lecture 14: searching for planets orbiting other stars iii: using spectra 1.the spectra of stars and...
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![Page 1: Lecture 14: Searching for planets orbiting other stars III: Using Spectra 1.The Spectra of Stars and Planets 2.The Doppler Effect and its uses 3.Using](https://reader030.vdocuments.us/reader030/viewer/2022020106/56649d4d5503460f94a2b3d1/html5/thumbnails/1.jpg)
Lecture 14: Searching for planets orbiting other stars III: Using Spectra
1. The Spectra of Stars and Planets 2. The Doppler Effect and its uses3. Using spectroscopy to measure orbits and masses
of exoplanets
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NASA Messenger space probe enters into orbit around Mercury
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NASA Messenger around Mercury: First Image
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Using Spectra for Remote Sensing
• Measuring spectral lines in the spectrum
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Using Spectra for Remote Sensing
• Forming spectral lines in the spectrum
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Venus in Front of the Sun
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
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The Sun in One Spectral Line
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Using Spectra for Remote Sensing
• Forming spectral lines in the spectrum
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Direct Detection of Planets• The best case to-date of a planet-like system detected ininfrared light:
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Indirect methods of planet detection
• Newton’s law of universal gravitation
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The Astrometric method
• Binary stars - Sirius A & B.
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The Astrometric method
• Not successful in planet discovery yet.
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The Doppler shift method
• Doppler shift is measured from the spectral lines of two stars in abinary system:
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Using Spectra for Remote Sensing
• Measuring spectral lines in the spectrum
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The Doppler shift
• What is a Doppler shift ? - true for all waves.
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The Doppler shift
• Doppler shift is measured from the spectral lines:
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Mass:
Radial velocities seenin star HD 209458 -the variation is dueto a planet that is lessmassive than Jupiter.
(Mazeh et al. 1999;Marcy et al. 2000)
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Mass:
• For HD 209458b:
Mp sin(i) = Ms vs P / 2 ap
= const. x (Ms /1.1MSun) Mjup
+ 0.018 + 0.1• Transit light curve helps derive the orbit
inclination: i = 86o.7 + 0.2
• Both Mp and Rp determined to better than 5%!
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Mass:
Radial velocities seenin star HD 168443 -they are due to 2 planets,each larger than ourJupiter.
(Marcy & Butler 2002;Mayor et al. 2002)
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The Spectra of Planets
• Mars
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Main points to take home:
1) Visible light: form of electromagnetic energy (radiation) to which our eyes are sensitive.
2) Spectrum: the amount of light of any given wavelength, emitted or reflected by an object.
3) Thermal spectrum: a simple spectrum that depends only on the object’s temperature.
4) Spectral lines: in emission or absorption; every atom and molecule has a specific set.