 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Orion |
| Pronunciation | /ˈbiːtəldʒuːz, |
| Right ascension | 05h 55m 10.30536s |
| Declination | +07° 24′ 25.4304″ |
| Characteristics | |
| Evolutionary stage | Red supergiant |
| Spectral type | M1–M2 Ia–ab |
| Apparent magnitude (V) | 0.50 (0.0–1.3) |
| Apparent magnitude (J) | −3.00 |
| Apparent magnitude (K) | −4.05 |
| U−B color index | +2.06 |
| B−V color index | +1.85 |
| Variable type | SRc |
| Astrometry | |
| Radial velocity (Rv) | +21.91 km/s |
| Proper motion (μ) | RA: 26.42 ± 0.25 mas/yr Dec.: 9.60 ± 0.12 mas/yr |
| Parallax (π) | 4.51 ± 0.80 mas |
| Distance | 222+48 −34 pc |
| Absolute magnitude (MV) | −5.85 |
| Details | |
| Mass | 11.6+5.0 −3.9 M☉ |
| Radius | 887 ± 203, 955±217 R☉ |
| Luminosity | 90000 – 150000 L☉ |
| Surface gravity (log g) | −0.5 cgs |
| Temperature | 3590 K |
| Metallicity [Fe/H] | +0.05 dex |
| Rotational velocity (v sin i) | 5 km/s |
| Age | 8.0–8.5 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
This orange blob shows the nearby star Betelgeuse, as seen by the Atacama Large Millimeter/submillimeter Array
(ALMA). This is the first time that ALMA has ever observed the surface
of a star and this first attempt has resulted in the highest-resolution
image of Betelgeuse available.
Betelgeuse, also designated α Orionis (Latinised to Alpha Orionis, abbreviated Alpha Ori, α Ori), is on average the ninth-brightest star in the night sky and second-brightest in the constellation of Orion. It is a distinctly reddish, semiregular variable star whose apparent magnitude varies between 0.0 and 1.3, the widest range of any first-magnitude star. Betelgeuse is one of three stars that make up the Winter Triangle asterism, and it marks the center of the Winter Hexagon. If the human eye could view all wavelengths of radiation, Betelgeuse would be the brightest star in the night sky.
Classified as a red supergiant of spectral type M1-2, the star is one of the largest stars visible to the naked eye. If Betelgeuse were at the center of the Solar System, its surface would extend past the asteroid belt, completely engulfing the orbits of Mercury, Venus, Earth, Mars, and possibly Jupiter. However, there are several other red supergiants in the Milky Way that could be larger, such as Mu Cephei and VY Canis Majoris. Calculations of its mass range from slightly under ten to a little over twenty times that of the Sun. It is calculated to be 640 light-years away, yielding an absolute magnitude
of about −6. Less than 10 million years old, Betelgeuse has evolved
rapidly because of its high mass. Having been ejected from its
birthplace in the Orion OB1 Association—which includes the stars in Orion's Belt—this runaway star has been observed moving through the interstellar medium at a speed of 30 km/s, creating a bow shock over four light-years wide. Betelgeuse is in a late stage of stellar evolution, and it is expected to explode as a supernova within the next million years.
In 1920, Betelgeuse became the first extrasolar star to have the angular size of its photosphere measured. Subsequent studies have reported an angular diameter (apparent size) ranging from 0.042 to 0.056 arcseconds, with the differences ascribed to the non-sphericity, limb darkening, pulsations, and varying appearance at different wavelengths. It is also surrounded by a complex, asymmetric envelope roughly 250 times the size of the star, caused by mass loss from the star itself. The angular diameter of Betelgeuse is only exceeded by R Doradus and the Sun.
Nomenclature
α Orionis (Latinised to Alpha Orionis) is the star's Bayer designation. The traditional name Betelgeuse is derived from the Arabic إبط الجوزاء Ibṭ al-Jauzā’, meaning "the underarm of Orion", or يد الجوزاء Yad al-Jauzā’, meaning "the hand of Orion" (see below). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Betelgeuse for this star. It is now so entered in the IAU Catalog of Star Names.
Observational history
Betelgeuse and its red coloration have been noted since antiquity; the classical astronomer Ptolemy described its color as ὑπόκιρρος (hypókirrhos), a term that was later described by a translator of Ulugh Beg's Zij-i Sultani as rubedo, Latin for "ruddiness". In the nineteenth century, before modern systems of stellar classification, Angelo Secchi included Betelgeuse as one of the prototypes for his Class III (orange to red) stars.
By contrast, three centuries before Ptolemy, Chinese astronomers
observed Betelgeuse as having a yellow coloration; if accurate, such an
observation could suggest the star was in a yellow supergiant phase around the beginning of the Christian era, a possibility given current research into the complex circumstellar environment of these stars.
Nascent discoveries
Sir John Herschel in 1867
The variation in Betelgeuse's brightness was first described in 1836 by Sir John Herschel, when he published his observations in Outlines of Astronomy. From 1836 to 1840, he noticed significant changes in magnitude when Betelgeuse outshone Rigel in October 1837 and again in November 1839.
A 10-year quiescent period followed; then in 1849, Herschel noted
another short cycle of variability, which peaked in 1852. Later
observers recorded unusually high maxima with an interval of years, but only small variations from 1957 to 1967. The records of the American Association of Variable Star Observers (AAVSO) show a maximum brightness of 0.2 in 1933 and 1942, and a minimum of 1.2, observed in 1927 and 1941. This variability in brightness may explain why Johann Bayer, with the publication of his Uranometria in 1603, designated the star alpha as it probably rivaled the usually brighter Rigel (beta). From Arctic latitudes, Betelgeuse's red color and higher location in the sky than Rigel meant the Inuit regarded it as brighter, and one local name was Ulluriajjuaq "large star".
In 1920, Albert Michelson and Francis Pease mounted a 6-meter interferometer on the front of the 2.5-meter telescope at Mount Wilson Observatory. Helped by John Anderson, the trio measured the angular diameter of Betelgeuse at 0.047", a figure which resulted in a diameter of 3.84 × 108 km (2.58 AU) based on the parallax value of 0.018". However, limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements.
The 1950s and 1960s saw two developments that would affect stellar convection theory in red supergiants: the Stratoscope projects and the 1958 publication of Structure and Evolution of the Stars, principally the work of Martin Schwarzschild and his colleague at Princeton University, Richard Härm.
This book disseminated ideas on how to apply computer technologies to
create stellar models, while the Stratoscope projects, by taking
balloon-borne telescopes 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.
