# 用語集（Glossary）

## A

accretion

Accumulation of dust and gas into larger bodies such as stars, planets and moons.
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. (4k jpg)
albedo
アルベド

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

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

（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

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)

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

= 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

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.

## B

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。 (写真 141k jpg38k jpg詳細)
Danish astronomer whose accurate astronomical observations formed the basis for Johannes Kepler's laws of planetary motion. (141k jpg; 38k jpg; more)

## C

caldera
カルデラ

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
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。 (写真 13k jpg詳細)
(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
カテナ

chain of craters.
cavus
カヴス

Hollow, irregular depressions.
chaos
カオス

distinctive area of broken terrain.
chasma
カズマ

canyon.
chromosphere

the lower level of the solar atmosphere between the photosphere and the corona
colles
コレス

small hills or knobs.
coma
コマ

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

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。 (470k html/gif; 12k gif; 129k jpg; 詳細)
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. (470k html/gif; 12k gif; 129k jpg; more)
corona
コロナ

ovoid-shaped feature.
corona
コロナ

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

a special telescope which blocks light from the disk of the Sun in order to study the faint solar atmosphere.
cosmic ray

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

bowl-shaped depression formed by the impact of a meteorite; depression around the orifice of a volcano.

## D

density

１立方センチ当たり何グラムか、あるいは１立方メートル当たり何キログラムかで計られます。例えば、水の密度は 1.0 g/cm3、鉄の密度は 7.9g/cm3、鉛の密度は 11.3g/cm3。
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
ディスク

the visible surface of the Sun (or any heavenly body) projected against the sky.
doppler effect
ドップラー効果

the apparent change in wavelength of sound or light caused by the motion of the source, observer or both. (see also)
dinosaurs

２億３千年前から６千５百年前の中生代に生きていた大型のは虫類。そのほとんどが巨大な 小惑星 あるいは 彗星の衝突により滅びてしまいました。
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
ドルスム

ridge.

## E

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 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
アインシュタイン, アルバート 1879-1955
ドイツ生まれのアメリカの物理学者。特殊および一般相対性理論を組み立てました。これら相対性理論と量子力学が、現代物理学の基礎になっています。（融合光速も参照のこと） (96k gif)
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)
ellipse

たまごのような形で、惑星の軌道の形がこの「楕円」です。惑星軌道の形が円でなく楕円であることは、ヨハネス・ケプラーによって発見されました。彼は、ティコ・ブラーエによる精密な観測にもとづいたのです。
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
エルグプセック
=10のマイナス10乗キロワット。（訳注：エルグプセックという単位は訳者の知る範囲では聞いたことがありません）
= 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" と書いた場合、これは　"1.23 かける10の４乗"という意味で、12,300 のことです。 "5.67e-8" と書いた場合には、　"5.67 かける10のマイナス8乗"という意味で、0.0000000567 のことです。
"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.

## F

facula

bright spot.
farrum
ファルム

pancake-like structure
filament
フィラメント

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
フィッシャー

a narrow opening or crack of considerable length and depth.
flare
フレア

a sudden eruption of energy on the solar disk lasting minutes to hours, from which radiation and particles are emitted.
flexus
フレクサス

cuspate (pointed) linear feature.
fluctus
フラクトゥス

flow terrain.
fossa
フォッサ

long, narrow, shallow depression.
Franklin, Benjamin 1706-1790
フランクリン、ベンジャミン 1706-1790
アメリカの政治家、作家、科学者。独立戦争の時には主要な役割を演じ、憲法起 草の手助けもしました。彼の多くの科学的・実用的な発明には、避雷針、２焦点めが ね、ストーブなどがあります。
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.

## G

Gaia Hypothesis
ガイア仮説
ギリシャ神話の大地の女神ガイアにちなんで名付けられました。全体としての地 球は生きた有機体とみなすべきであり、生物的なさまざまな作用が環境を安定させる のだと考える説です。1969年、イギリスの生物学者ジェイムズ・ラブロックによって 、最初に提言されました。
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
ガッレ、ヨハン・ゴットフリート 1812-1910
ドイツの天文学者。ルヴェリエの計算に基づいて、 ハインリッヒ・ルードヴィッヒ・ダレと共に、海王星 の観測を初めておこないました。海王星を最初に観測したのはガッレであるにもかか わらず、その発見の栄誉はアダムズ（ルヴェリエよりも前に 計算をおこなった）とルヴェリエに与えられることが多い。
German astronomer who, with Heinrich Louis d'Arrest, made the first observation ofNeptune based on calculations by Le Verrier. Though Galle was the first to observe Neptune, its discovery is usually credited toAdams (who made anearlier calculation) and Le Verrier.
Galilean Moons
ガリレオ衛星

