- accretion
-
Accumulation of dust
and gas into larger bodies such as stars, planets and moons.
- Adams, John Couch
1819-1892
-
English astronomer and
mathematician who, at the age of 24, was the first person to
predict the position of a planetary mass beyond
Uranus.
But, unfortunately, Adams did not publish his prediction.
Galle
confirmed the existance of
Neptune
based on independent calculations done by
Le Verrier.
(4k
jpg)
- albédo
-
the ratio of the amount
of light reflected by an object and the amount of incident
light; a measure of the reflectivity or intrinsic brightness of
an object (a white, perfectly reflecting surface would have an
albedo of 1.0; a black perfectly absorbing surface would have an
albedo of 0.0).
- formations
d'albédo
-
A dark or light marking
on the surface of an object that may not be a geological or
topographical feature.
- antipodal point
-
the point that is
directly on the opposite side of the planet
- aphelion
-
the point in its orbit
where a planet is farthest from the Sun; when refering to
objects orbiting the Earth the term apogee is used; the term
apoapsis is used for orbits around other bodies. (opposite of
perihelion)
- arcuate
-
having the form of a
bow; curved; arc-shaped
- Arago, Dominique
Francois Jean 1786 -
1853
-
French astronomer and
physicist and Director of the Paris Observatory, who discovered
the phenomenon of the production of magnetism by rotation
- d'Arrest,
Heinrich Louis
-
Danish astronomer who
assisted
Galle
with the first observations of
Neptune.
After receiving its predicted position from
Le Verrier,
Galle and d'Arrest began searching. With Galle at the eyepiece
and d'Arrest reading the chart, they scanned the sky and checked
that each star seen was actually on the chart. Just a few
minutes after their search began, d'Arrest cried out, "That star
is not on the map!" and earned his place in the history books. (90k
jpg)
- asteroid
-
(also "planetoid") a
medium-sized
rocky object orbiting the Sun; smaller than a planet, larger
than a meteoroid
- asteroid
number
-
asteroids are assigned
a serial number when they are discovered. It has no particular
meaning except that asteroid N+1 was discovered after asteroid
N. (see
appendix 5)
- atmosphere
-
= 1.013
bars =
1.03 kg/cm2 = 14.7 pounds per square inch, standard atmospheric
pressure at sea level on Earth.
- aurore
-
a glow in a planet's
ionosphere caused by the interaction between the planet's
magnetic field and charged particles from the Sun
- aurora borealis
-
the "Northern Lights";
caused by the interaction between the
solar wind,
the Earth's magnetic field and the upper atmosphere. A similar
effect happens in the southern hemisphere where it is known as
the aurora australis.
-
- bar
-
= 0.987
atmosphere
= 1.02 kg/cm2 = 100 kilopascal = 14.5 lbs/square inch.
- Barnard, Edward
Emerson 1857-1923
-
American astronomer;
discovered
Jupiter's
satellite
Amalthea
and Barnard's star, the second-nearest star system to the Sun.
- Barsoom
-
The local name for Mars
in Edgar Rice Burroughs' SF books.
- Bode, Johann Elert
1747-1826
-
German astronomer,
known for the bogus "Bode's
Law" which attempts to explain
the sizes of the planetary orbits.
- bolide
-
a
fireball
that produces a sonic boom
- Bond, William Cranch
1789-1859
-
One of the earliest
American astronomers of note; rose from poverty and overcame a
lack of formal education to become the first director of the
Harvard College Observatory where he studied
Saturn
and (with
Lassell)
discovered its moon
Hyperion.
- Brahe, Tycho
1546-1601
-
(a.k.a Tyge Ottesen)
Danish astronomer whose accurate astronomical observations
formed the basis for Johannes
Kepler's
laws of planetary motion. (141k
jpg;
38k jpg;
more)
-
- caldeira
-
crater formed by an
explosion or collapse of a volcanic vent.
