Term
|
Definition
| the angle subtended by the diameter of an object. ( Chapter 1) |
|
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Term
|
Definition
The angle between two points in the sky.
( Chapter 1) |
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Term
|
Definition
angular measure The size of an angle, usually expressed in degrees, arcminutes, and arcseconds.
(Chapter 1) |
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Term
|
Definition
One- sixtieth ( 1/ 60) of a degree, designated by the symbol '.
( Chapter 1) |
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Term
|
Definition
One- sixtieth ( 1/ 60) of an arcminute or 1/ 3600 of a degree, designated by the symbol ..
( Chapter 1) |
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Term
|
Definition
The semimajor axis of Earth’s orbit; the average distance between Earth and the Sun.
( Chapter 1) |
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Term
|
Definition
An explosion of all space that took place roughly 13.7 billion years ago and that marks the beginning of the universe.
( Chapter 1) |
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Term
|
Definition
An object whose gravity is so strong that the escape speed exceeds the speed of light.
(Chapter 1) |
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Term
|
Definition
A large assemblage of stars, nebulae, and interstellar gas and dust.
(Chapter 1) |
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Term
|
Definition
One thousand parsecs; about 3260 light- years.
(Chapter 1) |
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Term
|
Definition
A set of physical principles with which we can understand natural phenomena and the nature of the universe.
( Chapter 1) |
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Term
|
Definition
| The distance light travels in a vacuum in one year. ( Chapter 1) |
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Term
|
Definition
One million parsecs.
(Chapter 1) |
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Term
|
Definition
A fragment of a meteoroid that has survived passage through Earth’s atmosphere.
(Chapter 1) |
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Term
|
Definition
| The branch of physics based on Newton’s laws of motion. (Chapter 1) |
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Term
|
Definition
| A unit of distance; 3.26 light- years. (Chapter 1) |
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Term
|
Definition
| A pulsating radio source thought to be associated with a rapidly rotating neutron star. (Chapter 1) |
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Term
|
Definition
| A very luminous object with a very large redshift and a starlike appearance. (Chapter 1) |
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Term
|
Definition
| The International System of Units, based on the meter (m), the second (s), and the kilogram (kg). (Chapter 1) |
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Term
|
Definition
| A relationship between the angular and linear sizes of a distant object. (Chapter 1) |
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Term
|
Definition
| To extend over an angle. (Chapter 1) |
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Term
| supernova ( plural supernovae) |
|
Definition
| A stellar outburst during which a star suddenly increases its brightness roughly a millionfold. (Chapter 1) |
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Term
|
Definition
| A circle of latitude 23 1/ 2 ° north of Earth’s south pole. (Chapter 2) |
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Term
|
Definition
| The interval between two successive transits of the Sun’s center across the local meridian. (Chapter 2) |
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Term
|
Definition
| Time reckoned by the position of the Sun in the sky. ( Chapter 2) |
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Term
|
Definition
| A circle of latitude 23 1/ 2° south of Earth’s north pole. (Chapter 2) |
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Term
|
Definition
| The intersection of the ecliptic and the celestial equator where the Sun crosses the equator from north to south. Also used to refer to the date on which the Sun passes through this intersection. (Chapter 2) |
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Term
|
Definition
| A great circle on the celestial sphere 90° from the celestial poles. (Chapter 2) |
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Term
|
Definition
| An imaginary sphere of very large radius centered on an observer; the apparent sphere of the sky. (Chapter 2) |
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Term
|
Definition
| A term describing a star that neither rises nor sets but appears to rotate around one of the celestial poles. (Chapter 2) |
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Term
|
Definition
| A configuration of stars in the same region of the sky. (Chapter 2) |
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Term
|
Definition
| Angular distance of a celestial object north or south of the celestial equator. (Chapter 2) |
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Term
|
Definition
| Any apparent motion in the sky that repeats on a daily basis, such as the rising and setting of stars. (Chapter 2) |
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Term
|
Definition
| The apparent annual path of the Sun on the celestial sphere. (Chapter 2) |
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Term
|
Definition
The plane of Earth’s orbit around the Sun.