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
ガリレオ・ガリレイ 1564-1642
イタリアの天文学者、物理学者。星の研究をおこなうのに望遠鏡を使用した最初 の人。また、地球以外の天体で最初に衛星を発見した人でもあります（上の項目参照 ）。ガリレオは、コペルニクス太陽中心説の熱心な支持者でした。ガリレオに反発した教会は、その説は地 球が動くと説く異端であると言明し、ガリレオを投獄しました。教会はこの立場に３ ５０年間執着しましたが、１９９２年にガリレオは公式に免罪されました。(16k gif; 136k jpg)（ イタ リア、フローレンスにある科学史協会・博物館のガリレオ展も参照のこと）
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; 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)
George III 1738-1820
ジョージ３世 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

（惑星などに）入射する太陽放射は通過するが、惑星から放出される熱放射（赤 外放射）が大気によって吸収される場合に引き起こされる気温の上昇。（二酸化炭素 がその主な要因）
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).

## H

Hale, George Ellery 1868-1938
ヘール、ジョージ・エラリー 1868-1938
アメリカの天文学者。ヤーキーズ、ウィルソン山、パロマなどの天文台を設立し ました。(72k gif)
American astronomer who founded the Yerkes, Mt. Wilson and Palomar observatories. (72k gif)
Hall, Asaph 1829-1907
ホール、アサフ 1829-1907
アメリカの天文学者。火星の2つの衛星、ダイモスフォボスを発見しました。
American astronomer who discovered the two moons of Mars, Deimos and Phobos.
Halley, Edmund 1656-1742
ハレー、エドモンド 1656-1742
イギリスの天文学者。ニュートンの運動の法則を過去の 彗星のデータに適用し、今日彼の名前がつけられている彗星 の再出現を正確に予言しました。(12k jpg)
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)
heliocentric
ヘリオセントリック

Sun-centered; see Copernicus, Kepler, Galileo.
heliopause
ヘリオポーズ

the point at which the solar wind meets the interstellar medium or solar wind from other stars.
heliosphere
ヘリオスフィアー

the space within the boundary of the heliopause containing the Sun and solar system.
Herschel, Sir William 1738-1822
ハーシェル、サー・ウィリアム 1738-1822
イギリスの天文学者。天王星を発見し、800以上の 二重星と2,500の星雲のカタログをつくりました。(365k html/gif)
British astronomer who discovered Uranus and cataloged more than 800 double stars and 2,500 nebulae. (365k html/gif)
Hubble, Edwin P. 1889-1953
ハッブル、エドウィン 1889-1953
アメリカの天文学者。彼の観測によって、銀河は”島宇宙”であって、私達の 銀河系の内部にある星雲ではないことがわかりました。彼の最も偉大な発見は、銀河 の距離とその遠ざかっていく速さとの間に、比例関係があるのを見いだしたことです （訳注：私達から遠い銀河ほど、速い速さで遠ざかっています）。ハッブル宇宙望遠鏡は、彼を記念して名付けられました。(133k html/gif; 60k gif)
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)
Huygens, Christiaan 1629-1695
ハイゲンス、クリスチャン 1629-1695
オランダの物理学者、天文学者。土星の環の性質 をはじめて記述し（1655年）、衛星チタンを発見しま した。また率先して振り子時計を用いた人でもあります。(7k jpg; 詳細)
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)

## I

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.