- carbonate
-
a compound containing
carbon and oxygen (i.e. calcium carbonate a.k.a. limestone).
- Cassini, Giovanni Domenico
1625-1712
-
(a.k.a. Jean Dominique)
Italian-born French astronomer and first director of the
Royal
Observatory in Paris;
discoverer of four of
Saturn's
moons (Tethys,
Dione,
Rhea and
Iapetus)
and the major gap in its rings. (13k
jpg;
more)
- catena
-
chain of craters.
- cavus
-
Hollow, irregular
depression.
- chaos
-
distinctive area of
broken terrain.
- chasma
-
canyon.
- chromosphere
-
the lower level of the
solar
atmosphere between the
photosphere
and the
corona
- colles
-
small hills or knobs.
- coma
-
the dust and gas
surrounding an active
comet's
nucleus
- comet
-
a
medium-sized
icy object orbiting the Sun; smaller than a planet
- Congress
-
the legislative branch
of the US Government; has proven to be a much more hostile
environment for scientific spacecraft than the vastness of
space.
- convection
-
fluid circulation
driven by large temperature gradients; the transfer of heat by
this automatic circulation.
- Copernicus,
Nicolaus 1473-1543
-
Polish astronomer who
advanced the
heliocentric
theory that the Earth and other planets revolve around the Sun.
This was highly controversial at the time as the
Ptolemaic
view of the universe, which was the prevailing theory for over
1000 years, was deeply ingrained in the prevailing philosophy
and religion. (It should be noted, however, that the heliocentic
idea was first put forth by Aristarcus of Samos in the 3rd
century BC, a fact known to Copernicus but long ignored.) (470k
html/gif;
12k gif;
129k jpg;
more)
- corona
-
ovoid-shaped
feature.
- corona
-
the uppermost level of
the
solar
atmosphere, characterized by low densities and high temperatures
(> 1.0E+06° K).
- coronagraph
-
a special telescope
which blocks light from the disk of the
Sun in
order to study the faint solar atmosphere.
- cosmic ray
-
an extremely energetic
(relativistic) charged particle.
- crater
-
bowl-shaped depression
formed by the impact of a
meteorite;
depression around the orifice of a volcano.
-
- density
-
measured in grams per
cubic centimeter (or kilograms per liter); the density of water
is 1.0; iron is 7.9; lead is 11.3.
- disaster
-
literally "bad stars";
particularly apt in reference to a major asteroid impact.
- disk
-
the visible surface of
the Sun (or any heavenly body) projected against the sky.
- doppler effect
-
the apparent change in
wavelength of sound or light caused by the motion of the source,
observer or both. (see
also)
- dinosaurs
-
large reptiles that
lived in the Mesozoic Era from 230 to 65 million years ago; most
probably wiped out by the impact of a large
asteroid
or
comet.
- direct
-
rotation or orbital
motion in a counterclockwise direction when viewed from the
north pole of the primary (i.e. in the same sense to most
satellites); the opposite of
retrograde.
The north pole is the one on the same side of the
ecliptic
as the Earth's north pole. (The word "prograde" is sometimes
used to mean "direct" in this sense.)
- dorsum
-
ridge.
-
- excentrique
-
the eccentricity of an
ellipse (planetary orbit) is the ratio of the distance between
the focii and the major axis. Equivalently the eccentricity is
(ra-rp)/(ra+rp) where ra is the
apoapsis
distance and rp is the
periapsis
distance.
- effusive
eruption
-
a relative quiet
volcanic eruption which puts out basaltic lava that moves at
about the speed one walks; the lava is fluid in nature; the
eruptions at the Kilauea volcano on the island of Hawaii are
effusive
- Einstein, Albert
1879-1955
-
German-American
physicist; developed the Special and General
Theories of Relativity
which along with Quantum Mechanics is the foundation of modern
physics. (See
fusion,
speed of light)
(96k
gif)
- ellipse
-
oval. That the orbits
of the planets are ellipses, not circles, was first discovered
by Johannes
Kepler
based on the careful observations by
Tycho Brahe.
