Text at
http://howfarawayisit.com/documents/In this segment of our "How far away is it" video book, we cover the structure of the Milky Way galaxy.
After
a brief history of what we thought going into the 20th century and how
that changed, we give a high-level description of the three main
components: the galactic center with its black hole, the galactic disk
with its spiral arms, and the galactic halo stretching far out in all
directions.
Using the full power of the Hubble, Spitzer, and
Chandra space telescopes, we take a deep dive into the center of our
galaxy with its central bulge. We detail the evidence for the existence
of a supermassive black hole, Sagittarius A*, at the very center of the
galaxy's core. We cover and illustrate the work done by the UCLA
Galactic Centre Group in conjunction with the new Keck observatory on
top of the Mauna Kea volcano in Hawaii, and the Max Plank Institute for
Extraterrestrial Physics in Germany. This includes the obits of S0-2 and
S0-102 as they approach Sag A*. A look at the G2 Gas Cloud as it
approaches Sag A* is also included.
Next, we go a level deeper
into the nature of a Black Hole singularity. We review electron
exclusion pressure and neutron exclusion pressure forces that hold back
gravity for White Dwarfs and Neutron stars respectively. When that isn't
enough, we get the collapse is total. We cover the Schwarzschild
radius, event horizon, accretion disk and gamma-ray jets. In addition to
the supermassive black hole Sag A*, we show a few of the solar mass
black hole candidates including A0620-00, and GRO J1655-40.
We
then cover the structure of the galactic disk including: the bar core,
the two 3 Parsec arms, Scutum-Centaurus, Perseus, Sagittarius with its
Orion Spur, Norma and the Outer Arm. We review the locations of various
celestial objects we've seen in previous Milky Way segments, to show how
close to us they are. We also cover the disk's rotation and the Sun's
orbit. We end the galactic disk coverage by illustrating how far one
would have to go to take a picture that would include what we see in our
illustrations.
Next, we cover the galactic halo. We start with
Sharpley's globular cluster map that first showed that we were not at
the center of the galaxy. We cover the size of the halo, the inner and
outer halos orbital motion, and recent discoveries of massive amounts of
Hydrogen in the halo and this findings impact on the Dark Matter
debate.
We conclude with another look at the distance ladder that took us across the galaxy.
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