{"id":216,"date":"2022-02-11T15:56:01","date_gmt":"2022-02-11T15:56:01","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/astronomy\/?post_type=chapter&p=216"},"modified":"2022-02-11T16:22:45","modified_gmt":"2022-02-11T16:22:45","slug":"key-terms","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/astronomy\/chapter\/key-terms\/","title":{"raw":"Key Terms","rendered":"Key Terms"},"content":{"raw":"
\r\n
\r\n \t
angular momentum<\/dt>\r\n \t
the measure of the motion of a rotating object in terms of its speed and how widely the object\u2019s mass is distributed around its axis<\/dd>\r\n<\/dl>\r\n
\r\n \t
aphelion<\/dt>\r\n \t
the point in its orbit where a planet (or other orbiting object) is farthest from the Sun<\/dd>\r\n<\/dl>\r\n
\r\n \t
apogee<\/dt>\r\n \t
the point in its orbit where an Earth satellite is farthest from Earth<\/dd>\r\n<\/dl>\r\n
\r\n \t
asteroid belt<\/dt>\r\n \t
the region of the solar system between the orbits of Mars and Jupiter in which most asteroids are located; the main belt, where the orbits are generally the most stable, extends from 2.2 to 3.3 AU from the Sun<\/dd>\r\n<\/dl>\r\n
\r\n \t
astronomical unit (AU)<\/dt>\r\n \t
the unit of length defined as the average distance between Earth and the Sun; this distance is about 1.5 \u00d7 108<\/sup>\u00a0kilometers<\/dd>\r\n<\/dl>\r\n
\r\n \t
density<\/dt>\r\n \t
the ratio of the mass of an object to its volume<\/dd>\r\n<\/dl>\r\n
\r\n \t
eccentricity<\/dt>\r\n \t
in an ellipse, the ratio of the distance between the foci to the major axis<\/dd>\r\n<\/dl>\r\n
\r\n \t
ellipse<\/dt>\r\n \t
a closed curve for which the sum of the distances from any point on the ellipse to two points inside (called the foci) is always the same<\/dd>\r\n<\/dl>\r\n
\r\n \t
escape speed<\/dt>\r\n \t
the speed a body must achieve to break away from the gravity of another body<\/dd>\r\n<\/dl>\r\n
\r\n \t
focus<\/dt>\r\n \t
(plural: foci) one of two fixed points inside an ellipse from which the sum of the distances to any point on the ellipse is constant<\/dd>\r\n<\/dl>\r\n
\r\n \t
gravity<\/dt>\r\n \t
the mutual attraction of material bodies or particles<\/dd>\r\n<\/dl>\r\n
\r\n \t
Kepler\u2019s first law<\/dt>\r\n \t
each planet moves around the Sun in an orbit that is an ellipse, with the Sun at one focus of the ellipse<\/dd>\r\n<\/dl>\r\n
\r\n \t
Kepler\u2019s second law<\/dt>\r\n \t
the straight line joining a planet and the Sun sweeps out equal areas in space in equal intervals of time<\/dd>\r\n<\/dl>\r\n
\r\n \t
Kepler\u2019s third law<\/dt>\r\n \t
the square of a planet\u2019s orbital period is directly proportional to the cube of the semimajor axis of its orbit<\/dd>\r\n<\/dl>\r\n
\r\n \t
major axis<\/dt>\r\n \t
the maximum diameter of an ellipse<\/dd>\r\n<\/dl>\r\n
\r\n \t
momentum<\/dt>\r\n \t
the measure of the amount of motion of a body; the momentum of a body is the product of its mass and velocity; in the absence of an unbalanced force, momentum is conserved<\/dd>\r\n<\/dl>\r\n
\r\n \t
Newton\u2019s first law<\/dt>\r\n \t
every object will continue to be in a state of rest or move at a constant speed in a straight line unless it is compelled to change by an outside force<\/dd>\r\n<\/dl>\r\n
\r\n \t
Newton\u2019s second law<\/dt>\r\n \t
the change of motion of a body is proportional to and in the direction of the force acting on it<\/dd>\r\n<\/dl>\r\n
\r\n \t
Newton\u2019s third law<\/dt>\r\n \t
for every action there is an equal and opposite reaction (or:<\/em>\u00a0the mutual actions of two bodies upon each other are always equal and act in opposite directions)<\/dd>\r\n<\/dl>\r\n
\r\n \t
orbit<\/dt>\r\n \t
