Question

Multiple choice: Suppose you are searching for exoplanets using the radial velocity and transit techniques. Which exoplanets are you most likely to find?

(a) Jovian exoplanets orbiting with a large semimajor axis.

(b) Jovian exoplanets orbiting with a small semimajor axis.

(c) Terrestrial exoplanets orbiting with a large semimajor axis.

(d) Terrestrial exoplanets orbiting with a small semimajor axis.

(e) There is an equal chance of finding both jovian and terrestrial exoplanets, and an equal chance of finding ones with large and small semimajor axes.

Multiple choice: Imagine a star with a single exoplanet orbiting it. If the exoplanet’s mass were doubled, the observed Doppler-shift variations of the star would be _______. If the semimajor axis of the exoplanet’s orbit were doubled, the observed Doppler-shift variations of the star would have _______.

(a) larger; a shorter period;

(b) smaller; a longer period;

(c) larger; a longer period;

(d) the same; the same period; or

(e) smaller; a shorter period.

Multiple choice: Suppose you are measuring the brightness change of a star over time due to an exoplanet orbiting the star. What are the properties of this exoplanet that you can deduce directly from the star’s light curve (plot of brightness vs. time)?

(a) The exoplanet’s orbital period, and the ratio of its radius to the host star’s radius.

(b) The exoplanet’s orbital period and its distance from the host star.

(c) The exoplanet’s distance from its host star, and the ratio of its mass to the host star’s mass.

(d) The exoplanet’s distance from its host star and the exoplanet’s density.

(e) The composition of the exoplanet’s atmosphere.

Answer 1

Q1. a) Jovian exoplanets orbiting with a large semi-major axis. (Science massive exoplanets with larger major axis will intern mean the C.M of the star and exoplanet system will be relatively at more distance from the star causing a much more variations in speed of the star which means a more pronounced doppler shift in the star's spectra)

Q2. c) larger; longer period. (Doubling the mass of the exoplanet will shift the C.M. farther away from star so speed variation of the star will increase causing larger doppler shift, the increased semi-major axis means decreased angular velocity to conserve angular momentum thus an increase in time period)

Q3. a) The exoplanet's orbital period, and the ratio of its radius to the hoststar's radius. ( While the radial velocity method provides information about a planet's mass, the photometric method can determine the planet's radius. A theoretical transiting exoplanet light curve model predicts the following characteristics of an observed planetary system: transit depth (δ), transit duration (T), the ingress/egress duration (τ), and period of the exoplanet (P). The transit depth (δ) of a transiting light curve describes the decrease in the normalized flux of the star during a transit. This details the radius of an exoplanet compared to the radius of the star. Resource of this paragraph: Wikipedia)

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