A blue supergiant ( BSG ) is a hot, luminous star , often referred to as an OB supergiant . They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blue supergiants.
142-471: Rigel is a blue supergiant star in the constellation of Orion . It has the Bayer designation β Orionis , which is Latinized to Beta Orionis and abbreviated Beta Ori or β Ori . Rigel is the brightest and most massive component – and the eponym – of a star system of at least four stars that appear as a single blue-white point of light to the naked eye . This system
284-621: A B-V color index of −0.06. It contrasts strongly with reddish Betelgeuse. Culminating every year at midnight on 12 December, and at 9:00 pm on 24 January, Rigel is visible on winter evenings in the Northern Hemisphere and on summer evenings in the Southern Hemisphere . In the Southern Hemisphere, Rigel is the first bright star of Orion visible as the constellation rises. Correspondingly, it
426-407: A P Cygni profile after a star that shows this feature strongly in its spectrum. It is associated with mass loss where there is simultaneously emission from a dense wind close to the star and absorption from circumstellar material expanding away from the star. The unusual Hα line profile is observed to vary unpredictably. It is a normal absorption line around a third of the time. About a quarter of
568-416: A B–V color index of 1.85 – a figure which points to its pronounced "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 toward and away from Betelgeuse, depending on fluctuations in
710-734: A Norwegian ship, built in Copenhagen in 1924. It was requisitioned by the Germans during World War II and sunk in 1944 while being used to transport prisoners of war. Two US Navy ships have borne the name USS Rigel . The SSM-N-6 Rigel was a cruise missile program for the US Navy that was cancelled in 1953 before reaching deployment. The Rigel Skerries are a chain of small islands in Antarctica , renamed after originally being called Utskjera. They were given their current name as Rigel
852-408: A blue supergiant again, less luminous than the first time but more unstable. If such a star can pass through the yellow evolutionary void it is expected that it becomes one of the lower luminosity LBVs. The most massive blue supergiants are too luminous to retain an extensive atmosphere and they never expand into a red supergiant. The dividing line is approximately 40 M ☉ , although
994-593: A cutlass by the maiden Bįhi (Sirius). The Lacandon people of southern Mexico knew it as tunsel ("little woodpecker"). Rigel was known as Yerrerdet-kurrk to the Wotjobaluk koori of southeastern Australia, and held to be the mother-in-law of Totyerguil ( Altair ). The distance between them signified the taboo preventing a man from approaching his mother-in-law. The indigenous Boorong people of northwestern Victoria named Rigel as Collowgullouric Warepil . The Wardaman people of northern Australia know Rigel as
1136-707: A daughter of Rehua ( Antares ), the chief of all-stars. Its heliacal rising presages the appearance of Matariki (the Pleiades ) in the dawn sky, marking the Māori New Year in late May or early June. The Moriori people of the Chatham Islands , as well as some Maori groups in New Zealand, mark the start of their New Year with Rigel rather than the Pleiades. Puaka is a southern name variant used in
1278-436: A diameter of 0.047″ , 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″ . 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
1420-530: A diameter of 3.84 × 10 km ( 2.58 AU ) based on the parallax value of 0.018 ″ . But limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements. The 1950s and 1960s saw two developments that affected stellar convection theory in red supergiants: the Stratoscope projects and the 1958 publication of Structure and Evolution of the Stars , principally
1562-546: A diameter of 25 million miles, or approximately 28.9 R ☉ , smaller than its neighbor Aldebaran . Due to their closeness to each other and ambiguity of the spectrum, little is known about the intrinsic properties of the members of the Rigel BC triple system. All three stars seem to be near equally hot B-type main-sequence stars that are three to four times as massive as the Sun. Stellar evolution models suggest
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#17327724077711704-548: A distance of roughly 131 pc or 427 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 6.55 ± 0.83 was calculated, hence a much tighter error factor yielding a distance of roughly 152 ± 20 pc or 500 ± 65 ly . In 2008, measurements using
1846-547: A dust cloud that blocked the starlight coming from about a quarter of Betelgeuse's surface. Hubble captured signs of dense, heated material moving through the star's atmosphere in September, October and November before several telescopes observed the more marked dimming in December and the first few months of 2020. By January 2020, Betelgeuse had dimmed by a factor of approximately 2.5 from magnitude 0.5 to 1.5 and
1988-518: A few hours to several days, but again no clear period. Rigel's color index varies slightly, but this is not significantly correlated with its brightness variations. From analysis of Hipparcos satellite photometry, Rigel is identified as belonging to the Alpha Cygni class of variable stars, defined as "non-radially pulsating supergiants of the Bep–AepIa spectral types". In those spectral types,
2130-519: 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. First overtone pulsations of 185 days have been observed, and
2272-400: A few thousand years and so these stars are rare. Higher mass red supergiants blow away their outer atmospheres and evolve back to blue supergiants, and possibly onwards to Wolf–Rayet stars. Depending on the exact mass and composition of a red supergiant, it can execute a number of blue loops before either exploding as a type II supernova or finally dumping enough of its outer layers to become
2414-533: A little over twenty times that of the Sun . For various reasons , its distance has been quite difficult to measure; current best estimates are of the order of 400–600 light-years from the Sun ;– a comparatively wide uncertainty for a relatively nearby star. Its absolute magnitude is about −6. With an age of less than 10 million years, Betelgeuse has evolved rapidly because of its large mass, and
