The spectral class of a star is a designated class of a
star describing the ionization of its chromosphere, what
atomic excitations are most prominent in the light, giving
an objective measure of the temperature in this chromosphere.
O Dark Blue
28,000 - 50,000 K
Ionized atoms, especially helium
O stars are very hot and very luminous, being bluish in
color; in fact, most of their output is in the ultraviolet
range. These are the rarest of all main sequence stars.
About 1 in 3,000,000 of the main sequence stars in the solar
neighborhood are Class O stars. Some of the most massive
stars lie within this spectral class.
10,000 – 28,000 K
Neutral helium, some hydrogen
2.1 - 16
1.8 - 6.6
Alpha Eridani A (B3V-IV)
B stars are extremely luminous and blue. As O and B stars
are so powerful, they only live for a very short time, and
thus they do not stray far from the area in which they were
A Light Blue
7,500 – 10,000 K
Strong hydrogen, some ionized metals
1.4 – 2.1
1.4 - 1.8
Sirius A (A0-1V)
Class A is a light blue star that is made up of strong hydrogen
and some ionized metals. The temperature ranges from 7,500
to 10,000 degress K.
6,000 – 7,500 K
Hydrogen and ionized metals, calcium and iron
1.04 – 1.4
1.15 – 1.4
Procyon A (F5V-IV)
Class F star is white and is made up of hydrogen and ionized
metals. Also in the star there is calcium and iron. The
temperature in this type of star is between 6,000 and 7,500
5,000 – 6,000 K
Ionized calcium, both neutral and ionized metals
0.8 – 1.04
0.96 – 1.15
G-class (or G-type) star is a stellar classification for
stars composed of both neutral and ionized atoms of metallic
substances, including ionized calcium, emitting in the neighborhood
of 5,000 to 6,000 Kelvin, generally referred to as being
yellow in color. G-type stars in the main sequence tend
to be median in terms of absolute magnitude, and in the
"cooler" half of the stellar classification system.
Yellow G-type stars can range in size from yellow giants
to the more diminutive yellow dwarf.
3,500 – 5,000 K
0.45 – 0.8
0.7 – 0.96
Alpha Centauri B (K0-3V)
K class (also K type or orange star) is a type of star that
is made up of neutral metals. The temperature is around
3,500 through 5,000 Kelvin. Some K stars are giants and
supergiants, such as Arcturus, while orange dwarfs, like
Alpha Centauri B, are main sequence stars.
2,500 – 3,500 K
Ionized atoms, especially helium
M is by far the most common class. About 76% of the main
sequence stars in the solar neighborhood are Class M stars.
Although most Class M stars are red dwarfs, the class also
hosts most giants and some supergiants such as Antares and
Betelgeuse, as well as Mira variables.
A protostar is a star in the very earliest stage of development,
when interstellar gas is still undergoing gravitational
collapse, and nuclear fusion at the core has just begun.
The Argolis Cluster is an example of a protostar cluster.
Collapsing protostars sometimes emit E-band bursts and
are often marked by high levels of magnetascopic interference,
which impair sensor function.
In theory, a type-6 protostar could be used to generate
A flare star is a type of star which regularly experiences
brief, random outbursts of solar flares over its surface
disrupting energy patterns in its system and sometimes endangering
The rare hypergiant star is one which shares similar characteristics
with a supergiant star, but is 100 times more massive than
Sol. The theoretical lifespan of a hypergiant is one to
two million years. Supposedly, like its supergiant companions,
a hypergiant star will go supernova when it exhausts its
supply of fuel and gravity crushes the inert remains.
The Enterprise NX-01 was the first Earth ship to research
a red hypergiant at close range in 2152; it was nearly a
billion kilometers in circumference and was not expected
to go supernova for another one hundred or two hundred years.
A neutron star is a type of remnant that can result from
the gravitational collapse of a massive star during a Type
II, Type Ib or Type Ic supernova event. Such stars are composed
almost entirely of neutrons, which are subatomic particles
without electrical charge and a slightly larger mass than
protons. Neutron stars are very hot and are supported against
further collapse because of the Pauli exclusion principle.
This principle states that no two neutrons (or any other
fermionic particle) can occupy the same place and quantum
Some neutron stars, called pulsars, emit beams of electromagnetic
radiation from their poles.
A red dwarf is a small, cool, very faint, main sequence
star with a surface temperature under about 4,000 K. Red
dwarves are the most common type of star.
Proxima Centauri and 40 Eridani C are examples of red dwarf
A red giant is a very large, relatively cool star, formed
when a main sequence star runs out of hydrogen and begins
fusing helium. Some red giants are considered B class stars.
Supergiants are among the most massive stars.
Supergiants can have masses from 10 to 70 solar masses and
brightness from 30,000 up to hundreds of thousands times
the solar luminosity. They vary greatly in radii, usually
from 30 to 500, or even in excess of 1,000 solar radii.
The Stefan-Boltzmann law dictates that the relatively cool
surfaces of red supergiants radiate much less energy per
unit area than those of blue supergiants; thus, for a given
luminosity red supergiants are larger than their blue counterparts.
Supergiants occur in every spectral class from young blue
class O supergiants stars to highly evolved red class M
supergiants. Rigel, the brightest star in the constellation
Orion is a typical blue-white supergiant, whereas Betelgeuse
and Antares are red supergiants.
A T-Tauri type star is one in the earliest phase of its
lifespan. The type is named for the first discovered star
of this type, seen from Earth as part of the Taurus constellation.
Small, extremely unstable wormholes are a phenomenon sometimes
encountered in T-Tauri systems - in the century between
2267 and 2367, thirty-nine had been mapped.
A white dwarf is a star formed when a red giant runs out
of helium fuel after losing most of its mass into space.
White dwarfs are the only natural source of vertion particles.
In 2370, a network emergent circuit nodes aboard the Enterprise-D
collected vertions from the white dwarf Tambor Beta-6 to
sustain their growth, but the supply from a single star
A yellow dwarf is a classification of star which is undergoing
hydrogen-helium conversion. Sol is a well-known yellow dwarf
Such a star has about 0.8 to 1.2 solar masses and a surface
temperature of between 5,300 and 6,000 K.
A yellow dwarf star will fuse hydrogen for approximately
10 billion years, until it is exhausted at the center of
the star. When this happens, the star expands to many times
its previous size and becomes a red giant, such as Aldebaran.
Eventually the red giant sheds its outer layers of gas,
which become a planetary nebula, while the core cools and
contracts into a compact, dense white dwarf