STAR
CLASSIFICATIONS
A star is a body massive enough to trigger a nuclear reaction at its core.
Types of Star:
Lazarus star:
is a super nova remnant which, instead of being forced inward into neutron-star
mode, survives as a normal star. After expansion into red giant phase, Lazarus
stars collapse and undergo supernova for a second time.
Neutron
Star:
is usually type B-0 and measures only a few kilometres in diametre. An early
main sequence star that has completed the nuclear burning processes often explodes.
The reactive force of the explosion and the stars self-gravitation eject
shell electrons (as in a white dwarf) and nuclear positrons. This leaves a neutroneum
core, possibly covered by a thin degenerate matter shell.
Population
I:
stars are old stars well down the main sequence (class F, G, K, and M stars)
and short on heavier elements. Planetary systems accompanying Population I stars
primarily consist of gas giants without accompanying satellites.
Population
2:
stars are younger stars showing traces of heavier elements, hydrogen, and helium.
Planetary systems accompanying Population 2 stars include gas giants, stony
worlds, satellite companions and planetoid and comet shells.
Red
Giant Star:
The red giant phase is common in the evolution of many less massive stars. When
core hydrogen is exhausted, gravitational collapse ignites hydrogen shell burning
outside the core. The stars envelope expands far beyond the photosphere
limit. The stars atmosphere is relatively cool.
Runaway
Star:
is a star with a velocity significantly different from its neighboring stars.
Supernova:
when a massive young star exhausts its core hydrogen it undergoes second-stage
gravitational collapse. The resulting core temperature increase leads to runaway
nuclear burning of helium, carbon, nitrogen and an explosion that blasts the
stars outer layer into space. Supernova explosions are the major source
of metals and other galactic elements.
T
Tauri Star:
is one manifestation of a star in formation undergoing initial nuclear burning.
Dwarf Stars
'Dwarf' is a category comprising various small and dim energy-radiating or formerly
energy-radiating objects.
Black
Dwarf:
is an object of stellar mass that has undergone gravitational collapse, reaching
minimum potential energy and maximum entropy. Black dwarfs are sub-planetary
size and do not radiate.
Brown
Dwarf:
is a gaseous body producing much more energy through self-gravitation than it
receives from the ambient medium, but which is not massive enough to initiate
internal fusion reaction and, therefore, not truly a star. Brown dwarfs hot
enough to produce visible light (substellar objects) are listed as Class S planets.
They are both also known as supergiant gas planets. Some giant gas planets (Class
A) may produce slightly more energy than they receive, but they are not generally
considered to be brown dwarfs.
Red
Dwarf:
is a main sequence star of type M. The vast majority of stars in the galaxy
are red dwarfs: small, dim and long lived.
White
Dwarfs:
primarily degenerate matter, this main sequence star, usually of type G-late
A, has completed nuclear burning processes and has collapsed into a configuration
roughly the size of a small planet. White dwarfs radiate at various levels of
intensity through self-gravitational collapse. Nuclear burning occurs only on
the surface through accretion of unburned matter from other sources; in such
cases, nuclear ignition can regularily occure and is the source of the recurrent
nova effect. The spectral class of white dwarf stars is usually prefixed
with a 'D'.
Spectral Types
There are seven major spectral types of stars, forming a continuous band of
types from 0 through M: 0 B A F G K M
These are divided into ten numbered subtypes. For example:
A1 A2 A3 A4 A5 A6 A7 A8 A9 A0
Stars at the '0' end of this band are hotter (around 50,000 degrees K); bluer
in colour and more massive; those at the other end are cooler (around 2,000
degrees K), redder in colour and less massive. A conventional code for star
colour is:
Type 0 - Violet = White
Type A - White
Type B - Blue = White
Type F - Yellow = White
Type G -Yellow
Type K - Orange
Type M - Red
While a 'Giant' star may have a radius of up to 1,000 times that of Sol and
be up to 100,000 times as luminous, most of the stars are in the 'main sequence'
portion of their lifetimes and have values near the typical main sequence ones
for their type. Sol, Earths sun, is a type G. Its spectrum, as filtered
by Earths atmosphere, is the basis for standard illumination in Human
quarters.
Type 0 : (Violet-White)
Main Sequence Value Ranges: (Approximate)
Temperature: 30,000 - 50,000 K
Mass: 10 - 30 Solar Masses
Radius: 2.5 - 3.0 Solar Radii
Luminosity: 1,000 - 100,000 SOL
Type A: (White)
Main Sequence Value Ranges: (Approximate)
Temperature: 7,500 - 10,000 K
Mass: 2 - 3 Solar Masses
Radius: 1.5 - 2.0 Solar Radii
Luminosity: 5 - 10 SOL
Type
B: (Blue-White)
Main Sequence Value Ranges: (Approximate)
Temperature: 10,000 - 30,000 K
Mass: 3-5 Solar Masses
Radius: 2.0 - 3.5 Solar Radii
Luminosity: 10 - 1,000 SOL
Type
F: (Yellow - White)
Main Sequence Value Ranges: (Approximate)
Temperature: 6,000 - 7,500 K
Mass: 1 - 2 Solar Masses
Radius: 1.0 - 1.5 Solar Radii
Luminosity: 1 - 5 SOL
Type
G: (Yellow)
Main Sequence Value Ranges: (Approximate)
Temperature: 4,500 - 6,000 K
Mass: 8 - 1 Solar Masses
Radius: 0.8 - 1.0 Solar Radii
Luminosity: 0.1 - 1 SOL
Type
K: (Orange)
Main Sequence Value Ranges: (Approximate)
Temperature: 3,500 - 4,500 K
Mass: 0.5 - 0.8 Solar Masses
Radius: 0.5 - 0.8 Solar Radii
Luminosity: 0.01 - 0.1 SOL
Type
M: (Red)
Main Sequence Value Ranges: (Approximate)
Temperature: 2,000 - 3,500 K
Mass: 0.02 - 0.5 Solar Masses
Radius: 0.01 - 0.5 Solar Radii
Luminosity: 0.00001 - 0.01 SOL