## K

Kelvin (°K)
ケルビン(°K)
0°ケルビンは、絶対０度。 氷は273° K (= 0° C = 32° F )で融け、水は373° K (= 100° C = 212° F)で沸騰します。（ウィリ アムトムソン)によって定められました）
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
ケプラー、ヨハネス 1571-1630
ドイツの天文学者、数学者。現代天文学の創建者の一人とみなされ、有名な惑 星の運動に関する ３法則をまとめました。それらの法則は、惑星は太陽の周りを回っ ているというコペルニクスの理論を定量的にまとめた ものです。(16k jpg; 86k jpg; 詳細)
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)
kilogram (kg)
キログラム(kg)
= 1000 グラム = 2.2 ポンド、１リットルの水の質量。 (参照)
= 1000 grams = 2.2 pounds, the mass of a liter of water. (see also)
kilometer (km)
キロメートル(km)
= 1000 メートル = 0.62 マイル
= 1000 meters = 0.62 miles.
Kowal, Charles T. 1940-
コワル、チャールズ 1940-
アメリカの天文学者。木星の衛星レダ彗星状 の天体、小惑星2060番キロン(別名 95 P/キロ ン)を発見しました。
American astronomer; discovered Leda and the comet-like object 2060 Chiron (aka 95 P/Chiron).
Kuiper, Gerard 1905-1973
カイパー、ジェラード 1905-1973
オランダ生まれのアメリカの天文学者。の表面の 研究で最もよく知られています。ミランダネレイドを発見し、チタンに大気を見いだしました。
Dutch-born American astronomer best known for his study of the surface of the Moon; discovered Miranda and Nereid, found an atmosphere on Titan.

## L

labes ラベス

landslide.
labyrinthus
ラビリントゥス

intersecting valley complex.
lacus
ラクス

lake.
Lagrange, Joseph Louis 1736-1813
ラグランジュ、ジョゼフ・ルイ
フランスの数学者、天文学者（もともとはイタリア人で、ジュゼッペ・ルイジ ・ラグランジアという。トリノで生まれ、パリに移り住み、フランス市民となりまし た。）。天体力学の研究に多大な貢献をしました。３つの天体が正三角形の頂点に位 置し、その正三角形の形を保ったまま回転することができるということをラグランジ ュは示しました。もしその３つのうちの１つの質量が、他の２つに比べて十分に大き ければ、その三角形の形状は明らかに安定となります。このような天体はトロヤ群と呼ばれることがあります。（惑星に）先行する三角形の頂 点はリーディング・ラグランジュ・ポイントまたはL4と呼ばれ、追随する頂点はトレ イリング・ラグランジュ・ポイントまたはL５と呼ばれます。 (参照) (5k gif)
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
ラッセル、ウィリアム 1799-1880
イギリスの天文学者。海王星最大の衛星トリトンを発見しました。また（ボンドと ともに）土星の衛星ヒペリオ ンを発見しました。天文学に転向する以前は、はぶりのよい醸造者でした。
British astronomer, discovered Neptune's largest satellite, Triton and (with Bond)discoveredSaturn's moonHyperion.A successful brewer before turning to astronomy.
Le Verrier, Urbain Jean Joseph 1811-1877
ルヴェリエ、ユルバン・ジャン・ジョゼフ 1811-1877
フランスの天文学者。天王星の軌道に摂動を引き 起こしていた未知の惑星（海王星）。 （ガッレによって）確認されたその位置を最初に計算したのがルヴェリエでした。 。アダムズもその数カ月前に同じような予言をおこなってい ましたが。
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
ライダー

an instrument similar to radar that operates at visible wavelengths.
limb
リム

the outer edge of the apparent disk of a celestial body
light-year

= 9.46053e12 km (= 5,880,000,000,000 マイル = 63,239 天文単位）。光が一 年間に進む距離。
= 9.46053e12 km (= 5,880,000,000,000 miles = 63,239 AU); the distance traveled by light in a year.
linea
リネア

elongate marking.
liter
リットル
= 1000 cm3 = 1.06 クォート（米）
= 1000 cm3 = 1.06 US quarts
Lowell, Percival 1855-1916.
ローウェル、パーシヴァル 1855-1916
アメリカの天文学者。1894年、アリゾナにローウェル天文台を建設しました。 そこでの火星 の研究から、火星表面の直線模様（スキヤパレーリが最初に注目しました) は「運河」であり、し たがって火星には知的生命体が存在していると信じるようになりました。後に彼の後 継者達が、冥王星を発見しました。
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.

