Astronomy Ch 1

Front 1

Right Ascension

Back 1

The angular distance measured eastward around the sky from the vernal equinox.

Front 2

Declination

Back 2

The angular distance measured north or south from the celestial equator.

Front 3

Laws of Physics

Back 3

Approximate descriptions of what is observed in the physical world.

Front 4

Degrees

Back 4

1/360th of the circumfrence of a circle.

Front 5

Arcminute

Back 5

1/60th of a degree.

Front 6

Arcsecond

Back 6

1/60th of an arcminute, or 1/3600th of a degree.

Front 7

Celestial Equator

Back 7

The great circle on the celestial sphere, every point of which is exactly 90 degrees from the celestial poles.

Front 8

Vernal Equinox

Back 8

A point on the celestial sphere which astronomers use as the origin of the celestial coordinate system.

Front 9

Astronomy

Back 9

The study of extraterrestrial bodies and related aspects of the physical universe.

Front 10

Physical Universe

Back 10

Everything that can be sensed, measured, or observed.

Front 11

The Solat System

Back 11

A gravitationally bound system consisting of the Suna and all its satellites. Radius = 1 LY

Front 12

The Solar Neighborhood

Back 12

All of the stars within 100 parsecs of the Sun (or Solar System).

Front 13

The Milky Way Galaxy

Back 13

A gigantic, gravitationally bound system consisting of about 200 billion stars, including the Sun and Solar Neighborhood.

Front 14

The Local Group

Back 14

A gravitationally bound cluster of about 28 or so galaxies, including the Milky Way Galaxy.

Front 15

The Supercluster

Back 15

A cluster of many smaller clusters of galaxies, including our Local Group.

Front 16

The Universe, or Cosmos

Back 16

The largest scale of physical reality, consisting of other clusters and superclusters of galaxies, extending in a frothy-like distribution to the limit of visibility.

Front 17

Meter (m)

Back 17

One millionth of the distance between the pole and the equator of the Earth.

Front 18

Kilometer (km)

Back 18

One thousand meters

Front 19

Astronomical Unit (AU ot au)

Back 19

The average or mean distance of the Earth from the Sun.

Front 20

Light Year

Back 20

The distance that light travels in the time of one year.

Front 21

Parsec (pc)

Back 21

When the Earth is one parsec from the Sun, the Earth's orbital radius subtends an angle of 1 arcsecond.

Front 22

Rotation

Back 22

The motion of a body around and imaginary axis which passes through that body.

Front 23

Revolution

Back 23

The orbital motion of a body around a point called the center of gravity, or barycenter.

Front 24

Precession

Back 24

The wobbling motion of the axis of rotation.

Front 25

Terrestrial- Lunar Motion

Back 25

The Earth and Moon interact gravitationally in such a way that their individual centers revolve around a common center of gravity once every 27.33 days, or one sidereal month.

Front 26

Planet

Back 26

A type of body that moves in orbit around a star.

Front 27

Star

Back 27

A very hot, usually gaseous body that generates, or at one time did generate, energy through thermonuclear fusion of hydrogen into helium.

Front 28

Mass

Back 28

The amount of matter in a body.

Front 29

Size

Back 29

The dimension of a something, such as raduis, diameter, or volume.

Front 30

Density

Back 30

The amount of mass in a given volume.

Front 31

Satellite

Back 31

A body which moves in orbit around another more massive body.

Front 32

Weight

Back 32

An expression of the force of gravity between an object and another body.

Front 33

Force

Back 33

Something that causes an acceleration or change in velocity of an object.

Front 34

Gravity

Back 34

The force of attraction that exists between any two physical objects.

Front 35

Electromagnetism

Back 35

The force that dictates the structure and workings of an atom (the arrangement of electrons around the nucleus) and the interaction of radiation with matter.

Front 36

Nuclear or Strong Force

Back 36

The force that dictates the structure and workings of the nucleus of an atom, including nuclear reactions

Front 37

The Weak Interactions

Back 37

The force that expresses the interaction of subatomic particles including radioactive decay.

Front 38

Newton's First Law of Motion (the Law of Inertia)

Back 38

A motion of an object will remain constant until it is acted on by an unbalanced force.

Front 39

Newton's Second Law of Motion

Back 39

When an unbalanced force acts on an object, it produces an acceleration. The more massive the object, the smaller the acceleration will be. (a=f/m)

Front 40

Newton's Third Law of Motion

Back 40

When any two objects interact, they exert equal but oppositely directed forces on one another.

Front 41

The Celestial Sphere

Back 41

An imaginary sphere with the Earth at its center on which every object in the sky has a location