topic 11 Flashcards
what is the name of the dwarf planet not located in the kupier belt and where is it located?
ceres - located in asteroid belt
what does eccentricity of a comet tell you?
how squashed the ellipse is. 1 is a circle and going down is more squashed
what is a planet (3)
- orbits a star
- its gravity is strong enough to pull it into a sphere
- It has cleared it’s region of space of smaller bodies
what are the two tails of a comet?
ion and dust
explain the ion tail of a comet
trail of plasma streaming back from solar wind - points in exactly opposite direction of sun
explain the nucleus of a comet
solid comet core, ma be hidden by coma
explain the coma of a comet
vapour cloud surrounding the nucleus
explain the hydrogen envelope of a comet
invisible, irregular cloud surrounding the coma
explain the dust tail of a comet
prominent trail of dust and gases that curves backwards
describe short period comets (3)
- likely origin in kupier belt
- orbit < 200 y
- periods in hundreds of years
describe long period comets (3)
- likely origin in oort cloud
- orbit > 200y
- periods in thousands of years
what are comets orbits often like and what does this suggest? (4)
1) very eccentric (not circular)
2) very inclined to the ecliptic
3) retrograde
^ these suggest an origin outside of the solar system
describe the kupier belt (3)
- outer solar system, from orbit of neptune onwards
- 30 - 50 AU
- similar to asteroid belt, but mostly comets, centaurs, and dward planets
describe the heliosphere(2)
- upto a distance of 80-100 au in the direction the sun moves through interstellar space, many times that distance in the opposite direction
- termination shock: radiation from the sun reaching maximum distance around due to gravity
describe the oort cloud(3)
- in interstellar space (space between stars)
- 2000 au to 200k au
- mostly consisting of comets, with 1-2 % asteriods
describe mercury(3)
- no atmosphere
- appearance similar to our moon
- not much bigger than our moon
describe venus(4)
- thick carbon dioxide atmosphere
- the hottest planet in the solar system
- similar size to earth
- a day is longer than a year
describe earth(2)
- the only planet with liquid water
- only place in the universe (THAT WE KNOW) supports life
describe mars(4)
- evidence of water eriosion on the surface
- polar ice caps
- very thin atmosphere of mostly carbon dioxide
- 2 small moons, probably captured asteroids
describe jupiter(4)
- the largest planet
- a gas giant, mostly hydrogen and helium
- giant red spot is a storm that has lasted 400 years
- more than 75 moons-
the 4 galilean moons are historically important
describe saturn(3)
- another gas giant
- prominent ring system first seen by galileo - the remains of a moon that broke into pieces
- at least 53 moons including titan (only jupiter’s moon ganymede is bigger)
describe uranus(4)
- discovered in 1781 by william herschel
- mostly icy water, methane and ammonia with a hydrogen helium outer layers
- rotates on its side
- at least 27 moons, many named after shakespeare characters
describe neptune(4)
- another icy giant very similar to uranus
- its existence was predicted due to observed gravitational effects on neptune
- 14 moons including triton
- its retrograde orbit suggests that is was probably captured from the kupier belt
what is an astronomical unit?
the mean distance between the earth and sun
what’s the conversion for au to km?
1AU = 1.5 x 10^8km
when converting, which unit goes on the denominator?
the unit you start out with (ie - the unit you DON’T want)
what is a meteoroid (definition not differenciation)
meteoroids are smaller pieces of rock in space between 1m in diameter to tiny grains
what is a meteoroid
a piece of rock in space
what is a meteor
enters the earth’s atmosphere (a shooting star)
what is a meteorite
survives atmospheric heating and hits the surface
how are meteoroids formed
by collision of asteroids or other bodies
describe the composition of a meteoroid
crumbly rocky or metallic debris, mostly silcates, some iron and niken
what can the composition of a meteoroid tell us?
where it came from
where is a widmanstaten pattern found
in nickel-iron meteorites
how is a widmanstaten pattern formed
produced by exceptionably slow cooling over millions of years
what is the ecliptic?
the plane around the sun where all the planets orbit -23,5* away from the celestial equator
how did halley use the transit of venus
halley used the transit of venus to determine the value of 1AU
what is transit of venus
when venus is seen to pass over the face of the sun
how do we calculate the orbital radius of everything in the solar system (2)
if we know the distance between the two observers on earth and the angle between the two observed transits we can work out 1AU
we can then use keplers 3rd law to calculate the orbital radius of everything in the solar system
what is the first theory for water on earth?