2556-724: A mass of 24 ± 8 M ☉ . Although Rigel is often considered the most luminous star within 1,000 light-years of the Sun, its energy output is poorly known. Using the Hipparcos distance of 860 light-years (264 parsecs), the estimated relative luminosity for Rigel is about 120,000 times that of the Sun ( L ☉ ), but another recently published distance of 1,170 ± 130 light-years (360 ± 40 parsecs) suggests an even higher luminosity of 219,000 L ☉ . Other calculations based on theoretical stellar evolutionary models of Rigel's atmosphere give luminosities anywhere between 83,000 L ☉ and 363,000 L ☉ , while summing
2698-562: A more normal brightness range, reaching a peak of 0.0 visual and 0.1 V-band magnitude in April 2023. Infrared observations found no significant change in luminosity over the last 50 years, suggesting that the dimming was due to a change in extinction around the star rather than a more fundamental change. A study using the Hubble Space Telescope suggests that occluding dust was created by a surface mass ejection; this material
2840-538: A neutron star. The earliest known recording of the name Rigel is in the Alfonsine tables of 1521. It is derived from the Arabic name Rijl Jauzah al Yusrā , "the left leg (foot) of Jauzah" (i.e. rijl meaning "leg, foot"), which can be traced to the 10th century. "Jauzah" was a proper name for Orion; an alternative Arabic name was رجل الجبار rijl al-jabbār , "the foot of the great one", from which stems
2982-561: A period estimated to be 24,000 years. The inner stars of the triple system orbit each other every 10 days, and the outer star orbits the inner pair every 63 years. A much fainter star, separated from Rigel and the others by nearly an arc minute , may be part of the same star system. In 2016, the International Astronomical Union (IAU) included the name "Rigel" in the IAU Catalog of Star Names. According to
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#17327724077713124-509: A period of about 22 days. The radial velocity has since been measured to vary by about 10 km/s around a mean of 21.5 km/s . In 1933, the Hα line in Rigel's spectrum was seen to be unusually weak and shifted 0.1 nm towards shorter wavelengths, while there was a narrow emission spike about 1.5 nm to the long wavelength side of the main absorption line. This is now known as
3266-554: 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 . Observations in different regions of
3408-513: A possible period of 2.075 days. Rigel was observed with the Canadian MOST satellite for nearly 28 days in 2009. Milli-magnitude variations were observed, and gradual changes in flux suggest the presence of long-period pulsation modes. From observations of the variable Hα spectral line, Rigel's mass-loss rate due to stellar wind is estimated be (1.5 ± 0.4) × 10 solar masses per year ( M ☉ /yr)—about ten million times more than
3550-510: A rare period when variable star Betelgeuse temporarily outshone Rigel, resulting in Betelgeuse being designated "alpha" and Rigel designated "beta". However, closer examination of Bayer's method shows that he did not strictly order the stars by brightness, but instead grouped them first by magnitude, then by declination . Rigel and Betelgeuse were both classed as first magnitude , and in Orion
3692-498: A red supergiant is dense and slow, the wind from a blue supergiant is fast but sparse. When a red supergiant becomes a blue supergiant, the faster wind it produces impacts the already emitted slow wind and causes the outflowing material to condense into a thin shell. In some cases, several concentric faint shells can be seen from successive episodes of mass loss, either previous blue loops from the red supergiant stage, or eruptions such as LBV outbursts. Betelgeuse Betelgeuse
3834-510: 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 . This image, like earlier pictures, contained a bright patch indicating a region in
3976-553: A similar common proper motion . The pair would have an estimated orbital period of 24,000 years. Gaia Data Release 2 (DR2) contains a somewhat unreliable parallax for Rigel B, placing it at about 1,100 light-years (340 parsecs), further away than the Hipparcos distance for Rigel, but similar to the Taurus-Orion R1 association. There is no parallax for Rigel in Gaia DR2. The Gaia DR2 proper motions for Rigel B and
4118-578: 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 . Betelgeuse and its red coloration have been noted since antiquity ; the classical astronomer Ptolemy described its color as ὑπόκιρρος ( hypókirrhos = more or less orange-tawny), a term later described by a translator of Ulugh Beg 's Zij-i Sultani as rubedo , Latin for "ruddiness". In
4260-468: 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 . The near-infrared photospheric diameter of 43.33 mas at the Hipparcos distance of 152 ± 20 pc equates 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
4402-402: A trigonometric parallax of 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 7.63 ± 1.64 mas , which equated to
Rigel - Misplaced Pages Continue
4544-399: Is a red supergiant star in the constellation of Orion . It is usually the tenth-brightest star in the night sky and, after Rigel , the second-brightest in its constellation. It is a distinctly reddish, semiregular variable star whose apparent magnitude , varying between +0.0 and +1.6, has the widest range displayed by any first-magnitude star . Betelgeuse is the brightest star in
4686-414: Is a defining point of the classification sequence for supergiants. The overall spectrum is typical for a late B class star, with strong absorption lines of the hydrogen Balmer series as well as neutral helium lines and some of heavier elements such as oxygen, calcium, and magnesium. The luminosity class for B8 stars is estimated from the strength and narrowness of the hydrogen spectral lines, and Rigel
4828-556: Is a member of the loosely defined Taurus-Orion R1 Association , somewhat closer at 1,200 light-years (360 parsecs). Rigel is thought to be considerably closer than most of the members of Orion OB1 and the Orion Nebula . Betelgeuse and Saiph lie at a similar distance to Rigel, although Betelgeuse is a runaway star with a complex history and might have originally formed in the main body of the association. Hierarchical scheme for Rigel's components The star system of which Rigel