Imaging breakthroughs
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1988/9 UV HST images of Betelgeuse showing asymmetrical pulsations with corresponding spectral line profiles
Astronomers in the 1970s saw some major advances in astronomical imaging technology beginning with Antoine Labeyrie's invention of speckle interferometry, a process that significantly reduced the blurring effect caused by astronomical seeing. It increased the optical resolution of ground-based telescopes, allowing for more precise measurements of Betelgeuse's photosphere. With improvements in infrared telescopy atop Mount Wilson, Mount Locke and Mauna Kea in Hawaii, astrophysicists began peering into the complex circumstellar shells surrounding the supergiant, causing them to suspect the presence of huge gas bubbles resulting from convection. But it was not until the late 1980s and early 1990s, when Betelgeuse became a regular target for aperture masking interferometry, that breakthroughs occurred in visible-light and infrared imaging. Pioneered by John E. Baldwin and colleagues of the Cavendish Astrophysics Group, the new technique employed a small mask with several holes in the telescope pupil plane, converting the aperture into an ad-hoc interferometric array.
The technique contributed some of the most accurate measurements of
Betelgeuse while revealing bright spots on the star's photosphere. These were the first optical and infrared images of a stellar disk other than the Sun, taken first from ground-based interferometers and later from higher-resolution observations of the COAST telescope.
The "bright patches" or "hotspots" observed with these instruments
appeared to corroborate 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
with a resolution superior to that obtained by ground-based
interferometers—the first conventional-telescope image (or
"direct-image" in NASA terminology) of the disk of another star. Because ultraviolet light is absorbed by the Earth's atmosphere, observations at these wavelengths are best performed by space telescopes. Like earlier pictures, this image contained a bright patch indicating a region in the southwestern quadrant 2000 K hotter than the stellar 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°.
Recent studies
In a study published in December 2000, the star's diameter was measured with the Infrared Spatial Interferometer (ISI) at mid-infrared wavelengths producing a limb-darkened estimate of 55.2 ± 0.5 milliarcseconds (mas)—a figure entirely consistent with Michelson's findings eighty years earlier. At the time of its publication, the estimated parallax from the Hipparcos
mission was 7.63 ± 1.64 mas, yielding an estimated radius for
Betelgeuse of 3.6 AU. However, an infrared interferometric study
published in 2009 announced that the star had shrunk by 15% since 1993
at an increasing rate without a significant diminution in magnitude. Subsequent observations suggest that the apparent contraction may be due to shell activity in the star's extended atmosphere.
In addition to the star's diameter, questions have arisen about
the complex dynamics of Betelgeuse's extended atmosphere. The mass that
makes up galaxies is recycled as stars are formed and destroyed, and red supergiants are major contributors, yet the process by which mass is lost remains a mystery.
With advances in interferometric methodologies, astronomers may be
close to resolving this conundrum. In July 2009, images released by the European Southern Observatory, taken by the ground-based Very Large Telescope Interferometer (VLTI), showed a vast plume of gas extending 30 AU from the star into the surrounding atmosphere. This mass ejection was equal to the distance between the Sun and Neptune
and is one of multiple events occurring in Betelgeuse's surrounding
atmosphere. Astronomers have identified at least six shells surrounding
Betelgeuse. Solving the mystery of mass loss in the late stages of a
star's evolution may reveal those factors that precipitate the explosive
deaths of these stellar giants.
Observation
Image showing Betelgeuse (top left) and the dense nebulae of the Orion Molecular Cloud Complex (Rogelio Bernal Andreo)
In the night sky, Betelgeuse is easy to spot with the naked eye owing to its distinctive orange-red color. In the Northern Hemisphere,
beginning in January of each year, it can be seen rising in the east
just after sunset. By mid-September to mid-March (best in mid-December),
it is visible to virtually every inhabited region of the globe, except
for a few research stations in Antarctica
at latitudes south of 82°. In May (moderate northern latitudes) or June
(southern latitudes), the red supergiant can be seen briefly on the
western horizon after sunset, reappearing again a few months later on
the eastern horizon before sunrise. In the intermediate period
(June–July) it is invisible to the naked eye (visible only with a
telescope in daylight), unless around midday (when the Sun is below
horizon) on Antarctic regions between 70° and 80° south latitude.
Betelgeuse is a variable star whose brightness ranges between 0.0
and 1.3. There are periods when it will surpass Rigel to become the
sixth brightest star, and occasionally it will be even brighter than Capella. At its faintest Betelgeuse can fall behind Deneb and Beta Crucis, themselves both slightly variable, to be the 20th-brightest star.
Betelgeuse has a color index (B–V) of 1.85—a figure which points to its advanced "redness". The photosphere has an extended atmosphere, which displays strong lines of emission rather than absorption,
a phenomenon that occurs when a star is surrounded by a thick gaseous
envelope (rather than ionized). This extended gaseous atmosphere has
been observed moving away from and towards Betelgeuse, depending on
radial velocity fluctuations in the photosphere. Betelgeuse is the
brightest near-infrared source in the sky with a J band magnitude of −2.99. As a result, only about 13% of the star's radiant energy
is emitted in the form of visible light. If human eyes were sensitive
to radiation at all wavelengths, Betelgeuse would appear as the
brightest star in the night sky.
Various catalogues list up to nine faint visual companions to
Betelgeuse. They are at distances of about one to four arc-minutes and
all are fainter than 10th magnitude.
Star system
Betelgeuse
is generally considered to be a single isolated star and a runaway
star, not currently associated with any cluster or star-forming region,
although its birthplace is unclear.
Two spectroscopic companions have been proposed to the red supergiant star. Analysis of polarization
data from 1968 through 1983 indicated a close companion with a periodic
orbit of about 2.1 years. Using speckle interferometry, the team
concluded that the closer of the two companions was located at 0.06″±0.01″
(~9 AU) from the main star with a position angle (PA) of 273 degrees,
an orbit that would potentially place it within the star's chromosphere. The more distant companion was estimated at 0.51″±0.01″ (~77 AU) with a PA of 278 degrees. Further studies have found no evidence for these companions or have actively refuted their existence, but the possibility of a close companion contributing to the overall flux has never been fully ruled out.
High-resolution interferometry of Betelgeuse and its vicinity, far
beyond the technology of the 1980s and '90s, have not detected any
companions.
Distance measurements
NRAO's Very Large Array used to derive Betelgeuse's 2008 distance estimate
Parallax
is the apparent change of the position of an object, measured in
seconds of arc, caused by the change of position of the observer of that
object. As the Earth orbits the Sun, every star is seen to shift by a
fraction of an arc second, which measure, combined with the baseline
provided by the Earth's orbit gives the distance to that star. Since the
first successful parallax measurement by Friedrich Bessel
in 1838, astronomers have been puzzled by Betelgeuse's apparent
distance. Knowledge of the star's distance improves the accuracy of
other stellar parameters, such as luminosity that, when combined with an angular diameter, can be used to calculate the physical radius and effective temperature; luminosity and isotopic abundances can also be used to estimate the stellar age and mass. In 1920, when the first interferometric studies were performed on the star's diameter, the assumed parallax was 0.0180 arcseconds. This equated to a distance of 56 parsecs (pc) or roughly 180 light-years
(ly), producing not only an inaccurate radius for the star but every
other stellar characteristic. Since then, there has been ongoing work to
measure the distance of Betelgeuse, with proposed distances as high as
400 pc or about 1300 ly.
