Copy of Cosmic Distances

Cosmic Distances DISTANCE MODULUS ● For this lab, we will focus on two techniques that can be used to measure the distance modulus of objects in deep space – supernovas and Cepheid variable stars. Before we begin, though, we must understand what “distance modulus” means. ● Read through the background material on distance modulus . ● Use the distance modulus page to complete the following table. ● Are you having trouble with this table? Watch this teacher video for help . Object Apparent Magnitude (m) Absolute Magnitude (M) Distance Modulus (m - M) Distance (pc) Star A 2.4 2.4 0 10 Star B 6.02 5 1.02 16 Star C 10 8.01 1.99 25 Star D 8.5 0.5 8 389.11 ● Could one of the stars listed in the table above be an RR Lyrae star? Explain why or why not. Star D might be an RR Lyrae star, considering its characteristics. The observed distance of 398.11 parsecs falls within the typical range for RR Lyrae stars, often found in the galactic halo and globular clusters. Additionally, the absolute magnitude of 0.5 aligns with the anticipated range for RR Lyrae stars, typically around 0.600 ± 0.126. The consistency between the distance and absolute magnitude of Star D and the known features of RR Lyrae stars suggests a possibility that Star D belongs to this category. CEPHEIDS ● Next, read through the background information on Cepheid Variable Stars . ● Suppose that a Type II Cepheid has an apparent magnitude (m) of 12 and a pulsation period of 3 days. Use the chart at right along with the period to find the absolute magnitude (M). Calculate the distance modulus (m - M) and then use the table on the distance modulus page to determine the