4970-526: Is a part has at least four components. Rigel (sometimes called Rigel A to distinguish from the other components) has a visual companion , which is likely a close triple-star system. A fainter star at a wider separation might be a fifth component of the Rigel system. William Herschel discovered Rigel to be a visual double star on 1 October 1781, cataloguing it as star 33 in the "second class of double stars" in his Catalogue of Double Stars, usually abbreviated to H II 33, or as H 2 33 in
5112-498: 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 Earth-observed angular diameter of Betelgeuse is exceeded only by those of R Doradus and the Sun. Starting in October 2019, Betelgeuse began to dim noticeably, and by mid-February 2020 its brightness had dropped by a factor of approximately 3, from magnitude 0.5 to 1.7. It then returned to
5254-487: Is also the first star of Orion to set in most of the Northern Hemisphere. The star is a vertex of the " Winter Hexagon ", an asterism that includes Aldebaran , Capella , Pollux , Procyon , and Sirius . Rigel is a prominent equatorial navigation star , being easily located and readily visible in all the world's oceans (the exception is the area north of the 82nd parallel north ). Rigel's spectral type
5396-466: Is assigned to the bright supergiant class Ia. Variations in the spectrum have resulted in the assignment of different classes to Rigel, such as B8 Ia, B8 Iab, and B8 Iae. As early as 1888, the heliocentric radial velocity of Rigel, as estimated from the Doppler shifts of its spectral lines, was seen to vary. This was confirmed and interpreted at the time as being due to a spectroscopic companion with
5538-404: Is caused by stellar pulsations similar to those of Deneb . Further observations of radial velocity variations indicate that it simultaneously oscillates in at least 19 non-radial modes with periods ranging from about 1.2 to 74 days. Estimation of many physical characteristics of blue supergiant stars, including Rigel, is challenging due to their rarity and uncertainty about how far they are from
5680-427: Is classified as an Alpha Cygni variable due to the amplitude and periodicity of its brightness variation, as well as its spectral type. Its intrinsic variability is caused by pulsations in its unstable atmosphere. Rigel is generally the seventh-brightest star in the night sky and the brightest star in Orion, though it is occasionally outshone by Betelgeuse , which varies over a larger range. A triple-star system
5822-486: 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 or 724 +111 −156 ly. In 2020, new observational data from
Rigel - Misplaced Pages Continue
5964-619: Is easy to find with the naked eye. It is one of three stars that make up the Winter Triangle asterism , and it marks the center of the Winter Hexagon . It can be seen rising in the east at the beginning of January of each year, just after sunset. Between mid-September and mid-March (best in mid-December), it is visible to virtually every inhabited region of the globe, except in Antarctica at latitudes south of 82°. In May (moderate northern latitudes) or June (southern latitudes),
6106-462: Is estimated to be ten million times that of the Sun. With an estimated age of seven to nine million years, Rigel has exhausted its core hydrogen fuel, expanded, and cooled to become a supergiant. It is expected to end its life as a type II supernova , leaving a neutron star or a black hole as a final remnant, depending on the initial mass of the star. Rigel varies slightly in brightness, its apparent magnitude ranging from 0.05 to 0.18. It
6248-480: Is expected from theoretical models, which expect blue supergiants to be short-lived. This results in the blue supergiant problem , although unusual stellar interiors (such as hotter blue supergiants having oversized hydrogen-fusing cores and cooler ones having undersized helium-fusing cores) may explain this. It was once believed that blue supergiants originated from a "feeding" with the interstellar medium when stars passed through interstellar dust clouds, although
6390-544: Is expected to end its evolution with a supernova explosion, most likely within 100,000 years. When Betelgeuse explodes, it will shine as bright as the half-Moon for more than three months; life on Earth will be unharmed. 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 to be moving through
6532-411: 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 to Betelgeuse have been proposed. Analysis of polarization data from 1968 through 1983 indicated a close companion with a periodic orbit of about 2.1 years, and by using speckle interferometry ,
6674-521: Is likely to be fusing helium in its core. Due to strong convection of helium produced in the core while Rigel was on the main sequence and in the hydrogen-burning shell since it became a supergiant, the fraction of helium at the surface has increased from 26.6% when the star formed to 32% now. The surface abundances of carbon, nitrogen, and oxygen seen in the spectrum are compatible with a post-red supergiant star only if its internal convection zones are modeled using non-homogeneous chemical conditions known as
6816-530: 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, a short period of 185 days, and a longer secondary period around 2,100 days. The lowest reliably-recorded V-band magnitude of +1.614 was reported in February 2020. Radial pulsations of red supergiants are well-modelled and show that periods of
6958-440: Is listed in the General Catalogue of Variable Stars , but since its familiar Bayer designation is used instead of creating a separate variable star designation . Rigel is an intrinsic variable star with an apparent magnitude ranging from 0.05 to 0.18. It is typically the seventh-brightest star in the celestial sphere , excluding the Sun, although occasionally fainter than Betelgeuse. Rigel appears slightly blue-white and has
7100-409: Is located at a distance of approximately 860 light-years (260 pc ) from the Sun. A star of spectral type B8Ia, Rigel is 120,000 times as luminous as the Sun, and is 18 to 24 times as massive , depending on the method and assumptions used. Its radius is more than seventy times that of the Sun , and its surface temperature is 12,100 K . Due to its stellar wind , Rigel's mass-loss
7242-538: 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 the idea of dust shells and a molecular shell (MOLsphere) around Betelgeuse, and yielded diameters ranging from 42.57 to 44.28 mas with comparatively insignificant margins of error. In 2011,