## M

macula
マキュラ

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

literally "sea" (a very bad misnomer, still in use for historical reasons); really a large circular plain
Marius, Simon 1573-1624
マリウス、シモン 1573-1624
(別名メイヤー)ドイツの天文学者。木星ガリレオ衛星に名前を付けました。マリウスとガリレオは、とも に1610年にそれらの衛星を発見したと主張しました。おそらく別々に発見したのでし ょう。二人は優先権をめぐって、論争に巻き込まれるようになりました。マリウスは 望遠鏡でアンドロメダ星雲を観測した最初の人でもあり、またはじめて太陽黒点を観測した人でもありました。(詳細)
(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
メンサ

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
ミリバール
1バールの千分の1。海面上の標準気圧は1013ミリバール。
1/1000 of a bar. Standard sea-level pressure is about 1013 millibars.
minor planets
マイナー・プラネット

the official term used for asteroids.
mons
モンス

mountain (plural: montes)

## N

Neujmin, Grigoriy N.
ネウイミン、グリゴリー
ウクライナの天文学者。小惑星951番ガスプラを発 見しました。
Ukrainian astronomer; discovered the asteroid 951 Gaspra.
neutrino
ニュートリノ

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
ニュートン、アイザック 1642-1727
イギリスの牧師、科学者。古典的な 運動の法則と、 万有引力を発見しました。リンゴが落ちるのを見て引力を発見したという話は、たぶ ん作り話でしょう。(10k jpg)
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
ニコルソン、セス・バーンズ 1891-1963
アメリカの天文学者。木星の衛星のリシテ ア, アナンケ,カルメシノーペを発見しました 。また太陽黒点についても重要な研究をおこない ました。
American astronomer; discoveredLysithea, 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.

## O

oceanus

literally "ocean"; really a large circular plain
old
オールド
その形成以来、ほとんど変化を受けてこなかった惑星表面。典型的な特徴は、 無数の衝突クレーターが見られることです ( ヤングと比較せ よ)。
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
オールト、ヤン・ヘンドリック 1900-1992
オランダの天文学者。私達の銀河系の構造や回転に関する研究に、主な貢献を しました。専門以外では、彗星についても多少の研究をしま した。この研究の結果は、今や広く認められている次のような理論を生み出しました 。太陽はオールトの雲と呼ばれる、はるか遠くにある彗星 の材料となる雲にとりまかれており、それらの一部が時に彗星として太陽系内に投げ 込まれてくるのです。
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
オボイド

shaped like an egg

## P

palus
パルス
本来は「湿地」の意味ですが，実際には小さな平地。 （監修者中：月の暗い地域を示す語として使われており、「沼」と訳されています）
literally "swamp"; really a small plain
patera
パテラ (小皿)

shallow crater; scalloped, complex edge.
penumbra
ペナンブラ(半暗部) 太陽黒点の外周部のフィラメント状の領 域。
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
チャールズ・ディロン, パライン 1867-1951
アルゼンチンとアメリカで活躍した天文学者。ヒマリアエラーラを発見。
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
プラージュ( 羊斑: ようはん )。

bright regions seen in the solar chromosphere.
Pickering, William Henry 1858-1938
ウィリアム・ヘンリー, ピッカリング 1858-1938
アメリカの天文学者。彼の初期の火星の写真が, 火星に運河があると考えたローウ ェルの観察に反論する根拠となりました。フェーベの発見者でもあります。
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
プラニティア

low plain
planum
プラヌム

plateau or high plain
Pope, Alexander1688-1744
アレグザンダー, ポープ 1688-1744
イギリスの作家。風刺的な嘲笑叙事詩「錠前の略奪」と「ダンシアド」でよく知ら れれいます。
English writer best remembered for his satirical mock-epic poems The Rape of the Lock and The Dunciad.
prominence
プロミネンス (　紅炎 )

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
プロモントリウム (岬)

プトレマイオス（英語名　トレミー）, ２世紀
アレクサンドリアの天文学者, 数学者で地理学者。彼の天文学は, 全ての天体は地球 の廻りを回るという信念にもとずいていた。(10k gif; more)
Alexandrian astronomer, mathematician, and geographer who based his astronomy on the belief that all heavenly bodies revolve around the Earth. (10k gif; more)

## R

red giant

a star that has low surface temperature and a diameter that is large relative to the Sun.
regio
レジオ
領域（監修者注：惑星地名に使われています）
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

リゾナンス( 共鳴 )

A state in which one orbiting object is subject to periodic gravitational perturbations by another.
reticulum
レティキュラム( 網状組織 )

reticular(net-like) pattern

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
リフトバレー( 地溝 )
ほとんど平行にぶつかりあった断層（あるいは断層群）の間で, 地殻ブロックの沈下によってできた長い谷。
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
リマ

fissure.
Roche limit
ロッシュ限界

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. The Roche limit is calculated with the equation

