用語集（Glossary）
-
- accretion
降着（こうちゃく）
- 恒星や惑星あるいは衛星のような天体に、塵や気体が降り積もること。
Accumulation of dust and gas into larger bodies such as stars, planets and moons.
- Adams, John Couch 1819-1892
アダムズ, ジョン・カーチ 1819-1892
- イギリスの天文学者、数学者。当時未知であった天王星の先にある惑星の位置を
初めて予測しました（２４歳）。ルヴェリエも海王星の位置を
独立に計算し、それに基づきガッレが海王星の存在を確認した
ことから、この２人は海王星発見者はだれかをめぐる論争に巻き
込まれることになりました。(写真 4k jpg)
English astronomer and mathematician who, at the age of 24, was
the first person to predict the position of a planetary mass beyond
Uranus. After Galle
confirmed the existance of Neptune
based on independent calculations done by
Le Verrier, the two became embroiled in
a dispute over priority.
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- albedo
アルベド
- 天体に入射する光の量に対し、反射する光がどれくらいかを示す割合。
反射率の度合いであり、天体そのものの明るさです。
（完全に光を反射する白色表面のアルベドは1.0であり、完全に
光を吸収する黒色表面のアルベドは0.0です）
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).
- albedo feature
アルベド地形
- 天体面の明暗模様。この明暗は、地質や地形の違いによるものとは
限りません。
A dark or light marking on the surface of an object
that may not be a geological or topographical feature.
- antipodal point
対蹠（たいせき）点
- 惑星上の、ちょうど反対側の地点。
the point that is directly on the opposite side of the planet
- aphelion
遠日点（えんじつてん）
- 惑星が太陽から最も離れる、軌道上の１点。地球を回る天体について
いう場合には近地点という用語が使われます。その他の天体を回る軌道
についていう場合には、遠アプス点といいます。（近日点の反対）
（訳注：たとえば、木星を回る衛星軌道についていう場合、遠木点ということもあります）
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)
- asteroid number
小惑星番号
- 小惑星が発見されると、（訳注：軌道が正確に求められてから）
登録番号がつけられます。Ｎ番目の小惑星のあとにＮ＋１番目の小惑星
が発見されたという意味です。（付録５を参照）
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)
- astronomical unit (AU)
天文単位（AU）
- 149,597,870 km で、地球から太陽までの平均距離です。
= 149,597,870 km; the average distance from the
Earth to
the Sun.
- atmosphere
気圧（訳注：記号はatm；アトム）
- 大気の圧力という意味以外に、 1.01325 バール ＝ 101325 N/m2
という、海面上の標準的な気圧を１気圧とよんで気圧の単位に使用する
こともあります。
= 1.013 bars = 1.03 kg/cm2 = 14.7 pounds per square inch,
standard atmospheric pressure at sea level on Earth.
- aurora
オーロラ
- 惑星の電離層に発生する発光現象。太陽からやってくる電気を
帯びた粒子と、惑星の磁場とが関係しています。
a glow in a planets ionosphere caused by the interaction between the
planet's magnetic field and charged particles from the Sun
- aurora borealis
北極光
- 太陽からやってくる電気を帯びた粒子（太陽風）、地球の磁場、
そして地球上層の大気が関係しています。同じような現象が南半球でも
起こっており、南極光と呼ばれています。（訳注：極光（オーロラ）の
うち、北極付近現れるものを北極光、南極付近で現れるものを南極光
といいます）
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 austrailis.
-
- bar
バール
- = 1000 hPa （ヘクトパスカル）= 100000 kg・m/m2
= （約）0.9869 気圧
= 0.987 atmosphere = 1.02 kg/cm2 = 100 kilopascal =
14.5 lbs/square inch.
- Barnard, Edward Emerson 1857-1923
バーナード, エドワーズ・エマーソン 1857-1923
- アメリカの天文学者。木星の衛星アマルテア、そして太陽に２番目
に近い恒星である「バーナード星（せい）」の発見者。
American astronomer; discovered Jupiter's
satellite Amalthea
and Barnard's star, the second-nearest star system to the Sun.
- Barsoom
バルスーム
- ターザンで有名なアメリカの作家エドガー・ライス・バロウズのＳＦ作品に登場することばで、
「火星」を意味する「現地語」。
The local name for Mars in Edgar Rice Burroughs's SF books.
