Astronomy 1010-H Planetary Astronomy Fall_2015 Day-26

Astronomy 1010-HFall_2015Day-26

Planetary Astronomy

Course Announcements• How is the sunset/sunrise observing going?

• 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

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 AstronomyASTR-3010: History of AstronomyASTR-3040: Intro. To AstroBiologyPHYS-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.

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 7.2MATH 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 7.3MATH 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.

Concept Quiz Hot Protostars

We know that stars have different temperatures. Consider a newly forming star that was much hotter than the proto-Sun. What would we expect about its planets?

A. The planets orbit at random angles around the star.

B. Rocky planets might be formed over a wider range of distances than in our Solar System.

C. The star would be “naked,” without a surrounding disk.

Concept Quiz Other Planets

Which of these is not a reason why we can find planets around other stars?

A. The planet’s gravity causes the star to orbit.

B. We can take images and directly see the planets.

C. We can detect radio signals from life on the planets.

D. A star’s light could be affected by its planet.

Concept Quiz Protoplanets

Which of the following statements is false?

A. Planetary systems begin as a disk of material around a protostar.

B. Planetesimals accrete material to become planets.C. All the planetesimals in our Solar System have become

planets.

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 SCIENCEPROCESS OF SCIENCE