# Cosmic Times Master Glossary

**Note**: If a word has changed meaning through the course of the Cosmic
Times newspapers, alternate definitions are noted after the modern
definition.

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# A

Absolute

being independent of the system of measurement or external references.

acoustic

of or relating to sound

afterglow

Light emitted after removing the source of energy.

aggregate

An aggregate is an assemblage of various particles. In this case,
aggregates of many stars form nebulae or galaxies.

agog

eager, full of intense interest

Andromeda Galaxy

A large spiral galaxy visible to the naked eye, and the closest spiral
galaxy to the Milky Way. It lies 2.2 million light-years from Earth in
the constellation Andromeda in the Northern Hemisphere between Lacerta
and Perseus and south of Cassiopeia. Also known as Messier 31, M31, or
NGC 224.

anisotropy

The property of having measurements that differ when measured in a
different direction.

Archimedes

An ancient Greek physicist and mathematician. His discovery of how to
determine the volume of an irregular solid by water displacement is his
most famous principle -- Archimedes' Principle.

astronomical

Deals with Astronomy

astrophysicist

A person who studies the part of astronomy that deals principally with
the physics of the universe, including luminosity, density, temperature,
and the chemical composition of stars, galaxies, and the interstellar
medium.

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# B

bandwidths

The range of signal frequencies that can be carried on a communications
channel.

baryon

Any of the subatomic particles that interact via the strong nuclear
force. Most commonly, these are protons and neutrons. Their presence in
the universe is determined through their gravitational and
electromagnetic interactions.

binary stars

Binary stars are two stars that orbit around a common center of mass. An
X-ray binary is a special case where one of the stars is a collapsed
object such as a white dwarf, neutron star, or black hole, and the
separation between the stars is small enough so that matter is
transferred from the normal star to the compact star, producing X-rays
in the process.

black hole

an area in space with such a strong gravitational pull that no matter or
energy can escape from it. Black holes are so named because even light
cannot escape from them.

blackbody radiation

Blackbody radiation is produced by an object which is a perfect absorber
of heat. Perfect absorbers must also be perfect radiators. For a
blackbody at a temperature T, the intensity of radiation emitted I at a
particular energy E is given by Plank\'s law:

I(E,T) = 2 E^3^\[h^2^c^2^(e^E/kT^ - 1)\]^-1^

where h is Planck\'s constant, k is Boltzmann\'s constant, and c is the
speed of light.

blackbody temperature

The temperature of an object if it is re-radiating all the thermal
energy that has been added to it; if an object is not a blackbody
radiator, it will not re-radiate all the excess heat and the leftover
will go toward increasing its temperature.

Boltzmann constant

A constant that describes the relationship between temperature and
kinetic energy for molecules in an ideal gas. It is equal to
1.380622 x 10^-23^ J/K (see scientific notation).

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# C

celestial

Relating to the sky or the heavens

Cepheid

Type of variable star that exhibits a regular pattern of changing
brightness as a function of time. The period of the pulsation pattern is
directly related to the star\'s intrinsic brightness. Thus, Cepheid
variables are a powerful tool for determining distances in modern
astronomy.

COBE

The Cosmic Background Explorer satellite used to measure the diffuse
infrared and microwave radiation from the early universe to the limits
set by our astrophysical environment.

coma

The nebulous envelope around the nucleus of a comet

constellation

A constellation is a specific and recognizable grouping of stars.
Constellations are given names to distinguish them.

