Part B: Cepheid Variable Stars Some Background Info We call the total energy output of an astronomical source its Luminosity. It is measured in units of power (e.g. Watts), which is energy per time. The amount of energy we collect from an astronomical source depends on two factors: the source's energy output or luminosity, and the distance that source is from us. The apparent brightness of a source is most often called its Flux, and is measured in units of power per area of our telescope (e.g. Watts/m2). The relationship between luminosity and flux is Flux = Luminosity/(4 (distance)^2 ). Basically, we divide the total energy output of an object over the surface of a sphere (4r^2) surrounding it. The bigger the sphere, the more the energy is spread out, so the lower the flux. When we set the radius of the sphere equal to the distance from the source to our detector, we can calculate the flux detected. Cepheid Variables Suppose you observe two Cepheid Variable stars. CV1 is a local Milky Way star. It has a measured parallax, which determines its distance to be 1000 pc (which is 3x1019 m). When observing the light curve of CV1, you measure the period of its pulsation to be 10 days. You also measure its flux to be FCV1 = 9.5 x 10-11 W/m2. Give the pulsation period and the Leavitt relation plot, what is the luminosity of CV1? The Sun's luminosity is 3.8 x 1026 W. What is the luminosity of CV1 in Watts? Calculate the expected luminosity of CV1 using its distance

Part B: Cepheid Variable Stars some Background Info We call the total energy output of an astronomical source its Luminosity. lt is measured in units of power (e.g. Watts), which is energy per time. The amount of energy we collect from an astronomical source depends on two factors: the source's energy output or luminosity, and the distance that source is from us. The apparent brightness of a source is most often called its Flux, and is measured in units of power per area of our telescope (e.g. Watts/m*). The relationship between luminosity and flux is Flux = Luminosity 4m (distance}" Basically, we divide the total energy output of an object over the surface of a sphere (4mr*) surrounding it. The bigger the sphere, the more the energy is spread out, so the lower the flux. When we set the radius of the sphere equal to the distance from the source to our detector, we can calculate the flux detected. Cepheid Variables Suppose you observe two Cepheid Variable stars. C'V1 is a local Milky Way star. It has a measured parallax, which determines its distance to be 1000 pe (which is 3x10 m). When observing the light curve of CV1, you measure the period of its pulsation to be 10 days. You also measure its flux to be Foy; = 9.5% 10' Wim'. 1. Give the pulsation period and the Leavitt relation plot, what is the luminosity of CV1? 2. The Sun's luminosity is 3.8 x 10" W. What is the luminosity of C'V1 in Watts? 3. Calculate the expected luminosity of C1 using its distance and flux. Is this consistent