(Chapter 2) |
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Term
|
Definition
| The date used to define the coordinate system for objects on the sky. (Chapter 2) |
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Term
|
Definition
| One of the intersections of the ecliptic and the celestial equator. Also used to refer to the date on which the Sun passes through such an intersection. (Chapter 2) |
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Term
|
Definition
| The half of the meridian that lies below the horizon. (Chapter 2) |
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Term
|
Definition
| The interval between successive meridian passages of the mean Sun; the average length of a solar day. (Chapter 2) |
|
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Term
|
Definition
| A fictitious object that moves eastward at a constant speed along the celestial equator, completing one circuit of the sky with respect to the vernal equinox in one tropical year. (Chapter 2) |
|
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Term
| meridian ( or local meridian) |
|
Definition
| The great circle on the celestial sphere that passes through an observer’s zenith and the north and south celestial poles. (Chapter 2) |
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Term
|
Definition
| The crossing of the meridian by any astronomical object. (Chapter 2) |
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Term
|
Definition
| The point directly above Earth’s north pole where Earth’s axis of rotation, if extended, would intersect the celestial sphere. (Chapter 2) |
|
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Term
|
Definition
The study of the apparent positions of the planets and stars and how those positions change.
(Chapter 2) |
|
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Term
|
Definition
| A slow, conical motion of Earth’s axis of rotation caused by the gravitational pull of the Moon and Sun on Earth’s equatorial bulge. (Chapter 2) |
|
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Term
| precession of the equinoxes |
|
Definition
| The slow westward motion of the equinoxes along the ecliptic due to precession of Earth. (Chapter 2) |
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Term
|
Definition
| A coordinate for measuring the east- west positions of objects on the celestial sphere. (Chapter 2) |
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Term
|
Definition
| A clock that measures sidereal time. (Chapter 2) |
|
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Term
|
Definition
| The interval between successive meridian passages of the vernal equinox. (Chapter 2) |
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Term
|
Definition
| Time reckoned by the location of the vernal equinox. ( Chapter 2) |
|
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Term
|
Definition
| The orbital period of Earth about the Sun with respect to the stars. (Chapter 2) |
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Term
|
Definition
| The point directly above Earth’s south pole where Earth’s axis of rotation, if extended, would intersect the celestial sphere. (Chapter 2) |
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Term
|
Definition
| The point on the ecliptic where the Sun is farthest north of the celestial equator. Also used to refer to the date on which the Sun passes through this point. (Chapter 2) |
|
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Term
|
Definition
| A region on Earth where, by agreement, all clocks have the same time. (Chapter 2) |
|
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Term
|
Definition
| The period of revolution of Earth about the Sun with respect to the vernal equinox. (Chapter 2) |
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Term
|
Definition
| A circle of latitude 231/ 2° north of Earth’s equator. (Chapter 2) |
|
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Term
|
Definition
| A circle of latitude 231/ 2° south of Earth’s equator. (Chapter 2) |
|
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Term
|
Definition
| The half of the meridian that lies above the horizon. (Chapter 2) |
|
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Term
|
Definition
| The point on the ecliptic where the Sun crosses the celestial equator from south to north. Also used to refer to the date on which the Sun passes through this intersection. (Chapter 2) |
|
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Term
|
Definition
| The point on the ecliptic where the Sun reaches its greatest distance south of the celestial equator. Also used to refer to the date on which the Sun passes through this point. (Chapter 2) |
|
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Term
|
Definition
| The point on the celestial sphere directly overhead an observer. (Chapter 2) |
|
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Term
|
Definition
| A band of 12 constellations around the sky centered on the ecliptic. (Chapter 2) |
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Term
|
Definition
| An eclipse of the Sun in which the Moon is too distant to cover the Sun completely, so that a ring of sunlight is seen around the Moon at mid- eclipse. (Chapter 3) |
|
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Term
|
Definition
| The point in its orbit where a satellite or the Moon is farthest from Earth. (Chapter 3) |
|
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Term
|
Definition
| The cutting off of part or all the light from one celestial object by another. (Chapter 3) |
|
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Term
|
Definition
| The track of the tip of the Moon’s shadow along Earth’s surface during a total or annular solar eclipse. (Chapter 3) |
|
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Term
|
Definition
| The interval between successive passages of the Sun through the same node of the Moon’s orbit. (Chapter 3) |
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Term
|
Definition
| The phase of the Moon that occurs when the Moon is 90° east of the Sun. (Chapter 3) |
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Term
|
Definition
| phase of the Moon during which its full daylight hemisphere can be seen from Earth. (Chapter 3) |
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Term
|
Definition
