The mass of the exoplanet can be estimated from the orbital period, P (in years), and the radial velocity amplitude K (in m/s). The masses of exoplanets are usually measured in units of Jupiter's mass (e.g. 5 times the mass of Jupiter or 0.25 times the mass of Jupiter). This assumes that we are observing the planet in the plane of its orbit, and gives only an estimate of the minimum mass. The true mass could be greater.

7. Use P and K to estimate the mass of 51 Peg's planet from the formula.

M = [(P/12)^1/3*(K/13)] (M in Jupiter masses)

Mass in Jupiter masses =

Summarize your findings in the table below:

	Orbital Period	Semi-Major Axis	Mass in MJup
Jupiter	12 years	5.2 AU	1 MJup
51 Peg b

8. How does the mass of 51 Peg's planet compare to the mass of Jupiter?

9. What is the accepted mass for 51 Peg b (see Wikipedia)? Is your estimate within 10% of the accepted mass?

10. 51 Peg is a star similar to our sun, what is a difference might you expect between 51 Peg b and Jupiter based on their different distances from their stars? (Hint: it is not size.)