space physics- topic 6 Flashcards
how often does the earth spin in its axis
once every 24 h
how long does the earth take to orbit the sun
365 days
why do we experience seasons
his is because of the slight tilt of the Earth’s axis.
formula for orbital speed
2πr/ T
why does the moon shine
the Moon shines brightly because it reflects the light from the Sun
how long does the moon take to orbit the earth
a month
how is the earth tilted angle wise
23.5 degrees
why does the length of day vary
the tilt of the earth causes the length of night and day to vary according to latitude (north-south) location, and this changes throughout the year
what side of the moon faces the earth
the same side
what changes the phase of the moon we see
depends on the angle of the sun, the moon and the earth
what are planets
spheres of matter, orbiting the Sun
whats the order of the planets in the solar system
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune
describe each planet
mercury- small rocky planet
Venus- small rocky planet
earth- small rocky planet
Mars- small rocky planet
jupiter- gas giant planet
saturn- gas giant planet
uranus- gas giant planet
neptune- gas giant planet
dwarf planets
Small, rocky bodies orbiting the Sun, not big enough to be called planets. Pluto is an example.
asteroid belt
Millions of rocks, much smaller than planets, orbiting the Sun between Mars and Jupiter
comet
Balls of ice which orbit the Sun in elliptical orbits. When they come close to the Sun they heat up and some of the ice evaporates, becoming a visible tail.
what is a natural satellite
an object that orbits a planet or another body that is larger than itself
what are interstellar clouds
also known as nebulas, made from gas and dust all around the Universe and they are made from a variety of different elements
how did the solar system appear
dust from interstellar clouds clumped together beacuse of its own gravity, began to spin as a disc and eventually most ignited and became the sun.
particles in remaining disk combined by pull of gravity, these are the planets, called acretion model
most common elements in this acretion disk is hydrogen followed by helium, hydrogen and helium were pushed out and became giant gas planets, while iron became the rocky small planets close to the sun.
what is the relationship between mass, and gravitational field strength
The more mass an object has, the greater the gravitational field strength at its surface.
speed of light
3 x 10^8 m/s
equation for light to reach other planets
v= s/t
v=speed of light
s=distance light travels
t=time taken
what is the effect of distance on light and temperature intensity, and gravitational field strength
further away from the sun, less light intensity, weaker gravitational field strength
explain speed in eliptical orbits, and relationship
The planet moved faster during the part of the orbit where it was closest to the star
As the planet gets closer to the star, its gravitational potential energy is converted into kinetic energy – so it moves faster. As it travels away again, the kinetic energy is converted back into gravitational potential energy, so it slows down
when the orbital radius is greater, the planet moves more slowly,This is because the gravitational force of attraction from the Sun is weaker at these larger distances.
what is a star
a ball of gas which radiates energy in the form of electromagnetic waves.
but they are usually (unless they are dying) made of hydrogen and helium
what energy does our sun emit, does this vary between stars?
Our Sun emits most of its energy in the infrared, visible and ultraviolet regions of the electromagnetic spectrum (see subtopic 3.3). This can vary depending on the size and temperature of the star.
where does the energy from stars come from?
nuclear fusion reactions
hydrogen atoms are joined together with enough force to make them stick together (or fuse) into helium atoms. This reaction produces a lot of energy, and this energy is released from the star in the form of electromagnetic waves.
what is a stable star
a star that fuses hydrogen together, by nuclear fusion, to emit energy
what are galaxies
Galaxies are collections of billions of stars, all orbiting around a galactic centre which is usually a black hole
how is distance in space measured
in light years
what is a light year
the distance travelled by light waves through the vacuum of space in one Earth year.
how far is a light year
9.5 × 10ˆ15 m
how are stars formed
all stars are born from interstellar clouds of gas and dust. The element hydrogen must be present in the cloud for a star to form.