- erg/sec
-
= 1e-10 kilowatts.
- explosive
eruption
-
a dramatic volcanic
eruption which throws debris high into the air for hundreds of
miles; lava is low in silicate; can be very dangerous for people
near by; an example is Mount St. Helens in 1980
- exponential
notation
-
"1.23e4" means "1.23
times 10 to the fourth power" or 12,300; "5.67e-8" means "5.67
divided by 10 to the eighth power" or 0.0000000567.
-
- facula
-
bright spot.
- farrum
-
pancake-like structure
- filament
-
a strand of cool gas
suspended over the
photosphere
by magnetic fields, which appears dark as seen against the
disk of
the
Sun; a
filament on the
limb of
the Sun seen in emission against the dark sky is called a
prominence.
- fireball
-
a
meteor
brighter than
magnitude
-3
- fissure
-
a narrow opening or
crack of considerable length and depth.
- flare
-
a sudden eruption of
energy on the solar
disk
lasting minutes to hours, from which radiation and particles are
emitted.
- flexus
-
cuspate (pointed)
linear feature.
- fluctus
-
flow terrain.
- fossa
-
long, narrow, shallow
depression.
- Franklin, Benjamin
1706-1790
-
American public
official, writer, and scientist. Played a major part in the
American Revolution and helped draft the Constitution. His
numerous scientific and practical innovations include the
lightning rod, bifocal spectacles, and a stove.
-
- Gaia Hypothesis
-
named for the Greek
Earth goddess Gaea, holds that the Earth as a whole should be
regarded as a living organism and that biological processes
stabilize the environment. First advanced by British biologist
James Lovelock in 1969.
- Galle, Johann
Gottfried 1812-1910
-
German astronomer who,
with Heinrich Louis
d'Arrest,
made the first observation of
Neptune
based on calculations by
Le Verrier.
Though Galle was the first to observe Neptune, its discovery is
usually credited to
Adams
(who made an earlier calculation) and Le Verrier.
- Lunes
Galiléennes.
-
Jupiter's
four largest moons:
Io,
Europa,
Ganymede
and
Callisto;
discovered independently by
Galileo
and
Marius.
(Galileo proposed that they be named the Medicean stars, in
honor of his patron Cosimo II de Medici; the present names are
due to Marius)
- Galileo Galilei
1564-1642
-
Italian astronomer and
physicist. The first to use a telescope to study the stars.
Discoverer of the first moons of an extraterrestrial body (see
above). Galileo was an outspoken supporter of
Copernicus's
heliocentric
theory. In reaction to Galileo, the Church declared it heresy to
teach that the Earth moved and imprisoned him. The Church clung
to this position for 350 years; Galileo was formally exonerated
in 1992. (16k
gif;
136k jpg)
(See also the Galileo exhibit at
Institute and Museum of History of
Science, Florence ITALY and
The Galileo Project
from Rice)
- gegenschein
-
a round or elongated
spot of light in the sky at a point 180 degrees from the Sun.
Also called counterglow.
- George III
1738-1820
-
King of Great Britain
and Ireland (1760-1820). His government's policies fed American
colonial discontent, leading to revolution in 1776.
- geosynchronous orbit
-
a
direct,
circular, low
inclination
orbit in which the satellite's orbital velocity is matched to
the rotational velocity of the planet; a spacecraft appears to
hang motionless above one position of the planet's surface.
- granulation
-
a pattern of small
cells seen on the surface of the
Sun
caused by the convective motions of the hot solar gas.
- greenhouse
effect
-
increase in temperature
caused when incoming solar radiation is passed but outgoing
thermal radiation is blocked by the atmosphere (carbon dioxide
is the major factor). Very important on
Venus and
Earth but
largely absent on
Mars.
