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2.
OUR GALAXY
Galaxies are the places in the Universe where stars, nebulae and planets are
grouped together. The Earth is one of millions of celestial bodies found in our
galaxy, the Milky Way.
2.1.
The Milky Way
The name of our galaxy comes from its whitish appearance. We can often see it
on a cloudless night in areas without light pollution. It is also known El Camino de
Santiago.
The Milky Way is composed of millions of stars and has four arms. The Solar
System is located in the Orion Arm. The galaxy has three main parts: the nucleus,
the disk and the halo.
The
MilkyWay
is a spiral galaxy, located in a galaxy cluster called the
Local Group
,
together with other galaxies such as the Andromeda Galaxy and the Magellanic
Clouds.
Analyse
11.
Can you explain why the nucleus is brighter than the disk or halo?
Evaluate
12.
Do you think the Solar System is the only planetary system in the Milky
Way? Discuss and explain your answer.
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The structure of the Milky Way
Apply
10.
Look at the image above. Calculate:
a)
the dimensions of our galaxy in parsecs.
b)
the dimensions of our galaxy in AU.
Halo
: this surrounds the core and
the disk and contains isolated stars.
Disk
: this is formed by four arms
containing the youngest stars.
Nucleus
o
bulge
:
this is the centre of the galaxy
and it is formed by the oldest stars.
