Overview
From Our Star to the Cosmos – PHYS 1902 February 25, 2026 On Brightspace, please hand in a single document in pdf format with your answers. Please write clearly. If your objective is to learn, do not look up solutions online. All the material you need to solve this assignment is provided in the course lectures. Teamwork is allowed, but write on your own, in your own words. Replicated / copied / plagiarized assignments (this includes AI-generated answers) will receive a grade of zero. Estimated time: 10 hours max. Please let me know if it takes you much longer. Question 1 – Your thoughts on artificial intelligence (2 points) At the start of your file, please reflect on the future role of artificial intelligence in online courses such as this one. Should there be graded assessments, and if so how? Participation: any answer to this question will be given 2 points. I look forward to reading your thoughts on this issue. Question 2 – Chemical composition (4 points) Briefly explain how astronomers are able to obtain information on the chemical composition of stellar atmospheres. Question 3 – Spectral line (6 points) a) Using the Bohr model of the hydrogen atom, calculate the energy (in eV) of the photon emitted when an electron moves from from the third excited state (n = 4) to the first excited state (n = 2). b) What is this photon’s wavelength, in nm? c) What is the colour of this photon? d) What is the name of this spectral line? Question 4 – Kessler Observatory (5 points) The Kessler Observatory at Carleton University has a Schmidt-Cassegrain telescope with a diameter of 14 inches (355.6 mm). a) What is the telescope’s light-gathering power, in square centimetres? b) What is the telescope’s best possible angular resolution based on the diffraction limit? c) Telescope advertisements extol magnifying power. How can you improve the magnifying power of a reflecting telescope without changing the dimensions of the primary mirror? Question 5 – Fusion in the Sun (3 points) We have seen how much energy is produced by each fusion reaction of the proton-proton chain. Based on the Sun’s luminosity, how many kilograms of hydrogen are being converted into helium in the Sun’s core each second? Question 6 – Stellar radius (10 points) A star of spectral class B is observed with an apparent magnitude of 1.20 and an annual parallax angle of 0.004”. From measurements with standard filters, its surface temperature is measured to be 17,000 K. a) What is the distance to the star, in parsecs? b) What is the absolute magnitude of this star? c) What is the luminosity of this star, in terms of the solar luminosity? d) Based on this information, calculate the radius of the star, in solar radii. e) Classify the star based on colour and size. Is it a blue, yellow, or red star? Is it a supergiant, giant, average, or dwarf star?