Chapter 1-5 Definitions
zodiac
A band around the sky extending about 9 degrees above and below the ecliptic in which the Sun, Moon, and planets are always found
Scientific Argument
A careful presentation of hypothesis and evidence in a logical discussion
archaeoastronomy
A combination of archaeology and astronomy
Horoscope
A diagram showing the location of the Sun, Moon, and planets are always found.
Galaxy
A great cloud of stars, gas, and dust held together by the combined gravity of all of its matter.
Total lunar eclipse
A lunar eclipse in which the Moon completely enters Earth's dark shadow
Partial Lunar Eclipse
A lunar eclipse in which the Moon does not completely cover the Sun.
penumbral lunar eclipse
A lunar eclipse in which the Moon enters the penumbra of Earth's shadow but does not reach the umbra.
Flux
A measure of the light energy from a star that hits a collecting area of one square meter in one second.
Diamond ring effect
A momentary phenomenon seen during some total solar eclipses when the ring of the corona and a bright spot of photosphere resemble a large diamond set in a silvery ring.
Star
A self luminous ball of hot gas
total solar eclipse
A solar eclipse in which the Moon completely covers the bright surface of the Sun
partial solar eclipse
A solar eclipse in which the Moon does not completely cover the Sun.
Annular Eclipse
A solar eclipse in which the solar photosphere appears around the edge of the Moon in a bright ring, or annulus. The corona, chromosphere, and prominences cannot be seen.
Chromosphere
A thin layer of bright gas above the photosphere.
Geocentric Universe
A universe which has the Earth at the center
Heliocentric Universe
A universe which has the Sun at the center
Saros Cycle
An 18 year 11 1/3 day period after which the patent of lunar and solar eclipses repeats.
What is an Astronomical Unit?
An astronomical unit or an au is the average distance between the Earth and the sun. So the distance from the Sun to the Earth is 1 AU.
International Astronomical Union
An international society of astronomers that, among other activities, decides definitions and naming conventions for celestial objects and surface features. The IAU defined the constellation boundaries in 1930 and reclassified Pluto as a dwarf planet in 2006.
Dwarf Planet
An object that orbits the Sun and has pulled itself into a spherical shape but has not cleared its orbital lane of other objects.
eccentric
An off center circular path.
Evening Star
Any planet visible in the evening sky
Morning Star
Any planet visible in the sky shortly before sunrise
Empirical
Describes a phenomenon without explaining why it occurs.
Formula to convert difference between magnitude and flux
F(A)/F(B)= (Given #) ^ (mb-ma) mb - ma = (Given #) log (FA/FB)
Corona
Hands down my favorite beer (jk). The faint outer atmosphere of the Sun; composed of low-density, very hot, ionized gas. On Venus, round network of fractures and ridges up to 1000 km in diameter, caused by the intrusion of madam below the crust.
solar eclipse
Occurs when the Moon moves between Earth and the Sun
Constellations
One of the stellar patterns identified by name, usually of mythological gods, people, animals, or objects; also, the region of the sky containing that star pattern.
extrasolar planets
Planets that aren't in the solar system that are orbiting around other stars in the universe
First Principle
Something that is held to be obviously true and needs no further examination
Ecliptic
The apparent path of the Sun against the background of stars.
Photosphere
The bright visible surface of the Sun.
Apparent Visual Magnitudes (mv)
The brightness of star as seen by Human eyes on Earth
Lunar phase cycle
The changing appearance of the Moon as it revolves around the Earth
Uniform circular motion
The classical belief that the perfect heavens could move only by the combination of constant motion along circular orbits.
Lunar Eclipse
The darkening of the Moon as it moves through Earths shadow
Light Year
The distance that light travels in one year, approximately 9.5 x 10 ^12
Prominences
The eruptions that on the solar surface that mark the chromosphere.
Milky way
The great, cloudy wheel of stars ringing our sky (Our Galaxy).
Line of Nodes
The line across an orbit connecting the nodes; commonly applied to the orbit of the Moon.
Small angle formula
The mathematical formula that relates an object's linear diameter and distance to its angular diameter.
Revolution
The motion of a body around a point outside the body
Perigee
The orbital point of closest approach from Earth.
Apogee
The orbital point of greatest distance from Earth.
Totality
The period during a solar eclipse when the Sun's photosphere is completely hidden by the Moon, or the period during a lunar eclipse when the Moon is completely inside the umbra of Earth's shadow.
Autumnal equinox
The point where the Sun crosses the celestial sphere going Southward.
Winter solstice
The point where the Sun is furthest south
Summer solstice
The point where the Sun is the farthest North
Penumbra
The portion of a shadow that is only partially shaded
Precession
The slow moments of the celestial poles and equator across the sky.
Path of Totality
The track of the Moon's umbral shadow over Earth's surface. The Sun is totally eclipsed as seen from within this path.
Rotation
The turning of a body on its axis
Nodes
The two points where the Moon crosses the ecliptic
Vernal equinox
When point where the Sun crosses the celestial equator going northward .
Perihelion
When the Earth is at its closest point to the Sun
Aphelion
When the Earth is at its most distant point from the Sun
Eclipse Season
When the Sun is close to a node in the Moon's orbit.
Kepler's Three Laws of Planetary Motion
1. The orbits of the planets are ellipses with the Sun at one focus 2. A line from a planet to the Sun sweeps over equal areas in equal intervals of time 3. A planet's orbital period squared is proportional to its average distance from the Sun cubed Pyr^2=aAU^3
The Three Important Principles of the Sky
1. The sky appears to rotate westward around Earth each day, but that is a consequence of the eastward rotation of Earth. That rotation produces day and night. 2. Astronomers measure angular distance across the sky as angles and express them as degrees, arc minutes, and arc seconds. 3.What you can see of the sky depends on where you are on Earth. If you live in Australia, you can see many stars, constellations, and asterisms invisible from North America, but you would never see the Big Dipper