Space Physics Flashcards
How long does it take the Earth to rotate fully on its axis?
24 hours
What causes the apparant daily motion of the sun and the periodic cycle of day and night?
Due to the Earth’s rotation around its axis
How long does it take the Earth to orbit the sun
Approx 365 days
What causes the different seasons?
The combination of the orbiting of the Earth around the Sun and the Earth’s tilt
How long does it take the moon to orbit the Earth?
Approx one month
What causes the periodic nature of the Moon’s cycle?
The relative positions of our Sun, Earth, and Moon.
- the moon orbits earth and earth orbits the sun
average orbital speed equation
v = (2 x pi x r)/T
Describe the Solar System
Contains:
a) one star, the Sun
b) the eight named planets
c) minor planets that orbit the sun (like pluto and asteriods)
d) moons, that orbit the planets
e) smaller Solar system bodies (comets and natural satellites)
The eight planets in order of closest to the sun
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune
The four planets near to the sun are
rocky and small
(mercury, venus, earth and mars)
the four planets furthest from the Sun are
gaseous and large
(jupiter, saturn, uranus, neptune)
accretion process
- dust left over after the sun formed contained many heavy elements formed in a supernova explosion
- first the dust made a disc which rotated around the sun due to gravity
- slowly the dust started to clump together due to gravitational attraction between the particles
- the inner planets are rocky because the temperature near the sun meant that only elements with high melting points existed as solids
satellite
an object that orbits a larger object
natural satellites
Asteroids, comets, moons
Elliptical orbit
An orbit that has an oval shaped path (like an elongated circle). Due to the gravitational interactions amoung the sun, planets and other celestial bodies.
where is the sun in the elliptical orbits
at one focus of the orbital ellipse (not the center)
The strength of the gravitational field at the surface of a planet depends on…
the mass of the planet
The strength of the gravitational field around a planet decreases as..
the distance from the planet increases
The speed of light
3 x 10^8
equation for calculating time with speed of light
time = distance/speed
Why do planets orbit the Sun?
Because the Sun contains most of the mass of the Solar System
What keeps the object in orbit around the Sun?
The gravitational attraction of the Sun
What affects the strength of the Sun gravitational field?
Decreases when the orbital speed decreases as the distance from the Sun increases
Why does an object in ellipitcal orbit travel faster when closer to the Sun?
The closer, the stronger the gravitational pull
Describe the sun
- a star of medium size
- consisting mostly of hydrogen and helium
- radiates most of its energy in infrared, visible and ultraviolet regions of the EM spectrum
what powers the stars
Stars are powered by nuclear reactions that release energy
what sort of nuclear reactions occur in stable stars
The fusion of hydrogen into helium
what are galaxies made up of
many billions of stars
what is the star in the milky way
the sun
how can astronomical distances be measured?
In light years, where one light year is the distance travelled in the vacuum of space by light in one year
one light year is equal to
9.5 x 10^15 m
describe the life cycle of a star before the hydrogen runs out
- a star is formed from interstellar clouds of dust and gas that contain hydrogen
- a protostar is a interstellar cloud collasping and increasing in temp as a result of its internal gravitational attraction
- a protostar becomes a stable star when the inward force of gravitational attraction is balanced by an outward force due to high temp in centre of the star
- all stars eventually run out of hydrogen as fuel for the nuclear reaction
How are stars formed? (simple answer)
from interstellar clouds of gas and dust that contain hydrogen
whats a protostar
an interstellar cloud collasping and increasing in temperature as a result of its internal gravitational attraction
when does a protostar become a stable star
when the inward force of gravitational attraction is balanced by an outward force due to the high temperature in the centre of the star
what happens when most of the hydrogen in the centre of the star has been converted to helium
Most stars would expand to form red giants and more massive stars expand to form red supergiants
what does a red giant from a less massive star forms?
a planetary nebula with a white dwarf star at its centre
what happens when a red supergiant explodes?
it explodes as a supernova forming a nebula containing hydrogen and new heavier elements, leaving behind a neutron star or a black hole at its centre
what could a nebula from a supernova form
new stars with orbiting planets
describe the milky way
one of many billions of galaxies making up the universe. Has the diameter of 100,000 light years
redshift
increase in the observed wavelength of electromagnetic radiation emitted from receding stars and galaxies
- in distant galaxies the lines have shifted towards the red end of the specturm
how does the light emitted from distant galaxies appear as
appears redshifted in comparision with light emitted on the Earth
evidence supporting the big bang theory
the redshift in the light from distant galaxies
What is CMBR?
Cosmic microwave background radiation.
- microwave radiation of a specific frequency is observed at all points in space around us.
when was CMBR produced and how has it expanded
- produced shortly after the universe was formed
- the radiation expanded into the microwave region of the electromagnetic spectrum as the universe expanded
how can the speed at 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
hubble constant (Ho)
the ratio of the speed at which the galaxy is moving away from the Earth to its distance from the Earth
hubble constant formula
H0 = v/d
v = speed
d = distance
current estimate for the hubble constant (H0)
2.2 x 10^-18 per second
what does 1/H0 =
d/v
what does 1/H0 represent
- an estimate for the age of the Universe
- is the evidence for the idea that all the matter in the Universe was present at a single point
Properties of CMBR
- has the same intensity everywhere
- temperature corresponds to 2.7K
- there is structure in background intensity (has ripples)
How does CMBR support the big bang theory
Since this radiation was produced shrotly after the big bang and has now been redshifted/expanded into the microwave region
Why is our understanding of the earliest moments of the universe unreliable?
- no experimental evidence
- state of matter is unknown
- temperature too high to reproduce
