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Astronomy 4230
天文学概论
A Brief Course of Astronomy
张景波
哈尔滨工业大学物理系
哈尔滨市天文爱好者协会
Location: L331
Tel: 86414104
30hours 3hours/times
Sunday, 1st-3rd Class
Room: A413
http://jinux.hit.edu.cn
E-mail:[email protected]
Lectrure 1 Sky and Cosmos
宇宙的尺度
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Lecture 1, Astronomy 4230
J.B.Zhang
天球
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Lecture 1, Astronomy 4230
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地平坐标系
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赤道坐标系
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低平高度与纬度的关系
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Lecture 1, Astronomy 4230
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星座
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Lecture 1, Astronomy 4230
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星座
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星座
星座
猎户座
和
大犬座
大熊座和北斗七星
太阳的运动
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Lecture 1, Astronomy 4230
J.B.Zhang
太阳的表面特征
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Lecture 1, Astronomy 4230
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黄道十二宫
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太阳与四季
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太阳日和恒星日
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Lecture 1, Astronomy 4230
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月亮的运动
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Lecture 1, Astronomy 4230
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日食和月食
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Eclipsis
Lecture 1, Astronomy 4230
J.B.Zhang
月食 Lunar Eclipses
• Umbra: Inner core of total darkness
– The disc of the Sun is completely blocked.
• Penumbra: Outer, partial shadow
– Sun's disc is only partly blocked, with a bit peeking over
the edge.
• Lunar Eclipses are when the Moon passes through the
shadow of the Earth.
• They only occur during Full Moon when the Earth is
between the Moon and the Sun.
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
月食原理
Umbra
Penumbra
Sun
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Earth
Lecture 1, Astronomy 4230
J.B.Zhang
月食原理
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Lecture 1, Astronomy 4230
J.B.Zhang
Lunar Eclipses
• Total Length of Earth’s Umbra
– ~1.4 Million km long
– About 3.7x the mean Earth-Moon distance.
• Umbra's width at the distance of the Moon
– 9000 km
– ~2.6x the Moon's diameter.
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
Three Types of Lunar Eclipses
• Total Lunar Eclipse:
– Entire Moon is within the Earth's umbra.
– Can spend up to 1h 40m in the umbra
– Whole show can last ~6 hours
• Partial Lunar Eclipse:
– Only part of the Moon enters the umbra.
• Penumbral Eclipse:
– Moon misses the umbra completely, only passes through
the penumbral shadow.
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
Three Types of Lunar Eclipses
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
Total Lunar Eclipse
Partial Lunar Eclipse
(Note the ruddy scattered sunlight)
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Lecture 1, Astronomy 4230
J.B.Zhang
日食 Solar Eclipses
• Solar Eclipses occur when the Earth passes through
the shadow of the Moon.
• They only occur during New Moon when the Moon is
between the Earth and the Sun.
• Totality ‘incredibly’ spectacular
• The Moon's umbra is only 380,000 km long:
– Just long enough for the tip to touch the Earth.
– But not large enough to cover the entire Earth.
– Solar Eclipses seen only where the shadow passes overhead.
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
日食原理
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
Types of Solar Eclipses
• Total Solar Eclipse:
– The observer is inside the Moon's umbra.
– The Moon completely covers the Sun.
• Partial Solar Eclipse:
– The observer is inside the Moon's penumbra.
– Only see part of the Sun covered by the Moon.
• Annular Eclipse:
– The Moon is at or near apogee, and so is too small to
cover the Sun
– The Moon's umbra does not touch the Earth, so
observers in the shadow path see the Sun as a ring
("annulus").
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
Total Solar Eclipses
• Total Solar Eclipses are localized and short:
– The Moon's umbral shadow is at most 267 km
across on the Earth.
– Totality lasts at most about 7.5 minutes.
– Only observers in the umbra see a total solar
eclipse.
– Observers in the penumbra see a partial solar
eclipse.
– Everyone else sees nothing.
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Lecture 1, Astronomy 4230
J.B.Zhang
Rare Events – Why ?
• Eclipses are rare :
– From a given location on the Earth you see
• a Total Lunar Eclipse every 3 years (or so).
• a Total Solar Eclipse every 360 years.