Before the publication of the Hipparcos Catalogue (1997), there were two conflicting parallax measurements for Betelgeuse. The first, in 1991, gave a parallax of π = 9.8 ± 4.7 mas, yielding a distance of roughly 102 pc or 330 ly. The second was the Hipparcos Input Catalogue (1993) with a trigonometric parallax of π = 5 ± 4 mas, a distance of 200 pc or 650 ly.
Given this uncertainty, researchers were adopting a wide range of
distance estimates, leading to significant variances in the calculation
of the star's attributes.
The results from the Hipparcos mission were released in 1997. The
measured parallax of Betelgeuse was π = 7.63 ± 1.64 mas, which equated
to a distance of 131 pc or roughly 430 ly, and had a smaller reported
error than previous measurements.
However, later evaluation of the Hipparcos parallax measurements for
variable stars like Betelgeuse found that the uncertainty of these
measurements had been underestimated. In 2007, an improved figure of π = 6.55±0.83 was calculated, hence a much tighter error factor yielding a distance of roughly 152±20 pc or 520±73 ly.
In 2008, using the Very Large Array (VLA), produced a radio solution of π = 5.07±1.10 mas, equalling a distance of 197±45 pc or 643±146 ly. As the researcher, Harper, points out: "The revised Hipparcos parallax leads to a larger distance (152±20 pc) than the original; however, the astrometric solution still requires a significant cosmic noise
of 2.4 mas. Given these results it is clear that the Hipparcos data
still contain systematic errors of unknown origin." Although the radio
data also have systematic errors, the Harper solution combines the
datasets in the hope of mitigating such errors. An updated result from further observations with ALMA and e-Merlin gives a parallax of 4.51±0.8 mas and a distance of 222+34
−48 pc. Further observations have resulted in a slightly revised parallax of 4.51±0.80.
−48 pc. Further observations have resulted in a slightly revised parallax of 4.51±0.80.
Although the European Space Agency's current Gaia mission
was not expected to produce good results for stars brighter than the
approximately V=6 saturation limit of the mission's instruments,
actual operation has shown good performance on objects to about
magnitude +3. Forced observations of brighter stars mean that final
results should be available for all bright stars and a parallax for
Betelgeuse will be published an order of magnitude more accurate than
currently available.
Variability
AAVSO V-band light curve of Betelgeuse (Alpha Orionis) from Dec 1988 to Aug 2002
Betelgeuse is classified as a semiregular variable star,
indicating that some periodicity is noticeable in the brightness
changes, but amplitudes may vary, cycles may have different lengths, and
there may be standstills or periods of irregularity. It is placed in
subgroup SRc; these are pulsating red supergiants with amplitudes around
one magnitude and periods from tens to hundreds of days.
Betelgeuse typically shows only small brightness changes near to
magnitude +0.5, although at its extremes it can become as bright as
magnitude 0.0 or as faint as magnitude +1.3. Betelgeuse is listed in the
General Catalogue of Variable Stars with a possible period of 2,335 days. More detailed analyses have shown a main period near 400 days and a longer secondary period around 2,100 days.
Radial pulsations of red supergiants are well-modeled and show that periods of a few hundred days are typically due to fundamental and first overtone pulsation. Lines in the spectrum of Betelgeuse show doppler shifts indicating radial velocity
changes corresponding, very roughly, to the brightness changes. This
demonstrates the nature of the pulsations in size, although
corresponding temperature and spectral variations are not clearly seen. Variations in the diameter of Betelgeuse have also been measured directly.
The source of the long secondary periods is unknown, but they certainly aren't due to radial pulsations.
Interferometric observations of Betelgeuse have shown hotspots that are
thought to be created by massive convection cells, a significant
fraction of the diameter of the star and each emitting 5–10% of the
total light of the star.
One theory to explain long secondary periods is that they are caused by
the evolution of such cells combined with the rotation of the star. Other theories include close binary interactions, chromospheric magnetic activity influencing mass loss, or non-radial pulsations such as g-modes.
In addition to the discrete dominant periods, small-amplitude stochastic variations are seen. It is proposed that this is due to granulation, similar to the same effect on the sun but on a much larger scale. Aboriginal
people from the Great Victoria Desert of South Australia observed the
variability of Betelgeuse and incorporated it into their oral traditions
as Nyeeruna (Orion).
Nyeeruna generates fire-magic in his right hand (Betelgeuse) to gain
access to the Yugarilya sisters of the Pleiades, but is prevented from
doing so by the eldest sister Kambugudha (Hyades), who kicks sand into
his face, causing his fire-magic to dissipate in his humiliation. This
is described in the oral tradition as a cyclic process, with Nyeeruna's
right hand brightening and fading over time.
Diameter
On 13 December 1920, Betelgeuse became the first star outside the
Solar System to have the angular size of its photosphere measured.
Although interferometry was still in its infancy, the experiment proved
a success. The researchers, using a uniform disk model, determined that
Betelgeuse had a diameter of 0.047 arcseconds, although the stellar
disk was likely 17% larger due to the limb darkening, resulting in an estimate for its angular diameter of about 0.055". Since then, other studies have produced angular diameters that range from 0.042 to 0.069 arcseconds.
Combining these data with historical distance estimates of 180 to
815 ly yields a projected radius of the stellar disk of anywhere from
1.2 to 8.9 AU. Using the Solar System for comparison, the orbit of Mars is about 1.5 AU, Ceres in the asteroid belt 2.7 AU, Jupiter
5.5 AU—so, assuming Betelgeuse occupying the place of the Sun, its
photosphere might extend beyond the Jovian orbit, not quite reaching Saturn at 9.5 AU.
Radio
image from 1998 (pre-Harper) showing the size of Betelgeuse's
photosphere (circle) and the effect of convective forces on the star's
atmosphere
The precise diameter has been hard to define for several reasons:
- Betelgeuse is a pulsating star, so its diameter changes with time;
- The star has no definable "edge" as limb darkening causes the optical emissions to vary in color and decrease the farther one extends out from the center;
- Betelgeuse is surrounded by a circumstellar envelope composed of matter ejected from the star—matter which absorbs and emits light—making it difficult to define the photosphere of the star;
- Measurements can be taken at varying wavelengths within the electromagnetic spectrum and the difference in reported diameters can be as much as 30–35%, yet comparing one finding with another is difficult as the star's apparent size differs depending on the wavelength used. Studies have shown that the measured angular diameter is considerably larger at ultraviolet wavelengths, decreases through the visible to a minimum in the near-infrared, and increase again in the mid-infrared spectrum;
- Atmospheric twinkling limits the resolution obtainable from ground-based telescopes since turbulence degrades angular resolution.