the path of an object that is in revolution about another object or point<\/dd>\r\n<\/dl>\r\n
\r\n \t
orbital period (P<\/em>)<\/dt>\r\n \t
the time it takes an object to travel once around the Sun<\/dd>\r\n<\/dl>\r\n
\r\n \t
orbital speed<\/dt>\r\n \t
the speed at which an object (usually a planet) orbits around the mass of another object; in the case of a planet, the speed at which each planet moves along its ellipse<\/dd>\r\n<\/dl>\r\n
\r\n \t
perigee<\/dt>\r\n \t
the point in its orbit where an Earth satellite is closest to Earth<\/dd>\r\n<\/dl>\r\n
\r\n \t
perihelion<\/dt>\r\n \t
the point in its orbit where a planet (or other orbiting object) is nearest to the Sun<\/dd>\r\n<\/dl>\r\n
\r\n \t
perturbation<\/dt>\r\n \t
a small disturbing effect on the motion or orbit of a body produced by a third body<\/dd>\r\n<\/dl>\r\n
\r\n \t
satellite<\/dt>\r\n \t
an object that revolves around a planet<\/dd>\r\n<\/dl>\r\n
\r\n \t
semimajor axis<\/dt>\r\n \t
half of the major axis of a conic section, such as an ellipse<\/dd>\r\n<\/dl>\r\n
\r\n \t
velocity<\/dt>\r\n \t
the speed and direction a body is moving\u2014for example, 44 kilometers per second toward the north galactic pole<\/dd>\r\n<\/dl>\r\n<\/div>\r\n
This book was adapted from the following: Fraknoi, A., Morrison, D., & Wolff, S. C. (2016). Key Terms. In Astronomy<\/i>. OpenStax. https:\/\/openstax.org\/books\/astronomy\/pages\/3-key-terms under a Creative Commons Attribution License 4.0<\/a><\/div>\r\n
Access the entire book for free at https:\/\/openstax.org\/books\/astronomy\/pages\/1-introduction<\/a><\/div>","rendered":"
\n
\n
angular momentum<\/dt>\n
the measure of the motion of a rotating object in terms of its speed and how widely the object\u2019s mass is distributed around its axis<\/dd>\n<\/dl>\n
\n
aphelion<\/dt>\n
the point in its orbit where a planet (or other orbiting object) is farthest from the Sun<\/dd>\n<\/dl>\n
\n
apogee<\/dt>\n
the point in its orbit where an Earth satellite is farthest from Earth<\/dd>\n<\/dl>\n
\n
asteroid belt<\/dt>\n
the region of the solar system between the orbits of Mars and Jupiter in which most asteroids are located; the main belt, where the orbits are generally the most stable, extends from 2.2 to 3.3 AU from the Sun<\/dd>\n<\/dl>\n
\n
astronomical unit (AU)<\/dt>\n
the unit of length defined as the average distance between Earth and the Sun; this distance is about 1.5 \u00d7 108<\/sup>\u00a0kilometers<\/dd>\n<\/dl>\n
\n
density<\/dt>\n
the ratio of the mass of an object to its volume<\/dd>\n<\/dl>\n
\n
eccentricity<\/dt>\n
in an ellipse, the ratio of the distance between the foci to the major axis<\/dd>\n<\/dl>\n
\n
ellipse<\/dt>\n
a closed curve for which the sum of the distances from any point on the ellipse to two points inside (called the foci) is always the same<\/dd>\n<\/dl>\n
\n
escape speed<\/dt>\n
the speed a body must achieve to break away from the gravity of another body<\/dd>\n<\/dl>\n
\n
focus<\/dt>\n
(plural: foci) one of two fixed points inside an ellipse from which the sum of the distances to any point on the ellipse is constant<\/dd>\n<\/dl>\n
\n
gravity<\/dt>\n
the mutual attraction of material bodies or particles<\/dd>\n<\/dl>\n
\n
Kepler\u2019s first law<\/dt>\n
each planet moves around the Sun in an orbit that is an ellipse, with the Sun at one focus of the ellipse<\/dd>\n<\/dl>\n
\n
Kepler\u2019s second law<\/dt>\n
the straight line joining a planet and the Sun sweeps out equal areas in space in equal intervals of time<\/dd>\n<\/dl>\n
\n
Kepler\u2019s third law<\/dt>\n
the square of a planet\u2019s orbital period is directly proportional to the cube of the semimajor axis of its orbit<\/dd>\n<\/dl>\n