-
- Hale, George Ellery
1868-1938
-
American astronomer who
founded the Yerkes, Mt. Wilson and Palomar observatories. (72k
gif)
- Hall, Asaph
1829-1907
-
American astronomer who
discovered the two moons of
Mars,
Deimos
and
Phobos.
- Halley, Edmond
1656-1742
-
English astronomer who
applied
Newton's
laws of motion to historical comet data and predicted correctly
the reappearance of the
comet
which now bears his name. (12k
jpg;
more)
- heliocentric
-
Sun-centered; see
Copernicus,
Kepler,
Galileo.
- heliopause
-
the point at which the
solar wind
meets the interstellar medium or solar wind from other stars.
- heliosphere
-
the space within the
boundary of the heliopause containing the
Sun and
solar system.
- Herschel, Sir
William 1738-1822
-
British astronomer who
discovered
Uranus
and cataloged more than 800 double stars and 2,500 nebulae. (365k
html/gif)
- Hubble, Edwin
Powell 1889-1953
-
American astronomer
whose observations proved that galaxies are "island universes",
not nebulae inside our own galaxy. His greatest discovery was
the linear relationship between a galaxy's distance and the
speed with which it is moving. The
Hubble Space Telescope
is named in his honor. (133k
html/gif;
60k gif;
bio material)
- Huygens,
Christiaan 1629-1695
-
Dutch physicist and
astronomer who first described the nature of
Saturn's
rings (1655) and discovered its moon
Titan;
also pioneered the use of the pendulum in clocks. (7k
jpg;
more)
-
- ice
-
used by planetary
scientists to refer to water, methane, and ammonia which usually
occur as solids in the outer solar system.
- inclination
-
the inclination of a
planet's orbit is the angle between the plane of its orbit and
the
ecliptic;
the inclination of a moon's orbit is the angle between the plane
of its orbit and the plane of its primary's equator.
- Inquisition,
The
-
A Renaissance Catholic
court instituted to seek out and prosecute heretics.
- inferior planets
-
the planets
Mercury
and
Venus are
called inferior planets because their orbits are closer to the
Sun than
is
Earth's
orbit.
- interplanetary magnetic field (IMF)
-
the magnetic field
carried with the
solar wind.
- ionosphere
-
a region of charged
particles in a planet's upper atmosphere; the part of the
Earth's
atmosphere beginning at an altitude of about 25 miles and
extending outward 250 miles or more.
-
-
- Kelvin (K)
-
0 Kelvin is absolute
zero; water melts at 273 K (= 0° C = 32° F); water boils at 373
K (= 100° C = 212° F). (developed by William
Thomson).
- Kepler, Johannes
1571-1630
-
German astronomer and
mathematician. Considered a founder of modern astronomy, he
formulated the famous
three laws
of planetary motion. They comprise a quantitative formulation of
Copernicus's
theory that the planets revolve around the Sun. (16k
jpg;
86k jpg;
more;
yet more)
- kilogram
(kg)
-
= 1000 grams = 2.2
pounds, the mass of a
liter of
water. (see
also)
- kilometer (km)
-
= 1000
meters =
0.62 miles.
- Kowal, Charles
T. 1940-
-
American astronomer;
discovered
Leda and
the
comet-like
object 2060 Chiron (aka 95 P/Chiron).
- Kuiper, Gerard
1905-1973
-
Dutch-born American
astronomer best known for his study of the surface of the
Moon;
discovered
Miranda
and
Nereid,
found an atmosphere on
Titan.
(Dr.Kuiper was solidly Americanized; his name is pronounced to
rhyme with "viper.") (22k
jpg)
-
- labes
-
landslide.
- labyrinthus
-
intersecting valley
complex.
- lacus
-
lake.