To overcome these challenges, researchers have employed various solutions. Astronomical interferometry, first conceived by Hippolyte Fizeau in 1868, was the seminal concept that has enabled major improvements in modern telescopy and led to the creation of the Michelson interferometer in the 1880s, and the first successful measurement of Betelgeuse. Just as human depth perception increases when two eyes instead of one perceive an object, Fizeau proposed the observation of stars through two apertures instead of one to obtain interferences
that would furnish information on the star's spatial intensity
distribution. The science evolved quickly and multiple-aperture
interferometers are now used to capture speckled images, which are synthesized using Fourier analysis to produce a portrait of high resolution. It was this methodology that identified the hotspots on Betelgeuse in the 1990s. Other technological breakthroughs include adaptive optics, space observatories like Hipparcos, Hubble and Spitzer,
and the Astronomical Multi-BEam Recombiner (AMBER), which combines the
beams of three telescopes simultaneously, allowing researchers to
achieve milliarcsecond spatial resolution.
Which part of the electromagnetic spectrum—the visible, near-infrared (NIR)
or mid-infrared (MIR)—produces the most accurate angular measurement is
still debated. In 1996, Betelgeuse was shown to have a uniform disk of
56.6 ± 1.0 mas. In 2000, the SSL team produced another measure of 54.7 ±
0.3 mas, ignoring any possible contribution from hotspots, which are
less noticeable in the mid-infrared.
Also included was a theoretical allowance for limb darkening, yielding a
diameter of 55.2 ± 0.5 mas. The earlier estimate equates to a radius of
roughly 5.6 AU or 1200 R☉, assuming the 2008 Harper distance of 197.0 ± 45 pc, a figure roughly the size of the Jovian orbit of 5.5 AU, published in 2009 in Astronomy Magazine and a year later in NASA's Astronomy Picture of the Day.
A team of astronomers working in the near-infrared announced in 2004,
that the more accurate photospheric measurement was 43.33 ± 0.04 mas.
The study also put forth an explanation as to why varying wavelengths
from the visible to mid-infrared produce different diameters: the star
is seen through a thick, warm extended atmosphere. At short wavelengths
(the visible spectrum) the atmosphere scatters light, thus slightly
increasing the star's diameter. At near-infrared wavelengths (K and L bands),
the scattering is negligible, so the classical photosphere can be
directly seen; in the mid-infrared the scattering increases once more,
causing the thermal emission of the warm atmosphere to increase the
apparent diameter.
Studies with the IOTA
and VLTI published in 2009 brought strong support to Perrin's analysis
and yielded diameters ranging from 42.57 to 44.28 mas with comparatively
insignificant margins of error.
In 2011, a third estimate in the near-infrared corroborating the 2009
numbers, this time showing a limb-darkened disk diameter of 42.49 ± 0.06
mas.
Consequently, if one combines the smaller Hipparcos distance from van
Leeuwen of 152 ± 20 pc with Perrin's angular measurement of 43.33 mas, a
near-infrared photospheric estimate would equate to about 3.4 AU or
730 R☉.
A 2014 paper derives an angular diameter of 42.28 mas (equivalent to a
41.01 mas uniform disc) using H and K band observations made with the
VLTI AMBER instrument.
Central to this discussion, it was announced in 2009, that the
radius of Betelgeuse had shrunk from 1993 to 2009 by 15%, with the 2008
angular measurement equal to 47.0 mas, not too far from Perrin's
estimate.
Unlike most earlier papers, this study encompassed a 15-year period at
one specific wavelength. Earlier studies have typically lasted one to
two years by comparison and have explored multiple wavelengths, often
yielding vastly different results. The diminution in Betelgeuse's apparent size
equates to a range of values between 56.0 ± 0.1 mas seen in 1993 to
47.0 ± 0.1 mas seen in 2008—a contraction of almost 0.9 AU in 15 years.
What is not fully known is whether this observation is evidence of a
rhythmic expansion and contraction of the star's photosphere as
astronomers have theorized, and if so, what the periodic cycle might be,
although Townes suggested that if a cycle does exist, it is probably a
few decades long.
Other possible explanations are photospheric protrusions due to
convection or a star that is not spherical but asymmetric causing the appearance of expansion and contraction as the star rotates on its axis.
The debate about differences between measurements in the
mid-infrared, which suggest a possible expansion and contraction of the
star, and the near-infrared, which advocates a relatively constant
photospheric diameter, remains to be resolved. In a paper published in
2012, the Berkeley team reported that their measurements were "dominated
by the behavior of cool, optically thick material above the stellar
photosphere," indicating that the apparent expansion and contraction may
be due to activity in the star's outer shells and not the photosphere
itself.
This conclusion, if further corroborated, would suggest an average
angular diameter for Betelgeuse closer to Perrin's estimate at
43.33 arcseconds, hence a stellar radius of about 3.4 AU (730 R☉) assuming the shorter Hipparcos distance of 498 ± 73 ly in lieu of Harper's estimate at 643 ± 146 ly. The Gaia spacecraft may clarify assumptions presently used in calculating the size of Betelgeuse's stellar disk.
Once considered as having the largest angular diameter of any star in the sky after the Sun, Betelgeuse lost that distinction in 1997 when a group of astronomers measured R Doradus
with a diameter of 57.0 ± 0.5 mas, although R Doradus, being much
closer to Earth at about 200 ly, has a linear diameter roughly one-third
that of Betelgeuse.
The generally reported radii of large cool stars are Rosseland radii,
defined as the radius of the photosphere at a specific optical depth of
two thirds. This corresponds to the radius calculated from the
effective temperature and bolometric luminosity. The Rosseland radius
differs from directly measured radii, but there are widely used
conversion factors depending on the wavelength used for the angular
measurements.
For example, a measured angular diameter of 55.6 mas corresponds to a
Rosseland mean diameter of 56.2 mas. The Rosseland radius derived from
angular measurements of the star's photosphere rather than an extended
envelope is 887 R☉.
Physical characteristics
(July 2008, outdated). Relative sizes of the planets in the Solar System and several stars, including Betelgeuse.
Size comparison of Betelgeuse, Mu Cephei, KY Cygni, and V354 Cephei, according to Emily Levesque.
