天文学是
1. Cosmos 宇宙
Cosmology 宇宙学
Cosmologist 宇宙学家
例句：Philosopher and physicist Stephen Hawking is probably the world's most famous cosmologist.哲学家和物理学家史蒂芬霍金也许是全球著名的宇宙学家之一。
2. Asteroid n.小行星 adj.星状的
Asteroid belt 小行星带
例句：Many asteroids have been placed in groups and families based on their orbital characteristics. 人们根据轨道特征对许多小行星进行分类。
3. Axis n.轴;轴心国(纳粹德国、
英文释义：an imaginary line that passes through Earth’s center and its North and South Poles;the center around which something rotates
例句：The Earth rotates on an axis between the north and south poles.地球绕着南北两极之间的地轴自转。
4. Big Bang n.宇宙大爆炸(一种关于宇宙起源的学说)
英文释义：theory that an explosion created the universe many billions of years ago
根据霍金的时间简史，大爆炸是宇宙开端的奇点;大挤压则是宇宙终结的奇点。
这个词还可以指1986年10月27日伦敦证交所的“创世大爆炸”改革
5. Black hole n. 黑洞(宇宙中包括光线在内的一切事物都会被吸入的区域)
英文释义：an area in outer space into which everything near it, including light, is pulled.
时空的一个区域，因为那里的引力是如此之强，以至于任何东西，甚至光都不能从该处逃逸出来。
6. Comet n.彗星
英文释义：an object in outer space that develops along, bright tail when it passes near the sun
来自于拉丁语cometa，长发。因形状如拖着的长头发而得名。
Halley’s comet 哈雷彗星
7. Constellation n. 星座
英文释义：a group of stars that forms a particular pattern and has a name.
A star in the constellation of Orion猎户座的一颗恒星
Zodiac 黄道带，指太阳、月亮及行星所行经区域构成的假想带
上个世纪70年代旧金山出现的自称“十二宫”的连环杀手。
Chinese Zodiac生肖
8. Dark matter n. 暗物质
英文释义：a type of matter that scientists think may exist that does not give off electromagnetic radiation but is quite abundant in the universe
“存在于星系、星团中以及也许在星系团之间的，不能被直接观测到的但是能用它的引力效应检测到的物质。宇宙物质的90%可能采取暗物质的状态”——《时间简史》
9. Ellipse n.椭圆
英文释义：an elongated circle, or oval shape;shape of planetary orbits
例句：If this is an ellipse around the Earth,then this would be perigee and this would be apogee.
如果这是一个围绕地球的椭圆形轨道，那么这是近地点，这是远地点。
Elliptical machine椭圆机
10. Equinox n.春分，秋分，昼夜平分点
英文释义：one of the two times in a year when night and day are of equal length
例句：Why was the rising Sun due east one day after the equinox?
为什么是春分后一天太阳正好从东方升起?
The spring equinox春分
11. Galaxy n.银河;星系
英文释义：a collection of stars, star systems,dust, and gas bound together by gravity
the Milky Way 银河
源自于希腊语galaxias，词根gala意为“乳汁”，古希腊人认为银河是天后赫拉的乳汁流淌而成的。
例句：There are three main types of galaxy: spiral,elliptical, and irregular
星系主要有三种类型：螺旋形、椭圆形、和形状不规则的星系。
12. Light year n. 光年(约为94605亿千米)
英文释义：the distance that light travels in one year; about 9.46 trillion kilometers
13. Meteor 流星
英文释义：any of the small solid galactic bodies that enter the earth's atmosphere
Astronomers track large meteors using radar天文学家使用雷达跟踪大型流星
Luminous meteors极光
14. Nebula n.星云
英文释义：clouds of gas or dust in the universe that are made visible by the light of neighboring stars
例句：Light takes as long as 1500 years to reach Earth from the distant Horsehead Nebula 光需要1500年从马头星云传播到地球
15. Gravity n.重力;
英文释义：the force of attraction between all masses in the universe
例句：Because of the moon's smaller mass, its gravity is only one sixth of that on Earth.由于月球的质量较小，其重力仅为地球的六分之一
Gravity另有“庄重”、“严肃”的意思
16. Orbit n./v.轨道;绕…作轨道运行
英文释义：the path of an object as it revolves around another object in space
例句：The satellite orbits the Earth every 48 hours. 这颗人造卫星每48小时绕地球运行一周
17. Rotation n.自转;旋转
英文释义：the spinning motion of a planet on its axis
例句：The Earth's rotation takes 24 hours. 地球自转需要24小时
18. solar eclipse 日蚀
英文释义：when the Moon passes between the Sun and the Earth
lunareclipse 月蚀
英文释义：when the Earth passes between the Sun and the Moon and casts a shadow on the Moon
19. Solstice n.至;至点
来自于古拉丁语“point at which the sun seems to stand still”字面意思即太阳停止的地方。
英文释义：the time that Earth’s poles point at their greatest angle toward or away from the Sun
Summer solstice 夏至
Winter solstice冬至
20. Tide n.海潮;潮汐
英文释义：the periodic rise and fall of the sea level under the gravitational pull of the Moon
Time and tide wait for no man.“岁月不待人”
Turn the tide 扭转局势;力挽狂澜