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Test

Question 1

Q: Name the type of nuclear reaction that produces energy in stars.
A: Nuclear fusion

Question 2

Q: Recall the type of star produced by the collapse of a star that is the same size as our Sun.
A: White dwarf

Question 3

a) Q: Define the term ‘spectral class’.
A: Classification that states the elements, temperature, and color of a star

b) Q: Name the device used to measure it.
A: Spectrometer

Question 4

Q: The ‘twins’ of the constellation Gemini are the stars Castor and Pollux. Explain how these two stars can have almost identical absolute magnitudes when Castor (50 ly) is almost 1.5 times further away than Pollux (33 ly).
A: Castor must have a smaller apparent magnitude (brighter) as it is further away from Pollux. Even though Castor and Pollux share the same absolute magnitude, Castor is brighter, but its distance from Pollux evens out the view.

Question 5

Q: Explain why stars in the main sequence get brighter as they get bigger.
A: A greater mass leads to a stronger gravitational force, which causes the star’s core to become more tightly compressed. This increased compression speeds up nuclear fusion, resulting in a faster conversion of hydrogen into helium and the production of more heat and light.

Question 6

Q: Predict what will happen to a star 15 times the size of our Sun when the hydrogen fuel in its core runs out.
A: If a star 15 times the size of our Sun runs out of hydrogen fuel, fusion will stop, halting the outward radiation pressure. The star will collapse inward, and fusion will happen in the outer layers, slowly cooling it down. As the star starts using helium as fuel and converting it into heavy elements such as carbon and oxygen, it will eventually run out. With no force to act against gravity, the star will collapse into an explosive supernova.

Question 7

a) Q: Betelgeuse is a star that is 640 light-years away. Calculate this distance in parsecs.
A:
640 / 3.26 = 196.319 ≈ 196

b) Q: Bellatrix is 75 parsecs from Earth. Calculate this distance in light years.
A:
75 × 3.26 = 244.5 ≈ 245

Question 8

Q: Rigel and Betelgeuse are the two brightest stars in the constellation Orion.
Rigel has an apparent magnitude of 0.18 and an absolute magnitude of –6.8.
Betelgeuse has an apparent magnitude of 0.6 and an absolute magnitude of –5.1.

a) Identify which of the two stars appears brighter.
A: Rigel

b) Identify which of the two stars produces more light.
A: Rigel

Question 9

Q: Calculate the density of:

a) The planet Jupiter, mass = 1.9 × 10²⁷ kg, volume = 1.4 × 10²⁴ m³

1.9 × 10²⁷ / 1.4 × 10²⁴ = 1.36 × 10³ kg/m³

b) The Sun, mass = 2.0 × 10³⁰ kg, volume = 1.4 × 10²⁷ m³

2.0 × 10³⁰ / 1.4 × 10²⁷ = 1.43 × 10³ kg/m³

c) A red giant, mass = 3.6 × 10³¹ kg, volume = 1.2 × 10³⁶ m³

3.6 × 10³¹ / 1.2 × 10³⁶ = 3 × 10⁻⁵ kg/m³

Question 10

Q: Contrast the terms absolute magnitude and apparent magnitude.
A: A star’s apparent magnitude is its brightness as viewed from Earth, whereas its absolute magnitude is how bright it would appear if it were placed 10 parsecs away.

Question 11

Q: Just as a year can be broken up into 365 days, a light-year can be broken up into 365 ‘light-days’. A light-year is 9.5 × 10¹² km (9.5 trillion kilometers).

a) Calculate the length of 1 light-day.

9.5 × 10¹² km / 365 = 2.60 × 10¹⁰ km

b) Calculate the length of 1 light-hour.

2.60 × 10¹⁰ km / 24 = 1.08 × 10⁹ km

c) Calculate the length of 1 light-minute.

1.08 × 10⁹ km / 60 = 1.81 × 10⁷ km

d) Given that the Earth is, on average, 150,000,000 km from the Sun, calculate this distance as a value in light-minutes.

150,000,000 / 300,000 = 500 km
500 / 60 = 8.33 light seconds

e) Interpret the answer to part d to give the time it takes for light from the Sun to reach Earth.
A: 8.33 minutes

Question 12

Q: The term supernova means ‘big, new star.’ Modern astronomers now understand that supernovae are not ‘new’ stars but stars that have suddenly become much brighter, so this term is misleading. Propose a more scientifically accurate name for this type of star.
A: Stellar Outburst

Question 13

a) Q: Critically analyze the accuracy of the term planetary nebula.
A: The term is misleading because it suggests a connection to planets, whereas planetary nebulae are actually the glowing shells of gas ejected by dying stars, typically red giants. The name originated in the 18th century when astronomers using early telescopes observed these objects and mistakenly thought they resembled planets due to their round, disk-like appearance.

b) Q: Propose a more appropriate term.
A: Cosmic Cloud