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#17327724077717384-736: Is no data on Betelgeuse in Gaia Data Release 2 , which was released in 2018. 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 +1.6. Betelgeuse
7526-469: Is proposed that this is due to granulation , similar to the same effect on the sun but on a much larger scale. 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
7668-427: Is separated from Rigel by an angle of 9.5 arc seconds . It has an apparent magnitude of 6.7, making it 1/400th as bright as Rigel. Two stars in the system can be seen by large telescopes, and the brighter of the two is a spectroscopic binary . These three stars are all blue-white main-sequence stars , each three to four times as massive as the Sun. Rigel and the triple system orbit a common center of gravity with
7810-401: Is subject to multiple cycles of increasing and decreasing brightness due to changes in its size and temperature. The astronomers who first noted the dimming of Betelgeuse, Villanova University astronomers Richard Wasatonic and Edward Guinan , and amateur Thomas Calderwood, theorize that a coincidence of a normal 5.9 year light-cycle minimum and a deeper-than-normal 425 day period are
7952-463: Is the 5°-long IC 2118 (Witch Head Nebula), located at an angular separation of 2.5° from the star, or a projected distance of 39 light-years (12 parsecs) away. From measures of other nebula-embedded stars, IC 2118's distance is estimated to be 949 ± 7 light-years (291 ± 2 parsecs). Rigel is an outlying member of the Orion OB1 association , which is located at a distance of up to 1,600 light-years (500 parsecs) from Earth. It
8094-512: 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 colour and higher location in
8236-487: 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
8378-557: 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. There
8520-470: The Ledoux Criteria . Rigel is expected to eventually end its stellar life as a type II supernova . It is one of the closest known potential supernova progenitors to Earth, and would be expected to have a maximum apparent magnitude of around −11 (about the same brightness as a quarter Moon or around 300 times brighter than Venus ever gets). The supernova would leave behind either a black hole or
8662-614: The Sun but smaller than a red supergiant , with surface temperatures of 10,000–50,000 K and luminosities from about 10,000 to a million times that of the Sun. They are most often an evolutionary phase between high-mass, hydrogen-fusing main-sequence stars and helium-fusing red supergiants, although new research suggests they could be the result of stellar mergers . The majority of supergiants are also blue (B-type) supergiants; blue supergiants from classes O9.5 to B2 are even more common than their main sequence counterparts. More post-main-sequence blue supergiants are observed than what
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#17327724077718804-487: 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
8946-469: The Very Large Array (VLA) produced a radio solution of 5.07 ± 1.10 mas , equaling 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
9088-477: The interstellar medium at a speed of 30 km/s , creating a bow shock over four light-years wide. Betelgeuse became the first extrasolar star whose photosphere 's angular size was measured in 1920, and subsequent studies have reported an angular diameter (i.e., apparent size) ranging from 0.042 to 0.056 arcseconds ; that range of determinations is ascribed to non-sphericity, limb darkening , pulsations and varying appearance at different wavelengths . It
9230-566: The spectral energy distribution from historical photometry with the Hipparcos distance suggests a luminosity as low as 61,515 ± 11,486 L ☉ . A 2018 study using the Navy Precision Optical Interferometer measured the angular diameter as 2.526 mas . After correcting for limb darkening , the angular diameter is found to be 2.606 ± 0.009 mas , yielding a radius of 74.1 +6.1 −7.3 R ☉ . An older measurement of
9372-510: The 'e' indicates that it displays emission lines in its spectrum, while the 'p' means it has an unspecified spectral peculiarity. Alpha Cygni type variables are generally considered to be irregular or have quasi-periods . Rigel was added to the General Catalogue of Variable Stars in the 74th name-list of variable stars on the basis of the Hipparcos photometry, which showed variations with a photographic amplitude of 0.039 magnitudes and
9514-619: The 19th century, before modern systems of stellar classification , Angelo Secchi included Betelgeuse as one of the prototypes for his Class III (orange to red) stars. Three centuries before Ptolemy, in contrast, Chinese astronomers observed Betelgeuse as yellow ; Such an observation, if accurate, could suggest the star was in a yellow supergiant phase around this time, a credible possibility, given current research into these stars' complex circumstellar environment. Aboriginal groups in South Australia have shared oral tales of
9656-564: 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
9798-460: The European name. In English, there are four common pronunciations of this name, depending on whether the first e is pronounced short or long and whether the s is pronounced /s/ or /z/ : 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, issued July 2016, included
9940-410: The Hipparcos proper motions for Rigel are both small, although not quite the same. In 1871, Sherburne Wesley Burnham suspected Rigel B to be a binary system, and in 1878, he resolved it into two components. This visual companion is designated as component C (Rigel C), with a measured separation from component B that varies from less than 0.1″ to around 0.3″ . In 2009, speckle interferometry showed
10082-573: The Hγ line give (9.4 ± 0.9) × 10 M ☉ /yr in 2006-7 and (7.6 ± 1.1) × 10 M ☉ /yr in 2009–10. Calculations using the Hα line give lower results, around 1.5 × 10 M ☉ /yr . The terminal wind velocity is 300 km/s . It is estimated that Rigel has lost about three solar masses ( M ☉ ) since beginning life as a star of 24 ± 3 M ☉ seven to nine million years ago. Rigel's distance from
