Stars and Planets Flashcards
What is the order of the planets?
Mercury Venus Earth Mars (asteroid belt) Jupiter Saturn Uranus Neptune - My Very Easy Method Just Speeds Up Naming
What is an astronomical unit?
The mean distance between the Earth and the Sun (approximately 150 000 000km).
How did the solar system come to be?
1) It was a gas cloud containing mainly hydrogen and helium and dust from a supernova.
2) Gravitational forces began to cause the cloud to collapse with particles sticking together.
3) The collapsed cloud began to spin, forming a disk shape.
4) The centre became the sun and the rest became the planets
5) Inner planets are rocky as the sun is too close for light gaseous elements to condense and were instead pushed further away.
6) Outer planets are gaseous because they are further away from the sun which allowed gaseous elements to condense and form gas giants.
What is the life cycle up to a main sequence star (like our sun).
Nebular
1) Stars are formed from large clouds mainly hydrogen and helium and dust which is called a Nebular.
Protostar (Gravity> Radiational pressure)
2) Gravity condenses this cloud together until the nebular becomes dense and more concentrated.
3) The temperature increases until hydrogen undergoes nuclear fusion.
4) This fusion produces a lot of energy and the core gets brighter and hotter until a Protostar is created.
Main Sequence Star (Gravity=Radiational Pressure)
5) Nuclear fusion with hydrogen is now fully underway and the star is much hotter and brighter than before.
The forces of gravity and radiational pressure are at equilibrium meaning the star is stable. Hydrogen fuses together to create Helium.
What is the life cycle from a low mass main sequence star to a Black Dwarf?
Red Giant
1) Once a main sequence star runs out of hydrogen to fuse with, the star will fuse helium together to create carbon.
2) This increases the radiation pressure acting outwards and expands the star until the forces of gravity and radiation pressure are at an equilibrium again.
3) The star left is a red giant which now emits red light.
White Dwarf
4) Once a red giant runs out of fuel (lighter elements) the reaction at the core will slow down and the radiation pressure will decrease.
5) The stars outer shell will drift away forming a planetary nebular leaving a condensed and shrunken core left.
6) This core is so dense and hot that it emits white light hence the name white dwarf.
Red dwarf to Black Dwarf
7) Once the white dwarf has cooled down it will begin to stop emitting light, heat or radiation- it will turn to a red dwarf to a black dwarf.
What is the life cycle from a high mass main sequence star to a Black Hole or Neutron star ?
Super Red Giant
1) Once a high mass main sequence star runs out of helium to fuse, it will start fusing heavier and heavier elements.
2) The radiational pressure will begin to increase dramatically causing the star to expand outwards creating a super red giant.
3) The star will keep fusing heavier and heavier elements together until an iron core is formed where no more energy can be got from fusion.
Super Nova
4) The radiational pressure reduces which causes the star to collapse in on itself but instead the star bounces off this iron core resulting in a huge explosion called a super nova.
5) This super nova will cause fusion of the heaviest elements.
Neutron Star or Black Hole.
6) The remaining matter will collapse in on itself due to the low gas and radiation pressure to form an incredibly dense Neutron Star or, if the mass is high enough, a Black Hole.
What are the two main forces action on a star?
1) Gravitational forces
2) Radiation and gas pressure (Radiational pressure)
What is a light year?
The distance a particle of light travels in a year in a vacuum.
Why do higher mass planets tend to have more moons?
They have a wider gravitational field that allows it to attract more masses that will collate together to form a moon in its obit.
What is the relationship between orbital radius and orbital period for the planets?
The higher radius is for an orbit, the longer the orbital period is as there is more distance to cover in the orbital circumference.
What two gases are all stars made from?
Hydrogen and Helium
