Unit 6 Flashcards
what is day and night caused by
the earth spinning on its axis
one revolution takes 24 hours
which way does the sun travel across the sky
the earths rotation causes the sun to go east to west
(rise in the east)
why do the seasons change
due to the motion of the earth
due to the tilt of the earth
how does the tilt of the earth change the seasons
the tilt is 23.5
during spring and summer, the northern hemisphere is tilted towards the sun so that the hours of daylight are greater. it recieves more solar radiation making it warm
during winter and autumn, the southern hemispher is tilted towards the sun
what is the moon
a satellite of the earth that travels in an approximately circular orbit
rotates on its own axis and orbit takes around a month
why does only one side of the moon show at all times
because it revolves on its own axis
why can we see the moon
due to reflected sunlight
doesnt produce any light by itself
how to find average orbital speed
circumference of the orbit/ time
2 x pi x radius
———————
time
what way does the moon rise
in the east and sets in the west
what does the solar system consist of
1 star(sun) and eight planets
what are the 4 inner planets
mercury, venus, earth, mars
what are the 4 outer planets
jupiter, saturn, uranus, neptune
what are all the planets in order, from the sun
mercury, venus, earth, mars, jupiter, saturn, uranus, neptune
features of the inner planets
they are small, solid and rocky.
also have high densities
features of the outer planets
large, cold and mainly consist of gases
density is low
have many moons and satellites
what are dwarf planets
like pluto
generally low density and thought to be composed of rock and ice
what are asteroids
rocks of various sizes which mostly orbit the sun between mars and jupiter
density is similar to that of inner planets
what is the accretion process
as material continued to rotate around the sun, gravitational attraction between small particles cause them to join together and grow in size
how was the sun formed
when gravitational attraction pulled together swirling clouds of hydrogen and gas( known as nebulae) in a region of space where the density is high
why are the inner planets made up of materials with high melting temperatures
as the sun grew in size , it became hotter and lighter molecules such as hydrogen wont be able to exist in a solid state
why are the outer planets less dense
because theyre further away from the sun, light molecules can exist in a solid icy form
what does the gravitational field strength of a planet depend on
the mass of the planet
the distance of the object from the planet
what happens when distance from the sun inreases
suns gravitational field decreases
orbital speeds of the planets decrease
why do planets orbit the sun
because the sun contains most of the mass of the solar system
how do objects with large elliptical orbits change speeds as they move around the sun
speed increases as it approaches the sun and decreases as it moves further away
some of the kinetic energy it has is transferred into potential energy as it moves away
features of the sun
a medium sized star, consisting mostly of hydrogen and helium. It radiates its energy in the infrared, visible and ultraviolet regions of the electromagnetic specrtum
how are stars powered
through nuclear reactions that release energy and in stable stars, nuclear fusion of hydrogen into helium occurs
what are galaxies made up of
many billions of stars
what is our galaxy known as
the milky way
what are light years
they are the distance traveled in space by light in one year
used to measure astronomical distances
how much is one light year
9.5 x 10^15 m
what are stars formed from
interstellar clouds of gas and dust that contain hydrogen
what is a protostar
an interstellar cloud collapsing and increasing in temperature as a result of its internal gravitational attraction
when do protostars become stable stars
when the inward force of gravitational attraction is balanced by an outward force due to the high temperature in the center of the star
what happens when the star eventually runs out of hydrogen
there is no more energy for nuclear reactions
most stars expand to form red supergiants when most of the hydrogen has been converted to helium
what happens if a red giant is formed with a less massive star
a planetary nebula with a white dwarf star in the center is formed
what happens to red supergiants
it explodes as a supernova, forming a nebula containing hydrogen and new heavier elements, leaving behind a neutron star or a black hole
what is the diameter of the milky way
apporximately 100000 light year
what is redshift
an increase in the observed wavelength of electromagnetic radiation emitted from receding stars and galaxies
light emitted from distant galaxies appear redshifted in comparison to light on earth
what does redshift help prove
it provides evidence that the universe is expanding and supports the big bang theory
what is Cosmic Microwave Background Radiation
microwave radiation of a specific frequency that is observed at all points in space around
was produced shortly after the Universe was formed
how can the speed of which a galaxy is moving away from earth be found
from the change in wavelength of the galaxy’s starlight due to redshift
how can the distance of a far galaxy be determined
using the brightness of a supernova in that galaxy
what is the hubble constant
the ratio of the speed at which the galaxy is moving away from the earth to its distance from the earth
can be found with : speed of galaxy moving away(v) / distance of galaxy(D)
what is the current estimate of the hubble constant
2.2 x 10^-18
equation that estimates the age of the universe
d/v = 1/ hubble constant