10224-452: The IAU, this proper name applies only to the primary component A of the Rigel system. The system is listed variously in historical astronomical catalogs as H II 33, Σ 668, β 555, or ADS 3823. For simplicity, Rigel's companions are referred to as Rigel B, C, and D; the IAU describes such names as "useful nicknames" that are "unofficial". In modern comprehensive catalogs,
10366-488: The Red Kangaroo Leader Unumburrgu and chief conductor of ceremonies in a songline when Orion is high in the sky. Eridanus , the river, marks a line of stars in the sky leading to it, and the other stars of Orion are his ceremonial tools and entourage. Betelgeuse is Ya-jungin "Owl Eyes Flicking", watching the ceremonies. The Māori people of New Zealand named Rigel as Puanga , said to be
10508-508: 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 . The precise diameter has been hard to define for several reasons: The generally reported radii of large cool stars are Rosseland radii , defined as
10650-639: The South Island. In Japan, the Minamoto or Genji clan chose Rigel and its white color as its symbol, calling the star Genji-boshi ( 源氏星 ), while the Taira or Heike clan adopted Betelgeuse and its red color. The two powerful families fought the Genpei War ; the stars were seen as facing off against each other and kept apart only by the three stars of Orion's Belt . The MS Rigel was originally
10792-431: The Sun is below the horizon). Betelgeuse is a variable star whose visual magnitude ranges between 0.0 and +1.6 . There are periods during which it surpasses Rigel to become the sixth brightest star, and occasionally it will become even brighter than Capella . At its faintest, Betelgeuse can fall behind Deneb and Beta Crucis , themselves both slightly variable, to be the twentieth-brightest star. Betelgeuse has
10934-412: The Sun is somewhat uncertain, different estimates being obtained by different methods. Old estimates placed it 166 parsecs (or 541 light years) away from the Sun. The 2007 Hipparcos new reduction of Rigel's parallax is 3.78 ± 0.34 mas , giving a distance of 863 light-years (265 parsecs) with a margin of error of about 9%. Rigel B, usually considered to be physically associated with Rigel and at
11076-399: The Sun. As such, their characteristics are mainly estimated from theoretical stellar evolution models . Its effective temperature can be estimated from the spectral type and color to be around 12,100 K . A mass of 21 ± 3 M ☉ at an age of 8 ± 1 million years has been estimated by comparing evolutionary tracks, while atmospheric modeling from the spectrum gives
11218-582: The VLTI AMBER instrument. In 2009 it was announced that the radius of Betelgeuse had shrunk from 1993 to 2009 by 15%, with the 2008 angular measurement equal to 47.0 mas . Unlike most earlier papers, this study used measurements at one specific wavelength over 15 years. 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 . The observed contraction
11360-497: The Washington Double Star Catalogue. Friedrich Georg Wilhelm von Struve first measured the relative position of the companion in 1822, cataloguing the visual pair as Σ 668. The secondary star is often referred to as Rigel B or β Orionis B. The angular separation of Rigel B from Rigel A is 9.5 arc seconds to its south along position angle 204°. Although not particularly faint at visual magnitude 6.7,
11502-433: The angular diameter gives 2.75 ± 0.01 mas , equivalent to a radius of 78.9 R ☉ at 264 pc . These radii are calculated assuming the Hipparcos distance of 264 pc ; adopting a distance of 360 pc leads to a significantly larger size. Older distance estimates were mostly far lower than modern estimates, leading to lower radius estimates; a 1922 estimate by John Stanley Plaskett gave Rigel
11644-465: The arms of spiral galaxies , and in irregular galaxies . They are rarely observed in spiral galaxy cores, elliptical galaxies , or globular clusters , most of which are believed to be composed of older stars, although the core of the Milky Way has recently been found to be home to several massive open clusters and associated young hot stars. The best known example is Rigel , the brightest star in
11786-433: The close visual component Rigel C, is likely a physical triple-star system, although Rigel C cannot be detected in the spectrum, which is inconsistent with its observed brightness. In 1878, Burnham found another possibly associated star of approximately 13th magnitude. He listed it as component D of β 555, although it is unclear whether it is physically related or a coincidental alignment. Its 2017 separation from Rigel
11928-405: The complex circumstellar shells surrounding the supergiant, causing them to suspect the presence of huge gas bubbles resulting from convection. However, 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 J.E. Baldwin and colleagues of
12070-603: The constellation of Orion . Its mass is about 20 times that of the Sun, and its luminosity is around 117,000 times greater. Despite their rarity and their short lives they are heavily represented among the stars visible to the naked eye; their immense brightness is more than enough to compensate for their scarcity. Blue supergiants have fast stellar winds and the most luminous, called hypergiants , have spectra dominated by emission lines that indicate strong continuum driven mass loss. Blue supergiants show varying quantities of heavy elements in their spectra, depending on their age and
12212-548: The constellation representing the mythological Greek huntsman Orion , Rigel is his knee or (as its name suggests) foot; with the nearby star Beta Eridani marking Orion's footstool. Rigel is presumably the star known as " Aurvandil 's toe" in Norse mythology . In the Caribbean, Rigel represented the severed leg of the folkloric figure Trois Rois , himself represented by the three stars of Orion's Belt. The leg had been severed with
12354-507: The coolest and largest red supergiants develop from stars with initial masses of 15–25 M ☉ . It is not clear whether more massive blue supergiants can lose enough mass to evolve safely into old age as a Wolf Rayet star and finally a white dwarf, or they reach the Wolf Rayet stage and explode as supernovae , or they explode as supernovae while blue supergiants. Supernova progenitors are most commonly red supergiants and it
