THE SOUTHWORTH PLANETARIUM
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43.6667° N                   70.2667° W
Altitude:  10 feet below sea level
Founded January 1970
Julian Date: 245914.16
2019-2020:  CXI
           "Heavens below!"

THE DAILY ASTRONOMER
Thursday, March 5, 2020
Star Crossed


We know that astronomy can be frightening. After all, through astronomy we
have learned that we're all amalgams of stardust that somehow evolved the
capacity for self-reflection.  Moreover, while the molecules comprising
everything percolated through the bubbling mud, gushing floods and
smouldering lava, the Universe beyond expanded to immense proportions.  All
the while, myriad stars and their attendant planets coalesced out of the
gases so that now trillions upon trillions of stars and planets populate
the cosmos.   Add to that immensity the now serious notion of other
Universes and one can feel vanishingly small in a space-time system that
stretches ad infinitum in all directions.     It is little wonder that
astronomy can be terribly sleep disturbing.

So, whenever someone tells us that an astronomical concept has caused them
fear, we feel compelled to alleviate the anxiety the concept aroused.   The
other day a young couple told me that their seven year old daughter was
worried about the Sun "running into another star and causing a big
explosion."    You see, some planetarium jerk had just told her and her
fellow audience members that the galaxy contains billions of stars.  This
young lady, being very thoughtful and logical, assumed that the Sun was
moving through a teeming mass of stars like a commuter on a crowded subway.

Well.
The Sun is moving through the Milky Way Galaxy at quite the impressive
speed of 143 miles per second.  Also, according to recent estimates, the
Milky Way Galaxy does contain more than one hundred billion stars.    A
star speeding quickly through such a star-rich galaxy would seem to be
careening inexorably toward a stellar collision.         It isn't.

The closest star system to the Sun, Alpha Centauri, is 4.4 light years
away, a distance almost equal to 25 trillion miles.      By scale, if the
Sun were a softball in Portland, Maine, Alpha Centauri would be two
softballs and a small apple in Florida.    (Alpha Centauri is a triple star
system with its red dwarf, Proxima Centauri closest to us.)    By this
scale model, one can see how infrequent any stellar collisions would be
here in the Milky Way's spiral arms where the stellar density is 0.004
stars per cubic light year.      Stellar collisions are more frequent in
more dense regions around the nucleus and in globular clusters.  However,
the Sun isn't about to venture toward such areas.

Astronomers have looked into the question of eventual Sun-star encounters.
Their research should do much to calm your nerves.  According to current
models, the dwarf star Gliese 710 will come within 1.5 light years of the
Sun in about 1.4 million years.   It is currently 63 light years away, but
moving toward us at 15 kilometers per second.

Of all the worries that life has to offer, we can be well assured that our
Sun will not collide with any other star...at least not for the foreseeable
future and most likely, never.       Sometimes astronomy can be a comfort,
as well.




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