When we look to the heavens on a clear summer
evening, a shimmering pale band of light appears across the sky like a
huge celestial archway. One Greek mythological story describes
the Milky Way as a smear of milk, created when the baby Herakles
suckled from the goddess Hera.
When Hera realised that the suckling infant was not her own but the
illegitimate son of Zeus and another woman, she pushed it away and the
spurting milk became the Milky Way. What we are actually observing is
part of the Milky Way Galaxy. This is our star city and our Sun is just
one star of billions that live within the Milky Way.
The Summer Milky Way by Axel Mellinger
We do not see the shape of our Galaxy from our
perspective on Earth as we live within the spiral structure. To
visualise the shape of the Milky Way we would need to travel up
and above our Galaxy, travelling at the speed of light for
thousands of years. Our Galaxy is in the shape of a disc with an
elliptical bulge at the centre. The disc is made up of several spiral
arms and the arm that contains the Sun is called the Orion arm, also
known as the local spur or Orion spur. Radio observations in the '70's
have shown the presence of a bar structure this has been later
confirmed by infra-red observations obtained by the COBE satellite.
Recent evidence has shown that there is a black hole at the centre of
the Galaxy.
The exercises in this
section explain some of the scales and distances that astronomers and
scientists work with and an interactive exercise has been developed by
the Swedish partner from the Onsala Space Observatory showing how
astronomers utilise radio telescopes to map the Milky Way.
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 Explore the star population inside an open cluster!
Introduction  An open cluster (sometimes called a Galactic Cluster) is a group of
10s or 100s of stars that were born from the same initial cloud of gas
(mainly Hydrogen) and dust. When they are young (a few million or tens
of millions of years old), these clusters contain some very large,
bright stars (called O or B-type stars). The very youngest clusters
(usually less than 10 million years old) often still contain the
remains of the gas cloud from which the stars were born – this is seen
as nebulosity.
Cluster stars are very useful as they were
all formed from the same giant cloud (so they have the same chemistry),
and they are all at about the same distance from us (although they are
typically hundreds or thousands of light years away!). By observing a
group of stars in a cluster, we can assume they are all made of the
same stuff, and they are all the same distance away from us – so any
differences between them are really caused by their different mass.
In
this project you will be shown how to use Faulkes Telescope data to
measure the intensity of light from the stars in a cluster (a process
known as photometry), through different filters, and plot the colours
of the stars on a 'colour-magnitude diagram'. Once a measure of how
“red” or “blue” the stars are is made, more informtion about them can
be obtained– massive stars are usually very blue (hot), intermediate
mass stars (like the Sun) are yellow, and the very lowest mass stars
are red (cool).
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Read more...
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 If you wonder how to discover a new, extrasolar planet, try this !
Roger Ferlet (IAP); Olivier Marco, Ester Aranzana Martinez, Sandra Greiss, & Jeehae Chun (University Pierre Marie Curie)
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Read more...
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 Seven steps for a dwarf star
From Doppler to exoplanets
Exercice proposed by :
Roger FERLET, Institut d’Astrophysique de Paris, France
Michel FAYE, lycée Louis Le Grand , Paris , France
Suzanne
FAYE, Lycée Chaptal , Paris , France
Summary :
- SPECTROSCOPY
- ANIMATED MOTION OF SPECTRUM LINES
- MEASURE WAVELENGTH λ AND FLUX, OPTICAL SPECTRUM
- CALCULATING RADIAL VELOCITY OF THE STAR WITH DOPPLER SHIFT
- RADIAL VELOCITY OF THE STAR , AS A FUNCTION OF DATE
- DETERMINING THE MASS OF THE COMPANION IN BINARY SYSTEM
- DISCOVERING AN EXOPLANET WITH DOPPLER SHIFT OF A STAR
Download the exercise :  pdf 317.75 Kb
Download the data (zip file): exoplanet_doppler 541.04 Kb
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 Learn how to observe variable stars !!
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 Have you ever looked at some large
numbers and observed how many zeros there are? For scientists investigating our
place in Space and the wider universe the numbers can become extremely large. Scientists
can deal with these large numbers by abbreviating them. This concept is known
as powers of ten.
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 SALSA-Onsala ("Such A Lovely Small Antenna'') is a 2.3 m diameter radio telescope built at Onsala Space Observatory, Sweden, to introduce pupils, students and teachers to the marvels of radio astronomy. The sensitive receiver makes it possible to detect quickly the radio emission due to the spectral line of atomic hydrogen at a wavelength of 21 cm and to map the large-scale distribution of hydrogen in our galaxy, the Milky Way.
The radio telescope can be operated remotely over the internet. In this report, we first review some properties of the Milky Way, starting by describing the Galactic coordinate system and the geometry of a rotating disk. We describe how spectral measurements can be used to derive information about both the kinematics and the distribution of the gas in the Milky Way. Then, we outline the observational procedure of how to use the radio telescope for real-time observations. Finally, we discuss how the data can be analysed.
You can look at the radio telescope in the webcam here
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