Astrophysics Flashcards
What is the Universe?
Large collection of billions of galaxies
What is a Galaxy?
Large collection of stars
What are Planets? Many Vampires Eat Mothers Joyfully So Undress Now
•Large objects that orbit the Sun in circular orbits •There are 8 planets : Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune
What are Dwarf Planets and give an example?
- Plant like objects that aren’t big enough to be planets
* E.g. Pluto
What are Moons?
- Orbit planets with circular orbits
* Type of Natural satellite
What are Artificial Satellite?
- Ones humans have built
* Orbit Earth in circular orbits
What are Asteroids?
- Lumps of rock and metal that orbit the Sun
* Found in asteroid belt
What are Comets?
- Lumps of ice and dust that orbit the Sun
- Orbits are highly elliptical
- Some travel from near to Sun to outskirts of our solar system
How does Gravity provide the Force that creates Orbits?
- Object travelling in circle = changes direction = accelerating = there’s a force acting on it
- Centripetal force causing it - causes object to change direction because it’s moving
- Object keeps accelerating towards what its orbiting but velocity travelling in circle
- Gravitational force - gravitational attraction of Sun keeps planets + comets in their orbits
What happens the Closer you get to a Star or Plant?
- Stronger the gravitational force is
* The faster you need to go to remain in orbit
What are the different types of Orbit?
- Moons + planets are slightly elliptical
* Comets have very elliptical elongated orbits with the Sun at one focus
When do Comets travel faster?
- Nearer the sun
* Because increased pull of gravity makes it sped up the closer it gets to the sun
What are Geostationary Satellites and what are they Useful for?
- Artificial Earth satellites have orbital period of one day
- Useful in communications because they’re always over same part of plant
What is a Nebula?
Stars initially form from a cloud of dust and gas called nebula
What is a Protostar?
Force of gravity pulls gas/dust together to form a protostar
How is a Star Born from a Protostar?
- Temp rises as star gets denser and more particles collide
- High enough temp = hydrogen nuclei undergo nuclear fusion to form helium nuclei
- Give our a lot of energy, keeping core of star hot
- Star is born
What is a Main Sequence Star?
- Star enters long stable period - outward pressure caused by thermal expansion balances the force of gravity pulling everything inwards = main sequence star
- Heavier star = shorter its time on main sequence
What is a Red Giant and Red SuperGiant?
- Hydrogen in core runs out + force is larger than pressure of thermal expansion
- Stars compressed, until it’s dense + hot so energy makes outer layers of Star expand
- Red giant = smaller star
- Red supergiant = larger star
- Red because surface cools
What is a White Dwarf?
- Small star becomes unstable + ejects outer layers of dust + gas
- Leaves behind hot, dense solid core = a white dwarf
What is a SuperNova?
- Big stars glow brightly again as undergo more fusion to make heavier elements
- They expand + contract several times
- Balance shifts between gravity + thermal expansion
- They explode in supernova
What is a Neutron Star and a Black Hole?
- Exploding supernova throws outer layers of dust + gas
- Leaves dense core = neutron Star
- If Star is massive enough, it will collapse and become a black hole - super dense
What is Sequence of Star that has a Low Mass?
- Nebula
- Protostar
- Main sequence star
- Red giant
- White dwarf
What is Sequence of Star that has a High Mass?
- Nebula
- Protostar
- Main sequence star
- Red supergiant
- Supernova
- Neutron Star or black hole
What does a Stars Brightness depend on?
- It’s size + temperature + distance from Earth + absolute magnitude
- Bigger star + hotter star + closer to Earth + lower absolute magnitude = brighter