Betelgeuse is a very large, luminous but cool star classified as an M1-2 Ia-ab red supergiant. The letter "M" in this designation means that it is a red star belonging to the M spectral class and therefore has a relatively low photospheric temperature; the "Ia-ab" suffix luminosity class
indicates that it is an intermediate-luminosity supergiant, with
properties partway between a normal supergiant and a luminous
supergiant. Since 1943, the spectrum of Betelgeuse has served as one of
the stable anchor points by which other stars are classified.
Uncertainty in the star's surface temperature, diameter, and
distance make it difficult to achieve a precise measurement of
Betelgeuse's luminosity, but research from 2012 quotes a luminosity of
around 126000 L☉, assuming a distance of 200 pc. Studies since 2001 report effective temperatures ranging from 3,250 to 3,690 K.
Values outside this range have previously been reported, and much of
the variation is believed to be real, due to pulsations in the
atmosphere. The star is also a slow rotator and the most recent velocity recorded was 5 km/s—much slower than Antares which has a rotational velocity of 20 km/s.
The rotation period depends on Betelgeuse's size and orientation to
Earth, but it has been calculated to take 8.4 years to turn on its axis.
In 2004, astronomers using computer simulations speculated that
even if Betelgeuse is not rotating it might exhibit large-scale magnetic
activity in its extended atmosphere, a factor where even moderately
strong fields could have a meaningful influence over the star's dust,
wind and mass-loss properties. A series of spectropolarimetric observations obtained in 2010 with the Bernard Lyot Telescope at Pic du Midi Observatory
revealed the presence of a weak magnetic field at the surface of
Betelgeuse, suggesting that the giant convective motions of supergiant
stars are able to trigger the onset of a small-scale dynamo effect.
Mass
Betelgeuse
has no known orbital companions, so its mass cannot be calculated by
that direct method. Modern mass estimates from theoretical modelling
have produced values of 9.5–21 M☉, with values of 5 M☉–30 M☉ from older studies. It has been calculated that Betelgeuse began its life as a star of 15–20 M☉, based on a solar luminosity of 90,000–150,000. A novel method of determining the supergiant's mass was proposed in 2011, arguing for a current stellar mass of 11.6 M☉ with an upper limit of 16.6 and lower of 7.7 M☉,
based on observations of the star's intensity profile from narrow
H-band interferometry and using a photospheric measurement of roughly
4.3 AU or 955 R⊙. Model fitting to evolutionary tracks give a current mass of 19.4–19.7 M☉, from an initial mass of 20 M☉.
Motion
Orion OB1 Association
The kinematics of Betelgeuse are complex. The age of Class M supergiants with an initial mass of 20 M☉ is roughly 10 million years.
Starting from its present position and motion a projection back in time
would place Betelgeuse around 290 parsecs farther from the galactic plane—an implausible location, as there is no star formation region there. Moreover, Betelgeuse's projected pathway does not appear to intersect with the 25 Ori subassociation or the far younger Orion Nebula Cluster (ONC, also known as Ori OB1d), particularly since Very Long Baseline Array
astrometry yields a distance from Betelgeuse to the ONC of between 389
and 414 parsecs. Consequently, it is likely that Betelgeuse has not
always had its current motion through space but has changed course at
one time or another, possibly the result of a nearby stellar explosion. An observation by the Herschel Space Observatory in January 2013 revealed that the star's winds are crashing against the surrounding interstellar medium.
The most likely star-formation scenario for Betelgeuse is that it is a runaway star from the Orion OB1 Association.
Originally a member of a high-mass multiple system within Ori OB1a,
Betelgeuse was probably formed about 10–12 million years ago, but has evolved rapidly due to its high mass.
Like many young stars in Orion whose mass is greater than 10 M☉, Betelgeuse will use its fuel quickly and not live long. On the Hertzsprung–Russell diagram, Betelgeuse has moved off the main sequence and has swelled and cooled to become a red supergiant.
Although young, Betelgeuse has exhausted the hydrogen in its core,
causing the core to contract under the force of gravity into a hotter
and denser state. As a result, it has begun to fuse helium into carbon and oxygen and has ignited a hydrogen
shell outside the core. The hydrogen-burning shell and the contracting
core cause the outer envelope to expand and cool. Its mass is such that
the star will eventually fuse higher elements through neon, magnesium, and silicon all the way to iron, at which point it will collapse and explode, probably as a type II supernova.
Circumstellar dynamics
Image from ESO's Very Large Telescope showing the stellar disk and an extended atmosphere with a previously unknown plume of surrounding gas
In the late phase of stellar evolution, massive stars like Betelgeuse exhibit high rates of mass loss, possibly as much as 1 M☉ every 10,000 years, resulting in a complex circumstellar environment
that is constantly in flux. In a 2009 paper, stellar mass loss was
cited as the "key to understanding the evolution of the universe from
the earliest cosmological times to the current epoch, and of planet
formation and the formation of life itself". However, the physical mechanism is not well understood.
When Schwarzschild first proposed his theory of huge convection cells,
he argued it was the likely cause of mass loss in evolved supergiants
like Betelgeuse.
Recent work has corroborated this hypothesis, yet there are still
uncertainties about the structure of their convection, the mechanism of
their mass loss, the way dust forms in their extended atmosphere, and
the conditions which precipitate their dramatic finale as a type II
supernova. In 2001, Graham Harper estimated a stellar wind at 0.03 M☉ every 10,000 years, but research since 2009 has provided evidence of episodic mass loss making any total figure for Betelgeuse uncertain.[109] Current observations suggest that a star like Betelgeuse may spend a portion of its lifetime as a red supergiant, but then cross back across the H-R diagram, pass once again through a brief yellow supergiant phase and then explode as a blue supergiant or Wolf-Rayet star.
Artist's rendering from ESO
showing Betelgeuse with a gigantic bubble boiling on its surface and a
radiant plume of gas being ejected to at least six photospheric radii or
roughly the orbit of Neptune
Astronomers may be close to solving this mystery. They noticed a
large plume of gas extending at least six times its stellar radius
indicating that Betelgeuse is not shedding matter evenly in all
directions. The plume's presence implies that the spherical symmetry of the star's photosphere, often observed in the infrared, is not
preserved in its close environment. Asymmetries on the stellar disk had
been reported at different wavelengths. However, due to the refined
capabilities of the NACO
adaptive optics on the VLT, these asymmetries have come into focus. The
two mechanisms that could cause such asymmetrical mass loss, were
large-scale convection cells or polar mass loss, possibly due to
rotation.
Probing deeper with ESO's AMBER, gas in the supergiant's extended
atmosphere has been observed vigorously moving up and down, creating
bubbles as large as the supergiant itself, leading his team to conclude
that such stellar upheaval is behind the massive plume ejection observed
by Kervella.
