Unit 2: Astronomy Flashcards
(44 cards)
What is the Big Bang Theory?
The theory that the universe was the size of a penny and 15 billion years ago it suddenly started expanding outward very quickly.
What is a Nebula?
A nebula is a giant cloud of gas and dust.
Nebulae form from gas and dust thrown out by the explosion of a dying star.
Nebular Hypothesis
The theory that out solar system originated from the collapse of a nebula.
Came from Kant (Immanuel Kant) and Laplace (Pierre Simon Laplace) in the 1800’s.
Galaxy
Groups of stars, dusts, and gases, held together by gravity.
Universal Hierarchy
Universe
Galaxy
Solar System
Planets
Geocentric Model
The Earth is motionless and the center of the universe with everything revolving around it.
Heliocentric Model
The Sun is motionless and it the center of the universe with everything revolving around it.
Copernicus
Came up with the heliocentric model
Johannes Kepler (1600)
Came up the three planetary laws of motion and determined that the planets orbit the sun in and ellipse not a circle.
Kepler’s First Law
Stated that the orbits of the planets are elliptical
The sun is one of the foci of the ellipse
The major axis is the line that goes through both ends of the ellipse and the both foci
Each planet has a different orbital size
Astronomical Units
A planets average distance from the Sun
Kepler’s Second Law
A line between the sun and a planet sweeps equal areas in equal times.
Kepler’s Third Law
Kepler discovered a relationship between a planet’s ellipse and its orbital period.
P^2=a^3
P is a unit of time measured in Earth years, and a is a unit of length measured in astronomical units.
Eccentricity
The length of the major axis of the elliptical orbit
Perihelion
The point where a planet is closest to the Sun in its orbit
Aphelion
The point where a planet is the farthest away from the Sun in its orbit
What is the speed of light?
670,000,000 miles per hour
Precession
A wobble in Earth’s rotation. A slow motion of Earth’s axis that traces out a cone over a period of 26,000 years.
Caused by the gravitational pull of the sun and moon on Earth.
The change in direction of the axis not the change in the tilt.
Think of a spinning top.
Nutation
A wiggle of the precessional axis
1/2 degree change in tilt every 9 years
Takes 18 years for a cycle to complete
Causes El Nino and La Nina (increases seasonal effects)
Occurs due to the gravitational pull of the moon
Barycenter
The common center of mass which two or more objects revolve around
The Sun also rotates around a center of mass due to the pull of the planets
Rotation
The turning or spinning of an object on its axis
Gives us day and night
Revolution
A planets orbit around the sun
Solar Day
The time period from sunrise to sunset
What is the shape of the Earth?
The Earth is not a perfect sphere but is instead a sphere that is flattened at the poles and has a bulge around the equator. Earth’s circumference is bigger around the equator than around the poles because of the poles.
