Where are we in the Universe? Flashcards
What is a star?
A star is a large, glowing ball of gas that generates light and heat through nuclear fusion in its core. The sun is a star.
What is a planet?
A planet is a moderately large object that orbits a star and shines primarily by reflecting the light of its star.
What are the three criterion of a star?
- It orbits a star
- Is large enough for its gravity to make it round.
- has cleared most objects from its orbital path.
What is a dwarf planet?
This is a planet that has satisfied the first two but not the last criterion of being a planet. An example of this is Pluto.
What is a moon?
This is an object that orbits a planet. It also referred to as a satellite.
What is a satellite?
A satellite is an object that orbits another object.
What is an asteroid?
An asteroid is a relatively small and rocky object that orbits a star.
What is a comet?
A comet is a relatively small icy-rich body that orbits a star.
What is a small solar system body?
A small solar system body consists of an asteroid, a comet or any other objects that orbits a star but is too small to qualify as a planet or a dwarf planet
What is a solar system?
A solar system consists of the sun and all other material that orbits it including planets, dwarf planets, and small solar system bodies.
What is a star system?
A star system consists of a star(s) and any planets and any other materials that orbit it.
What is a galaxy?
A galaxy is a great island of stars that are held together by their own gravity and orbit a common centre with a total mass that is equal to millions, billions and even trillions of stars.
What is a cluster of galaxies?
A cluster of galaxies is collection of galaxies found together by gravity.
What is a group of galaxies?
A group of galaxies is a small collection of galaxies that are held together by gravity.
What is a supercluster of galaxies?
A supercluster of galaxies is a gigantic region of space where many groups and clusters of galaxies are packed more closely together than elsewhere in the universe.
What is the universe?
The universe is the sum total of all matter and energy. That is, all galaxies and everything within them.
What is the observable universe?
The observable universe is the portion of the entire universe that can be seen from earth. It is probably only a small portion of the entire universe.
What is an Astronomical Unit?
This is the average distance between the earth and the sun. It is about 150 million kilometres. it is also the measurement of the semi major axis of the earth’s orbit.
What is a light year?
A light year is the distance that light can travel in one year. It is about 10 trillion kilometres (more precisely 9.46 trillion kilometres).
What is rotation?
This is the spinning of the earth around its axis. For example, earth rotates once each day around its axis.
What is an orbit? What is another name for it?
This is the orbital motion of one object around another due to gravity. For example, earth orbit the sun once each year.
What is the expansion of the universe?
This is the increase in the average distance between galaxies as time progresses.
What is an axis?
This is an imaginary lines that connects the north and south poles.
How old is the universe?
The universe is about 14 billion years old.
