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天文学

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金星の地形学多様な地名と地質学的特徴の体系的まとめ

金星地形惑星地質学ヴァリス
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The heart-shaped Tombaugh Regio, on Pluto, is named after the dwarf planet's discoverer Clyde Tombaugh.

惑星命名法太陽系天体の地名決定ルールと国際基準

惑星命名法IAU国際天文学連合天体地名
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Orbits and trajectories of Mariner 2, Venera 4, Pioneer Venus Orbiter, and Venus Express

Venus Express欧州初の金星探査機が明かした大気の謎

Venus Express欧州宇宙機関ESA金星探査
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Precessional movement of Earth. Earth rotates (white arrows) about once a day around its rotational axis (red); this axis itself rotates slowly (white circle), completing a rotation in approximately 26,000 years[1]

地軸の歳差運動地球の回転軸が描く26,000年の巨大なサイクル

歳差運動地軸春分点天文学
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Sagan (age 16) in the 1951 Rahway High School yearbook

カール・セーガン宇宙の神秘を世界に届けた科学の伝道師

カール・セーガンコスモス天文学SETI
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The positive pole of a planet is defined by the right-hand rule: if the fingers of the right hand are curled in the direction of the rotation then the thumb points to the positive pole. The axial tilt is defined as the angle between the direction of the positive pole and the normal to the orbital plane. The angles for Earth, Uranus, and Venus are approximately 23°, 97°, and 177° respectively.

自転軸の傾き（黄道傾斜角）が惑星の気候と季節に与える影響

自転軸の傾き黄道傾斜角季節のメカニズム地球の公転
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Lakshmi Planum (left) and Maxwell Montes (right) in a Magellan radar map. The highlands are covered in bright "snow," rising 5 km (3.1 mi) above the dark lava flows of the neighboring plain.[1]

金星の「雪」の正体高地を白く染める金属化合物の謎

金星金星の雪硫化鉛硫化ビスマス
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A comet was mentioned in the Anglo-Saxon Chronicle and by the Venerable Bede in the year 729 CE.[13][14]

彗星の正体と宇宙の旅氷と塵の天体が描き出す神秘

彗星ハレー彗星オールトの雲エドモンド・ハレー
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Transits of Venus across the face of the Sun were, for a long time, the best method of measuring the astronomical unit, despite the difficulties (here, the so-called "black drop effect") and the rarity of observations.

天文単位（au）とは？太陽系を測る基準となる距離の定義と歴史

天文単位au地球・太陽間距離天文学
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Retrograde orbit: the satellite (red) orbits in the direction opposite to the rotation of its primary (blue/black)

逆行運動のメカニズム天文学における回転と公転の方向性

逆行順行天文学公転方向
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A sidereal day is one Earth rotation relative to the stars; a solar day is one Earth rotation relative to the Sun. The Earth rotates about 366 times per 'normal' 365-day year relative to the stars, so Earth's sidereal day is about four minutes shorter than Earth's solar day. (Angle exaggerated for visibility.)

恒星時とは？太陽時との違いと天文学における重要性を解説

恒星時太陽時恒星日太陽日
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At left, tidally locked, the Moon rotates at the same rate it orbits the Earth, keeping the same face toward the planet. At right, not tidally locked, if the Moon did not rotate then the face would change over the course of an orbit. Viewed from north; not to scale.

潮汐ロックの仕組みと宇宙における影響

潮汐ロック同期回転天文学月
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