**Copernicus**

A Polish astronomer, born in the 15th century, who challenged the
existing views by suggesting that the sun was the center of the solar
system and the universe instead of Earth.

cosmic microwave background (CMB)

The background of radiation mostly in the frequency range 3 x 10^8^ to 3
x 10^11^ Hz discovered in space in 1965. It is believed to be the
cosmologically redshifted radiation released by the Big Bang itself.

cosmic ray

Atomic nuclei (mostly protons) and electrons that are observed to strike
the Earth\'s atmosphere with exceedingly high energies.

cosmology

The astrophysical study of the history, structure, and dynamics of the
universe.

cosmological constant

A constant term (labeled Lambda) that Einstein added to his general
theory of relativity in the mistaken belief that the Universe was
neither expanding nor contracting. The cosmological constant was found
to be unnecessary once observations indicated the Universe was
expanding. Had Einstein believed what his equations were telling him, he
could have claimed the expansion of the Universe as perhaps the greatest
and most convincing prediction of general relativity; he called this the
\"greatest blunder of my life\".

cosmos

The universe as a whole

**contortion**

A twisting or deforming action.

**cubit**

An ancient measure of length equal to the distance between the elbow and
the fingertips or approximately 18 inches.

culminating

Coming to completion

Cygnus A

A radio source in the constellation Cygnus in the Northern Hemisphere

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# D

dark energy

Dark energy is a hypothesized form of energy in space that exerts a
negative pressure. This changes the gravitational effect to account for
the differences between the theoretical and observational results of
gravitational effects on visible matter.

dark matter

Name given to the mass whose existence is deduced from the analysis of
galaxy rotation curves but which until now, has escaped all detections.
There are many theories on what dark matter could be. Not one, at the
moment, is convincing enough and the question is still a mystery.

**deviation**

The difference between a value in a frequency distribution and the
average

**dissipate**

To spread thin and eventually vanish.

Doppler effect

The apparent change in wavelength of sound or light caused by the motion
of the source, observer or both. Waves emitted by a moving object as
received by an observer will be
[blueshifted](http://imagine.gsfc.nasa.gov/docs/dict_ad.html#blueshift)
(compressed) if approaching,
[redshifted](http://imagine.gsfc.nasa.gov/docs/dict_qz.html#redshift)
(elongated) if receding. It occurs both in sound and light. How much the
[frequency](http://imagine.gsfc.nasa.gov/docs/dict_ei.html#frequency)
changes depends on how fast the object is moving toward or away from the
receiver.

dwarfed

Appearing smaller or inferior

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# E

**electro-weak force**

The unification of the electromagnetic force and the weak nuclear force

electromagnetic spectrum

The full range of frequencies, from radio waves to gamma rays, that
characterizes light.

emission

The production of light, or more generally, electromagnetic radiation by
an atom or other object.

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# F 

fledgling

New or inexperienced

fluctuations

Variations in the primordial universe

fluorescing

The emission of electromagnetic radiation, (especially visible light)
stimulated e by the absorption of incident radiation and lasting only as
long as the incident radiation is continued.

**fusion**

Joining together -- used in atomic science to indicate the joining of
particles in a nucleus.

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height="2.0833333333333332e-2in"}

# G

**galactic disk**

The galactic disc is the plane in which the spirals, bars and discs of
disc galaxies exist. This area tends to have more gas and dust, and
younger stars than galactic bulges, or galactic haloes.

galaxy

A component of our universe made up of gas and a large number (usually
more than a million) of stars held together by gravity. When
capitalized, Galaxy refers to our own Milky Way Galaxy.

General Relativity

The geometric theory of gravitation developed by Albert Einstein,
incorporating and extending the theory of special relativity to
accelerated frames of reference and introducing the principle that
gravitational and inertial forces are equivalent. The theory has
consequences for the bending of light by massive objects, the nature of
black holes, and the fabric of space and time.

General Relativity is an extension of the Special Theory of Relativity
to include gravitation and acceleration.

globular clusters

A spherically symmetric collection of stars which shared a common
origin. The cluster may contain up to millions of stars spanning up to
50 parsecs.

**Grand Unified Theory**

The Grand Unified Theory attempts to combine the four forces that are
known (gravity, electromagnetism, strong nuclear, and weak nuclear) into
one theory.

**gravitational waves**

Ripples in space-time caused by the motion of objects in the universe.
The most notable sources are orbiting neutron stars, merging black
holes, and collapsing stars. Gravitational waves are also thought to
emanate from the Big Bang.

