The exercises are now available on the web and in six booklets (100 pages in total), titled:

"General Introduction"
(an overview of the exercise series),

"Toolkits"
(explanation of basic astronomical and mathematical techniques),

"Exercise
1: Measuring the Distance to Supernova 1987A",

"Exercise
2: The Distance to Messier 100 as Determined by Cepheid Variable Stars",

"Exercise
3: Measuring the Distance to the Cat's Eye Nebula" and

"Exercise
4: Measuring a Globular Star Cluster's Distance and Age".

The booklets are sent free-of-charge to high-school teachers on request and may be downloaded as PDF files from the web site. More exercises will follow in the future.

Contact: info@astroex.org, www.astroex.org

**Exercise
1 - Measuring the Distance to Supernova 1987A**

Quick Summary

The geometry of
the nearest ring around Supernova 1987A (SN1987A) is introduced. We then define
the scale of the Hubble image of the supernova so that the angular diameter
of the ring and also the inclination of the ring relative to the plane of the
sky can be found. Observations from Earth show how light from the supernova
reached the different parts of the ring. Using light intensity measurements
and the speed of light, the physical dimensions of the ring can be found. Once
both the angular and the physical size of the ring have been determined, we
can determine the distance to SN 1987A itself.

**Exercise
2 - The Distance to Messier 100 as Determined By Cepheid Variable Stars**

Quick Summary (click here for the complete exercise)

In this exercise
we measure the period and apparent magnitudes of Cepheid variables in the galaxy
M100. The absolute magnitude is derived using the Period-Luminosity relation
and the distance to M100 can then be determined using the distance relation.
Finally we calculate a value for the Hubble constant (using a value for the
recession velocity of M100 observed by other scientists) and estimate the age
of the Universe.

**Exercise
3 - Measuring the Distance to the Cat's Eye Nebula**

Quick Summary

We measure the
angular expansion velocity of the Cat's Eye Nebula by careful investigation
of two Hubble images taken in 1994 and 1997. With the help of tangential velocity
measurements from an earlier scientific paper, it is possible to determine the
distance to the nebula. We also derive the distance by looking at how much the
radial intensity profiles of prominent features in the two images have changed
between 1994 and 1997.

**Exercise
4 - Measuring a Globular Star Cluster's Distance and Age**

Quick Summary

We measure blue
(mB) and green (visual, mV) magnitudes of selected stars in the outer regions
of a globular cluster shown on VLT images, convert the (mB-mV) values into stellar
surface temperatures (T) and plot the mV values as a function of the T values
on a Hertzsprung-Russell diagram. The cluster's Main Sequence, seen in the plotted
diagram, is compared with a distance-calibrated standard Main Sequence from
the nearby Hyades cluster. The distance to the cluster can be determined by
Main Sequence fitting and using the distance modulus. The cluster's age, which
incidentally places a lower limit on the age of the Universe, can be estimated
from the position of the turn-off point on the Main Sequence.

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