Praxis Middle School Science-Astronomy Flashcards
steady state theory
this theory held that the universe was static and that it did not evolve, having always maintained a balance of the same general properties through replacement of dying starts and galaxies by new stars and galaxies
big bang theory
a massive explosion that scattered mass, matter, and energy throughout the universe, which then formed galaxies as matter cooled during the next half-billion years
the concept of a massive explosion (in the big bang theory) is supported by…
the disruption of background radiation and the measurable fact that the galaxies are moving away from each other at great speed.
oscillating universe hypothesis
as the universe oscillates galaxies will move away from one another and will in time slow down and stop; then a gradual movement toward each other will activate another big bang
astronomical unit (au)
within our solar system, the standard unit of distance measurement
the mean distance between the sun and the earth
or 1 AU= 1.495979 x 10^11m
planetary nebulae
cold clouds of dust and gas within a galaxy
prostar
the initial stage of star formation
here, cloudlike spheres of the nebula begin to shrink under the influence of its own weak gravity into a knot of gasesthe initial stage of star formation
nuclear fusion
the process by which hydrogen atoms fuse together to form helium atoms, releasing massive amounts of energy
a star’s life cycle depends on its…
initial mass.
just as a star’s mass determines its length of life, however, it also determines the pattern it follows in the last stages of existence
giant star
10 to 100 times the diameter of the sun, created when hydrogen-depleted stars begin to consume the heavier elements produced by fusion
white dwarf star
a small, slowly cooling, extremely sense star
no larger than 10,000 km in diameter
black dwarfs
the final phase of a lower main sequence start life cycle
a dead star
binary star
one of two suns in the same solar system
nova
the sudden brightening of a lower main sequence star caused by the explosion of the star
supergiant star
an exceptionally bright star, 10 to 1,000 times the diameter of the sun
supernova
the massive explosion of an upper main sequence supergiant star caused by the detonation of carbon within the star
a supernova releases more energy than…
earth’s sun will produce in its entire life cycle
neutron star
the very small imploded core of a collapsed supergiant star that rotates at a high speed and has a strong magnetic field
pulsar
a neutron star that has captured gas from space or other stars and emits a sweeping beam of ionized gas radiation
black hole
a volume of space created by an imploded supergiant from which no form of radiation can escape
singularity
the inner core of an imploded supergiant, compacted by a supernova into an object of zero radius and infinite density
most cosmologists believe that the earth is the direct result of a…
supernova
our solar system is composed mostly of
matter assembled from a star or stars that disappeared billions of years ago
accretion
the clumping together of small particles into larger masses
sun
the nearest star to earth that produces solar energy by the process of nuclear fusion, converting hydrogen into helium
parts of the sun
- core: the inner portion, where fusion takes place
- photosphere: considered the surface of the sun, produces sunspots (cool, dark areas that can be seen on its surface)
- chromosphere: colored red by hydrogen gas
- solar flares: produce excited protons and electrons that shoot outward from the chromosphere at great speeds reaching earth, disturb radio reception, and affect magnetic field on earth
- solar prominences: gases that shoot outward from the chromosphere
- corona: the transparent area of sun visible only during a total eclipse
solar radiation
energy traveling from the sun that radiates into space
the planets in our solar system
mercury venus earth mars jupiter saturn uranus neptune
the inner planets
mercury
venus
earth
mars
the outer planets
jupiter
saturn
uranus
neptune
mercury
closest planet to the sun
surface has craters and rocks
atmosphere composed of hydrogen, helium and sodium
venus
has a slow rotation when compared to earth’s
rotates in the opposite direction from the other planets, called retrograde rotation
atmosphere composed of mostly carbon dioxide
earth
considered a water planet, with 70% water of its surface
gravity holds the masses of water in place
the different temperatures observed allow for different states of water to exist
atmosphere composed of mainly oxygen and nitrogen
the only planet known to support life
mars
has a surface that contains numerous craters, active and extinct volcanoes, and ridges & valleys with extremely deep fractures
iron oxide makes the surface seem rust colored and skies seem pink
atmosphere composed of mostly carbon dioxide, oxygen, nitrogen, argon, and water vapor
it has polar regions with ice caps composed of water
two satellites
jupiter
largest planet in the solar system
has 16 moons
atmosphere composed of hydrogen, helium, methane, and ammonia
white colored bands of clouds indicate rising gases, and dark colored bands of clouds indicate descending gases, caused by heat in jupiter’s core
it’s great red spot is thought to be a hurricane type cloud
it has a strong magnetic field
saturn
second largest planet
beautiful rings of ice, rock, and dush particles circling it
atmosphere composed of hydrogen, helium, methane, and ammonia
has 20-plus satellites
uranus
a gaseous planet with 10 dark rings, 15 satellites and retrograde resolution
atmosphere made of hydrogen, helium, and methane
neptune
another gaseous planet with an atmosphere consisting of hydrogen, helium and methane
3 rings, 2 satellites
color of the seas
asteroids
rocky fragments that may be the remains of the birth of the solar system that never formed a planet
comets
masses of frozen gases, cosmic dust, and small rocky particles
meteoroids
particles of rock and metal of various sizes floating in space
meteor
a burning meteoroid falling through the earth’s atmosphere; also called a shooting star
meteorites
meteors that strike the earth’s surface
giant impact hypothesis
explains the origin of earth’s moon as part of the residue of a collision with another body that earth’s gravitation pulled into orbit
eclipse
occurs when a stellar body is shadowed by another and, as a result, is rendered invisibile
umbra
the central region of the shadow caused by an eclipse, which receives no light from the sun
penumbra
the lighter outer edges of the shadow created during a partial eclipse where some light hits
phases of the moon
the apparent changes in the shape of the moon caused by the absence or presence of reflected sunlight as the moon orbits around the earth
the orbital pattern of the moon in relation to the sun and earth determines…
the extent of lunar illumination, and consequently, what illuminated shape is presented to the earth
seasonal change on earth is caused by
the orbit and axial tilt of the planet in relation to the sun’s ecliptic, the rotational path of the sun
the 4 key points on the ecliptic that vary slightly in relation to leap years
winter solstice- dec 21st. shortest day of the year in the northern hemisphere
summer solstice- june 21st. longest day of the year in the northern hemisphere.
vernal equinox- march 21st. marks beginning of spring.
autumnal equinox-sept. 21st. marks the beginning of autumn.
geosynchronous orbit
an orbit around the earth that has an orbital period matching the earth’s sidereal rotation period
