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 Alpha
Orionis
(α Orionis)
conhecida como Betelgeuse é uma estrela
de brilho variável sendo a 10ª ou 12ª estrela
mais brilhante no firmamento. É também a segunda
estrela mais brilhante na constelação de Orion.
Apesar de ter a designação α ("alpha") na
Classificação de Bayer, ela não é mais brilhante
que Rigel (β Orionis).
Betelgeuse é na
verdade mais brilhante do que Rigel no
comprimento de onda infravermelho, mas não nos
comprimentos de onda visíveis, Betelgeuse é uma
estrela supergigante vermelha, e uma das maiores
estrelas conhecidas, sendo de grande interesse
para a astronomia. O diâmetro angular de
Betelgeuse foi medido pela primeira vez em
1920-1921 por Michelson e Pease, sendo uma das
cinco primeiras a serem medidas usando um
interferómetro no telescópio de 100 polegadas do
Monte Wilson. O seu diâmetro varia entre 500 e
900 vezes o do Sol. No diâmetro máximo, a
estrela seria maior que a órbita de Saturno se
colocada no lugar do Sol. Apesar de ser apenas
14 vezes mais massiva que o Sol, é cerca de
algumas centenas de milhões de vezes maior em
volume, como uma bola de futebol comparada a um
grande estádio de futebol. A sua proximidade à
Terra e o seu enorme tamanho fazem dela a
estrela com o terceiro maior diâmetro angular
vista da Terra , menor apenas que o Sol e R
Doradus. É uma das 12 estrelas em que os
telescópios atuais podem visualizar o seu disco
real.
Supernova
Os astrónomos
prevêem que Betelgeuse pode passar por uma
explosão supernova tipo II. No entanto, as
opiniões estão divididas quanto ao momento em
que isto deve ocorrer. Alguns sugerem que a
variabilidade atual como um sinal de que já está
na fase de queima de carbono do seu ciclo de
vida, e deve sofrer uma explosão supernova
aproximadamente nos próximos mil anos. Cépticos
discordam com esse ponto de vista e afirmam que
a estrela deve sobreviver muito mais tempo.
Mas, na internet há
centenas de rumores que a supernova vai explodir
esse ano de 2012 e Jucelino Luz, enviou cartas
avisando autoridades que a população poderá
ficas sossegada que não será nesse ano sua
explosão. Veja um trecho abaixo na carta
original.
Há consenso de que
tal supernova seria um evento astronómico
espectacular, mas não seria uma ameaça para a
vida na Terra, dada a enorme distância a que se
encontra. Mas a estrela vai tornar-se pelo menos
10000 vezes mais brilhante, o que significa um
brilho equivalente ao de uma Lua crescente.
Entretanto alguns crêem que ela pode chegar ao
brilho de uma Lua cheia (mv = -12.5). Esse
fenómeno deve durar por alguns meses, parecendo
uma pequena Lua cheia com a cor de uma lâmpada
incandescente à noite e facilmente visível
durante o dia. Após esse período a estrela vai
apagar-se gradualmente até que após alguns meses
ou anos desapareça complectamente e Orion perca
o ombro direito.
 O
nome é uma contração do árabe
يد الجوزا
yad
al-jawzā, ou "a mão do (guerreiro, homem) do
centro". Jauza, o do centro, inicialmente se
referia a Gémeos entre os Árabes, mas a algum
momento decidiram referir-se a Orion por este
nome. Durante a Idade Média o primeiro caracter
do nome
,
y (ﻴ,
com dois ponto sob ele), foi erroneamente
traduzido para o Latim como um b (ﺒ,
com um
ponto apenas), e Yad al-Jauza tornou-se
Bedalgeuze. Então, durante o Renascimento,
alguém tentou derivar o nome árabe deste nome
corrompido, e decidiu que ele foi escrito
originalmente como Bait al-Jauza. Esta pessoa
imaginativa então declarou que Bait seria
"braço" em Árabe, para surpresa dos árabes em
todo o mundo. O linguista sem nome da Renascença
então "corrigiu" a grafia para Betelgeuse, e o
termo moderno nasceu. Para que Betelgeuse
tivesse o sentido do "braço do centro", o
original deveria ser
ابط Ibţ (al-Jauza).
Jucelino Luz ,garante que coisas mais perigosas
na Terra que devemos nos preocupar e nesse
momento crucial de mudanças climáticas devemos
urgentemente tomar medidas cabíveis para
minimizar os problemas do Planeta.
