THE SOUTHWORTH PLANETARIUM
207-780-4249 www.usm.maine.edu/planet
70 Falmouth Street Portland, Maine 04103
43.6667° N, 70.2667° W
Founded January 1970
"To demonstrate that we are, indeed, capable of gracious
good manners, we will wish the Broncos and their celebrated
quarterback/artifact luck as they are devoured by the Carolina
juggernaut."
THE DAILY ASTRONOMER
Monday, January 25, 2016
Tide of Questions I
Last week, we received a tide of questions posed by students at
Portland's Breakwater School. Or, more correctly, Bernie Reim,
co-host of "Radio Astronomy,"* received these questions. Reim and his
cohort -a dolt whose name escapes me- attempted in vain to answer all
the questions. They managed to address only about half. However, we
decided to devote two DA articles to answering them all. By
answering them straight away, we save ourselves the trouble of having
to inscribe them all on parchment before pushing them into Pandora's
over stuffed jar.
We regret that we do not have the students' names and therefore cannot
attribute the questions to their specific authors. However, we
thank Breakwater School for these queries. We hope the answers prove
helpful.
DO YOU THINK THERE WILL BE A SUPERMASSIVE BLACK HOLE?
Oh, we KNOW there are supermassive black holes. Astronomers
believe that supermassive black holes reside at the cores of most
galaxies. Supermassive black holes can be millions of times more
massive than the Sun and have event horizons are large as Mercury's
orbit: an immense size for a black hole!
CAN YOU HEAR IN SPACE?
This answer will devastate "Star Wars" fans who love the roaring
whoosh sound generated by spacecraft as they tear through the void.
Unfortunately, no sound is possible in the outer space vacuum.
Sound needs a medium. For instance, as this very moment, I am
listening to the serene sounds particular to Sunday evenings. Wind
gusts through trees; the occasional car engine, and a philosophically
minded neighbor frantically jumping up and down on the pavement while
screaming, "The game was rigged! To hell with it! It was rigged!! To
hell with it!!!"
Were I suddenly to suck all of the air off Earth, I wouldn't be able
to hear any of these sounds at all.
On a side note, scientists once believed that a substance called
"aether" pervaded outer space. They reasoned that such a medium was
necessary so as to allow light, which travels as a wave,** to
propagate through space. Their attempts to detect the aether, most
notably during the famous Michaelson-Morley experiment (1887), were
unsuccessful. Physicists now know that, unlike sound, light needs
no medium through which to travel.
WHY IS THE SUN YELLOW?
Well, the Sun ISN'T yellow! When seen in outer space, the Sun
appears white. Like all stars, the Sun generates light photons along
all wavelengths. Each star has a "peak wavelength," defined as the
wavelength at which a star's generated its greatest amount of energy.
The Sun's peak wavelength is about 500 nm (nm = one billionth of a
meter), which is within the green part of the spectrum. The Sun
appears yellow because of Earth's atmosphere, which scatters blue
light around the sky. The yellow light isn't scattered and appears
to define the Sun's color. Were we to remove the atmosphere, the
Sun would appear intensely white. We'd have no sound, either. Of
course, if the air were suddenly gone, that would be the least of our
problems.
WHERE DID THE BUBBLE COME FROM (THAT EXPLODED IN THE BIG BANG)?
Here, we crash headlong into metaphysical speculation.
Cosmologists, those scientists who study the history and structure of
the Universe as a whole, cannot explain its ultimate origin.
Physical laws break down within the very first fractions of a second
after the Big Bang.. (0.00000000000000000000000000000000000000001
sec, to be specific.) This negligibly small time period following
the Big Bang, defined as the "Planck Wall," is a profound mystery.
We don't know how the Universe actually started. We also don't
know what preceded the Universe's birth. There is even a problem
with that question because that event created space, energy, matter
and time. As time, itself, was created, the question "what was
before the Big Bang?" is unaskable.
WHAT COLORS ARE STARS?
Stars can exhibit many colors. As mentioned previously in the
segment pertaining to the Sun's color, a star produces light at
various wavelengths. The star's temperature determines the peak
wavelength. Cooler stars, such as Betelgeuse (in Orion) and
Antares (in Scorpius), are cool and therefore appear reddish because
they'll produce more red light than any other color in the visible
spectrum. Hotter stars, such as Rigel (also in Orion), will appear
blue-white, as they'll produce more higher energy blue photons than
any other photons along the visible spectrum. Although we see the
stars as non-descript white dots, the sky is actually brilliantly
colorful. We can't perceive most of this color because are eyes
cannot perceive color at low light levels. Stars can be
blue-white, white, orange, or reddish.
WHAT'S IN BETWEEN THE STARS AND PLANETS?
Lots and lots of empty space! For instance, the nearest star to the
Sun, Proxima Centauri, is 4.2 light years away. This distance is
equal to about 25 trillion miles. If the Sun were a softball sized
sphere in Portland, Maine, Proxima Centauri would be a small apple in
Key West, Florida. Along with the empty space, of course, one can
have vast swaths of dust. Denser regions of dust and gas collect in
what we call "nebulae." Astronomers have to take this dust into
account when observing stars, as the most distant stars will appear
dimmer than they should be owing to the presence of obscuring dust.
This obscuration is properly known as "interstellar extinction."
ARE WE ALONE IN THE GALAXY? WHAT IS THE NEAREST PLANET THAT CAN
SUSTAIN LIFE? WHEN WILL WE DISCOVER LIFE ON ANOTHER PLANET?
We decided to combine these three questions as the phrase "We don't
know" is an appropriate response for all of them. Presently, we
only know of one life-harboring world in the Universe and we're living
on it. However, it seems highly unlikely that Earth is the only
such planet in the galaxy, let alone the cosmos. Astronomers have
found more than 2000*** exo-planets (planets in orbit around other
stars) and will most definitely discover tens of thousands more.
From these discoveries, they estimate that the Milky Way Galaxy could
contain hundreds of billions of planets. In fact, the planet
population could surpass the star population. The greater the
number of planets, the greater the likelihood that life exists
elsewhere in the galaxy. Personally, it seems highly probable that
the Galaxy teems with life forms, considering that our Universe is so
prodigiously creative. We just don't yet know where the nearest
hospitable planet is located or even if any exist. We also don't know
when we will actually find any.
HOW LONG DO PLANETS LAST?
Well, that depends on the star around which the planets revolve. We
know that the planets around the Sun will remain for billions of more
years. Eventually, the Sun will expand into a red giant once it
depletes it core hydrogen reserves. (The Sun fuses hydrogen into
helium to generate energy.) The Sun will likely envelope and therefore
incinerate Mercury, Venus and perhaps even Earth. However, it will
never expand out to Mars. When the Sun eventually perishes and
becomes a hot, planet-sized white dwarf, the other planets will remain
in orbit around it. Now, more massive stars can explode as
supernova. Such an explosion is so powerful, it would obliterate
the planets around it. Of course, the resultant debris could
reconstitute itself to form a new planet.
The short answer is that all the solar system's planet will persist
for billions of years more.
TOMORROW, WE ANSWER THE REST OF THE QUESTIONS...
*"Radio Astronomy" is a weekly, half-hour astronomy chat show
broadcast on WMPG (90.9 FM) at 1:00 p.m. every Friday.
**Yes, light is both a wave and a particle, which is why we have
quantum physics!
***2046 confirmed exo-planet discoveries as of Jan 22, 2016
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