Astronomy 1010 Planetary Astronomy Fall_2015 Day-26

Course Announcements SW-chapter 7 posted: due Fri. Oct. 30 SW-chapter 8 posted: due Wed. Nov. 4 Exam-3 Wed. Nov. 4: Ch. 6,7, 8 I will collect the L-T books on Monday, Nov. 23

Useful Information for Next Lab Extra-Solar Planets NAAP Lab Print the instructions BEFORE you come to class!

Take more astronomy! Registration for the Spring semester starts soon so think about taking more astronomy. ASTR-1010/1011: Planetary Astro & lab (Tell your friends) ASTR-1020/1021: Stellar Astronomy & lab (Reg. + Honors) ASTR-2020: Problems in Stellar Astronomy ASTR-3010: History of Astronomy ASTR-3040: Intro. To AstroBiology PHYS-2468: Intro. To Physics Research ASTR-3030/3031: Instrumentation & Techniques

 Planets can gather gasses from the disk by core accretion-gas capture.  This creates the primary atmosphere.  Low-mass planets cannot hold on to their primary atmospheres.  Some low-mass planets later emit gasses from their interiors (e.g., from volcanoes), producing a secondary atmosphere.  Each of the four terrestrial planets lost its primary atmosphere.

 Low-mass planets lose their primary atmospheres.  Recall that temperature measures the average speed of motion of gas atoms.  If the gas moves quickly enough, it will escape the planet.  Low-mass planets have low escape velocities.  Also, hot planets will have fast-moving gas particles.

 The four inner planets are rocky.  The four outer planets are gaseous giants.  Asteroids and comets are leftover planetesimals, while moons formed from the giant planets’ accretion disks.

Lecture Tutorial: Temp. & Formation of Our Solar System: pg. 111 Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Take time to understand it now!!!! Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group.

i_Clicker Questions Solar System Characteristics: Formation Temperatures Planets Densities

 The physical processes that led to the Solar System should be commonplace.  We can see young stars with disks.  Extrasolar planet: a body that orbits a star and has a mass less than 13 Jupiters.

 We have found more than 1000 confirmed extrasolar planets, or “exoplanets.”  Four main techniques to find these planets: Spectroscopic radial velocity method Transit method Microlensing method Direct imaging

Spectroscopic radial velocity method:  Gravity is a mutual force, so both stars and planets orbit one another.  Motion can be detected by Doppler shifts.  Some stars have periodic velocity changes; therefore, they are orbited by planets.

 In the spectroscopic radial velocity method, the Doppler shift of the star’s wobble can be used to estimate the mass and orbit of the planet.  M is the combined mass, and the star’s mass is much bigger than the planet’s. MATH TOOLS 7.2

 A planet passing in front of a star (transiting) can decrease the total brightness of the star.  Microlensing makes a star temporarily brighter, through a planet’s gravity focusing its light.

 By measuring the amount by which a star’s light is dimmed during a planet’s transit as well as the length of time the planet is in front of the star, you can estimate the size of the planet. MATH TOOLS 7.3

Direct imaging:  It is very difficult to directly see a faint planet in the bright glow of its star.  A few dozen planets have been identified this way so far.

 Many known planets have 1 to ten times the mass of Jupiter.  Some of these orbit close to their stars and are called hot Jupiters.  It is easier to find these very large planets due to the greater “wobble” they cause for their stars.

 Most planetary systems found to date do not resemble ours.  Researhers have also found mini-Neptunes and super-Earths.  Planet locations, orbital inclination angles, and orbital directions are different than our Solar System.

 Kepler Mission seeks to find rocky planets using transits in the habitable zone of their stars.  Potential conditions for liquid water.

i_Clicker Questions Extra-Solar Planets: ESP Orbit Animation Radial Velocity Curve

 Different scientists can reach the same conclusions.  Beginning from fundamental observations, theorists, planetary scientists, and stellar astronomers converge to the collapsing nebula hypothesis. PROCESS OF SCIENCE