Asymmetric shells
In
addition to the photosphere, six other components of Betelgeuse's
atmosphere have now been identified. They are a molecular environment
otherwise known as the MOLsphere, a gaseous envelope, a chromosphere, a
dust environment and two outer shells (S1 and S2) composed of carbon monoxide (CO). Some of these elements are known to be asymmetric while others overlap.
Exterior view of ESO's Very Large Telescope (VLT) in Paranal, Chile
At about 0.45 stellar radii (~2–3 AU) above the photosphere, there
may lie a molecular layer known as the MOLsphere or molecular
environment. Studies show it to be composed of water vapor and carbon
monoxide with an effective temperature of about 1500±500 K.
Water vapor had been originally detected in the supergiant's spectrum
in the 1960s with the two Stratoscope projects but had been ignored for
decades. The MOLsphere may also contain SiO and Al2O3—molecules which could explain the formation of dust particles.
Interior view of one of the four 8.2-meter Unit Telescopes at ESO's VLT
The asymmetric gaseous envelope, another cooler region, extends for
several radii (~10–40 AU) from the photosphere. It is enriched in oxygen
and especially in nitrogen relative to carbon. These composition anomalies are likely caused by contamination by CNO-processed material from the inside of Betelgeuse.
Radio-telescope images taken in 1998 confirm that Betelgeuse has a highly complex atmosphere, with a temperature of 3450±850 K, similar to that recorded on the star's surface but much lower than surrounding gas in the same region.
The VLA images also show this lower-temperature gas progressively cools
as it extends outward. Although unexpected, it turns out to be the most
abundant constituent of Betelgeuse's atmosphere. "This alters our basic
understanding of red-supergiant star atmospheres", explained Jeremy
Lim, the team's leader. "Instead of the star's atmosphere expanding
uniformly due to gas heated to high temperatures near its surface, it
now appears that several giant convection cells propel gas from the
star's surface into its atmosphere."
This is the same region in which Kervella's 2009 finding of a bright
plume, possibly containing carbon and nitrogen and extending at least
six photospheric radii in the southwest direction of the star, is
believed to exist.
The chromosphere
was directly imaged by the Faint Object Camera on board the Hubble
Space Telescope in ultraviolet wavelengths. The images also revealed a
bright area in the southwest quadrant of the disk.
The average radius of the chromosphere in 1996 was about 2.2 times the
optical disk (~10 AU) and was reported to have a temperature no higher
than 5500 K.
However, in 2004 observations with the STIS, Hubble's high-precision
spectrometer, pointed to the existence of warm chromospheric plasma at
least one arcsecond away from the star. At a distance of 197 pc, the
size of the chromosphere could be up to 200 AU.
The observations have conclusively demonstrated that the warm
chromospheric plasma spatially overlaps and co-exists with cool gas in
Betelgeuse's gaseous envelope as well as with the dust in its
circumstellar dust shells (see below).
This infrared image from the ESO's VLT shows complex shells of gas and dust around Betelgeuse – the tiny red circle in the middle is the size of the photosphere.
The first claim of a dust shell surrounding Betelgeuse was put forth
in 1977 when it was noted that dust shells around mature stars often
emit large amounts of radiation in excess of the photospheric
contribution. Using heterodyne interferometry,
it was concluded that the red supergiant emits most of its excess
radiation from positions beyond 12 stellar radii or roughly the distance
of the Kuiper belt at 50 to 60 AU, which depends on the assumed stellar radius.
Since then, there have been studies done of this dust envelope at
varying wavelengths yielding decidedly different results. Studies from
the 1990s have estimated the inner radius of the dust shell anywhere
from 0.5 to 1.0 arcseconds, or 100 to 200 AU.
These studies point out that the dust environment surrounding
Betelgeuse is not static. In 1994, it was reported that Betelgeuse
undergoes sporadic decades long dust production, followed by inactivity.
In 1997, significant changes in the dust shell's morphology in one year
were noted, suggesting that the shell is asymmetrically illuminated by a
stellar radiation field strongly affected by the existence of
photospheric hotspots.
The 1984 report of a giant asymmetric dust shell 1 pc (206,265 AU) has
not been corroborated by recent studies, although another published the
same year said that three dust shells were found extending four
light-years from one side of the decaying star, suggesting that
Betelgeuse sheds its outer layers as it moves.
Although the exact size of the two outer CO shells remains elusive, preliminary estimates suggest that one shell extends from about 1.5 to 4.0 arcseconds and the other expands as far as 7.0 arcseconds.
Assuming the Jovian orbit of 5.5 AU as the star radius, the inner shell
would extend roughly 50 to 150 stellar radii (~300 to 800 AU) with the
outer one as far as 250 stellar radii (~1,400 AU). The Sun's heliopause is estimated at about 100 AU, so the size of this outer shell would be almost fourteen times the size of the Solar System.
Supersonic bow shock
Betelgeuse
is travelling supersonically through the interstellar medium at a speed
of 30 km/second (i.e. ~6.3 AU/year) creating a bow shock. The shock is not created by the star, but by its powerful stellar wind
as it ejects vast amounts of gas into the interstellar medium at a
speed of 17 km/s, heating the material surrounding the star, thereby
making it visible in infrared light. Because Betelgeuse is so bright, it was only in 1997 that the bow shock was first imaged. The cometary structure is estimated to be at least one parsec wide, assuming a distance of 643 light-years.
Hydrodynamic
simulations of the bow shock made in 2012 indicate that it is very
young—less than 30,000 years old—suggesting two possibilities: that
Betelgeuse moved into a region of the interstellar medium with different
properties only recently or that Betelgeuse has undergone a significant
transformation producing a changed stellar wind.
A 2012 paper, proposed that this phenomenon was caused by Betelgeuse
transitioning from a blue supergiant (BSG) to a red supergiant (RSG).
There is evidence that in the late evolutionary stage of a star like
Betelgeuse, such stars "may undergo rapid transitions from red to blue
and vice versa on the Hertzsprung-Russell diagram, with accompanying
rapid changes to their stellar winds and bow shocks."
Moreover, if future research bears out this hypothesis, Betelgeuse may
prove to have traveled close to 200,000 AU as a red supergiant
scattering as much as 3 M☉ along its trajectory.
Life phases
Hertzsprung–Russell diagram identifying supergiants like Betelgeuse that have moved off the main sequence
Betelgeuse is a red supergiant that has evolved from an O-type main sequence star. Its core will eventually collapse, producing a supernova explosion and leaving behind a compact remnant. The details depend on the exact initial mass and other physical properties of that main sequence star.
Main sequence
The
initial mass of Betelgeuse can only be estimated by testing different
stellar evolutionary models to match its current observed properties.