Because of gravity, the interstellar cloud starts to collapse upon itself and all the hydrogen (and other elements) clump together. As this happens, the temperature increases because hydrogen nuclei start fusing together. As gravity pulls in more material, the temperature increases further. At this stage, the star is called a protostar.
explain forces in a protostar
Gravity pulls material inwards towards the centre of the star, but as the temperature increases, the outwards force increases too. Eventually, the forces balance and the star becomes stable.
stellar nebula
The cloud of hydrogen and dust before a star is born is known as a stellar nebula.
protostar
The stellar nebula gradually collapses under its own gravity. As it collapses, the temperature increases, and it starts to emit light. This is a protostar.
average star
If the star has a relatively low mass, like our Sun, it forms an average sized stable star. The force of gravity is balanced by the outward force due to the high temperature in the centre.
red giant
When average stars begin to run out of hydrogen, the outer layers expand, and the star becomes a red giant.
plenetary nebula
When the red giant eventually runs out of fuel, the outer layers will spread out further while cooling down, eventually becoming a loose cloud of gas and dust. Despite the name, a planetary nebula has nothing to do with planets.
white dwarf
After the outer layers of the red giant have spread out, the core of the star remains. No fusion happens, but the temperature is still extremely high, so it glows white and so it is called a white dwarf.
massive star
If the star has a relatively high mass, around five times bigger than our Sun, it forms a massive stable star. The force of gravity is balanced by the outward force due to the high temperature in the centre.
red supergiant
When massive stars begin to run out of hydrogen, the outer layers expand, and the star becomes a red supergiant
supernova
A red supergiant is so massive that it has a huge amount of gravity. When the star finally runs out of fuel, this gravity pulls all the matter back into the centre. This creates a huge amount of pressure, which causes the star to violently explode. This explosion is called a supernova and it is one of the brightest events in the Universe. A supernova can create a stellar nebula, which in turn can form new stars and planets.
neutron star
After the supernova, the core of the star is left behind. There is so much mass and therefore so much gravity that atoms cannot even exist and are crushed together to form a block of neutrons. This is known as a neutron star.
black hole
After the supernova, If the star’s core is massive enough, even neutrons cannot exist because gravity is crushing them together with so much force. All the matter in the core of the star is crushed together to a single point, creating the most dense object in the Universe, a black hole.
processes of a star (of small mass)
stellar nebula, protostar, averga star, red giant, planetary nebula, white dwarf
process of a star (of large mass)
stellar nebula, protostar, massive star, red supergiant, supernova, neutron star, blackhole
Which property of light is affected by its frequency?
colour
when galaxies are not moving relative to the Earth…
we see no change in the observed wavelength of light from the galaxy.
When galaxies are moving away from the Earth…
we see an increase in the observed wavelength of light from the galaxy.
When galaxies are moving towards the Earth….
we see a decrease in the observed wavelength of light from the galaxy.
the further away the galaxy is from Earth….
the more light is redshifted
Light from the beginning of the Universe is called….
cosmic microwave background radiation (CMBR) and it is detectable everywhere in the Universe.
explain redshift and relationship with speed and distance
If light is redshifted, it means the galaxy is moving away from us. The more the light is redshifted, the faster the galaxy is moving away from us. All the galaxies we can see are moving away from each other, and the further away they are from us, the faster they are moving.
what is the CMBR
The microwave radiation left over from the Big Bang, which is observed everywhere in the Universe.
what happened to radiation from big bang
The whole Universe was emitting a huge amount of radiation . Ever since then, this radiation has been travelling across the Universe. It is now extremely faint and has been redshifted so much that it is now in the microwave region of the electromagnetic spectrum
hubbles constant explanation
the relationship between how fast galaxies were receding (moving away) from us and their distance from Earth. do this by measuring how bright something is and how bright it looks from earth
hubbles constant formula
hubbles constant= receeding speed/ galaxy distance
hubbles constant number
2.2×10ˆ−18
what does big bang theory state
at the beginning of the Universe all the matter was in the same place, including the matter that would one day make up the Earth and the galaxy we are measuring
the age of the universe formula
1/ Hubbles constant
or
distance from galaxy / receeding speed
why do planets orbit the sun
because the sun contains most of the mass of the solar system
what is the force that keeps the objects around orbit of the sun
the gravitational attraction of
the Sun
what decreases as distance from the sun increases
strength of gravitational field and orbital speed
what is the galaxy the sun is found in
the milky way
what is relevant distance of others stars in milky way, to sun comparison
other stars that make up the Milky Way are
much further away from the Earth than the
Sun is from the Earth
approximate diameter of the milky way
100 000 light years