Mario Ronco
Filho – Jornalista
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 Betelgeuse
history
Betelgeuse,
also known by its Bayer designation Alpha
Orionis (α
Orionis, α Ori),
is the eighth brightest star in the night sky
and second brightest star in the constellation
of Orion, outshining its neighbor Rigel (Beta
Orions) only rarely. Distinctly reddish-tinted,
it is a semi regular variable star whose
apparent magnitude varies between 0.2 and 1.2,
the widest range of any first magnitude star.
The star marks the upper right vertex of the
Winter Triangle and center of the Winter
Hexagon.
Classified as a
red supergiant, Betelgeuse is one of the largest
and most luminous stars known. If it were at the
center of our Solar System, its surface would
extend past the asteroid belt possibly to the
orbit of Jupiter and beyond, wholly engulfing
Mercury, Venus, Earth and Mars. However, with
distance estimates in the last century that have
ranged anywhere from 180 to 1,300 light years
from Earth, calculating its diameter, luminosity
and mass have proven difficult. Betelgeuse is
currently thought to lie around 640 light years
away, yielding a mean absolute magnitude of
about −6.05.
In 1920, Alpha Ori
was the first star (after the Sun) to have its
angular diameter measured. Since then,
researchers have used a number of telescopes to
measure this stellar giant, each with different
technical parameters, often yielding conflicting
results. Current estimates of the star's
apparent diameter range from about 0.043 to
0.056 arc seconds. This is a moving target at
best, as Betelgeuse appears to change shape
periodically. Because of limb darkening,
variability, and angular diameters that vary
with wavelength, the star remains a perplexing
mystery. To complicate matters further,
Betelgeuse has a complex, asymmetric envelope
caused by colossal mass loss involving huge
plumes of gas being expelled from its surface.
There is even evidence of stellar companions
orbiting within this gaseous envelope, possibly
contributing to the star's eccentric behavior.
Astronomers believe Betelgeuse is only 10
million years old, but has evolved rapidly
because of its high mass. It is thought to be a
runaway star from the Orion OB1 Association,
which also includes the late type O and B stars
in Orion's belt—Alnitak,
 Alnilam
and Mintaka. Currently in a late stage of
stellar evolution, Betelgeuse is expected to
explode as a type II supernova, possibly within
the next million years.
Betelgeuse and its
red coloration have been noted since antiquity;
the classical astronomer Ptolemy described its
color as ὑπόκιρρος (hypókirros), a term which
was later described by a translator of Ulugh
Beg's Zij-i Sultani as rubedo, Latin for "ruddiness".
In contrast, the historical record of Chinese
astronomers during the first century BC mention
Betelgeuse as having a yellow color. Prior to
the modern systems of stellar classification,
Angelo Secchi had created his own system of
spectral analysis with Antares and Betelgeuse as
the prototypes for his Class III (orange to red)
stars.
With the history
of astronomy intimately associated with
mythology and astrology prior to the scientific
revolution, the red star, like the planet Mars
that derives its name from a Roman war god, has
been closely associated with the martial
archetype of conquest for millennia, and by
extension the motif of death and rebirth. In
South African mythology, Betelgeuse was a lion
watching in a predatory manner the three zebras
represented by Orion's belt
The variation in
Betelgeuse's brightness was first described in
1836 by Sir John Herschel, when he published his
observations in Outlines of Astronomy; he noted
an increase in activity from 1836–1840, followed
by a subsequent reduction. In 1849, he noted a
shorter cycle of variability which peaked in
1852. Later observers recorded unusually high
maxima with an interval of several years, but
only small variations from 1957 to 1967. The
records of the American Association of Variable
Star Observers (AAVSO) show a maximum apparent
magnitude (brightness) of 0.2 in the years 1933
and 1942, with a minimum fainter than magnitude
1.2 in both 1927 and 1941This variability in
brightness may explain why Johann Bayer, with
the publication of his Uranometria in 1603,
designated the star alpha as it may have rivaled
the usually brighter Rigel (beta).
In 1920, Albert
Michelson and Francis Pease mounted a 6 meter
(20 ft) interferometer on the front of the 2.5
meter (100 inch) telescope at Mount Wilson
Observatory. Helped by John Anderson, the trio
measured the angular diameter of α Orion is at
0.047", a figure which resulted in a diameter of
3.84 × 108 km (240 million miles or 2.58 AU)
based on the then-current parallax value of
0.018". However there was known uncertainty
owing to limb darkening and measurement errors—a
central theme which would be the focus of
scientific inquiry for almost a century.