The unknowns of both the models and the current properties mean that
there is considerable uncertainty in Betelgeuse's initial appearance,
but its mass is usually estimated to have been in the range of 10–25 M☉, with modern models finding values of 15–20 M☉.
Its chemical makeup can be reasonably assumed to have been around 70%
hydrogen, 28% helium, and 2.4% heavy elements, slightly more metal-rich
than the Sun but otherwise similar. The initial rotation rate is more
uncertain, but models with slow to moderate initial rotation rates
produce the best matches to Betelgeuse's current properties. That main sequence version of Betelgeuse would have been a hot luminous star with a spectral type such as O9V.
A 15 M☉ star would take between 11.5 and 15
million years to reach the red supergiant stage, with more
rapidly-rotating stars taking the longest. Rapidly-rotating 20 M☉ stars take only 9.3 million years to reach the red supergiant stage, while 20 M☉ stars with slow rotation take only 8.1 million years. These form the best estimates of Betelgeuse's current age, as the time since its zero age main sequence stage, is estimated to be 8.0–8.5 million years as a 20 M☉ star with no rotation.
After core hydrogen exhaustion
Celestia depiction of Orion as it might appear from Earth when Betelgeuse explodes as a supernova, which can be brighter than the supernova that exploded in 1006
Betelgeuse's time spent as a red supergiant can be estimated by
comparing mass loss rates to the observed circumstellar material, as
well as the abundances of heavy elements at the surface. Estimates range
from 20,000 years to a maximum of 140,000 years. Betelgeuse appears to
undergo short periods of heavy mass loss and is a runaway star moving rapidly through space, so comparisons of its current mass loss to the total lost mass are difficult. The surface of Betelgeuse shows enhancement of nitrogen, relatively low levels of carbon, and a high proportion of 13C relative to 12C, all indicative of a star that has experienced the first dredge-up.
However, the first dredge-up occurs soon after a star reaches the red
supergiant phase and so this only means that Betelgeuse has been a red
supergiant for at least a few thousand years. The best prediction is
that Betelgeuse has already spent around 40,000 years as a red
supergiant, having left the main sequence perhaps one million years ago.
The current mass can be estimated from evolutionary models from
the initial mass and the expected mass lost so far. For Betelgeuse, the
total mass lost is predicted to be no more than about one M☉, giving a current mass of 19.4–19.7 M☉, considerably higher than estimated by other means such as pulsational properties or limb-darkening models.
All stars more massive than about 10 M☉ are expected to end their lives when their core collapses, typically producing a supernova explosion. Up to about 15 M☉, a type II-P supernova is always produced from the red supergiant stage.
More massive stars can lose mass quickly enough that they evolve
towards higher temperatures before their cores can collapse,
particularly for rotating stars and models with especially high mass
loss rates. These stars can produce type II-L or type IIb supernovae
from yellow or blue supergiants, or type Ib/c supernovae from Wolf-Rayet
stars. Models of rotating 20 M☉ stars predict a peculiar type II supernova similar to SN 1987A from a blue supergiant progenitor. On the other hand, non-rotating 20 M☉ models predict a type II-P supernova from a red supergiant progenitor.
The time until Betelgeuse explodes depends on the predicted
initial conditions and on the estimate of the time already spent as a
red supergiant. The total lifetime from the start of the red supergiant
phase to core collapse varies from about 300,000 years for a rotating
25 M☉ star, 550,000 years for a rotating 20 M☉ star, and up to a million years for a non-rotating 15 M☉
star. Given the estimated time since Betelgeuse became a red
supergiant, estimates of its remaining lifetime range from a "best
guess" of under 100,000 years for a non-rotating 20 M☉ model to far longer for rotating models or lower-mass stars.
Betelgeuse's suspected birthplace in the Orion OB1 Association is the
location of several previous supernovae. It is believed that runaway
stars may be caused by supernovae, and there is strong evidence that OB
stars μ Columbae, AE Aurigae and 53 Arietis all originated from such explosions in Ori OB1 2.2, 2.7 and 4.9 million years ago.
A typical type II-P supernova emits 2×1046 J of neutrinos and produces an explosion with a kinetic energy of 2×1044 J. As seen from Earth, it would have a peak apparent magnitude of about −12.4. It may outshine the full moon
and would be easily visible in daylight. This type of supernova would
remain at roughly constant brightness for 2–3 months before rapidly
dimming. The visible light is produced mainly by the radioactive decay
of cobalt, and maintains its brightness due to the increasing transparency of the cooling hydrogen ejected by the supernova.
Due to misunderstandings caused by the 2009 publication of the star's 15% contraction, apparently of its outer atmosphere,
Betelgeuse has frequently been the subject of scare stories and rumors
suggesting that it will explode within a year, leading to exaggerated
claims about the consequences of such an event.
The timing and prevalence of these rumors have been linked to broader
misconceptions of astronomy, particularly to doomsday predictions
relating to the Mayan calendar. Betelgeuse is not likely to produce a gamma-ray burst and is not close enough for its x-rays, ultraviolet radiation, or ejected material to cause significant effects on Earth.
Following Betelgeuse's supernova, a small dense remnant will be left behind, either a neutron star or black hole. This is predicted to be a neutron star of approximately 1.5 M☉.
Ethnological attributes
Spelling and pronunciation
Betelgeuse has been known as Betelgeux, and in German Beteigeuze (according to Bode). Betelgeux and Betelgeuze were used until the early 20th century, when the spelling Betelgeuse became universal. Consensus on its pronunciation is weak and is as varied as its spellings:
- /ˈbɛtəldʒuːz/ BET-əl-jooz – Oxford English Dictionary and Royal Astronomical Society of Canada
- /ˈbiːtəldʒuːz,
-dʒɜːz/ BEET-təl-jooz – Oxford English Dictionary - /ˈbiːtəldʒuːs/ BEET-əl-joos – (Canadian Oxford Dictionary, Webster's Collegiate Dictionary)
- /bɛtəlˈɡɜːrz/ bet-əl-GURZ – (Martha Evans Martin, The Friendly Stars)
Etymology
Betelgeuse is often mistranslated as "armpit of the central one". In his 1899 work Star-Names and Their Meanings, American amateur naturalist Richard Hinckley Allen stated the derivation was from the ابط الجوزاء Ibṭ al-Jauzah, which he claimed degenerated into a number of forms including Bed Elgueze, Beit Algueze, Bet El-gueze, Beteigeuze and more, to the forms Betelgeuse, Betelguese, Betelgueze and Betelgeux. The star was named Beldengeuze in the Alfonsine Tables, and Italian Jesuit priest and astronomer Giovanni Battista Riccioli had called it Bectelgeuze or Bedalgeuze.
Paul Kunitzsch, Professor of Arabic Studies at the University of
Munich, refuted Allen's derivation and instead proposed that the full
name is a corruption of the Arabic يد الجوزاء Yad al-Jauzā' meaning "the Hand of al-Jauzā'", i.e., Orion.
