Lec20-Apr2

Lec20-Apr2 - Astro 109 Lecture 20: Extrasolar Planets...

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Astro 109 Lecture 20: Extrasolar Planets April 2 Apr. 2 Questions about reading or homework? Apr. 2 Key Concepts Center of Mass Detection of exoplanets Astrometric and Doppler Techniques Transiting exoplanets Microlensing Properties of known exoplanets Large masses Small orbital radii Gaseous Apr. 2 Modify Kepler’s 1 st law Newton’s 3 rd law: if Sun pulls on Earth, then Earth also pulls on Sun. Both move! E ! ect is small in Solar System. One of the ways we detect extrasolar planets. From Lecture 9 F = ma a = F m Apr. 2 Center of Mass r 1 M 1 = r 2 M 2 r 1 r 2 = M 2 M 1 v 1 v 2 = M 2 M 1 Apr. 2 Center of Mass
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Apr. 2 r 1 r 2 = M 2 M 1 r 1 = r 2 × M 2 M 1 =7 . 8 × 10 11 m × 1 . 9 × 10 27 kg 2 . 0 × 10 30 kg . 4 × 10 8 m Apr. 2 The semimajor axis of Jupiter’s orbit is 5.2 AU = 7.8 " 10 11 m. Jupiter’s mass is 1.9 " 10 27 kg, while the Sun’s mass is 2.0 " 10 30 kg. What is the radius of the Sun’s “wobble” due to Jupiter? How big is that compared with the size of the Sun (radius 7.0 " 10 8 m)? Example v = distance time = 2 π r 1 P = 2 π × (7 . 4 × 10 8 m) 3 . 7 × 10 8 s = 12 m / s = 45 km / hr Apr. 2 How fast does the Sun move as it “wobbles”? The period of Jupiter’s orbit is 11.86 yr = 3.7 " 10 8 s. Example Apr. 2 α = r 1 D × 206265 arcsec = 7 . 4 × 10 8 m 10 17 m × 206265 arcsec =0 . 002 arcsec Apr. 2 Suppose we were observing the Sun’s wobble from D = 10 light-years # 10 17 m away. What would the angular size of the wobble be?
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This note was uploaded on 09/15/2011 for the course PHYS 109 taught by Professor Pryor during the Spring '09 term at Rutgers.

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Lec20-Apr2 - Astro 109 Lecture 20: Extrasolar Planets...

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