- Bode, Johann 1747-1826
ボーデ, ヨハン 1747-1826
- ドイツの天文学者。惑星軌道の大きさに関する見かけの規則性
「ボーデの法則」で知られています。
German astronomer, known for the bogus
"Bode's Law" which attempts to
explain the sizes of the planetary orbits.
- Bond, William Cranch 1789-1859
ボンド, ウィリアム・クランチ 1789-1859
- アメリカ初期の著名な天文学者のひとり。貧しく、きちんとした
教育も受けませんでしたが、こうした境遇を乗り越えて、ハーバード大学
天文台の初代天文台長になりました。そこで、土星の研究をし、ラッセルと
ともに、土星の衛星「ヒペリオン」を発見。
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
ブラーエ, ティコ 1546-1601
- デンマークの天文学者。彼の行った正確な天体観測が、惑星運動に
関するケプラーの法則の基礎となりました。
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Danish astronomer whose accurate astronomical observations formed
the basis for Johannes Kepler's laws of planetary motion.
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-
- caldera
カルデラ
- 火山噴火や火山の陥没でできたクレーター。
crater formed by an explosion or collapse of a volcanic vent.
- carbonate
炭酸塩
- 炭素と酸素を含む化合物で、石灰岩の主成分である炭酸カルシウムなど。
a compound containing carbon and oxygen (i.e. calcium carbonate a.k.a. limestone).
- Cassini, Giovanni Domenico 1625-1712
カッシーニ, ジョヴァーンニ・ドメニコ 1625-1712
- （ジャン・ドミニーク の名でも知られる）イタリア生まれのフランス
の天文学者で、パリ天文台初代台長。
土星の衛星のうち４つ（テティス、
ディオーネ、レア、
イアペトゥス）と、リングのなかの大きなすきま
「カッシーニの間隙（かんげき）」を発見。
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(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.
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- catena
カテナ
- 惑星や衛星地形を示すことばで、クレーターのつながったもの。
クレーター列。
chain of craters.
- cavus
カヴス
- 惑星や衛星の地形を示すことばで、くぼ地、不規則な陥没。
Hollows, irregular depressions.
- chaos
カオス
- 惑星や衛星の地形を示すことばで、たいへん乱れた地域のこと。
distinctive area of broken terrain.
- chasma
カズマ
- 惑星や衛星の地形を示すことばで、峡谷（きょうこく）のこと。
canyon.
- chromosphere
彩層
- 太陽大気の下の方の層で、光球とコロナの間にあります。
the lower level of the solar atmosphere
between the photosphere
and the corona
- colles
コレス
- 惑星や衛星の地形を示すことばで、小さな丘のこと。
small hill or knob.
- coma
コマ
- 彗星の核を包む、塵やガス
the dust and gas surrounding an active comet's nucleus
- Congress
（アメリカの）議会
- アメリカ政府の立法機関。宇宙探査機にとっては、広大な宇宙空間
よりもはるかに手強い相手です。
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
対流
- 温度差が大きいために、液体や気体が循環すること。
fluid circulation driven by large temperature gradients; the
transfer of heat by this automatic circulation.
- Copernicus, Nicolaus 1473-1543
コペルニクス, ニコラウス 1473-1543
- ポーランドの天文学者。地球や他の惑星が太陽のまわりを回るという
太陽中心説（地動説）を唱えました。当時は千年以上にわたり広まっていた
プトレマイオスの考えが宗教や哲学にも深く根づいていたため、
このような考えはたんへんな議論を巻き起こしました。
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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.
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- corona
コロナ
- 金星やミランダなどの惑星や衛星の地形を示すことばで、オボイド型（卵形）の地形。
ovoid-shaped feature.
- corona
コロナ
- 太陽大気の最も外側の部分です。コロナの密度は薄いのですが、
１００万度を越える高温です。
the uppermost level of the solar atmosphere,
characterized by low densities and high temperatures (> 1.0E+06° K).
- coronagraph
コロナグラフ
- 淡い太陽大気を調べるため、円い太陽像をさえぎる特殊な望遠鏡。
a special telescope which blocks light from the
disk of the Sun in order to
study the faint solar atmosphere.
- cosmic ray
宇宙線
- きわめてエネルギーの高い（相対論的な）荷電粒子。
an extremely energetic (relativistic) charged particle.
- crater
クレーター
- 隕石の衝突によってできたくぼみ。または火山噴火口のまわりにできたくぼみ。
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.
- 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.
-
- eccentricity
- 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 erruption
- 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)
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- 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 erruption
- 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.
