The AstraEA space telescope used stellar parallax with a precision of 2.4×10−42.4 \times 10^{-4}2.4×10−4 arcseconds to determine the distance to stars.
One of the stars studied was Vega-Prime. Data about this star is in the table below:
| Parameter | Value |
|---|---|
| Parallax angle | 1.2×10−31.2 \times 10^{-3}1.2×10−3 arcseconds |
| Radius | 1.5×1010 m1.5 \times 10^{10}\text{ m}1.5×1010 m |
| Mass | 4.0×1031 kg4.0 \times 10^{31}\text{ kg}4.0×1031 kg |
| Surface temperature | 9500 K9500\text{ K}9500 K |
| Temperature of the atmosphere of the star | 3.6×106 K3.6 \times 10^6\text{ K}3.6×106 K |
Estimate the maximum stellar distance in parsecs (pc) that could be measured using AstraEA.
Calculate the percentage uncertainty in the calculated value of the distance to Vega-Prime.
A continuous stream of particles called a stellar wind flows from the surface of the star into the surrounding space. These particles include protons of mass 1.67×10−27 kg1.67 \times 10^{-27}\text{ kg}1.67×10−27 kg. Assume that the atmosphere is modelled as an ideal gas.
Show that the typical kinetic energy of a proton in the atmosphere of the star is about 7.5×10−17 J7.5 \times 10^{-17}\text{ J}7.5×10−17 J.
The gravitational potential energy of a proton in the outer layer of the star is −3.0×10−16 J-3.0 \times 10^{-16}\text{ J}−3.0×10−16 J. Calculate the gravitational potential energy UUU at the maximum distance from the star that a proton could reach.
Calculate the distance from the centre of the star reached by this proton.
Explain why the star has a stellar wind that reaches a much greater distance from the star than found in (iii).
66 exam-style questions on OCR A A Level Physics Astrophysics and cosmology, covering Stars, Electromagnetic radiation from stars, and Cosmology. Each one has a worked solution and a mark scheme showing where the marks go.