Tutorial 3.0 Stellar physics A star emits electromagnetic radiation with a peak wavelength of 6.8 × 10–7 m. Use Wien’s law (λmaxT = 3 × 10–3) to calculate the surface temperature of the star. Calculate the power of the radiation emitted by each square metre of the star’s surface where the star is assumed to be a black body. Stefan–Boltzmann constant = 5.67 × 10–8 J s–1 m–2 K–4. The Sun has a radius of 7.0 × 108 m and a surface temperature of 5800 K. Calculate the power emitted per m2 from the Sun’s surface. Calculate the luminosity of the Sun. Calculate the apparent brightness of the Sun as seen from the Three measurements of a distant star are possible from Earth. These measurements are: apparent brightness = 4.3 × 10–9 W m–2 peak emitted wavelength = 2.4 × 10–7 m distance to star (parallax method) = 8.5 × 1017 m Use Wien’s law = 3 × 10–3) to calculate the surface temperature of the star. Calculate the energy emitted by each square of the star’s surface per second. Calculate the luminosity of the star. Calculate the radius of the star. 4. A star is 86 ly from Earth and has a luminosity of 4.8 × 1028 W m–2. Calculate the apparent brightness of the star. 5. The apparent brightness of a star is 6.2 × 10–8 W m–2. The star is 16 ly from Calculate the luminosity of the star. 6. A star with luminosity 2.1 × 1030 W m–2 has an apparent brightness of 7.9 × 10–8 W m–2 when viewed from Earth. Calculate the distance of the star from (a) in metres (b) in light years. 7. A star with radius 7.8 × 108 m and surface temperature 6300 K has an apparent brightness of 1.8 × 10–8 W m–2. Calculate its distance from the Earth. 8. A star with radius 9.5 × 109 m and surface temperature 5900 K is 36 ly from Calculate the apparent brightness of the star.
Tutorial 3.0 Stellar physics A star emits electromagnetic radiation with a peak wavelength of 6.8 × 10–7 m. Use Wien’s law (λmaxT = 3 × 10–3) to calculate the surface temperature of the star. Calculate the power of the radiation emitted by each square metre of the star’s surface where the star is assumed to be a black body. Stefan–Boltzmann constant = 5.67 × 10–8 J s–1 m–2 K–4. The Sun has a radius of 7.0 × 108 m and a surface temperature of 5800 K. Calculate the power emitted per m2 from the Sun’s surface. Calculate the luminosity of the Sun. Calculate the apparent brightness of the Sun as seen from the Three measurements of a distant star are possible from Earth. These measurements are: apparent brightness = 4.3 × 10–9 W m–2 peak emitted wavelength = 2.4 × 10–7 m distance to star (parallax method) = 8.5 × 1017 m Use Wien’s law = 3 × 10–3) to calculate the surface temperature of the star. Calculate the energy emitted by each square of the star’s surface per second. Calculate the luminosity of the star. Calculate the radius of the star. 4. A star is 86 ly from Earth and has a luminosity of 4.8 × 1028 W m–2. Calculate the apparent brightness of the star. 5. The apparent brightness of a star is 6.2 × 10–8 W m–2. The star is 16 ly from Calculate the luminosity of the star. 6. A star with luminosity 2.1 × 1030 W m–2 has an apparent brightness of 7.9 × 10–8 W m–2 when viewed from Earth. Calculate the distance of the star from (a) in metres (b) in light years. 7. A star with radius 7.8 × 108 m and surface temperature 6300 K has an apparent brightness of 1.8 × 10–8 W m–2. Calculate its distance from the Earth. 8. A star with radius 9.5 × 109 m and surface temperature 5900 K is 36 ly from Calculate the apparent brightness of the star.
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