- Lagrange, Joseph
Louis 1736-1813
-
French (originally
Italian, Giuseppe Luigi Lagrangia; born in Turin, moved to Paris
and became a French citizen) mathematician and astronomer; made
a number of contributions to the study of celestial mechanics.
Lagrange showed that three bodies can lie at the apexes of an
equilateral triangle which rotates in its plane. If one of the
bodies is sufficiently massive compared with the other two, then
the triangular configuration is apparently stable. Such bodies
are sometimes refered to as
Trojans.
The leading apex of the triangle is known as the leading
Lagrange point or L4; the trailing apex is the trailing Lagrange
point or L5. (see
also) (5k
gif)
- Lassell, William
1799-1880
-
British astronomer,
discovered
Neptune's
largest satellite,
Triton
and (with
Bond)
discovered
Saturn's
moon
Hyperion.
A successful brewer before turning to astronomy. (22k
jpg;
more)
- Le Verrier,
Urbain Jean Joseph
1811-1877
-
French mathematician
whose prediction of the position of an undiscovered planet (Neptune)
that caused perturbations in the orbit of
Uranus
was the first to be confirmed (by
Galle)
though
Adams had
made a similar but unpublished prediction some months earlier.
- lidar
-
an instrument similar
to radar that operates at visible wavelengths.
- limb
-
the outer edge of the
apparent
disk of a
celestial body
- lumière zodicale
-
a faint glow from light
scattered off of
interplanetary dust
along the plane of the
ecliptic.
- light-year
-
= 9.46053e12 km (=
5,880,000,000,000 miles = 63,239 AU); the distance traveled by
light in a year.
- linea
-
elongate marking.
- liter
-
= 1000 cm3 = 1.06 US
quarts
- Lowell, Percival
1855-1916.
-
American astronomer. He
founded the Lowell Observatory in Arizona (1894), where his
studies of
Mars led
him to believe that the linear markings (first noted by
Schiaparelli)
on the surface were "canals" and therefore that the planet was
inhabited by intelligent beings. His successors later discovered
Pluto.
-
- macula
-
dark spot.
-
magnétosphères
-
the region of space in
which a planet's magnetic field dominates that of the
solar wind.
- magnetotail
-
the portion of a
planetary magnetosphere which is pushed in the direction of the
solar wind.
- 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
visible star has magnitude 6, with the scale rule such that a
decrease of one unit represents an increase in apparent
brightness by a factor of 2.512. Also called apparent magnitude.
- mare
-
literally "sea" (a very
bad misnomer, still in use for historical reasons); really a
large circular plain
- Marius, Simon
1573-1624
-
(a.k.a. Mayr) German
astronomer who gave
Jupiter's
"Galilean"
moons their names. He and
Galileo
both claimed to have discovered them in 1610 and likely did so
independently. They become involved in a dispute over priority.
Marius was also the first to observe the Andromeda Nebula with a
telescope and one of the first to observe
sunspots.
(more)
- mensa
-
mesa, flat-topped
elevation.
- metal
-
used by astrophysicists
to refer to all elements except hydrogen and helium, as in: "the
universe is composed of hydrogen, helium and traces of metals".
- meteor
-
(also "shooting star"
or "falling star") a bright streak of light in the sky caused by
the entry into Earth's atmosphere of a meteoroid or a small icy
particle. Very large, bright ones are called
fireballs
and
bolides
- meteorite
-
a
rock of
extra-terrestrial origin found on Earth
- meteoroid
-
a
small
rocky object orbiting the Sun; smaller than an asteroid
- millibar
-
1/1000 of a
bar.
Standard sea-level pressure is about 1013 millibars.
- minor planets
-
the official term used
for
asteroids.
- mons
-
mountain (plural:
montes)
-
- Neujmin,
Grigoriy N.
-
Ukrainian astronomer;
discovered the asteroid
951 Gaspra.
- neutrino
-
a fundamental particle
supposedly produced in massive numbers by the nuclear reactions
in stars. They are very hard to detect since the vast majority
of them pass completely through the Earth without interacting.
