4.8.1 - Solar System; stability of orbital motions; satellites Flashcards
List all celestial objects our solar system.
- the Sun
- Eight planets
- Dwarf planets
- Natural satellites (the moons that orbit planets)
What is a nebula?
a large cloud of dust and gas in space
Describe the formation of a star.
Massive clouds of dust and gas in space are pulled together by their gravitational attraction.
As the clouds join, they become more and more concentrated before forming a protostar.
As more clouds join, the protostar eventually becomes dense and hot enough such that nuclear fusion of hydrogen begins in the core.
The outward pressure of expanding hot gas from the fusion reactions lead to an equilibrium between the gravitational collapse of a star and the expansion of a star due to fusion energy.
Describe the life cycle of a star similarly sized to the Sun after it’s formation.
After the star runs out of hydrogen nuclei to fuse in it’s core, the star swells out and cools to become a red giant. Helium and other light elements in the core fuse to form heavier elements.
When there are no more light elements in the core, fusion stops and no more radiation is released. The lack of outward force from nuclear fusion causes the start to collapse over it’s own gravitational force.
The star heats up as it collapses so it becomes a white dwarf. The star eventually cools and fades to become a black dwarf.
Describe the life cycle of a star larger than the Sun after it’s formation.
After the star runs out of hydrogen nuclei to fuse in it’s core, the star swells out to become red supergiant’s. The star then collapses, causing the star’s core to become more and more compressed. The star then explodes in a supernova to form a neutron star or a black hole.
How are elements lighter than iron produced?
Fusion processes in stars produce all of the naturally occurring elements.
How are elements heavier than iron produced?
Elements heavier than iron are produced in a supernova.
How are elements distributed around the universe?
The explosion of a massive star (supernova) distributes the elements throughout the universe.
Why can stars not form elements higher than iron through fusion?
Nuclei larger than iron cannot be formed by this process because too much energy is needed.
Describe (two) differences between geostationary and monitoring satellites.
- Geostationary satellites’ orbits usually take roughly 24h whereas the orbits of monitoring satellites are usually 2-3h long.
- Geostationary satellites’ orbits are usually 36,000km above (in line with) the equator whereas monitoring satellites are usually much lower in orbit.
What is the main difference between a planet and a moon?
Planets orbit a star (the Sun), whereas moons orbit other planets.
What is a satellite?
An object in space that orbits or circles around a larger object.
For circular orbits, how can the force of gravity can lead to changing velocity but unchanged speed?
In a stable orbit, the direction of motion and the direction of centripetal force are in balance such that the resultant force maintains the orbit. This means that if either force changes, this will result in a change in resultant force and therefore a change in the shape of the orbit. This changes the radius of the orbit.