\n
major axis<\/dt>\n
the maximum diameter of an ellipse<\/dd>\n<\/dl>\n
\n
momentum<\/dt>\n
the measure of the amount of motion of a body; the momentum of a body is the product of its mass and velocity; in the absence of an unbalanced force, momentum is conserved<\/dd>\n<\/dl>\n
\n
Newton\u2019s first law<\/dt>\n
every object will continue to be in a state of rest or move at a constant speed in a straight line unless it is compelled to change by an outside force<\/dd>\n<\/dl>\n
\n
Newton\u2019s second law<\/dt>\n
the change of motion of a body is proportional to and in the direction of the force acting on it<\/dd>\n<\/dl>\n
\n
Newton\u2019s third law<\/dt>\n
for every action there is an equal and opposite reaction (or:<\/em>\u00a0the mutual actions of two bodies upon each other are always equal and act in opposite directions)<\/dd>\n<\/dl>\n
\n
orbit<\/dt>\n
the path of an object that is in revolution about another object or point<\/dd>\n<\/dl>\n
\n
orbital period (P<\/em>)<\/dt>\n
the time it takes an object to travel once around the Sun<\/dd>\n<\/dl>\n
\n
orbital speed<\/dt>\n
the speed at which an object (usually a planet) orbits around the mass of another object; in the case of a planet, the speed at which each planet moves along its ellipse<\/dd>\n<\/dl>\n
\n
perigee<\/dt>\n
the point in its orbit where an Earth satellite is closest to Earth<\/dd>\n<\/dl>\n
\n
perihelion<\/dt>\n
the point in its orbit where a planet (or other orbiting object) is nearest to the Sun<\/dd>\n<\/dl>\n
\n
perturbation<\/dt>\n
a small disturbing effect on the motion or orbit of a body produced by a third body<\/dd>\n<\/dl>\n
\n
satellite<\/dt>\n
an object that revolves around a planet<\/dd>\n<\/dl>\n
\n
semimajor axis<\/dt>\n
half of the major axis of a conic section, such as an ellipse<\/dd>\n<\/dl>\n
\n
velocity<\/dt>\n
the speed and direction a body is moving\u2014for example, 44 kilometers per second toward the north galactic pole<\/dd>\n<\/dl>\n<\/div>\n
This book was adapted from the following: Fraknoi, A., Morrison, D., & Wolff, S. C. (2016). Key Terms. In Astronomy<\/i>. OpenStax. https:\/\/openstax.org\/books\/astronomy\/pages\/3-key-terms under a Creative Commons Attribution License 4.0<\/a><\/div>\n
Access the entire book for free at https:\/\/openstax.org\/books\/astronomy\/pages\/1-introduction<\/a><\/div>\n","protected":false},"author":33,"menu_order":7,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[48],"contributor":[],"license":[],"class_list":["post-216","chapter","type-chapter","status-publish","hentry","chapter-type-numberless"],"part":148,"_links":{"self":[{"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/pressbooks\/v2\/chapters\/216","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/wp\/v2\/users\/33"}],"version-history":[{"count":1,"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/pressbooks\/v2\/chapters\/216\/revisions"}],"predecessor-version":[{"id":217,"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/pressbooks\/v2\/chapters\/216\/revisions\/217"}],"part":[{"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/pressbooks\/v2\/parts\/148"}],"metadata":[{"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/pressbooks\/v2\/chapters\/216\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/wp\/v2\/media?parent=216"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/pressbooks\/v2\/chapter-type?post=216"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/wp\/v2\/contributor?post=216"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/astronomy\/wp-json\/wp\/v2\/license?post=216"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}