| The line where the plane of Earth’s orbit intersects the plane of the Moon’s orbit. (Chapter 3) |
|
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Term
|
Definition
| An eclipse of the Moon by Earth; a passage of the Moon through Earth’s shadow. (Chapter 3) |
|
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Term
|
Definition
| The appearance of the illuminated area of the Moon as seen from Earth. (Chapter 3) |
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Term
|
Definition
| The phase of the Moon when the dark hemisphere of the Moon faces Earth. (Chapter 3) |
|
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Term
|
Definition
| A lunar eclipse in which the Moon does not appear completely covered. (Chapter 3) |
|
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Term
|
Definition
| A solar eclipse in which the Sun does not appear completely covered. (Chapter 3) |
|
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Term
| penumbra (of a shadow) ( plural penumbrae) |
|
Definition
| The portion of a shadow in which only part of the light source is covered by an opaque body. (Chapter 3) |
|
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Term
|
Definition
| A lunar eclipse in which the Moon passes only through Earth’s penumbra. (Chapter 3) |
|
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Term
|
Definition
| The point in its orbit where a satellite or the Moon is nearest Earth. (Chapter 3) |
|
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Term
|
Definition
| A particular cycle of similar eclipses that recur about every 18 years. (Chapter 3) |
|
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Term
|
Definition
| The period of the Moon’s revolution about Earth with respect to the stars. (Chapter 3) |
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Term
|
Definition
| Hot, faintly glowing gases seen around the Sun during a total solar eclipse; the uppermost regions of the solar atmosphere. (Chapter 3) |
|
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Term
|
Definition
| An eclipse of the Sun by the Moon; a passage of Earth through the Moon’s shadow. (Chapter 3) |
|
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Term
|
Definition
| The rotation of a body with a period equal to its orbital period; also called 1- to- 1 spin- orbit coupling. (Chapter 3) |
|
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Term
|
Definition
| The period of revolution of the Moon with respect to the Sun; the length of one cycle of lunar phases. Also called the lunar month. (Chapter 3) |
|
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Term
|
Definition
| The phase of the Moon that occurs when the Moon is 90° west of the Sun. (Chapter 3) |
|
|
Term
| totality ( lunar eclipse) |
|
Definition
| The period during a total lunar eclipse when the Moon is entirely within Earth’s umbra. (Chapter 3) |
|
|
Term
| totality ( solar eclipse) |
|
Definition
| The period during a total solar eclipse when the disk of the Sun is completely hidden. (Chapter 3) |
|
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Term
|
Definition
| A lunar eclipse during which the Moon is completely immersed in Earth’s umbra. (Chapter 3) |
|
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Term
|
Definition
| A solar eclipse during which the Sun is completely hidden by the Moon. (Chapter 3) |
|
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Term
| umbra ( of a shadow) ( plural umbrae) |
|
Definition
| The central, completely dark portion of a shadow. (Chapter 3) |
|
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Term
|
Definition
| The phase of the Moon that occurs between third quarter and new moon. (Chapter 3) |
|
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Term
|
Definition
| The phase of the Moon that occurs between full moon and third quarter. (Chapter 3) |
|
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Term
|
Definition
| The phase of the Moon that occurs between new moon and first quarter. (Chapter 3) |
|
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Term
|
Definition
| The phase of the Moon that occurs between first quarter and full moon. (Chapter 3) |
|
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Term
|
Definition
| The rate at which an object’s velocity changes due to a change in speed, a change in direction, or both. (Chapter 4) |
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Term
|
Definition
| The point in its orbit where a planet is farthest from the Sun. (Chapter 4) |
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Term
|
Definition
| The curve of intersection between a circular cone and a plane; this curve can be a circle, ellipse, parabola, or hyperbola. (Chapter 4) |
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Term
|
Definition
| The geometric arrangement of a planet in the same part of the sky as the Sun, so that the planet is at an elongation of 0°. (Chapter 4) |
|
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Term
|
Definition
| A stationary circle in the Ptolemaic system along which another circle ( an epicycle) moves, carrying a planet, the Sun, or the Moon. (Chapter 4) |
|
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Term
|
Definition
| The apparent eastward movement of a planet seen against the background stars. (Chapter 4) |
|
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Term
|
Definition
| A number between 0 and 1 that describes the shape of an ellipse. (Chapter 4) |
|
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Term
|
Definition
| A conic section obtained by cutting completely through a circular cone with a plane. (Chapter 4) |
|
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Term
|
Definition
| The angular distance between a planet and the Sun as viewed from Earth. (Chapter 4) |
|
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Term
|
Definition
| A moving circle in the Ptolemaic system about which a planet revolves. (Chapter 4) |
|
|
Term
| focus ( of an ellipse; plural foci) |
|
Definition
| One of two points inside an ellipse such that the combined distance from the two foci to any point on the ellipse is a constant. (Chapter 4) |
|
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Term
|
Definition
| An Earth-centered theory of the universe. |
|
|
Term
| greatest eastern elongation |
|
Definition
The configuration of an inferior planet at its greatest angular distance east of the Sun.
