# Physics - Objects in the Universe

> Source: https://ollybritton.com/notes/a-level/physics/topics/objects-in-the-universe/ · Updated: 2022-01-18 · Tags: school, physics, astrophysics

## Flashcards
### 2022-01-18
##### What are the four characteristics of a planet (ORFC)??
1. It is in __O__rbit around a star
2. It has a mass large enough that gravity makes it __R__ound
3. It has no __F__usion reactions
4. It has __C__leared its orbit of most other objects

##### What is the difference between a planet and a dwarf planet??
A dwarf planet has not cleared its neighbourhood.

##### What is an asteroid??
An small, uneven and un-icy object that orbits the sun.

##### What are planetary satellites??
A body in orbit around a planet.

##### What are the two big categories of planetary satellites??
* Moons
* Satellites

##### What are comets??
Small, icy and irregular bodies made up of ice that orbit the sun in mainly eccentric elliptical orbits.

##### What sort of orbit does a comet have??
Highly eccentric and elliptical.

##### What are the two main differences between an asteroid and a comet??
* Comets are icy, whereas asteroids aren't.
* Comets have highly eccentric and elliptical orbits, whereas asteroids have near-circular orbits.

##### What is a solar system??
One or more stars with planets orbiting.

##### What is the mnemonic for the order of the planets??
* My
* Very
* Eager
* Mother
* Just
* Served
* Us
* Noodles

##### What is the order of planets from the sun??
* Mercury
* Venus
* Earth
* Mars
* Jupiter
* Saturn
* Uranus
* Neptune

##### What is a nebula??
A giant, diffuse cloud of dust and gas.

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