holes

Sometimes a star is so massive that when it goes through the supernova stage, the core actually never stops collapsing and becomes a singularity, or black hole. There are only two ways for a black hole to be visible. As it moves across a starry background, its warping effect can be seen as it distorts the light around the event horizon. The other way is for the black hole to have a huge fuel source that is falling into the event horizon, creating an accretion disk. Without an accretion disk and adequate background light sources, the only way to detect a black hole is by its extremely powerful gravimetric attraction. If one has no way to detect gravimetric fields, distortion of background light sources, or an accretion disk, then the only way to detect a black hole is by colliding with it. And I do not think I need to detail those results.

There is a current proposal to change the name of black holes to MECO : magnetospheric eternally collapsing object. However, I prefer the term "black hole," or "singularity."

First of the possible black holes
Core of NGC 7052

Here is a nice 18m 48s video about the "Largest Black Holes in the Universe" @YouTube . You will have to tolerate ads... However, you can click past them (I think, I could).