THE USM SOUTHWORTH PLANETARIUM
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43.6667° N                   70.2667° W
Altitude:   10 feet below sea level
Founded January 1970
Julian date:  24586769.5
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THE DAILY ASTRONOMER
Monday, July 15, 2019
Alpha Centauri

Good afternoon!
Ok, let's try this:   close your eyes and count to 2.
Well, that was easy, wasn't it?     Now,  during that brief moment when you
had your eyes closed, an abundance of photons left the photospheres of the
three stars comprising the Alpha Centauri system. At a distance of 4.37
light years, Alpha Centauri is the closest star system to the Sun.   A
minuscule part of the light that escaped those stars during that closed-eye
moment will reach Earth in early December 2023!    Imagine that!     The
light that left those stars is traveling unimpeded through outer space at
186,290 miles per second.  (Those photos are already 2.5 million miles from
the stars by now.)   Every second of every day without hindrance, the light
will move toward Earth at the maximum possible velocity.    All the same,
more than four years will elapse before that light arrives here.

But, who will see that light?
Well, it is popularly believed that Alpha Centauri is only visible in the
Southern Hemisphere.  In fact, any observer south of 30 degrees north
latitude can see Alpha Centauri.      Skywatchers in Florida can see it,
for instance.    However, Alpha Centauri is easiest to see in the southern
hemisphere.  For observers south of 30 degrees south latitude, Alpha
Centari is circumpolar, or always visible, along with its close companion,
Crux, the "Southern Cross."

[image: planetsatalp.jpg]*Alpha Centauri *and the Beta Centauri, the bright
star immediately to its right, are companions of the famous Southern Cross,
also known as "Crux."

While we quite logically cite Alpha Centauri as humanity's first
interstellar destination, we remind ourselves rather soberly that humans
have ventured only a quarter of a million miles from Earth, equal to less
than 1.5 light seconds.   Voyager 1, the most distant spacecraft, has been
traveling away from Earth for more than four decades and is almost 21 light
hours from its home world. Voyager would require tens of thousands of years
to reach Alpha Centuri if it were actually traveling in its direction. It
isn't.*

It is possible that by the time we do visit the Alpha Centauri system, we
could encounter some form of life.     So far, astronomers have confirmed
only one planet finding: an Earth-like planet in orbit around Proxima
Centauri.  Although Proxima Centauri is a red dwarf and about 20,000 times
fainter than the Sun, its one confirmed planet is within the star's
habitable zone: where conditions might be conducive to life.     This
statement is not to suggest that life must exist there:  after all, Venus
and Mars are both Earth-like worlds revolving within the Sun's habitable
zone.    However, as humans slowly develop the technology necessary for
long distance space travel, we might discover through observations of the
planet's atmosphere traces of gases indicative of metabolic activity.
That could give us the impetus to explore Alpha Centauri and begin our
arduous, but exciting odyssey through the galaxy.        Alpha Centauri is
our first step, one that is unfathomably far away.



*Assuming it isn't captured, the Voyager 1 craft is destined to come within
1.6 light years of the star AC+79 3888 in about 40,000 years