12496-409: The current consensus is that blue supergiants are evolved high-mass stars, larger and more luminous than main-sequence stars. O-type and early B-type stars with initial masses around 10–300 M ☉ evolve away from the main sequence in just a few million years as their hydrogen is consumed and heavy elements (with atomic numbers of 26 (Fe) and less) start to appear near the surface of
12638-427: The dimming could have come from a short-term minimum coinciding with a long-term minimum producing a grand minimum, a 416-day cycle and 2010 day cycle respectively, a mechanism first suggested by astronomer L. Goldberg . In April 2023, astronomers reported the star reached a peak of 0.0 visual and 0.1 V-band magnitude. As a result of its distinctive orange-red color and position within Orion, Betelgeuse
12780-573: The distance of Betelgeuse, with proposed distances as high as 400 pc or about 1,300 ly . Before the publication of the Hipparcos Catalogue (1997), there were two slightly conflicting parallax measurements for Betelgeuse. The first, in 1991, gave a parallax of 9.8 ± 4.7 mas , yielding a distance of roughly 102 pc or 330 ly . The second was the Hipparcos Input Catalogue (1993) with
12922-453: The driving factors. Other possible causes hypothesized by late 2019 were an eruption of gas or dust or fluctuations in the star's surface brightness. By August 2020, long-term and extensive studies of Betelgeuse, primarily using ultraviolet observations by the Hubble Space Telescope , had suggested that the unexpected dimming was probably caused by an immense amount of superhot material ejected into space. The material cooled and formed
13064-407: The efficiency with which the products of nucleosynthesis in the core are convected up to the surface. Quickly rotating supergiants can be highly mixed and show high proportions of helium and even heavier elements while still burning hydrogen at the core; these stars show spectra very similar to a Wolf Rayet star. Many blue supergiant stars are Alpha Cygni variables . While the stellar wind from
13206-419: The electromagnetic spectrum—the visible, near-infrared ( NIR ), mid-infrared (MIR), or radio—produce very different angular measurements. In 1996, Betelgeuse was shown to have a uniform disk of 56.6 ± 1.0 mas . In 2000, a Space Sciences Laboratory team measured a diameter of 54.7 ± 0.3 mas , ignoring any possible contribution from hotspots, which are less noticeable in the mid-infrared. Also included
13348-456: The existence of surrounding dust and gas shells would give a diameter of 41.9 mas . 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
13490-490: 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
13632-531: The ground between May and August because it is too close to the Sun. Before entering its 2020 conjunction with the Sun, Betelgeuse had reached a brightness of +0.4 . Observations with the STEREO-A spacecraft made in June and July 2020 showed that the star had dimmed by 0.5 since the last ground-based observation in April. This is surprising, because a maximum was expected for August/September 2020, and
13774-399: The main sequence, have extremely high luminosities, high mass loss rates, and are generally unstable. Many of them become luminous blue variables (LBVs) with episodes of extreme mass loss. Lower mass blue supergiants continue to expand until they become red supergiants. In the process they must spend some time as yellow supergiants or yellow hypergiants , but this expansion occurs in just
13916-439: The mass-loss rate from the Sun . More detailed optical and K band infrared spectroscopic observations, together with VLTI interferometry, were taken from 2006 to 2010. Analysis of the Hα and Hγ line profiles, and measurement of the regions producing the lines, show that Rigel's stellar wind varies greatly in structure and strength. Loop and arm structures were also detected within the wind. Calculations of mass loss from
14058-486: The most likely explanation for the dimming of the star. A study that uses observations at submillimetre wavelengths rules out significant contributions from dust absorption. Instead, large starspots appear to be the cause for the dimming. Followup studies, reported on 31 March 2020 in The Astronomer's Telegram , found a rapid rise in the brightness of Betelgeuse. Betelgeuse is almost unobservable from
14200-401: The most likely solution for Betelgeuse's 2170-day secondary periodicity, fluctuating radial velocity, moderate radius and low variation in effective temperature. The candidate companion would have a semi-major axis of 8.60 ± 0.33 AU . 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
14342-449: The next minimum should occur around April 2021. However Betelgeuse's brightness is known to vary irregularly, making predictions difficult. The fading could indicate that another dimming event might occur much earlier than expected. On 30 August 2020, astronomers reported the detection of a second dust cloud emitted from Betelgeuse, and associated with recent substantial dimming (a secondary minimum on 3 August) in luminosity of
14484-474: The night sky at near-infrared wavelengths. Its Bayer designation is α Orionis , Latinised to Alpha Orionis and abbreviated Alpha Ori or α Ori . With a radius between 640 and 764 times that of the Sun, if it were at the center of our Solar System , its surface would lie beyond the asteroid belt and it would engulf the orbits of Mercury , Venus , Earth , and Mars . Calculations of Betelgeuse's mass range from slightly under ten to
14626-400: The overall difference in brightness from Rigel A (about 6.6 magnitudes or 440 times fainter) makes it a challenging target for telescope apertures smaller than 15 cm (6 in). At Rigel's estimated distance, Rigel B's projected separation from Rigel A is over 2,200 astronomical units (AU). Since its discovery, there has been no sign of orbital motion, although both stars share
14768-506: The photosphere. Betelgeuse is the brightest near-infrared source in the sky with a J band magnitude of −2.99; only about 13% of the star's radiant energy is emitted as visible light. If human eyes were sensitive to radiation at all wavelengths, Betelgeuse would appear as the brightest star in the night sky. 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. Betelgeuse
14910-488: The physical radius and effective temperature ; luminosity and isotopic abundances can also be used to estimate the stellar age and mass . When the first interferometric studies were performed on the star's diameter in 1920, the assumed parallax was 0.0180 ″ . This equated to a distance of 56 pc or roughly 180 ly , producing not only an inaccurate radius for the star but every other stellar characteristic. Since then, there has been ongoing work to measure
