Asteroids, Comets and
NEOs
Asteroids, comets and NEOs Teacher Worksheet Notes
Te a c h e r W o r k s h e e t
Notes
Author: Sarah Roberts
Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Solar System Activities
Q1. Answers to the crossword puzzle are given below
Across
Down
1. Ceres
1. Coma
3. Meteorite
2. Rocky
5. Asteroid
3. Meteor
7. Kuiper
4. Tail
10. Comet
6. Impact
11. Solar
8. Evaporates
13. NEO
9. Short Period
15. Gas
10. Circular
16. Dust
12. Orbit
17. Elliptical
14. Snowball
19. Long period
18. Ice
21. Belt
20. Oort
22. Meteoroid
Q2. Answers given in bold in the table below
Object
Distance (x106 km)
Distance (AU)
Mercury
57.9
0.4
Venus
108.2
0.7
Earth
150
1
Mars
227.9
1.5
Asteroid Belt
405
2.7
Jupiter
778
5.2
Saturn
1427
9.5
Faulkes Telescope Project - 2 of 17
Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Object
Distance (x106 km)
Distance (AU)
Uranus
2850
19
Neptune
4497
30.0
Pluto
5913
39.4
Kuiper Belt
4500 - 7500
30-50
Asteroid Activities
Q1.
One bus = 11m, Ceres = 914km = 914,000m.
So,
914,000
= 83,091
11
or approx. 83 thousand buses would stretch across the diameter of Ceres.
€
Q2. See Google Earth worksheet
Q3.
a) Field of view of FTN = 4.6 arcminutes = 60x60x4.6 arcseconds (there are 60
arcseconds in an arc minue).
One CCD is 2048x2048 pixels
So there are
4.6 × 60
= 0.13
2048
arcseconds per pixel
in an FTN image.
€ binned to improve the quality of the images. Essentially, binning
b) FTN images are
means combining pixels on the CCD to create larger pixels. So, in the case of FTN, a
2x2 square of pixels is taken from which just one pixel is created - this single pixel
has twice the width and 4 times the area of the original pixel. Thus, after binning, the
CCD of FTN has effectively been reduced to 1024x1024 pixels in size. Binning of the
FTN CCD effectively reduces the CCD size to 1024 pixels square.
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Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Thus, the scale-size of a binned FTN image is
4.6 × 60
= 0.27
1024
arcseconds per pixel
€
c). Depending on where you measure across the asteroid, its size should range from
about 10 - 15 pixels.
d). From b), the scale-size of an FTN image is 0.27 arcseconds per pixel. If we
assume the asteroid is 12 pixels in the diameter, this is 12x0.27 arcseconds, or
approx 3 arcseconds in diameter.
Q4.
a) There are 31 556 926 seconds in 1 year, so one orbit of Ceres will take
4.6 × 31556926s = 145.162 ×10 6 s
b) Ceres is
€
2.77 ×150,000 = 4.05 ×10 8 km
from the Sun.
€
c)
Sun
Ceres
radius
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Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
d) Distance travelled in one orbit = circumference of the circle
So, distance travelled:
2πr = 2 × π × 4.05 ×10 8 km = 2.54 ×10 9 km
e) Vel =
€
2.54 ×10 9 km
= 17.53kms−1
6
145.162 ×10 s
€
Q5.
a) Plot day number on the x-axis and altitude on the y axis
b) The gradient should be in the region of -0.44. The y-intercept should be about 19.
The equation of the line of best fit is given by:
y = −0.44 x + 19
c) When Ceres sets, altitude will be 0, therefore y=0.
€
Substituting y=0 into the equation
above and rearranging, gives
0.44 x = 19
x = 44
€
So Ceres will set in 44 days. €
Faulkes Telescope Project - 5 of 17
Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Comet Activities
Q1.
Q2. A comet doesn’t always have a tail - the tail develops as it nears the Sun, and its
gases and dust evaporates.
Q3. A comet’s tail never points towards the Sun because they are caused by the
Solar wind and radiation pressure (the ‘push’ that light gives off when it falls on
something). This means that if a comet is moving away from the Sun, the tail will be
in front of the comet, not trailing behind! (see Appendix 1 for a more detailed
explanation of how the Solar Wind and radiation pressure create tails in a comet).
Q4.
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Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Q5.
Comets
Asteroids
Found beyond Pluto
Found between Mars and
Jupiter
Made of ice and dust ‘dirty’ snowball
Made of rock
Has a tail
Don’t have tails
Have very elliptical orbits
Have nearly circular orbits
Have orbits at varied
angles from the plane of
the Solar System
Have orbits closely aligned
with the plane of the Solar
System
NEOs
Q1.
1
KE = mv 2
2
a) So, for a 1kg asteroid travelling at 20km/s, the K.E. is given by:
€
1
(1)(20 ×10 3 ) 2 = 2 ×10 8 J
2
( the velocity must be converted to m/s)
€
Faulkes Telescope Project - 7 of 17
Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
b)
1
KE = (1)(70 ×10 3 ) 2 = 2.45 ×10 9 J
2
€
2.45 ×10 9
= 12.25
2 ×10 8
The same asteroid hitting€at a faster velocity gives off 12 and a quarter times more
energy in a collision with the Earth.
c)
1
KE = (2)(20 ×10 3 ) 2 = 4 ×10 8 J
2
Increasing the mass of the object by a factor of 2 increases the K.E. of the collision
by a factor 2 also.
