Why wouldn’t we expect to discover an Earth-like planet by observing a Doppler shift?

Extrasolar Systems The goal of this homework is to understand defining characteristics of extrasolar systems and


1.0 Detection 1.1) (10pts) Astronomers primarily detect extrasolar planets two ways: using the transit method, and using the radial velocity method. What are the benefits and constraints of both methods? (Hint: what can we understand about the extrasolar system by observing it directly/indirectly, what can’t we understand?)

1.2) (6pts) In the figure to the left, there is a planet whose orbital period is 8 days. What would we expect the Doppler shift spectrum to look like for this system? Sketch your answer as simulated data points in the graph.

1.3) (4pts) Why wouldn’t we expect to discover an Earth-like planet by observing a Doppler shift? What are some of the characteristics of the planets observed through this method?

2.0 Comparing Extrasolar Planets to our Own

2.1) (12pts) Describe the characteristics of our Solar System. What are the planets like closer to the Sun and farther from the Sun? Would you expect this to be a “standard model” for solar systems elsewhere in the galaxy? Why or why not?

CID: Score: ______/94

The figure to the left is a graph that plots the eccentricity of a planet’s orbit versus the orbital distance of the planet from its sun. The red triangles represent exoplanets Astronomers have discovered and the blue squares are the planets around our Sun.

2.2) (6pts) How do the planets in our solar system compare to the discovered extrasolar planets? Are there any trends you see in the figure above?

2.3) (8pts) Reread your two answers for 2.1 and 2.2. If you said our Solar System could be a “standard model” for other solar systems in the Milky Way, do you still agree? Why or why not. If you, from question 2.1, said our solar system cannot be a standard model, how can you use the figure above to support your argument?

CID: Score: ______/94

3.0 Extrasolar Jovian Planets

The figure to the left shows the number of extrasolar planets according to their Jupiter masses. For reference, 0 (on the x-axis) equals the mass of Jupiter.

3.1) (12pts) What does the graph tell us about the majority of extrasolar planets that we have discovered? What are their characteristics? What kinds of exoplanets do astronomers search for? What can be concluded from the data in the chart to the right?

3.2) (6pts) Do you think the graph above gives Astronomers a good idea of what the majority of extrasolar planets are like? Why or why not?

3.3) (10pts) Do you believe the planets in extrasolar systems are mostly Jovian planets or do you think they are just easier to detect? Do you think our solar system is unique for having terrestrial planets, why or why not? What are the complications in finding terrestrial planets, specifically ones that could be habitable?

CID: Score: ______/94

4.0 Extrasolar Systems’ Orbitals

The adjacent figure above the orbits of the

planets in our solar system

4.1) (8pts) What are the defining factors of the planets’ orbitals in our Solar System? Do most of them lie on a similar plane? How about the orientation of the planet’s inclination to the sun? Would you expect most extrasolar orbits to be the same? Why or why not?

4.2) (12pts)The figure above shows three identical planets that orbit their sun at different inclinations, for A, B, and C. The orbital plane of each planet is marked with a horizontal grey bar. Draw out the Doppler shift spectrum (similar to question 1) that we would receive from this exoplanet.