Download PH507 - University of Kent

PH507/T1
UNIVERSITY OF KENT: SCHOOL OF PHYSICAL SCIENCES
THE MULTIWAVELENGTH UNIVERSE
2006
Class Test 1:
1. Calculate the luminosity (in units of the solar luminosity) of a blackbody of Saturn’s
radius that has a temperature of 1000 K? Explain the steps you take in the derivation.
The surface temperature of the Sun is 5780 K. The radii of Saturn and the Sun are
6.00 x 107 m and 6.96 x 108 m, respectively. [Hint – you don’t need to know the
absolute value of the solar luminosity]
[20]
2. Suppose two stars have the same luminosity, but one is an A star and one is a K star.
Which has the larger radius and why?
[5]
3. Calculate the parallax in arcseconds of a star for which the apparent magnitude is equal
to its absolute magnitude.
[10]
4. The apparent magnitude of a star is modified by the extinction A() according to: m()
= M() + 5 log d – 5 + A(). Determine the extinction which would produce an
optical depth of 10.
[15]
5. What is the best observational method for detecting the presence of massive planets
with short orbital periods and why?
[10]
6. Planets with which property are observed to have low eccentricity ? How is the metal
abundance of the central star observed to be related to the detection of planets? [20]
7. In which type of star are the Balmer lines strongest: A, K or O? Explain why in terms
of (a) the classification system and (b) how photosphere properties influence the
formation of hydrogen spectral lines.
[20]