Within this case you learn that stars that seem "fixed" on the sky
may actually move, even if their motion is so slow for the naked eye
to be undetectable. You compare two photographs of the Barnard's Star
taken several years apart and will be able to estimate its
displacement on the sky. Your estimate will be very close to actual
measurements.
Within this use case you learn about the difference between intrinsic
linear size and apparent angular size, a difference that is frequently
at the center of astronomical problems. Star clusters are the objects
used to illustrate this difference. You also learn some basic facts
about star clusters, whose distribution in space has helped us to
understand the structure of our Milky Way. Thanks to Aladin, you will
be able to explore their distribution on the sky on your own.
Within this use case you learn about the constellations of the
Zodiac, i.e. those crossed by the apparent path of the Sun during the
year. Together with some characteristics the orbital motion of the
Earth, in this use case you also find a short excursion into history
of astronomy. The use case also introduces the precession of the
equinoxes.
Within this use case you discover the shape and thickness of the disc
of our own Galaxy by counting stars within and around the Milky Way.
With the use of both Aladin and Stellarium you draw the line
corresponding to the disc of the Milky Way in a coordinate diagram.
Within this use case you meet representatives of the most interesting
categories of celestial objects. From stellar clusters to galaxies.
All objects are from the Messier catalog that includes some of the
most viewed objects of the deep sky.
Within this case you discover the geometry of the orbit of the Moon
and the nature of its phases. As special case of the circumstances of
Moon's orbit, the use case introduces the eclipses, both of Moon and
Sun.
Within this use case you recognize a physical association of stars
close in space as opposed to a superpositon created by projection
effects of stars very far one from the others. The key measure is
distance derived from parallax. With the true members of the
association (open cluster) you create a Herzsprung-Russell diagram as
in the tutorial “the stars” (ivo://edu.gavo.org/eurovo/aida_stars).
The Herzsprung-Russell diagram of stellar clusters is very important
because of the low noise of few unrelated stars.
If used in the classroom this advanced use case requires a reasonable
understanding of histograms and bidimensional scatter diagrams. It is
also rather long to perform from beginning to end.
Within this use case you discover the shapes of galaxies and their
classification according to the Hubble diagram. You are offered
sequences of galaxies with different morphologies and are asked to
order them. The morphological classification of galaxies is still in
use even if we have discovered that the Hubble diagram "per se" has no
direct physical or evolutionary meaning. Besides introducing the main
shapes of galaxies, the use case offer a demonstration of the
classification process, a fundamental tool of astronomers.
