telescopes - 1 We've used spectra to find planets around...

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Unformatted text preview: 1 We've used spectra to find planets around other stars. Star wobbling due to gravity of planet causes small Doppler shift of its absorption lines. Amount of shift depends on velocity of wobble. Also know period of wobble. This is enough to constrain the mass and orbit of the planet. As of today ~600 extrasolar planets known. Here are the first few discovered. Molecules Two or more atoms joined together. They occur in atmospheres of cooler stars, cold clouds of gas, planets. Examples H 2 = H + H CO = C + O CO 2 = C + O + O NH 3 = N + H + H + H (ammonia) CH 4 = C + H + H + H + H (methane) They have - electron energy levels (like atoms) - rotational energy levels - vibrational energy levels Molecule vibration and rotation 2 Searching for Habitable planets around other stars Reminder: Test #1 Sep 13 Topics: Fundamentals of Astronomy The Copernican Revolution Radiation and the Electromagnetic Spectrum Atoms and Spectroscopy Telescopes Methods Conceptual Review and Practice Problems Intro-Chap 3 Review lectures (on-line) and know answers to clicker questions Try practice quizzes on-line Review: Monday @ 3:25pm in RH103 Bring: Two Number 2 pencils Simple calculator (no electronic notes) Reminder: There are NO make-up tests for this class Test #1 Useful Equations P 2 a 3 Keplers laws, including: Newtons laws, including: F = ma m=mass, a=acceleration F = G m 1 m 2 R 2 Gravitation: Speed of electromagnetic waves: c = Energy = h max energy 1 T Wiens Law: Stefans Law: L = A T 4 where the area A = 4 r 2 for a sphere P=period, a=semi-major axis Telescopes Light Hitting a Telescope Mirror small mirror far from 2 stars Light rays from any single point of light are essentially parallel . But the parallel rays from the second star come in at a different angle. small mirror far from 2 stars Light rays from a distant source, parallel to the "mirror axis" all meet at one point, the focus . Parallel light rays at another angle meet at another point in same vertical plane, the focal plane. CCD 3 Optical Telescopes - Refracting vs. Reflecting Refracting telescope Focuses light with a lens (like a camera). <-- object (point of light) image at focus Problems: - Lens can only be supported around edge. - "Chromatic aberration". - Some light absorbed in glass (especially UV, infrared)....
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telescopes - 1 We've used spectra to find planets around...

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