15052-401: 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 1990s, has not detected any companions. A more recent study found that a not yet directly-observed, dust-modulating stellar-mass companion of 1.17 ± 0.7 M ☉ would be
15194-547: The process by which mass is lost remains a mystery. With advances in interferometric methodologies, astronomers may be close to resolving this conundrum. Images released by the European Southern Observatory in July 2009, 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
15336-414: The pulsations of Rigel are powered by nuclear reactions in a hydrogen-burning shell that is at least partially non-convective. These pulsations are stronger and more numerous in stars that have evolved through a red supergiant phase and then increased in temperature to again become a blue supergiant. This is due to the decreased mass and increased levels of fusion products at the surface of the star. Rigel
15478-653: The quantity and velocity of material being expelled from the star. Occasional very high-velocity outflows have been inferred, and, more rarely, infalling material. The overall picture is one of large looping structures arising from the photosphere and driven by magnetic fields. Rigel has been known to vary in brightness since at least 1930. The small amplitude of Rigel's brightness variation requires photoelectric or CCD photometry to be reliably detected. This brightness variation has no obvious period. Observations over 18 nights in 1984 showed variations at red, blue, and yellow wavelengths of up to 0.13 magnitudes on timescales of
15620-444: 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, with corrections for limb darkening and the observation wavelength. For example, a measured angular diameter of 55.6 mas would correspond to a Rosseland mean diameter of 56.2 mas, while further corrections for
15762-424: The rarely used variant names Algebar or Elgebar . The Alphonsine tables saw its name split into "Rigel" and "Algebar", with the note, et dicitur Algebar. Nominatur etiam Rigel. Alternate spellings from the 17th century include Regel by Italian astronomer Giovanni Battista Riccioli , Riglon by German astronomer Wilhelm Schickard , and Rigel Algeuze or Algibbar by English scholar Edmund Chilmead . With
15904-404: The ratio of the fundamental to overtone periods gives valuable information about the internal structure of the star and its age. The source of the long secondary periods is unknown, but they cannot be explained by 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
16046-493: 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, centered around mid June), it is invisible to the naked eye (visible only with a telescope in daylight), except around midday low in the north in Antarctic regions between 70° and 80° south latitude (during midday twilight in polar night , when
16188-438: The relatively homogeneous type II-P and are produced by red supergiants, blue supergiants are observed to produce supernovae with a wide range of luminosities, durations, and spectral types, sometimes sub-luminous like SN 1987A, sometimes super-luminous such as many type IIn supernovae. Because of their extreme masses they have relatively short lifespans and are mainly observed in young cosmic structures such as open clusters ,
16330-411: The same distance, has a Gaia Data Release 3 parallax of 3.2352 ± 0.0553 mas , suggesting a distance around 1,000 light-years (310 parsecs). However, the measurements for this object may be unreliable. Indirect distance estimation methods have also been employed. For example, Rigel is believed to be in a region of nebulosity , its radiation illuminating several nearby clouds. Most notable of these
16472-457: The sky than Rigel meant the Inuit regarded it as brighter, and one local name was Ulluriajjuaq ("large star"). In 1920, Albert A. Michelson and Francis G. Pease mounted a six-meter interferometer on the front of the 2.5-meter telescope at Mount Wilson Observatory , helped by John August Anderson . The trio measured the angular diameter of Betelgeuse at 0.047 ″ , a figure that resulted in
16614-605: The solar atmosphere. Astronomers saw some major advances in astronomical imaging technology in the 1970s, 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
16756-517: The southwestern quadrant 2,000 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°. In a study published in December 2000,
16898-475: The space-based Solar Mass Ejection Imager aboard the Coriolis satellite and three different modeling techniques produced a refined parallax of 5.95 +0.58 −0.85 mas, a radius of 764 +116 −62 R ☉ , and a distance of 168.1 +27.5 −14.4 pc or 548 +90 −49 ly, which, if accurate, would mean Betelgeuse is nearly 25% smaller and 25% closer to Earth than previously thought. Although
17040-460: 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
17182-488: 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
17324-480: The star showed signs of rebrightening. On 22 February 2020, Betelgeuse may have stopped dimming altogether, all but ending the dimming episode. On 24 February 2020, no significant change in the infrared over the last 50 years was detected; this seemed unrelated to the recent visual fading and suggested that an impending core collapse may be unlikely. Also on 24 February 2020, further studies suggested that occluding "large-grain circumstellar dust " may be
17466-644: 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 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
17608-502: The star. In June 2021, the dust was explained as possibly caused by a cool patch on its photosphere and in August a second independent group confirmed these results. The dust is thought to have resulted from the cooling of gas ejected from the star. An August 2022 study using the Hubble Space Telescope confirmed previous research and suggested the dust could have been created by a surface mass ejection. It conjectured as well that