- Newton, Isaac
1642-1727
-
English cleric and
scientist; discovered the classical laws of
motion
and
gravity;
the bit with the apple is probably apocryphal. (10k
jpg)
- Nicholson, Seth
Barnes 1891-1963
-
American astronomer;
discovered
Lysithea,
Ananke,
Carme and
Sinope;
also did important work on
sunspots.
- nuclear fusion
-
a nuclear process
whereby several small nuclei are combined to make a larger one
whose mass is slightly smaller than the sum of the small ones.
The difference in mass is converted to energy by
Einstein's
famous equivalence E=mc2. This is the source of the
Sun's
energy therefore ultimately of (almost) all energy on Earth.
-
- oceanus
-
literally "ocean";
really a large circular plain
- old
-
a planetary surface
that has been modified little since its formation typically
featuring large numbers of impact craters (compare
young).
- Oort, Jan Hendrik
1900-1992
-
Dutch astronomer made
major contributions to knowledge of the structure and rotation
of our galaxy. More or less as a sideline, Oort studied
comets as
well. The result of this work was a theory, now widely accepted,
that the Sun is surrounded by a distant cloud of comet-stuff,
now called the
Oort cloud,
bits of which are occasionally hurled into the solar system as
comets.
- ovoid
-
shaped like an egg
-
- palus
-
literally "swamp";
really a small plain
- parsec
-
= 206265
AU = 3.26
light year
- patera
-
shallow crater;
scalloped, complex edge.
- penumbra
-
literally, "dim light";
the outer filamentary region of a
sunspot.
- perihelion
-
the point in its orbit
where a planet is closest to the Sun. when refering to objects
orbiting the Earth the term perigee is used; the term periapsis
is used for orbits around other bodies. (opposite of
aphelion)
- Perrine, Charles
Dillon 1867-1951
-
Argentine-American
astronomer who discovered
Himalia
and
Elara.
- perturb
-
to cause a planet or
satellite to deviate from a theoretically regular orbital motion
.
- photosphere
-
the visible surface of
the
Sun;
sunspots
and
faculae
are observed in the photosphere.
- plage
-
bright regions seen in
the
solar
chromosphere.
- Pickering,
William Henry 1858-1938
-
American astronomer.
His photographs of Mars, among the earliest obtained, provided a
basis for his opposition to
Lowell's
observations of supposed canals on Mars. Discovered
Phoebe.
- planitia
-
low plain.
- planum
-
plateau or high plain.
- Pope, Alexander
1688-1744
-
English writer best
remembered for his satirical mock-epic poems The Rape of the
Lock and The Dunciad.
- prominence
-
a strand of relatively
cool gas in the
solar
corona
which appears bright when seen at the edge of the Sun against
the blackness of space.
- promontorium
-
cape; headland
- Ptolemy
87-150
-
(aka Claudius
Ptolemaeus) Alexandrian astronomer, mathematician, and
geographer who based his astronomy on the belief that all
heavenly bodies revolve around the Earth. (10k
gif;
more)
-
-
- red giant
-
a star that has low
surface temperature and a diameter that is large relative to the
Sun.
- regio
-
region.
- Relativity,
Theory of
-
more accurately
describes the motions of bodies in strong gravitational fields
or near the
speed of light
than
newtonian
mechanics. All experiments done to date agree with relativity's
predictions to a high degree of accuracy. (Curiously,
Einstein
received the
Nobel prize
in 1921 not specifically for Relativity but rather for his 1905
work on the photoelectric effect and "services to Theoretical
Physics".) (see
Spacetime Wrinkles,
an excellent WWW site from NCSA)
- résolution
-
the amount of small
detail visible in an image; low resolution shows only large
features, high resolution shows many small details
- resonance
-
A state in which one
orbiting object is subject to periodic gravitational
