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Astronomy 1010
Planetary Astronomy
Fall_2015
Day-26
Course Announcements
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SW-chapter 7 posted: due Fri. Oct. 30
SW-chapter 8 posted: due Wed. Nov. 4
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Exam-3 Wed. Nov. 4: Ch. 6,7, 8
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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:
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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.
MATH TOOLS 7.2
 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.
 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.
MATH TOOLS 7.3
 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.
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
PROCESS OF SCIENCE
 Different scientists
can reach the same
conclusions.
 Beginning from
fundamental
observations,
theorists, planetary
scientists, and
stellar astronomers
converge to the
collapsing nebula
hypothesis.