The Universe - Terms to definitions Flashcards
What is the universe?
Everything, including all space, matter, and energy.
What is the sun?
The star in the center of our solar system.
What is a planet?
A celestial body that orbits a star, has enough mass to form into a round shape, and has cleared its orbit of any objects of similar size.
What is an orbit?
The elliptical path of a celstial object or spacecraft around a star, planet, or moon.
What is a solar system?
A group of planets and other bodies that revolve around a star.
What is a galaxy?
A concentration of stars, gas, dust, and dark matter held together by gravity.
What is a moon?
An object that orbits a planet or something else that is not a star.
What is a star?
A large celestial body made mostly of hydrogen and helium which produces light and heat from the churning nuclear forces insied its core.
What is absolute magnitude
The brightness of a star as seen from 10 parsecs away.
What is apparent magnitude?
How bright a star looks from earth.
How much is a light year?
9.46 trillion km
The distance that light travels in a year
How much is an Astronomical Unit (AU)?
150 million km
The radius of earth’s orbit
How much is a parsec (PC)?
3.2 light years
206,265 AU
30.9 trillion km
The distance at which one AU subtends an angle of one arc second (1/3600°)
What is Hubble’s Law?
v = HD
H = hubble’s constant
D = distance
v = recessional velocity
Hubble’s law says that the further away an object, the faster it is moving away.
What is the doppler effect?
The shift in a wave’s frequency when its source is moving closer (higher) or away (lower).
What is red shift and blue shift
Red shift and blue shift are the result of the doppler effect when a source of light is moving closer (blue) or away (red).
What is a black hole?
A region of space in which nothing can escape because of its strong gravitational pull.
What is an event horizon?
A boundary around a black hole which nothing can escape.
What is a singularity?
The centre of a black hole, which has infinite density.
What is a photon sphere?
A region around a black hole where light orbits in a circular path.