€
Faulkes Telescope Project - 8 of 17
Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Extra Activities
Guess the object - based on the board game, Taboo
This is a fun way of making the students really think about the objects they are trying
to describe. Cut out the cards underneath and ask the students to try and describe
the object given at the top of the card, but without using the 3 words underneath. This
game has been amended from the association for astronomy education website
where more astronomy resources can be found. ( http://www.aae.org.uk/)
METEORITE
METEOR
COMET
OORT CLOUD
rock
shooting star
dirty snowball
Solar system
landed
dust
ice
comet
Earth
atmosphere
gas
long
KUIPER BELT
ASTEROID BELT
COMA
NUCLEUS
short
asteroid
cloud
centre
comet
Mars
evaporate
ice
orbit
orbit
gas
dust
SOLAR SYSTEM
ORBIT
NEOs
CERES
planets
path
collide
asteroid
orbit
travels
Earth
orbit
Sun
planets
impact
largest
Faulkes Telescope Project - 9 of 17
Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Impact craters
The aim of this activity is to investigate the factors which affect the size of an impact
crater on Earth. This done by dropping objects of different sizes and densities into a
container of flour and cocoa and observing and measuring the craters formed.
Students must plan the experiment, including what variables to change and
investigate, they must carry out the experiment in a controlled and scientific manner,
and finally, they must analyse their results and from them, draw conclusions
regarding how impact craters are formed on Earth.
In the investigation, objects of differing densities (marbles, ball bearings and golf
balls) and various sizes will be dropped from a known height onto a surface of flour
and cocoa. Once dropped, the kinetic energy of these objects will blast a crater into
the surface, sending out rays (ejecta rays) around the object. Students will note the
shape/extent of these rays, and once the object is removed from the crater, they can
also measure its diameter. Results of this investigation can be presented graphically
or verbally, and conclusions drawn regarding the nature of impact craters on Earth.
Any improvements that can be made on the experiment can then be discussed. The
investigation is best done in groups of at least 3 students, one to drop the impact
object, one to time, and one to collect the results. Students should be encouraged to
discuss what they think are the main factors affecting the sizes of impact craters, and
write down their predictions for any trends in their results i.e. larger impact objects will
create larger craters etc.
Apparatus: Impact objects - Marbles of different sizes
Golf Balls
Stainless steel ball bearings
Saucepans/containers large enough for objects to be dropped in
Cocoa
Flour
Rulers
Newspaper (unless you are doing the activity outside)
Electronic measuring scales
Stopwatch
Faulkes Telescope Project - 10 of 17
Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Preliminary Method:
1. Lay down the newspaper and put the saucepan/container in the middle.
2. Fill the container to a depth of about 10cm with the flour.
3. Sprinkle the surface of the flour with a thin layer of cocoa powder. Make sure it is
evenly spread and flat.
4. Note what the test field looks like.
5. Measure the mass of each impact object and note its mass in kg (see Appendix 1
for explanation of difference bewteen mass and weight).
6. Measure the diameter of each impact object in metres. This can be done most
easily by holding up two rulers either side of the marble, and using a third ruler to
measure the distance between them. Note the diameter and therefore, radius
measurement in m.
7. Using the formula,
density =
mass
volume
calculate the density of each impact object used.
€
Experimental Method:
1. Hold the impact object directly above the container of flour/cocoa. Measure the
distance to the container. (Note: since the time taken for the impact object to hit the
flour/cocoa is to be timed, this distance should be made as large as possible to
minimise timing errors).
2. Drop the impact object from this height, starting the stopwatch as this is done. The
stopwatch must be stopped once the impact object has hit the flour/cocoa.
3. Before removing the impact object from the container, look at the ejecta rays that
have formed. Sketch them and make any comments regarding their shape/extent etc.
4. Remove the impact object and measure the crater diameter and ejecta ray
diameter. Make a note of these values.
5. Flatten the flour/cocoa surface once more, and repeat the experiment twice more
with the same impact object.
6. Using impact objects of different size/density (choose one or the other), repeat
steps 1-5, noting the results throughout the investigation.
The results can be noted down in table form, using the example overleaf as a guide.
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Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Time
taken (s)
Impact
Object 1
radius
___m
Average
time taken
(s)
Crater
Diameter
(m)
1st drop
_______
2nd drop
_______
3rd drop
_______
______
1st drop
_______
______
2nd drop
_______
3rd drop
_______
______
1st drop
_______
______
2nd drop
_______
3rd drop
_______
Average
crater
diameter
(m)
______
______
______
______
density
___kgm-3
Impact
Object 2
radius
______
______
______
___m
density
___kgm-3
Impact
Object 3
radius
______
______
______
___m
______
density
___kgm-3
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Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Results:
1. The kinetic energy of each impact object dropped can be found using
1
KE = mv 2
2
and knowing that the velocity (speed in this case) can be found using
€
speed =
distance
time
Using the two equations above, calculate the K.E. of each impact object as it hit the
surface of the flour/cocoa.