**gravity**

a fundamental physical force that is responsible for interactions which
occur because of mass between particles, between large bodies of matter
(as stars and planets), and between particles (as photons) and large
bodies of matter.

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# H

Holmdel Horn

Radio antenna located in Holmdel, NJ used by Penzias and Wilson when
they came across the cosmic microwave background radiation. The Horn
Antenna is a National Historic Landmark

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# I

infrared

Electromagnetic radiation at wavelengths longer than the red end of
visible light and shorter than microwaves (roughly between 1 and 100
microns). Almost none of the infrared portion of the electromagnetic
spectrum can reach the surface of the Earth, although some portions can
be observed by high-altitude aircraft (such as the Kuiper Observatory)
or telescopes on high mountaintops (such as the peak of Mauna Kea in
Hawaii).

Integrated Sachs-Wolfe Effect

The Sachs-Wolfe effect, named after Rainer Kurt Sachs and Arthur Michael
Wolfe, is a property of the cosmic microwave background radiation (CMB),
in which photons are gravitationally redshifted, and the spectrum
appears uneven.

**intrinsic brightness**

Intrinsic brightness is also called absolute magnitude tells how bright
a star would be without the effects of distance or absorption due to
interstellar dust or gas.

intrinsic luminosity

The intrinsic luminosity of a star is its actual brightness and
magnitude, not simply its apparent brightness that we can witness from
earth. A star's intrinsic luminosity can be determined from its apparent
brightness and its distance from earth.

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# J

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# K

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# L

**light year**

A unit of length used in astronomy that equals the distance light
travels in a year. At the rate of 300,000 kilometers per second (671
million miles per hour), 1 light-year is equivalent to 9.46053 x 10^12^
km, 5,880,000,000,000 miles or 63,240 AU.

luminosity

The rate at which a star or other object emits energy, usually in the
form of electromagnetic radiation. The luminosity of a star depends on
BOTH its temperature (hotter stars give out more energy) \-- and its
radius (surface area increases as radius increases).

**luminosity-decline relation**

A correction factor for supernovae that are dimmer than the standard
Type Ia supernova which allows astronomers to measure distance more
accurately.

luminous

Emitting light

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# M

**MACHOS**

MAssive Compact Halo Objects -- one possible type of Dark Matter.

Magellanic Clouds

The two Magellanic Clouds are irregular dwarf galaxies, which are the
Milky Way's closest neighbors. Historically they have been though to be
orbiting our Galaxy, but recent research suggests that they members of
our Local Group of galaxies, but are just passing by. They are visible
from the southern hemisphere.

magnitude

The degree of brightness of a celestial body designated on a numerical
scale, on which the brightest star has magnitude -1.4 and the faintest
star visible without a telescope has magnitude 6. So, the lower the
number, the brighter the star; the higher the magnitude, the dimmer the
star. A decrease of one magnitude represents an increase in apparent
brightness by a factor of 2.512; also called apparent magnitude.

**Megahertz**

One million hertz where each hertz is one vibration per second. This is
the frequency of the radio wave.

**microwave**

Electromagnetic radiation that has a longer wavelength (between 1 mm and
30 cm) than visible light. Microwaves can be used to study the Universe,
communicate with satellites in Earth orbit, and cook popcorn.

**minuscule**

Very small

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# N

Near-infrared telescopes.

Near-infrared telescopes collect light in the region of the
electromagnetic spectrum just below visible light. Whereas, most
infrared radiation is warm, near-infrared waves are not hot at all -- in
fact, you cannot even feel them. These shorter wavelengths are the ones
used by your TV\'s remote control.

nebula

A diffuse mass of interstellar dust and gas. A reflection nebula shines
by light reflected from nearby stars. An emission nebula shines by
emitting light as electrons recombine with protons to form hydrogen. The
electrons were made free by the ultraviolet light of a nearby star
shining on a cloud of hydrogen gas. A planetary nebula results from the
explosion of a solar-like type star.

