Unit 2: Astronomy Flashcards
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.
What is the tilt of Earth’s axis?
Earth’s axis is tilted to about 23.5 degrees.
How long does a complete cycle of the moon take?
29.5 Days
Perigee
The closest point in the Moon’s orbit to the Earth
Apogee
The furthest point in the Moon’s orbit to the Earth
Nuclear Fusion
The process of combing two Hydrogen molecules to form a Helium molecule.
Some neutrons are lost and released as energy which is what creates solar energy.
Corona
Outer layer that creates solar wind
It’s temperature can go over 1 million degrees Celsius
Photosphere
Surface layer that is responsible for most of the Sun’s visible light.
Its temperature is about 6,000 degrees Celsius.
Sunspots
Cooler areas of the Sun’s surface that appear darker
The study of sunspots lead to the discovery that the Sun rotates
Solar Flares
Explosive outbursts from the Sun containing UV rays, radio waves, and x-ray radiation that take about one day to reach Earth.
Differential Heating
Land and water surfaces absorb heat at different rates.
Land absorbs heat quickly but cools quickly too.
Water absorbs heat slowly but also cools slowly.
Electromagnetic Radiation
Heat energy from the Sun
What is Solar Radiation composed of?
40% at wavelengths of infrared (IR) or longer
50% at visible wavelengths
10% at wavelengths of ultraviolet (UV)
What is the Electromagnetic Spectrum?
In terms of shortest wavelength to longest wavelength Gamma Rays X-Rays UV Rays Visible Light (ROYGBIV) Infrared Waves Radio Waves
What parts of the atmosphere absorb gamma rays, x-rays, and ultraviolet rays?
The Thermosphere and Mesosphere
What part of the atmosphere absorbs UV rays?
The Stratosphere
True or false:
Infrared radiation can be absorbed by carbon dioxide and water vapor.
True
Totals of Solar Energy
20% of energy is absorbed by the atmosphere
30% of energy is scattered back to space
50% of energy is absorbed by Earth’s surface
Solar Winds
A continuous stream of electrically charged particles that are given off by the Sun’s magnetic field
It takes solar winds 4.5 days to reach Earth.
Spring Tide
When the difference between high tides and low tides is the greatest.
Occurs during a tidal bulge
Neap Tide
When the difference between a high tide and a low tide is the highest.
