通识课 天文学概论
第一章 宇宙概观
1.1 太阳系 1.2 恒星世界 1.3 银河系及河外星系
1.1
1.1.1 太阳 1.1.2 太阳系行星 1.1.3 地球 1.1.4 日月食 1.1.5 太阳系的物质分布
1.1.1 太阳
太阳大气（the Solar Atmosphere）
日冕
只有在日食 期间可观测 到
Magnetic South Poles
In sun spots, magnetic field lines emerge out of the photosphere.
磁力线（Magnetic Field Lines）
Magnetic South Pole
Sun Spots are related to magnetic activity on the photosphere
太阳黑子 (3)
Magnetic field in sunቤተ መጻሕፍቲ ባይዱspots is about 1000 times stronger than average.
Magnetic North Poles
Only appear dark against the bright sun. Would still be brighter than the full moon when placed on the night sky!
太阳黑子（2）
Active Regions
Visible
Ultraviolet
Visible in Ha emission.
Each one lasting about 5 – 15 min.
太阳大气层
Visible Photosphere
Sun Spot Regions
Corona
Ultraviolet Chromosphere
Coronal activity, seen in visible
太阳表面
Solar Activity, seen in soft X-rays
黑子中的磁场
（Magnetic Fields in Sun Spots）
Magnetic fields on the photosphere can be measured through the Zeeman effect
Computer model of the magnetic carpet
太阳风（the Solar Atmosphere）
Constant flow of particles from the sun.
Velocity ≈ 300 – 800 km/s
Sun is constantly losing mass: 107 tons/year
• Visible, UV, and X-ray lines from highly ionized gases
• Temperature increases gradually from ≈ 4500 oK to ≈ 10,000 oK, then jumps to ≈ 1 million oK
Filaments
light
日冕磁场
• Corona contains very low-density, very hot (1 million oK) gas
• Coronal gas is heated through motions of magnetic fields anchored in the photosphere below (“magnetic carpet”)
日冕
光球的能力传输
Energy generated in the sun’s center must be transported outward.
In the photosphere, this happens through
对流
Cool gas （Convection）
sinking down
= analysis of vibration patterns visible on the solar surface:
Approx. 10 million wave patterns!
太阳黑子（Sun Spots）
Cooler regions of the photosphere (T ≈ 4240 K).
Transition region
Chromospheric structures visible in Ha emission (filtergram)
针状体
Spicules: Filaments of cooler gas from the photosphere, rising up into the chromosphere.
Bubbles of hot
gas rising up
≈ 1000 km
Bubbles last for ≈ 10 – 20 min.
米粒组织（Granulation）
… is the visible consequence of convection
色球（Chromosphere）
• Region of sun’s atmosphere just above the photosphere.
(≈ 10-14 of its mass per year)
日震（Helioseismology）
The solar interior is opaque (i.e. it absorbs light) out to the photosphere.
Only way to investigate solar interior is through Helioseismology
色球
人眼看到的太阳
光球
Heat Flow
太阳内部
光球（photosphere）
• Apparent surface layer of the sun • Depth ≈ 500 km • Temperature ≈ 5800 oK • Highly opaque (H- ions)
• Absorbs and re-emits radiation produced in the solar interior