venus…earth’s twin. reminder: where is venus in the solar system right now did anybody see it in...
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Venus…Earth’s twin
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Reminder: where is Venus in the solar system right now
Did anybody see it in the night sky the last two night?
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Venus in ultraviolet light
What is under The clouds?
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The planet Venus: the Earth’s twin (in a limited sense)
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A comparison of Earth and Venus
• Semimajor axis of orbit: 0.7233 (V) 1.000 (E)
• Orbital eccentricity: 0.007 (V), 0.017 (E) • Diameter: 12104 km (V) 12756 (E) !• Mass: 0.815 Earth masses (V) 1.00
Earth masses (E) !!• As spheres, Venus and Earth are very
similardemo
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Seeing through the clouds of Venus with Radio Astronomy!
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The Goldstone (California) tracking station and planetary radar
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So what does radio astronomy or radar astronomy do for you?
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First result: light is a wave (electromagnetic wave)
Wave characterized by wavelength, amplitudeDEMO
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Amazing fact of nature: wide range of wavelengths of electromagnetic waves
EM radiation includes gamma rays, x-rays, ultraviolet, Light, infrared, microwave, radio
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Concept from physics crucial for astronomy: the spectrum of light
DEMO
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The Physics of Spectrum Formation, Kirchoff’s Laws
and Wien’s Law• Hot opaque solid or liquid produces a
continuous spectrum• Hot, tenuous gas observed against dark
background produces emission line spectrum• Cold, tenuous gas observed against bright
background produces absorption spectrum• See Figure 16.6
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Kirchoff’s Laws of Radiation
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Kirchoff’s First Law + Wien’s Law
• Hot, opaque objects produce continuous spectrum
• The hotter the object, the bluer it is
• Wien’s Law wmax = 2.9E-03/T
• The hotter an object, the brighter it is
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Radio astronomy and application of Kirchoff’s Laws and Wien’s Law allow us to measure the surface temperature of Venus
(done first in the late 1950s)
• Surface temperature is 730K
• That corresponds to 855 degrees Fahrenheit
• What is responsible for this sort of temperature?
• The answer also lies in Kirchoff’s Laws