Historically, the term nebula referred to any fuzzy patch in the sky
that could not be resolved by telescopes. Up until 1920, this included
galaxies. The term "nebula" to mean "galaxy" was in use is publications
until at least the mid-1940s.

**neutrinos**

A fundamental particle produced in massive numbers by the nuclear
reactions in stars; they are very hard to detect because the vast
majority of them pass completely through the Earth without interacting.

**neutron**

An uncharged particle in the nucleus of an atom

**Newton**

Physicist known for Three Laws of Motion, Law of Universal Gravitation
and invention of calculus.

NGC 3521

A spiral galaxy in the constellation Leo

NGC 972

A spiral galaxy in the constellation Ares

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# O

optical telescopes

A telescope that collect light in the region of the electromagnetic
spectrum that is visible light.

oscillating

Swinging to and from a position

oscillating universe

A theory stating that the gravitational attraction of the mass within
the universe will eventually slow down and stop the expansion of the
universe eventually resulting in a 'Big Crunch' where all the matter in
the universe will be contracted into a small volume of high density

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height="2.0833333333333332e-2in"}

# P

parsecs

The distance to an object which has a parallax of one arc second. It is
equal to 3.26 light years, or 3.1 x 1018 cm. A kiloparsec (kpc) is equal
to 1000 parsecs. A megaparsec (Mpc) is equal to a million (106) parsecs.

photographic plates

Early photography used a light-sensitive emulsion of silver salts
applied to a glass plate. In this context, a photographic plate can be
considered another term for a photograph.

polarization

A special property of light; light has three properties, brightness,
color and polarization. Polarization is a condition in which the planes
of vibration of the various rays in a light beam are at least partially
aligned.

**Pravda**

A newspaper in former the Soviet Union

primordial

Primordial matter refers to the matter in the universe that was first
formed, and has been in existence since the existence of the universe
itself.

**pulsar**

A rotating neutron star which generates regular pulses of radiation.
Pulsars were discovered by observations at radio wavelengths but have
since been observed at optical, X-ray, and gamma-ray energies.

**pulsation**

A regular variation of light intensity of a star.

**Pythagoras**

Ancient Greek mathematician and philosopher best know for the
Pythagorean Theorem for right triangles.

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# Q

**quantum fluctuations**

A temporary change in energy at a given point due to variations
predicted by the Heisenberg Uncertainty Principle. These variations
could have caused inflation.

**quarks**

Subatomic particles that make up baryons and mesons. Three quarks are
needed to make a proton or a neutron.

quasar

An enormously bright object at the edge of our universe which emits
massive amounts of energy. In an optical telescope, they appear
point-like, similar to stars, from which they derive their name (quasar
= quasi-stellar). Current theories hold that quasars are one type of AGN

quintessence

A hypothetic form of dark energy, a scalar field that accelerated the
expansion of the universe.

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height="2.0833333333333332e-2in"}

# R

radial velocity

The speed at which an object is moving away or toward an observer. By
observing spectral lines, astronomers can determine how fast objects are
moving away from or toward us; however, these spectral lines cannot be
used to measure how fast the objects are moving across the sky.

radiation

Energy emitted in the form of waves (light) or particles (photons)

**red shift**

A consequence of the Doppler Effect where all the spectral lines are
moved to longer (redder) wavelengths when the source is moving away from
the receiver.

remnant

Left over; a surviving trace or vestige

**ROSAT**

The ROentgen SATellite that was an X-ray satellite launched in 1990

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# S

schema

a framework, outline or model

Scorpius

A constellation named the Scorpion located in the Southern Hemisphere
near Libra and Sagittarius .It contains the bright red star Antares

Special Relativity

theory of space time based on two postulates (1) the speed of light is
the same for any observer regardless of the speed of either the observer
or the source (2) the mathematical forms of the equations of physics are
invariant in any inertial reference frame.

spectrum (pl. spectra)

A plot of the intensity of light at different frequencies. Or the
distribution of wavelengths and frequencies.

spherical galaxy

A galaxy that has a shape similar to a sphere.

spiral nebulae

Historic term for a spiral galaxy, which changed in the 20th century. A
spiral galaxy belongs to one of the three main classes of galaxy. Spiral
galaxies consist of a flat, rotating disk of stars, gas and dust, and a
central concentration of stars known as the bulge.