Beginning with this first angular measurement at
visible wavelengths, researchers have since
conducted multiple investigations ranging from
the ultraviolet to the mid infrared with
controvertible results.
 The
1950s and '60s saw important scientific
developments, the two Stroboscope projects and
the 1958 publication of Structure and Evolution
of the Stars, principally the work of Martin
Schwarzschild and his close colleague at
Princeton University, Richard Harm. This book
taught a generation of astrophysicists how to
use nascent computer technology to create
stellar models while the Stroboscope projects,
by taking instrumented balloons above the
Earth's turbulence, produced some of the finest
images of solar granules and sunspots ever seen,
thus confirming the existence of convection in
the solar atmosphere. Both developments would
prove to have a significant impact on our
understanding of the structure of red supergiant
like Betelgeuse.
The 1970s saw
several notable advances in interferometer from
the Berkeley Space Sciences Laboratory working
in the infrared and Antoine Labeyrie in the
visible, when researchers began to combine
images from multiple telescopes and later
invented "fringe-tracking" technology. But it
was not until the late 1980s and early 1990s,
when Betelgeuse became a regular target for
aperture masking interferometer that significant
breakthroughs occurred in visible-light and
infrared imaging. Pioneered by John E. Baldwin
and other colleagues of the Cavendish
Astrophysics Group, the new technique
contributed some of the most accurate
measurements of Betelgeuse to date while
revealing a number of bright spots on the star's
photosphere These were the first optical and
infrared images of a stellar disk other than the
Sun, first from ground-based interferometers and
later from higher-resolution observations of the
COAST telescope, with the "bright patches" or "hotspots"
potentially corroborating a theory put forth by
Schwarzschild decades earlier of massive
convection cells dominating the stellar surface
In 1995, the
Hubble Space Telescope's Faint Object Camera
captured an ultraviolet image of comparable
resolution—the first conventional-telescope
image (or "direct-image" in NASA terminology) of
the disk of another star. The image was taken at
ultraviolet wavelengths since ground-based
instruments cannot produce images in the
ultraviolet with the same precision as Hubble.
Like earlier images, this ultraviolet image also
contained a bright patch, indicating a hotter
region of about 2,000K, in this case on the
southwestern portion of the star's surface.
Subsequent ultraviolet spectra taken with the
Goddard High Resolution Spectrograph suggested
that the hot spot was one of Betelgeuse's poles
of rotation. This would give the rotational axis
an inclination of about 20° to the direction of
Earth, and a position angle from celestial North
of about 55°.Jucelino Luz had sent many letters
about it and he told about its explosion ….
Betelgeuse is
already old for its size class and is expected
to explode relatively soon compared to its age.
Solving the riddle of mass-loss will be the key
to knowing when a supernova may occur, an event
expected anytime in the next million years.
Supporting this hypothesis are a number of
unusual features that have been observed in the
interstellar medium of the Orion Molecular Cloud
Complex, which suggest that there have been
multiple supernova explosions in the recent
past. Betelgeuse's suspected birthplace in the
Orion OB1 Association is the probable location
for such supernovae. Since the oldest subgroup
in the association has an approximate age of 12
million years, the more massive stars likely had
sufficient time to evolve to this stage. Also,
because
runaway stars are
believed to be caused by supernova explosions,
there is strong evidence that OB stars μ
Columbae, AE Aurigae and 53 Arietis all
originated with such an explosion in Ori OB1
2.2, 2.7 and 4.9 million years ago.
Since then,
researchers have turned their attention to
analyzing the intricate dynamics of the star's
extended atmosphere and little else has been
published on the possibility of orbiting
companions, although as Xavier Haubois and his
team reiterate in 2009, the possibility of a
close companion contributing to the overall flux
has never been fully ruled out. Dommanget's
double star catalog (CCDM) lists at least four
adjacent stars, all within three arc minutes of
this stellar giant, yet aside from apparent
magnitudes and position angles, little else is
known. As the decade unfolds and new
technologies are brought to unraveling the
star's enigmatic past, we will likely see
conclusive evidence, one way or another, of any
potential star system. Given the planned
capabilities of the upcoming Gaia mission, a
confirmation could occur any time after the
mission's scheduled launch in December 2012. But
Jucelino´s dreams guarantee that Betelgeuse will
not blow up in 2012, 2013, 2014…
Mario Ronco
Filho – Jornalista ( colaborador )
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