European mistransliteration into medieval Latin led to the first character y (ﻴ, with two dots underneath) being misread as a b (ﺒ, with only one dot underneath).
During the Renaissance, the star's name was written as بيت الجوزاء Bait al-Jauzā' ("house of Orion") or بط الجوزاء Baţ al-Jauzā', incorrectly thought to mean "armpit of Orion" (a true translation of "armpit" would be ابط, transliterated as Ibţ). This led to the modern rendering as Betelgeuse. Other writers have since accepted Kunitzsch's explanation.
The last part of the name, "-elgeuse", comes from the Arabic الجوزاء al-Jauzā', a historical Arabic name of the constellation Orion, a feminine name in old Arabian legend, and of uncertain meaning. Because جوز j-w-z, the root of jauzā', means "middle", al-Jauzā' roughly means "the Central One". The modern Arabic name for Orion is الجبار al-Jabbār ("the Giant"), although the use of الجوزاء al-Jauzā' in the name of the star has continued. The 17th-century English translator Edmund Chilmead gave it the name Ied Algeuze ("Orion's Hand"), from Christmannus. Other Arabic names recorded include Al Yad al Yamnā ("the Right Hand"), Al Dhira ("the Arm"), and Al Mankib ("the Shoulder"), all appended to "of the giant", as منكب الجوزاء Mankib al Jauzā'.
Dunhuang Star Chart, circa AD 700, showing 参宿四 Shēnxiùsì (Betelgeuse), the Fourth Star of the constellation of Three Stars
Other names
Other names for Betelgeuse included the Persian Bašn "the Arm", and Coptic Klaria "an Armlet". Bahu was its Sanskrit name, as part of a Hindu understanding of the constellation as a running antelope or stag. In traditional Chinese astronomy, Betelgeuse was known as 参宿四 (Shēnxiùsì, the Fourth Star of the constellation of Three Stars) as the Chinese constellation 参宿 originally referred to the three stars in the girdle of Orion. This constellation was ultimately expanded to ten stars, but the earlier name stuck. In Japan, the Taira, or Heike, clan adopted Betelgeuse and its red color as its symbol, calling the star Heike-boshi, (平家星), while the Minamoto, or Genji, clan had chosen Rigel and its white color. The two powerful families fought a legendary war in Japanese history, the stars seen as facing each other off and only kept apart by the Belt.
In Tahitian lore, Betelgeuse was one of the pillars propping up the sky, known as Anâ-varu, the pillar to sit by. It was also called Ta'urua-nui-o-Mere "Great festivity in parental yearnings". A Hawaiian term for it was Kaulua-koko "brilliant red star". The Lacandon people of Central America knew it as chäk tulix "red butterfly".
Astronomy writer Robert Burnham Jr. proposed the term padparadaschah which denotes a rare orange sapphire in India, for the star.
Mythology
With the history of astronomy intimately associated with mythology and astrology before 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.
Other cultures have produced different myths. Stephen R. Wilk has
proposed the constellation of Orion could have represented the Greek
mythological figure Pelops,
who had an artificial shoulder of ivory made for him, with Betelgeuse
as the shoulder, its color reminiscent of the reddish yellow sheen of
ivory.
In the Americas, Betelgeuse signifies a severed limb of a man-figure (Orion)—the Taulipang
of Brazil know the constellation as Zililkawai, a hero whose leg was
cut off by his wife, with the variable light from Betelgeuse linked to
the severing of the limb. Similarly, the Lakota people of North America see it as a chief whose arm has been severed. The Wardaman people of northern Australia knew the star as Ya-jungin
"Owl Eyes Flicking", its variable light signifying its intermittent
watching of ceremonies led by the Red Kangaroo Leader Rigel. In South African mythology, Betelgeuse was perceived as a lion casting a predatory gaze toward the three zebras represented by Orion's Belt.
A Sanskrit name for Betelgeuse is ārdrā "the moist one", eponymous of the Ardra lunar mansion in Hindu astrology. The Rigvedic God of storms Rudra presided over the star; this association was linked by 19th-century star enthusiast Richard Hinckley Allen to Orion's stormy nature.
The constellations in Macedonian folklore represented agricultural
items and animals, reflecting their village way of life. To them,
Betelgeuse was Orach "the ploughman", alongside the rest of Orion
which depicted a plough with oxen. The rising of Betelgeuse at around
3 a.m. in late summer and autumn signified the time for village men to
go to the fields and plough. To the Inuit, the appearance of Betelgeuse and Bellatrix
high in the southern sky after sunset marked the beginning of spring
and lengthening days in late February and early March. The two stars
were known as Akuttujuuk "those (two) placed far apart",
referring to the distance between them, mainly to people from North
Baffin Island and Melville Peninsula.
The opposed locations of Orion and Scorpius, with their corresponding bright red variable stars Betelgeuse and Antares,
were noted by ancient cultures around the world. The setting of Orion
and rising of Scorpius signify the death of Orion by the scorpion. In
China they signify brothers and rivals Shen and Shang. The Batak of Sumatra marked their New Year with the first new moon
after the sinking of Orion's Belt below the horizon, at which point
Betelgeuse remained "like the tail of a rooster". The positions of
Betelgeuse and Antares at opposite ends of the celestial sky were
considered significant and their constellations were seen as a pair of
scorpions. Scorpion days marked as nights that both constellations could
be seen.
In popular culture
As one of the brightest and best-known stars, Betelgeuse has featured
in many works of fiction. The star's unusual name inspired the title of
the 1988 film Beetlejuice, and script writer Michael McDowell was impressed by how many people made the connection. In the popular science fiction series The Hitchhiker's Guide to the Galaxy by Douglas Adams, Ford Prefect was from "a small planet somewhere in the vicinity of Betelgeuse."
Two American navy ships were named after the star, both of them World War II vessels, the USS Betelgeuse (AKA-11) launched in 1939 and USS Betelgeuse (AK-260) launched in 1944. In 1979, a French supertanker named Betelgeuse was moored off Whiddy Island discharging oil when it exploded, killing 50 people in one of the worst disasters in Ireland's history.
The Dave Matthews Band song "Black and Blue Bird" references the star. The Philip Larkin poem "The North Ship", found in the collection of the same name, references the star in the section titled "Above 80° N", which reads:
'A woman has ten claws,' /
Sang the drunken boatswain; / Farther than Betelgeuse, / More brilliant than Orion / Or the planets Venus and Mars, / The star flames on the ocean; / 'A woman has ten claws,' /
Sang the drunken boatswain.
Humbert Wolfe wrote a poem about Betelgeuse, which was set to music by Gustav Holst.
