DP Physics Questionbank

(i) Calculate $\frac{b_{\text{A}}}{b_{\text{B}}}=\frac{\text{apparent brightness of Alpha Centauri A}}{\text{apparent brightness of Alpha Centauri B}}$.

(ii) The luminosity of the Sun is 3.8 × 10²⁶ W. Calculate the radius of Alpha Centauri A.

Determine the distance of Theta 1 Orionis in AU.

State what is meant by a main sequence star.

Discuss how Theta 1 Orionis does not collapse under its own weight.

The surface temperature of the Sun is about 6000 K. Estimate the surface temperature of Theta 1 Orionis.

The radius of a typical neutron star is 20 km and its surface temperature is 10⁶ K. Determine the luminosity of this neutron star.

State the most abundant element in the core and the most abundant element in the outer layer.

Show that the apparent brightness $b\propto \frac{A{T}^4}{d^2}$, where $d$ is the distance of the object from Earth, $T$ is the surface temperature of the object and $A$ is the surface area of the object.

The astronomical unit ($\mathrm{AU}$) and light year ($\mathrm{ly}$) are convenient measures of distance in astrophysics. Define each unit.

$\mathrm{AU}$:

$\mathrm{ly}$:

Two of the brightest objects in the night sky seen from Earth are the planet Venus and the star Sirius. Explain why the equation $b\propto \frac{A{T}^4}{d^2}$ is applicable to Sirius but not to Venus.

Estimate, in $\text{pc}$, the distance to Eta Aquilae A using the parallax angle in the table.

Estimate, in $\text{pc}$, the distance to Eta Aquilae A using the luminosity in the table, given that $L_{\odot }=3.83\times {10}^{26} \mathrm{W}$.

Estimate, in $\text{pc}$, the distance to Eta Aquilae A using the luminosity in the table, given that $L_{\odot }=3.83\times {10}^{26} \mathrm{W}$.

Estimate, in $\mathrm{pc}$, the distance to Eta Aquilae A using the parallax angle in the table.

The luminosity of the Sun L${}_{\odot }$ is 3.85 × 10²⁶ W. Determine the luminosity of Gacrux relative to the Sun.

The distance to Gacrux can be determined using stellar parallax. Outline why this method is not suitable for all stars.

Main sequence stars are in equilibrium under the action of forces. Outline how this equilibrium is achieved.

A main sequence star P, is 1.3 times the mass of the Sun. Calculate the luminosity of P relative to the Sun.

Distinguish between the solar system and a galaxy.

Distinguish between a planet and a comet. 

The following data are available for the Sun.

Surface temperature  = 5800 K

Luminosity                  = $L_{\odot }$

Mass                          = $M_{\odot }$

Radius                       = $R_{\odot }$

Epsilon Indi has a radius of 0.73 $R_{\odot }$. Show that the luminosity of Epsilon Indi is 0.2 $L_{\odot }$.

The following data are available for the Sun.

Surface temperature  = 5800 K

Luminosity                  = $L_{\odot }$

Mass                          = $M_{\odot }$

Radius                       = $R_{\odot }$

Epsilon Indi has a radius of 0.73 $R_{\odot }$. Show that the luminosity of Epsilon Indi is 0.2 $L_{\odot }$.

Determine the peak apparent brightness of δ-Cephei as observed from Earth.

During its evolution, the Sun is likely to be a red giant of surface temperature 3000 K and luminosity 10⁴ L_☉. Later it is likely to be a white dwarf of surface temperature 10 000 K and luminosity 10-4 L_☉. Calculate the $\frac{\text{radius of the Sun as a white dwarf}}{\text{radius of the Sun as a red giant}}$.

The surface temperature of Eta Cassiopeiae B is 4100 K. Determine the ratio $\frac{\mathrm{radius} \mathrm{of} \mathrm{the} \mathrm{Eta} \mathrm{Cassiopeiae} \mathrm{A}}{\mathrm{radius} \mathrm{of} \mathrm{the} \mathrm{Eta} \mathrm{Cassiopeiae} \mathrm{B}}$.

The distance of the Eta Cassiopeiae system from the Earth is 1.8 × 10¹⁷m. Calculate, in terms of $L_{\odot }$, the luminosity of Eta Cassiopeiae A.