Standard candles

An object in the universe of known luminosity that can be used to
calculate distances.

Steady State Universe Model

Model designed by Fred Hoyle and others wherein new material is created
as the universe expands.

**strong nuclear force**

One of the four fundamental forces. The strong nuclear force or
interaction is the strongest of the fundamental forces. It holds the
nucleus together. It is the interaction of quarks and gluons in the
nucleus.

**supernova (plural: supernovae)**

(a)The death explosion of a massive star, resulting in a sharp increase
in brightness followed by a gradual fading. At peak light output, these
type of supernova explosions (called Type II supernovae) can outshine a
galaxy. The outer layers of the exploding star are blasted out in a
radioactive cloud. This expanding cloud, visible long after the initial
explosion fades from view, forms a supernova remnant (SNR).

\(b\) The explosion of a white dwarf that has accumulated enough
material from a companion star to achieve a mass equal to the
Chandrasekhar limit. These types of supernovae (called Type Ia) have
approximately the same intrinsic brightness, and can be used to
determine distances.

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# T

telecommunications

Telecommunication is the system by which auditory and visual information
is transmitted by television, radio, or phone.

theory

a testable explanation of observations made in an experiment.

Theory of General Relativity

The geometric theory of gravitation developed by Albert Einstein,
incorporating and extending the theory of special relativity to
accelerated frames of reference and introducing the principle that
gravitational and inertial forces are equivalent. The theory has
consequences for the bending of light by massive objects, the nature of
black holes, and the fabric of space and time

**Type 1a supernovae**

See b above, in supernova definition. Supernovae of predictable
intrinsic brightness that can be used as a "standard candle".

**Type 2 supernovae**

Supernova that do not have the telltale lines of hydrogen in the
spectrum.

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# U

undulations

A wavelike motion in a medium without permanent movement of the
particles.

Universe

Everything that exists, including the Earth, planets, stars, galaxies,
and all that they contain; the entire cosmos.

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# V

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# W

wavelength

The distance between adjacent peaks in a series of periodic waves. Also
see electromagnetic spectrum.

**white dwarf**

A star that has exhausted most or all of its nuclear fuel and has
collapsed to a very small size. Typically, a white dwarf has a radius
equal to about 0.01 times that of the Sun, but it has a mass roughly
equal to the Sun\'s. This gives a white dwarf a density about 1 million
times that of water!

**Wien\'s displacement law**

For a blackbody, the product of the wavelength corresponding to the
maximum radiance and the thermodynamic temperature is a constant. As a
result, as the temperature rises, the maximum of the radiant energy
shifts toward the shorter wavelength (higher frequency and energy) end
of the spectrum.

Wilkinson Microwave Anisotropy Probe (WMAP)

A NASA satellite designed to detect fluctuations in the cosmic microwave
background. From its initial results published in Feb 2003, astronomers
pinpointed the age of the universe, its geometry, and when the first
stars appeared.

**WIMPs**

Weakly Interacting Massive Particles that might be a candidate for dark
matter in the universe. They interact through the weak nuclear force and
gravity.

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# X

**X-ray**

Electromagnetic radiation of very short wavelength and very high-energy;
X-rays have shorter wavelengths than ultraviolet light but longer
wavelengths than gamma rays.

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height="2.0833333333333332e-2in"}

# Y

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height="2.0833333333333332e-2in"}

# Z

zenith

the zenith at a given point is the local vertical direction pointing
away from direction of the force of gravity at that location