- 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.
- 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.
- Galilean Moons
- 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 imprisioned
him. The Church clung to this position for 350 years until Galileo was formally
exonerated in 1992.
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(See also the Galileo exhibit at Institute and Museum of History of Science, Florence ITALY)
- 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).
-
- Hale, George Ellery 1868-1938
- American astronomer who founded the Yerkes, Mt. Wilson and Palomar observatories.
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- Hall, Asaph 1829-1907
- American astronomer who discovered the two moons of Mars,
Deimos and Phobos.
- Halley, Edmund 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.
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- 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 broundary 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.
- Hubble, Edwin P. 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
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- 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.
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-
- 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 particales 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.
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- 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.
-
- labes
- landslide.
- labyrinthus
- intersecting valley complex.
- lacus
- lake.
- Lagrange, Joseph Louis 1736-1813
- French 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)
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- 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.
- Le Verrier, Urbain Jean Joseph 1811-1877
- French astronomer 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 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
- 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 markings he saw on the surface were "canals" and therefore
that the planet was inhabited by intelligent beings.
His successors later discovered Pluto.
-
- macula
- dark spot.
- magnetosphere
- 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
- sea. (a very bad misnomer, still in use for historical reasons)
- 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.
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- 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".
- millibar
- 1/1000 of a bar. Standard sea-level pressure is about 1013
millibars.
- minor planets
- another term used for asteroids.
- mons
- mountain.
-
- 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.
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- 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
- ocean.
- 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
- swamp.
- patera
- shallow crater; scalloped, complex edge.
- penumbra
- 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.
- Ptolemy, 2nd century AD
- 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 for Relativity but rather for his 1905
work on the photoelectric effect.)
- resolution
- 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 perturbations by another.
- retrograde
- rotation or orbital motion in a clockwise direction when viewed
from the north pole of the primary
(i.e. in the opposite sense to most satellites);
the opposite of direct.
The north pole is the one on the same side of the ecliptic as the Earth's
north pole.
- rift valley
- an elongated valley formed by the depression of a block of the
planet's crust between two faults or groups of faults of approximately
parallel strike.
- rima
- fissure.
- Roche limit
- the closest a fluid body can orbit to its primary without being
pulled apart by tidal forces. A solid body may
survive within the Roche limit if the tidal forces do not exceed its
structural strength.
- rupes
- scarp.
-
- scarp
- line of cliffs produced by faulting or erosion.
- scopulus
- lobate or irregular scarp.
- semimajor axis
- the semimajor axis of an ellipse (e.g. a planetary orbit) is 1/2 the length
of the major axis which is a segment of a line passing thru the foci of
the ellipse with endpoints on the ellipse itself.
The semimajor axis of a planetary orbit is also the average distance from the
planet to its primary.
The periapsis and
apoapsis distances can be calculated from the semimajor
axis and the eccentricity by rp = a(1-e) and ra = a(1+e).
- Shakespeare, William 1564-1616
- English playwright and poet; wrote some
good
skits.
- shepherd satellite
- (or 'shepherd moon') a satellite which constrains the extent of a planetary ring
through gravitational forces. (See Pandora for a
nice image.)
- sidereal
- of, relating to, or concerned with the stars. Sidereal rotation is that
measured with respect to the stars rather than with respect to the Sun or
the primary of a satellite.
- silicate
- a compound containing silicon and oxygen (e.g. olivine)
- sinus
- bay.
- solar cycle
- the approximately 11-year quasi-periodic variation in frequency or
number of solar active events.
- solar nebula
- the cloud of gas and dust that began to collapse
about 5 billion years ago to form the solar system.
- solar wind
- a tenuous flow of gas and energetic charged particles, mostly
protons and electrons -- plasma -- which stream from the
Sun; typical
solar wind velocities are near 350 kilometers per second.
- speed of light
- = 299,792,458 meters/second (186,000 miles/second).
Einstein's Theory
of Relativity implies that nothing can go faster
than the speed of light; Scotty and Geordi know better.
- spicules
- grass-like patterns of gas seen in the solar atmosphere.
- stellar classification
- Stars given a designation consisting of a letter and a number
according to the nature of their spectral lines which corresponds
roughly to surface temperature. The classes are: O, B, A, F, G, K, and M;
O stars are the hottest; M the coolest. The numbers are simply subdivisions
of the major classes. The classes are oddly sequenced because they
were assigned long ago
before we understood their relationship to temperature.