€
2. Plot the results of the investigation on a scatter plot i.e. impact object density vs.
crater diameter or impact object diameter vs. crater diameter.
Discussion:
Discuss the following:
a) how did the size of the impact object affect the size of the crater? How did it affect
the ejecta rays?
b) how did the density of the impact object affect the size of the crater? Did this affect
the ejecta rays?
c) do the bigger craters have more rays around them?
d) how do the diameters of the craters compare to the diameters of the impact
objects? Are they bigger/smaller/same size?
e) What happened to the cocoa as the impact object was dropped?
f) Was the flour visible at any time during the investigation i.e. in some impacts, or all
impacts or none?
g) What does this investigation tell us about craters on the surfaces of planets?
h) How could this investigation be improved?
i) What were the main sources of error in the investigation? How can these be
minimised?
j) Does K.E. affect the size of the craters made? If so, how?
k) Were the results as expected? Did they match any predictions you made prior to
carrying out the investigation?
Faulkes Telescope Project - 13 of 17
Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Toilet Roll Solar system
This activity illustrates the relative distances between objects in the Solar System and
the Sun. It is best done in the school yard/field, as it takes approx. 26 metres to
measure out the distances. This is an excellent activity for showing just how far apart
the planets are in the Solar System, and gives the students more perspective of the
immense distances in space.
Apparatus: Pen
Toilet roll
Distance table of Solar System objects
Method:
Make a dot on the seam of the first sheet of toilet paper - this represents the Sun.
Write ‘Sun’ somewhere near the dot so that you know what it is!
Using the table of distances given below, mark the distances to each object in the
Solar System along the length of the toilet roll. The number in the table is the number
of sheets of toilet roll needed to reach that particular object in the Solar System,
relative to the Sun. At each distance, mark a dot and name the object alongside the
dot until you reach Pluto.
Go outside to the school yard or field and carefully unravel the toilet roll. Get a
student to stand alongside each planet, so that the distances can be seen more
clearly.
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Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Solar System Object
Approx. number of
sheets of toilet paper
from the Sun
Mercury
2.0
Venus
3.7
Earth
5.1
Mars
7.7
Ceres (represents
asteroid belt)
14.0
Jupiter
26.4
Saturn
48.4
Uranus
97.3
Neptune
152.5
Pluto
200.0
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Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
Appendix 1.
Solar wind
The solar wind is a stream of highly energetic particles, mainly protons and electrons,
but with some heavier ions, which are streaming off from the Sun. Its source is the
Sun’s corona, or the outer atmosphere. The temperature is so high in the Sun’s
corona, that not even gravity can hold these energetic particles in place, and they
blow off at velocities of up to 400km/s!
The energetic particles blown out in the solar wind are responsible for the gas tail that
can be seen in a comet. The particles ionise the neutral gas in the comet’s coma, and
the magnetic field of the solar wind then sweeps these ions out of the coma and into
a long gas tail, almost exactly opposite in direction to the Sun.
Radiation pressure
The definition of radiation pressure is the force per unit area exerted by
electromagnetic (EM) radiation. So, in simple terms it can be thought of as the ‘push’
that EM radiation (or, in the case of the Sun, light ) gives when it falls on something. It
is the radiation pressure from the Sun that causes the dust tail in a comet to form.
Dust particles from the coma are pushed out by this pressure, also in an orientation
which is opposite in direction to the Sun.
Since both the Solar wind and radiation pressure act to push particles in the opposite
direction of the Sun, when a comet is moving away from the Sun, the tails will appear
in front of the comet, not behind it!
Weight vs. Mass
When we talk about weight and mass, it is easy to confuse the two. However, we
must be careful in their distinction. The mass of an object does not change - it can be
thought of as a measure of the amount of matter in an object. It is a scalar quantity
(i.e. has no direction) and is measured in units of kg.
The weight of an object is a measure of how much gravity is acting on an object of
mass, m. In other words, weight =mass x acceleration due to gravity (g). Since
gravity has a direction, weight also has direction, and is therefore a vector quantity. It
is measured in units of Newtons (N).
To illustrate the difference between mass and weight, we can consider how much a
ball of mass 1kg would weigh if it were placed on the Moon, compared to the Earth.
Faulkes Telescope Project - 16 of 17
Asteroids, comets and NEOs - Teacher Worksheet Notes
Asteroids, comets and NEOs - Teacher Worksheet Notes
On Earth, the acceleration due to gravity (the acceleration of a freely falling body
directed towards the centre of gravity, in the case the Earth) is 9.8 ms-2 . So, a 1kg
mass on Earth weighs
1× 9.8 = 9.8N
On the Moon, the acceleration due to gravity is about 6 times less than that on Earth.
Its value is 1.6 ms-2. So, on the Moon, the same 1kg mass ball would weigh
€
1×1.6 = 1.6N
Thus, although the mass of the ball remains the same, the object would weigh only
one-sixth as much on the Moon since the force of gravity is six times weaker than it is
€
on Earth.
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