the water and rock was all accreted together to form the proto-earth, so the water was always there
what is the second theory for water on earth
smaller icy bodies may have been dislodged from their orbits and brought to earth after its formation
what is the third theory for water on earth
theia (giant impact hypothesis for formation of mooon) brought water from the outer solar sustem when it collided to form the earth and moon
TRUE or FALSE there isn’t evidence to support all three of the water on earth theories
FALSE - there in fact IS evidence to support ALL THREE of the water on earth theories
describe human eye
around only 3mm in diameter and can only detect a few photons
describe the drawbacks of human eye
a body with too small a SOLID ANGLE(how big something looks in the sky) in our field of view, and which is too dim, will not be visible
our eyes have limited sensitivity to light, especially when it is dark
why can we see more with a telescope than the naked eye
we can see much more with a telescope than we can with the naked eye - this is because a telescope has a much larger aperture than our pupil so much more light enters it.
describe objective lens(3)
- collects light
- more light can be captured using a
telescope with a larger aperture than our pupils - lenses can be used to capture even more light
what are the two types of telescope
refracting and reflecting
what differentiates the two types of telescope
refracting: contains lenses
reflecting:contains mirrors
what do the lenses do in a refracting telescope
the objective lens captures and focuses the light to produce an image
the eyepiece lens magnifies this image
what type of lense does a galilean telescope use?
a concave and a convex lens
what are the advantages of a galilean telescope
- the image is upright, not upside down
- for the same length of telescope you can get better magnification
what type of lenses does a keplerian telescope use?
two convex lenses
what are advantage of a Keplerian telescope
larger field view (bigger image)
what are the two types of reflecting telescope
newtonian and cassergrain
which reflecting telescope is more complicated? and describe it
cassegrain is more complicated design.
shorter tube for same magnification
list the advantages of reflecting telescopes(5)
- it is much easier to make a large mirror than it is to make a large lens
- a large mirror can have a large aperture
- a large mirror can have a very large focal length
- multiple mirrors can make this even larger
- chromatic aberation is not a problem with mirrors
explain chromatic aberration
different wavelengths of light may be refracted by different amounts. This causes a blurred image with coloured edges
define magnification
how many times the image is bigger than the object
how do you calculate magnification
m = focal length of objective/focal length of eyepiece
define resolution
the ability of an optical instrument to distinguish between two points of light
what are the two factors for resolution
1) the size of the aperture (the diameter of the objective lens)
larger aperture = better resolution
2) the wavelength that you are observing in
larger wavelength = poorer resolution
what is light grasp proportional to
the amount of light entering telescope is proportional to the diameter of the aperture squared
a telescope with double the diameter has…??
a telescope with double the diameter has four times the area, so four times the “light grasp”
how many arcmins in 1 degree
1 degree = 60 arcmins
define field of view
how much of the sky(the angle) that we can see through our telescope
what did galileo discover with a telescope (4)
- the moons surface had mountains and craters - the moon was not smooth
- the phases of venus - sun is at centre of solar system
- four moons around jupiter - not all bodies revolve around sun
- the milky way contained stars - not just a band of cloud in space
explain a fly by space probe
does not land on or orbit the target but just flies past taking measurements and images
give an advantage of a fly by space probe
lots of measurements can be taken and transmitted back to earth, including images
give a disadvantage of a fly by space probe
each body can only be flown by once, so not all parts of the bodies can be analysed
give a real-life example of a fly by space probe
NEW HORIZONS
explain an orbiter space probe
goes into orbit around the target body
give an advantage of an orbiter space probe
entire body can be observed, more time to gather data
give a disadvantage of an orbiter space probe
a lot of fuel is used to get a probe into orbit and data is limited to what can be obtained from space
give a real-life example of an orbiter space probe
juno
explain an impactor space probe
collides with the surface of the body. It can take measurements as it approaches the body and measurements can be made of the plume of debris by telescopes
give an advantage of an impactor space probe
passes through body’s atmosphere and can dislodge material on the surface of the body to investigate compositions
give a disadvantage of an impactor space probe
the impact probe has to send data back to earth via relay probe which also has to be sent to space and has to be at right place and right time → difficult as impacts can be unpredictable
give a real life example of an impactor space probe
deep impact
explain a lander space probe
lands on body
give an advantage of a lander space probe
more detailed observations can be made of the immediate area around probe + experiments can be performed on the surface of a body
give a disadvantage of a lander space probe
high faliure rate, probe can only examine the area close to where it landed
give a real life example of a lander space probe
philae
give some advantages of manned missions(4)
- humans can cope with situations that robots can’t
- humans are much more versatile than robots
- humans are adaptable
- manned missions are stepping stones towards human colonisation
give some disadvantages of manned missions (6)
- we need to keep the astronouts alive
- manned missions are much more expensive
- being in space for a long time isn’t good for your health (low gravity and radiation)
- we have to worry about bringing them back
- human lives at risk
- training astronauts is expensive and takes a long time
explain escape velocity
in order to escape earth, a spacecraft must reach escape velocity - decreases with altitude