17750-483: The star. These stars usually become blue supergiants, although it is possible that some of them (particularly the more massive ones) evolve directly to Wolf–Rayet stars . Expansion into the supergiant stage occurs when hydrogen in the core of the star is depleted and hydrogen shell burning starts, but it may also be caused as heavy elements are dredged up to the surface by convection and mass loss due to radiation pressure increases. Blue supergiants are newly evolved from
17892-604: The stars of each class appear to have been ordered north to south. Rigel has many other stellar designations taken from various catalogs, including the Flamsteed 19 Orionis (19 Ori), the Bright Star Catalogue entry HR 1713, and the Henry Draper Catalogue number HD 34085. These designations frequently appear in the scientific literature, but rarely in popular writing. Rigel
18034-429: 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 of 273°, an orbit that would potentially place it within the star's chromosphere . The more distant companion was at 0.51″ ± 0.01″ (≈77 AU) with a position angle of 278°. Further studies have found no evidence for these companions or have actively refuted their existence, but
18176-431: The time, it is a double-peaked line, that is, an absorption line with an emission core or an emission line with an absorption core. About a quarter of the time it has a P Cygni profile; most of the rest of the time, the line has an inverse P Cygni profile, where the emission component is on the short wavelength side of the line. Rarely, there is a pure emission Hα line. The line profile changes are interpreted as variations in
18318-483: The top 10 brightest stars in the sky to outside the top 20, noticeably dimmer than its near neighbor Aldebaran . Mainstream media reports discussed speculation that Betelgeuse might be about to explode as a supernova, but astronomers note that the supernova is expected to occur within approximately the next 100,000 years and is thus unlikely to be imminent. By 17 February 2020, Betelgeuse's brightness had remained constant for about 10 days, and
18460-742: The two almost identical components separated by 0.124″ , with visual magnitudes of 7.5 and 7.6, respectively. Their estimated orbital period is 63 years. Burnham listed the Rigel multiple system as β 555 in his double star catalog or BU 555 in modern use. Component B is a double-lined spectroscopic binary system, which shows two sets of spectral lines combined within its single stellar spectrum . Periodic changes observed in relative positions of these lines indicate an orbital period of 9.86 days. The two spectroscopic components Rigel Ba and Rigel Bb cannot be resolved in optical telescopes but are known to both be hot stars of spectral type around B9. This spectroscopic binary, together with
18602-693: The variable brightness of Betelgeuse for at least 1,000 years. The variation in Betelgeuse's brightness was described in 1836 by Sir John Herschel 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
18744-434: The whole multiple star system is known as WDS 05145-0812 or CCDM 05145–0812. The designation of Rigel as β Orionis ( Latinized to beta Orionis ) was made by Johann Bayer in 1603. The "beta" designation is usually given to the second-brightest star in each constellation, but Rigel is almost always brighter than α Orionis ( Betelgeuse ). Astronomer J.B. Kaler speculated that Bayer assigned letters during
18886-538: 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
19028-406: 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
19170-402: Was 44.5 ″ , almost due north at a position angle of 1°. Gaia DR2 finds it to be a 12th magnitude sunlike star at approximately the same distance as Rigel. Likely a K-type main-sequence star , this star would have an orbital period of around 250,000 years, if it is part of the Rigel system. A spectroscopic companion to Rigel was reported on the basis of radial velocity variations, and its orbit
19312-438: 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 1,200 R ☉ , assuming the 2008 Harper distance of 197.0 ± 45 pc , a figure roughly the size of the Jovian orbit of 5.5 AU . In 2004, a team of astronomers working in the near-infrared announced that the more accurate photospheric measurement
19454-438: Was believed that only red supergiants could explode as supernovae. SN 1987A , however, forced astronomers to re-examine this theory, as its progenitor, Sanduleak -69° 202 , was a B3 blue supergiant. Now it is known from observation that almost any class of evolved high-mass star, including blue and yellow supergiants, can explode as a supernova although theory still struggles to explain how in detail. While most supernovae are of
19596-535: Was cast millions of miles from the star, and then cooled to form the dust that caused the dimming. The star's designation is α Orionis (Latinised to Alpha Orionis ), given by Johann Bayer in 1603. The traditional name Betelgeuse was derived from the Arabic يد الجوزاء Yad al-Jawzā’ "the hand of al-Jawzā’ [i.e. Orion]". An error in the 13th-century reading of the Arabic initial yā’ ( يـ ) as bā’ ( بـ —a difference in i‘jām ) led to
19738-424: 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. A pulsating semiregular variable star , Betelgeuse
19880-552: Was even calculated, but subsequent work suggests the star does not exist and that observed pulsations are intrinsic to Rigel itself. Rigel is a blue supergiant that has exhausted the hydrogen fuel in its core, expanded and cooled as it moved away from the main sequence across the upper part of the Hertzsprung–Russell diagram . When it was on the main sequence, its effective temperature would have been around 30,000 K . Rigel's complex variability at visual wavelengths
20022-495: Was reported still fainter in February in The Astronomer's Telegram at a record minimum of +1.614, noting that the star is currently the "least luminous and coolest" in the 25 years of their studies and also calculating a decrease in radius. Astronomy magazine described it as a "bizarre dimming", and popular speculation inferred that this might indicate an imminent supernova . This dropped Betelgeuse from one of
20164-459: Was used as an astrofix . Mount Rigel , elevation 1,910 m (6,270 ft), is also in Antarctica. Blue supergiant Blue supergiants are found towards the top left of the Hertzsprung–Russell diagram , above and to the right of the main sequence. By analogy to the red giant branch for low-mass stars , this region is also called the blue giant branch . They are larger than
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