• Why not :
– Each full moon = lunar eclipse
– Each New Moon = solar eclipse ??
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Lecture 1, Astronomy 4230
J.B.Zhang
Why Eclipses are rare
• Moon’s orbit not perfectly aligned with
Ecliptic :
– ~5° tilt from Ecliptic
– Where the moon's orbit crosses the Ecliptic defines
the "Line of Nodes"
– Only get eclipses when the line of nodes and the
Sun line up at Full or New Moon.
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Lecture 1, Astronomy 4230
J.B.Zhang
The Eclipse Year
• Line of Nodes aligns with Sun every 346.6
days. ("Eclipse Year“)
• But, it must be a Full or New Moon when the
nodes line up to have an eclipse.
• This happens only very rarely.
• Check out Fred Espenak’s Eclipse page
• http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html
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Lecture 1, Astronomy 4230
J.B.Zhang
日地月关系
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Lecture 1, Astronomy 4230
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行星的运动
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Lecture 1, Astronomy 4230
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水星 Mercury
金星 Venus
地球 Earth
火星 Mars
木星 Jupiter
土星 Saturn
天王星 Uranus
海王星 Neptune
冥王星
Pluto
行星的运动
• Mercury
Venus
Mars
Jupiter
Saturn
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Lecture 1, Astronomy 4230
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• Star-like
Appearance
• close to
Ecliptic
• Two
separate
cases :
– always
close to
Sun (Venus,
Mercury)
– appearance
at any point
of time
during
night/day
(Mars,
Jupiter,
Saturn)
内行星 Inferior Planets
• Mercury, Venus, ‘inferior’ planets
• Inferior Conjunction:
– Planet is between the Earth and the Sun.
• Superior Conjunction:
– Planet on the other side of the Sun from
Earth.
• During both conjunctions, the inferior planet
appears to rise and set with the Sun.
• Maximum Eastern Elongation:
– Planet is furthest East of the Sun as seen
from the Earth (28º Mercury, 47º Venus)
– Rises & sets after the Sun ("evening star")
• Maximum Western Elongation:
– Planet is furthest West of the Sun as seen from the Earth.
– Rises & sets before the Sun ("morning star")
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Lecture 1, Astronomy 4230
J.B.Zhang
金星的视运动
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Lecture 1, Astronomy 4230
J.B.Zhang
外行星 Superior Planets
• Opposition:
– Planet is opposite the Sun in the sky.
– Rises as the Sun sets
– Highest in the sky at midnight.
• Conjunction:
– Planet is on the same side of the sky as the
Sun.
– Rises with the Sun
• Eastern Quadrature:
– Planet at right angles to the Earth-Sun line.
– Planet rises at noon, sets at midnight.
• Western Quadrature:
– Planet at right angles to the Earth-Sun line.
– Planet rises at midnight, sets at noon.
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
火星的视运动
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Lecture 1, Astronomy 4230
J.B.Zhang
行星的视运动
• In general, the planets move eastward relative to the "fixed"
stars.
– Called "Direct Motion".
– Motion is non-uniform (not at the same speed).
• Sometimes, however, the planets appear to
–
–
–
–
Slow down & stop!
Start moving westward, or RETROGRADE,
Slow down & stop again,
Resume moving eastward again.
• Apparent retrograde motion is observed in all planets.
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
Summary
• Summary of Celestial Motions
– Fixed Stars:
• Uniform daily motion about the celestial poles.
– The Sun:
• Daily motion around the celestial poles (rising and setting).
• Eastward drift along the Ecliptic over a year, a little faster in winter,
slower in summer.
– The Moon:
• Daily motion around the celestial poles.
• Eastward motion near the Ecliptic over a month.
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
Summary
• Summary of Celestial Motions
– The Planets:
• Daily motions about the celestial poles.
• Generally eastward motion near the Ecliptic at different
speeds for each planet.
• Occasional westward "retrograde" motions.
• Superior Planets are brighter at opposition, fainter at
conjunction.
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang
Homework
1.有一颗恒星1月1日在晚上10:00时升起，那
么它于下列日期将在什么时候升起？
(1) 1月4日
(2) 1月30日
(3) 7月1日
E-mail: [email protected]
before mar 12
Mar 5, 2006
Lecture 1, Astronomy 4230
J.B.Zhang