Types of Stars

This page lists the types of stars in the Milky Way.

Types of Stars

 * Black Dwarf: A dead star, having radiated all its heat.
 * Black Hole: The singularity which results from the death of a supermassive star more than 20 Sol masses.
 * Brown Dwarf: A failed star, resembling a gas giant. Little or no nuclear fusion. 0.013-0.08 Sol masses (13 to 75 Jupiter masses). 20% chance of binary system with a low mass star.
 * Main Sequence Star: The majority of stars are main sequence stars with masses 0.1-200 Sol Masses. Within main sequence stars, hydrogen is converted to helium. Categorized as O, B, A, F, G, K, M by mass, with O being the most massive and M being the least massive.
 * Neutron Star: The core of a dead supermassive star.
 * Protostar: A star in its earliest stages
 * Pulsar: A neutron star which releases charged particles.
 * Red Giant: An unstable star in its late stages
 * Supermassive Star: A massive, short-lived star formed from massive protostars. Create a supernova when exploded.
 * White Dwarf: Post red giant star. Relatively stable. Very dense.

Orbits

 * Planetary orbits can be determined by multiplying the orbit of a gas giant by 1.42<x<2.00 (for outer planets) and dividing by 1.42<x<2.00 (for inner planets)
 * No orbit may be closer than 0.15 AU

Stellar Lifespans

 * O, B and A type stars have lifespans of a few million years

Stellar Habitability

 * Planets within the habitable zone of an M type star will face considerable solar weather
 * Large F stars and G, K and M stars release plentiful UV light, resulting in reduced atmosphere within the habitability zone
 * Binary Stars result in planets have unstable orbits

Star Requirements for Habitability

 * Ideal mass: 0.6-1.4 sol masses

Galactic Habitability

 * Planets in the galactic bulge will have unstable orbits and will be exposed to massive amounts of radiation due to close proximity to the galactic core
 * Planets within a galactic arm will be drenched in radiation and may be torn apart
 * Optimal planet-forming area is in the galactic disk between arms
 * Systems further from the galactic core will have less heavy elements

Close Systems

 * Star separation, in order to facilitate planet formation, should be between 0.15-6 AU (tends towards lower value)
 * Average distance from primary star to barrycentre (b) = separation of stars x (Msecondary/Mprimary+Msecondary)
 * Eccentricity (e) between 0.4 and 0.7 (tending towards the lower value)
 * Max Distance from barrycentre = b(1+e)
 * Min Distance from barrycentre = b(1-e)
 * Overall maximum (MaxO) = Max(Primary) + Max(Secondary)
 * Overall minimum (MinO) = Min(Primary) + Min(Secondary) : this value must not be >0.1 AU
 * Forbidden zone (where no planets form) is between 1/3MinO (inner) and 3MinO (outer)
 * Habitable world must exist beyond 4MaxO AU

Far Systems

 * Star separation should be between 120-600 AU (tending towards the larger)
 * Barrycentre, Eccentricity and Max/Min as in close systems
 * Inner Planetary Limit  (I) = 0.1 x M
 * Outer Planetary Limit (O) = 40 x M
 * Forbidden zone should fall outside outer limit

Multiple-Star Systems

 * Stars are grouped into subsystems of 1 or 2 stars
 * Primary star is most massive, which each subsequent star lesser in mass
 * Overall mass of primary subsystem must be greater than the other subsystems
 * Average separation is between 1200 AU and 60 000 AU
 * Barrycentre, Eccentricity and Max/Min as in close systems

Star Statistics

 * Luminosity (L) = M^3 where M is equal to mass (1M = 1 Sol Mass)
 * Diameter (D) = M^0.74 (1D = 1 Sol Diameter)
 * Surface Temperature (T) = M^0.505 (1T = 1 Sol Temperature)
 * Lifespan (V) = M^-2.5 (1V = 1 Sol Life)
 * Habitability Zone (H) = sqrtL x 0.95 (min) and sqrtL x 1.37 (max) (1H = 1AU)
 * Inner Planetary Limit  (I) = 0.1 x M
 * Outer Planetary Limit (O) = 40 x M
 * Frost Line (F) = 4.85 x sqrtL
 * Apparent Brightness (AB) = L/D^2
 * Apparent Brightness of a planet = Albedo x L(radius of planet being observed)^2/D^2 x d^2 (where D is the distance from the planet of observance to the star and d is the distance from the planet of observance to the planet being observed). Greater than 1.3x10^-7 may be observed by the naked eye, and less than 1.2x10^-9 may not.
 * Small angle approximation ($) = d/D (where d is the diameter of the object being observed and D is the distance between the object and the observer). $(Sol) = 0.5 degrees