O and B stars are rare but very bright; M stars are numerous but dim.
The Sun is designated G2.
- sublime (or sublimate)
- to change directly from a solid to a gas without becoming liquid
- sulcus
- subparallel furrows and ridges.
- sunspot
- an area seen as a dark spot on the
photosphere of the Sun;
sunspots are
concentrations of magnetic flux, typically occurring in
bipolar clusters or groups; they appear dark because they are cooler than
the surrounding photosphere.
- superior planets
- the planets Mars, Jupiter,
Saturn, Uranus,
Neptune and Pluto
are called superior planets because their
orbits are farther from the Sun
than Earth's orbit.
- synchronous orbit radius
- the orbital radius at which the satellite's orbital period is equal to the
rotational period of the planet. A synchronous satellite with an
orbital inclination
of zero (same plane as the planet's equator)
stays fixed in the sky from the perspective of an observer on the
planet's surface (such orbits are commonly used for communications
satellites).
- synchronous rotation
- said of a satellite if the period of its rotation about its axis is
the same as the period of its orbit around its primary. This implies
that the satellite always keeps the same hemisphere facing its primary
(e.g. the Moon). It also implies that one
hemisphere (the leading hemisphere) always faces in the direction of the
satellite's motion while the other (trailing) one always faces backward.
-
- tectonic
- deformation forces acting on a planet's crust.
- terminator
- the dividing line between the illuminated and the unilluminated
part of the moon's or a planet's disk.
- terra
- extensive land mass.
- tessera
- tile; polygonal ground.
- tholus
- small domical mountain or hill.
- Thomson, William 1824-1907
- aka Lord Kelvin, British physicist who developed the
Kelvin scale
of temperature supervised the laying of a trans-Atlantic cable.
(10k gif)
- tidal heating
- frictional heating of a satellite's interior due to flexure
caused by the gravitational pull of its parent planet and possibly
neighboring satellites.
- Tombaugh, Clyde 1906-
- American astronomer; discovered Pluto.
(4k gif)
- Trekkie
- a devotee of the science fiction program Star Trek.
- Trojan
- an object orbiting in the Lagrange points of
another (larger) object. This name derives from a generalization of the
names of
two of the largest asteroids in
Jupiter's
Lagrange points: 624 Hektor and 911 Agamemmnon.
Saturn's satellites
Helene,
Calypso and
Telesto are also sometimes called Trojans.
-
- umbra
- the dark central region of a sunspot.
- undae
- dunes.
-
- vallis
- sinuous valley.
- Van Allen, James A.
- American physicist who discovered the Earth's
radiation belts (that now bear
his name) with an instrument aboard the first successful Amerian satellite,
Explorer 1.
- vastitas
- widespread lowlands.
- Verne, Jules 1828-1905
- French writer who is considered the founder of modern science fiction.
His novels include "Journey to the Center of the Earth" and "From the Earth
to the Moon".
- volatile
- As a noun, this refers to substances that are gasses at ordinary temperatures.
In astronomy it includes hydrogen, helium, water, ammonia, carbon dioxide
and methane.
-
- white dwarf
- a whitish star of high surface temperature and low intrinsic
brightness with a mass approximately equal to
that of a Sun but
with a density many times larger.
-
-
- young
- When used to describe a planetary surface "young" means that the visible
features are of relatively recent origin, i.e. that older features have
been destroyed (e.g. by erosion or lava flows). Young surfaces exhibit few
impact craters and are typically varied and complex.
In contrast an "old" surface
is one that has changed relatively little over geologic time. The surfaces of
Earth and Io are young; the
surfaces of Mercury and
Callisto are old.
-
Other Glossaries
- Terms and
People
from LANL (high overlap with the above)
- Solar-Terrestrial Terms
- Planetary Ring Terms
- Comet Definitions
- Commonly Used Acronyms in Astronomy
- Glossary of Spaceflight Terminology from JPL
- Laws, rules, principles, effects, paradoxes, limits, constants, experiments, & thought-experiments in physics
- Biographical Dictionary (brief but numerous entries)
- Biographies of Mathematicians, including some who were also astronomers and/or physicists (includes many portraits).
- Institute and Museum of History of Science, Florence ITALY (Biographies in the Galileo exhibit)
- Astronomiae Historia / History of Astronomy
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ビル・アーネット著；1995年 7月 1日更新
山田陽志郎 訳；1995年**月**日更新