Stars and Galaxies in the Universe

Free sample questions

Stars and Galaxies in the Universe — sample Science questions with answers

1. Question 1

   What is the main source of energy for stars like the Sun?

   • AChemical combustion of hydrogen gas
   • BNuclear fusion of hydrogen into helium
   • CNuclear fission of uranium
   • DChemical reaction between hydrogen and oxygen

   Answer: B. Nuclear fusion of hydrogen into helium

   Stars like the Sun produce energy through nuclear fusion, where hydrogen atoms ($\text{H}$) combine to form helium ($\text{He}$) at very high temperatures and pressures in their cores.

2. Question 2

   The closest star to Earth is

   • AProxima Centauri
   • BSun
   • CSirius
   • DAlpha Centauri A

   Answer: B. Sun

   The Sun is the closest star to Earth, at a distance of about $1.5\times 10^8$ km. Proxima Centauri is the second closest star after the Sun.

3. Question 3

   The appropriate unit to measure the distance between stars is

   • AKilometre
   • BMetre
   • CLight year
   • DCentimetre

   Answer: C. Light year

   Distances between stars are enormous, so kilometres are impractical. A light year, the distance light travels in one year, is an appropriate unit. For example, $1$ light year = $9.46\times 10^{12}$ km.

4. Question 4

   What is the meaning of 'light year'?

   • AThe time taken by light to circle the Earth
   • BThe distance travelled by light in one year
   • CThe time taken by Earth to orbit the Sun
   • DThe distance travelled by Earth in one year

   Answer: B. The distance travelled by light in one year

   A light year is a unit of distance, not time. It refers to the distance light travels in a vacuum in one year, which is $9.46\times 10^{12}$ km.

5. Question 5

   The star with the highest surface temperature is usually

   • ARed
   • BYellow
   • CBlue
   • DWhite

   Answer: C. Blue

   Blue stars like Rigel have very high surface temperatures ($>25,000\text{K}$), while red stars like Betelgeuse are cooler ($\approx 3,500\text{K}$). The hotter the star, the bluer its colour.