THE SOUTHWORTH PLANETARIUM
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Founded January 1970
Julian Date: 2458794.16
2019-2020:  XLVIII
                   “Never let the future disturb you. You will meet it, if
you have to, with the same weapons of reason which today arm you against
the present.”
                     -Marcus Aurelius

THE DAILY ASTRONOMER
Thursday, November 7, 2019
Andromeda Incoming!


[image: 960x0.jpg]

Astronomy forces us to confront the disquieting notion that not only are
our lives negligibly brief, but the sleep that rounds them encompasses
billions of years in both past and future.  So much transpired prior to our
births and even more will happen after our deaths.    Although astronomy
can't extend our lives beyond the biological bounds, it can help us
understand what will occur in the distant future, just as it has enabled us
to know what happened in the remote past.      For instance, we know that
our home galaxy, the Milky Way, is destined for a catastrophic collision
with the Andromeda Galaxy in about 4 - 6 billion years!   Although this
collision isn't imminent, computer models demonstrate quite clearly that it
is inevitable.

One can see the Andromeda Galaxy this very evening, but looking toward the
eastern evening sky.   This massive spiral galaxy appears as a smudge of
light within the constellation Andromeda, hence the name.  Such an enormous
galaxy appears so small because of its 2.2 million light years distance.
 (It is the most distant object visible to the unaided eye)*

[image: great-square.jpg]

To understand why two galaxies currently separated by 2.2 million light
years of space are actually moving toward each other, we should remember
that all massive objects gravitationally attract all other massive objects.
  Although the Universal expansion is drawing most galaxies away from each
other, the Milky Way and Andromeda Galaxies are so close that their mutual
gravitational attraction is causing them to move toward each other.  This
approach speed is approximately 300,000 miles per hour.   Though this
velocity is immense by terrestrial standards, it is glacial by galactic
terms.   Of course, as the distance between the galaxies decreases, this
approach speed will increase dramatically.


[image: 578746main_vv340_665.jpg]
* A view on our future:*   VV340,  also known as
a galactic "exclamation point, " shows us two galaxies
in the early stages of their collision.   Over the course of
millions of years, these two massive bodies will violently
merge together.    Image:  NASA.gov

Even though we won't know precisely what will occur during this collision,
we do know that the two galaxies will undergo a series of collisions as
they move back and forth through their mutual gravitational influence.
During this multi-million year long process, the galaxies will expel
innumerable stars into the vast gulfs of intergalactic space.  Eventually,
the turbulence will abate and the remaining stars will become incorporated
into a super galaxy containing nearly one trillion stars.  This stellar
population will include the stars within both bodies and those created by
the sudden collisions of the galaxies' substantial gas stores.

Astronomers have observed galaxies throughout the Universe in various
stages of merger and collision.    These observations have lent them
greater insight into the mechanisms involved in such dynamic galactic
interactions.  While we can't truly know if our Sun, which will be a well
matured star close to the end of its life cycle, will remain in the galaxy
or if it will be expelled, we can know that when we observe that light
smudge in Andromeda tonight, we'll be looking at a large spiral galaxy that
will ultimately become part of our own galactic home....in deep time.




*That tectonic pulse that just rattled your desk was the 120 decibel yawp
emanating from some astronomy people who insist that they've seen more
distant galaxies, such as the Triangulum Galaxy (M33), 2.78 million light
years away  or even Bode's Galaxy, which is 12 million light years away!
Well.    The Andromeda Galaxy is the most distant object known to be within
the usual naked eye limit of magnitude 6.0.    The Triangulum Galaxy and
Bode's Galaxy are both too faint to be within this limit.  HOWEVER, some
smart alecks endowed with keen eyesight, under dark pristine skies, and
immense amounts of time at their disposal, might be able to see these other
worlds.   Those of us who spend inordinate amounts of time in the dark
underground don't see quite as clearly.    On the other hand, we've evolved
IR sensing capabilities and always know what type of wine to serve with
boiled rodents,



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