(Chapter 4) |
|
|
Term
| greatest western elongation |
|
Definition
The configuration of an inferior planet at its greatest angular distance west of the Sun.
(Chapter 4) |
|
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Term
|
Definition
| A conic section formed by cutting a circular cone with a plane at an angle steeper than the sides of the cone. (Chapter 4) |
|
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Term
|
Definition
| The configuration when an inferior planet is between the Sun and Earth. (Chapter 4) |
|
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Term
|
Definition
planet that is closer to the Sun than Earth is.
(Chapter 4) |
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Term
|
Definition
| The statement that each planet moves around the Sun in an elliptical orbit with the Sun at one focus of the ellipse. (Chapter 4) |
|
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Term
|
Definition
The statement that a planet sweeps out equal areas in equal times as it orbits the Sun; also called the law of equal areas.
(Chapter 4) |
|
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Term
|
Definition
| A relationship between the period of an orbiting object and the semimajor axis of its elliptical orbit. (Chapter 4) |
|
|
Term
| law of universal gravitation |
|
Definition
| formula deduced by Isaac Newton that expresses the strength of the force of gravity that two masses exert on each other. (Chapter 4) |
|
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Term
|
Definition
| An ocean tide that occurs when the Moon is near first-quarter or third- quarter phase. (Chapter 4) |
|
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Term
|
Definition
| The branch of physics based on Newton’s laws of motion. ( Chapter 1, Chapter 4) |
|
|
Term
| Newton’s first law of motion |
|
Definition
| The statement that a body remains at rest, or moves in a straight line at a constant speed, unless acted upon by a net outside force; the law of inertia. (Chapter 4) |
|
|
Term
| Newton’s form of Kepler’s third law |
|
Definition
| A relationship between the period of two objects orbiting each other, the semimajor axis of their orbit, and the masses of the objects. (Chapter 4) |
|
|
Term
| Newton’s second law of motion |
|
Definition
| relationship between the acceleration of an object, the object’s mass, and the net outside force acting on the mass. (Chapter 4) |
|
|
Term
| Newton’s third law of motion |
|
Definition
The statement that whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body.
(Chapter 4) |
|
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Term
|
Definition
| The notion that a straightforward explanation of a phenomenon is more likely to be correct than a convoluted one. (Chapter 4) |
|
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Term
|
Definition
| The configuration of a planet when it is at an elongation of 180° and thus appears opposite the Sun in the sky. (Chapter 4) |
|
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Term
|
Definition
A conic section formed by cutting a circular cone at an angle parallel to one of the sides of the cone.
(Chapter 4) |
|
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Term
|
Definition
| The apparent displacement of an object due to the motion of the observer. (Chapter 4) |
|
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Term
|
Definition
| The point in its orbit where a planet or comet is nearest the Sun. (Chapter 4) |
|
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Term
|
Definition
| The interval of time between successive geometric arrangements of a planet and an astronomical object, such as the Sun. ( Chapter 4) |
|
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Term
|
Definition
| The definitive version of the geocentric cosmogony of ancient Greece. (Chapter 4) |
|
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Term
|
Definition
The apparent westward motion of a planet with respect to background stars.
(Chapter 4) |
|
|
Term
| semimajor axis ( of an ellipse) |
|
Definition
One- half of the major axis of an ellipse.
(Chapter 4) |
|
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Term
|
Definition
| The orbital period of one object about another as measured with respect to the stars. (Chapter 4) |
|
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Term
|
Definition
| Distance traveled divided by the time elapsed to cover that distance. (Chapter 4) |
|
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Term
|
Definition
| An ocean tide that occurs at new moon and full moon phases. ( Chapter 4) |
|
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Term
|
Definition
| The configuration of a planet being behind the Sun as viewed from Earth. ( Chapter 4) |
|
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Term
|
Definition
planet that is more distant from the
Sun than Earth is. (Chapter 4) |
|
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Term
|
Definition
The interval between successive occurrences of the same configuration of a planet.
(Chapter 4) |
|
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Term
|
Definition
A gravitational force whose strength and/ or direction varies over a body and thus tends to deform the body.
(Chapter 4) |
|
|
Term
| universal constant of gravitation |
|
Definition
The constant of proportionality in Newton’s law of gravitation.
( Chapter 4) |
|
|
Term
|
Definition
| The speed and direction of an object’s motion. (Chapter 4) |
|
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Term
|
Definition
A cloud of interstellar gas and dust.
(Chapter 1) |
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|