RL = 2.456*R*(p'/p)^(1/3)

where p' is the density of the planet, p is the density of the moon, and R is the radius of the planet. (more)

## S

scarp
スカープ

line of cliff produced by faulting or erosion.
Schaparelli, Giobanni Virginio 1835-1910
ジョバーンニ・ヴィルジーニョ, スキヤパレーリ　1835-1910
イタリアの天文学者で, １８７７年に初めて火星の "運河" を観察しました。彼が観察し た模様には, 直線部分と解釈したものがあり, これらの線を "道筋" を意味する "canali( カナーリ )" と名付けました。しかしこのイタリア語は誤って英語の " channels( 運河 )" と訳され，不可解な直線性と結びついて人工的な構造 を示すものとされて話題が加熱しました。火星における知的生命体の可能性に関す る推論が大衆紙に出，天文学者でさえもそのドラマチックな可能性に魅力を感じて いまし た。それら天文学者の中の一番手がパーシヴァル・ローウェルで，彼は スキヤパレーリをはるかに越える熱心さで火星の観測を行いました。
Italian astronomer who in 1877 first observed the "canals" on Mars. He believed that the features he observed included straight lines that joined in a complicated pattern. He called these lines 'canali', which means 'channels'. However, the Italian word was mistranslated into the English word 'canals'. That, combined with the suspicious straightness of the lines, bespoke of artificial structures, and this created a furor. Speculations concerning the possibility of intelligent life on Mars sprang up in the popular press. Even astronomers felt the pull of that dramatic possibility. Foremost among these was Percival Lowell, who carried matters far beyond Schiaparelli.
scopulus
スコプルス

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
ウィリアム，シェイクスピア
イギリスの劇作家で詩人。いくつかの優れた小喜劇を書きました。
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
ケイ酸塩
ケイ素と酸素を含んだ化合物( 例えば橄攬石: かんらん石: オリビン )。
a compound containing silicon and oxygen ( e. g. olivine)
sinus
シヌス

literally "bay"; really a small plain
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
スピキュール

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.
sublim (or sublimate)

to change directly from a solid to a gas without becoming liquid.
sulcus
スルクス
ほぼ平行な溝と尾根。（監修者注：惑星地形に使用）
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.

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. Most of the satellites in the solar system rotate synchronously.

## T

tectonic
テクトニック。

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
テッサラ。
タイルの意味。多角形のパターンでできた地形。
tile; terrain formed of polygonal pattern.
tholus
トルス。

small domical mountain or hill.
Thomson, William 1824-1907
ウィリアム，トムソン。1824-1907
ケルヴィン卿としても知られています。温度のケルヴィン目盛りの考案者であるイギリス の物理学者で, 大西洋横断ケーブルの敷設を監督しました。(10k gif)
aka Lord Kelvin, British physicist who developed the Kelvin scale of temperature. Also 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, Clide 1906-
クライド, トンボー。 1906-
アメリカの天文学者。冥王星を発見しました。(4k gif)
American astronomer; discovered Pluto. (4k gif)
Trekkie
トレッキー。
ＳＦ番組スタートレックの愛好者。
a devotee of the science fiction program Star Trek.
Trojan
トロヤ群

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.

## U

umbra

the dark central region of a sunspot.
undae
ウンダエ。

dunes (literally 'waves').

## V

vallis
ヴァリス。

sinuous valley (plural: valles)
Van Allen, James A.
ジェームズ, Ａ, ヴァンアレン。
アメリカの物理学者で, アメリカで最初に成功した人工衛星エクスプローラ1号に 載せた装置で地球の放射能帯( 現在では彼の名をつけている)を発見。
American physicist who discovered the Earth's radiation belts (that now bear his name) with an instrument aboard the first successful American satellite, Explorer 1.
vastitas
ヴァスティタス。

Verne, Jules 1823-1905
ジュール, ヴェルヌ。1823-1905
フランスの作家。現代のＳＦの創始者とみなされています。彼の小説に「地球の中心 への旅」と「地球から月へ」がある。
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 gases at ordinary temperatures. In astronomy it includes hydrogen, helium, water, ammonia, carbon dioxide and methane.

## W

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.

## Y

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.

## Z

zodical light

a faint glow from light scattered off of interplanetary dust along the plane of the ecliptic.

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ビル・アーネット著；1996年 4月 5日更新