Texts: [5 marks] The Sun's centre is 5,906,400,000 km from Neptune's centre and the Sun's radius is 695,990 km; Neptune has a diameter of 49,528 km.[2] Draw a straight line from the Sun to Neptune. Calculate the closest distance between the Sun's surface and Neptune's surface along this line, then compare this to the distance between the Neptune and Sun centres. By comparing these two results, explain why astronomers generally use the centre-centre (not surface-surface) distance when talking about distances between astronomical objects.
[3 marks] Suppose that you are orbiting Neptune and observe a sunspot on the Sun that subtends an angle of 1.50 minutes of arc; knowing this angular size, determine the physical size of the sunspot in kilometers.
[2 marks] In Star Wars, Han Solo claims that the Millennium Falcon made the Kessel run in less than twelve parsecs. From an Earth-based astronomer's point of view, why is this statement nonsense?
[3 marks] Alpha Centauri AB is a double star in the constellation of Centaurus; it's the closest star system to Earth and these two stars are separated by 4.16" in the sky. You've borrowed a Skywatcher telescope from the Physics Lab at MacEwan University that has an aperture of 102 mm and a focal length of 1000.0 mm.
[1] Calculate the largest wavelength of light that you could use to resolve the two stars as separate points of light. In other words, for what wavelength of light is 4.16" the resolution angle of the Skywatcher?
[2] This binary is 4.367 light years from Earth. What is the distance, in AU, between the stars?
[10 marks] The Celestar 8 Deluxe telescope available in the Physics Lab is described on mêskanâs. The Celestar has an aperture of 203 mm and the focal length of the objective lens is 2032.0 mm. Using this information calculate the following:
[2] The light gathering power of the telescope relative to the human eye (which has a pupil size of 7 mm).
[2] The magnification of the telescope when the 15 mm focal length eyepiece is used.
[3] The resolution of the telescope under ideal conditions (no turbulence) measured in seconds of arc. Assume a visible wavelength of 550 nm.
[3] The diameter, in kilometers, of the smallest crater that you can observe on the Moon's surface with the Celestar telescope, assuming ideal seeing conditions (no atmospheric turbulence), visible light with wavelength 550 nm, and the distance to the Moon found on the course formula sheet.