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: 8641410430hours 3hours/timesSunday, 1st-3rd Class

Room: A413http://jinux.hit.edu.cn

E-mail:jinux@hit.edu.cn

Lectrure 1 Sky and Cosmos

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

宇宙的尺度

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

天球

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

地平坐标系

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

赤道坐标系

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Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

低平高度与纬度的关系

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

星座

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

星座

星座

星座

猎户座和

大犬座

大熊座和北斗七星

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

太阳的运动

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太阳的表面特征

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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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月亮的运动

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日食和月食 Eclipsis

Mar 5, 2006 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

Penumbra

Sun Earth

Umbra

月食原理

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

月食原理

Mar 5, 2006 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(Note the ruddy scattered sunlight)

Partial Lunar Eclipse

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

• 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.

日食 Solar Eclipses

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.

Mar 5, 2006 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 ??

Mar 5, 2006 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.

Mar 5, 2006 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

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

日地月关系

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

行星的运动

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

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

行星的运动

• Mercury Venus Mars Jupiter Saturn

• 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)

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

• 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")

内行星 Inferior Planets

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

金星的视运动

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

• 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.

外行星 Superior Planets

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

火星的视运动

Mar 5, 2006 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 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.

Summary

Mar 5, 2006 Lecture 1, Astronomy 4230 J.B.Zhang

• 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.

Summary

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: jinux@hit.edu.cn before mar 12