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