P6.2.1 - The Sun as a Star Flashcards
What is the closest star to Earth? [1]
the sun
How can astronomical distances be measured? [1]
in light-years
What is one light-year? [2]
distance travelled in space / light in one year
Why do the planets orbit the sun? [1]
the sun contains most of the mass of the solar system
Why is there a force that keeps an object in orbit around the sun? [1]
because of the gravitational attraction of the sun
What does the sun mostly consist of? [2]
- hydrogen
- helium
What does the sun radiate most of its energy in the form of? [3]
- infrared
- visible
- ultraviolet
What size is the sun? [1]
medium size
What is the equation for orbital speed? [2]
v = 2πr / T
Explain the equation for orbital speed. [3]
- v: average orbital speed in m/s
- 2πr: orbital radius in metres
- T: orbital period in seconds
What is the orbital period? [1]
the time it takes for an object to complete one full orbit
What happens as the distance from the sun increases? [2]
- the sun’s gravitational strength decreases
- orbital speeds of planets decrease
What does it mean that the sun’s gravitational strength decreases? [2]
- the farther a planet is from the sun, the weaker the gravitational pull it experiences
What does it mean the orbital speeds of planets decrease? [4]
- planets closer to the sun move faster in their orbits because they experience a stringer gravitational pull
- planets farther from the sun move slower because they feel less gravitational force, so they take longer to complete one orbit
Give an example of as the distance from the sun increases, the orbital speeds of planets decrease. [1]
mercury (closest to sun) orbits much faster than neptune (one of the farthest planets)
How are stars powered via nuclear reactions? [2]
- the energy of a star comes from nuclear fusion
- where atomic nuclei combine to form heavier nucleus and release lots of energy
How are stars powered via the fusion of hydrogen to helium? [2]
- in stable stars like the sun hydrogen nuclei fuse to form helium
- this releases energy in the form of heat and light
What keep a star shining? [1]
the heat and light released from hydrogen nuclei fusing into helium
How are stars powered via stable stars balance forces? [2]
- in a stable star the outward pressure from fusion energy balances the inward pull of gravity
- this prevents the star from collpasing or expanding uncontrollably
How do you calculate the time it takes light to travel a significant distance such as between objects in the solar system? [2]
time = distance / speed of light
What is the speed of light? [1]
3.0 × 10⁸ m/s
