text:
Always seeking new and engaging ways to share tips, advice and small business news with our community we're excited to announce our latest: Lunchtime Q&A with Small Biz Experts on Facebook. Once a month, to begin, we'll invite an individual knowledgeable in the world of small business to spend an hour on our Facebook page answering the questions our community has on their area of expertise.
Our inaugural Q&A will take place this Thursday, September 8th from 12:00 PM — 1:00 PM EST with featured guest host Ramon Ray.
Ramon is a journalist, technology evangelist, speaker, editor of Smallbiztechnology.com and author of "Technology Solutions for Growing Businesses" (Amacom) and most recently "Technology Resources for Growing Businesses". Ramon has written thousands of technology articles and news items for Smallbiztechnology.com and other media including: Open Forum, Inc. Magazine, New York Enterprise Report, Black Enterprise Magazine, CNet, Var Business, TechTarget, Entrepreneur.com, Small Business Resources and others. He has also written for technology vendors including Microsoft, FileMaker, and Everest. Often quoted in the media, Ramon has brought his unique dose of humor, technology insight and practical advice to many events too.
What: Lunchtime Q&A with Small Biz Experts on Facebook
When: Thursday, September 8th from 12:00 PM — 1:00 PM EST
Where: Network Solutions Facebook Page: http://www.facebook.com/networksolutions
Call To Action? Post your questions on the wall starting at 9:00 AM EST 9/8 or join the Q&A live at the scheduled time.
Image via Flickr (creative commons) by S1m0nB3rry
Google+Brought to you by Network Solutions®, a Web.com® service.


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Police repression of anti-cuts groups in Swindon & Taunton
Police are using threats and intimidation in an attempt to repress anti-cuts groups forming in towns across the region.
Yeah yeah, not exactly an exclusive we know. But we aren't talking about the cops coming down hard on organised groups of international anarchists having secret meetings with their leader Chris Knight. In Swindon, Wiltshire police have been harassing members of their local anti-cuts group who have been organising stalls and giving out flyers about the cuts in the town centre.
The cops, one, due to a spelling mistake on his ID card now known as Inspector Anger (can you be arrested by a cop with incorrect ID?) have been demanding the personal details of these shady leaflet distributers and making up laws to get them.
They have also received threatening e-mails and phone calls about the risks of non-compliance with the Police and some members have been visited in their homes by police searching for information. One sergeant threatened to ban all future actions by the group under section 14 of the public order act.
...It seems however that nothing overtly political has happened in Taunton for a very long time and as a result the Police panicked. The organisers were forced to have a Police liason and received regular calls from the local plod. Even the venue was visited and the land lady warned off allowing the gig to happen, being told it was a protest rather than a concert and another cop referring to it as a "mini Glastonbury"!
... Full article

subset: commoncrawl


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Español | Donate | Journals | Annual Meeting | Find an Allergist / Immunologist
Advocacy » Pollen Counts » AAAAI Store » Ask the Expert » Latest Research »
Published Online: October 5, 2011
Allergic sensitization has been studied in cross-sectional studies and the results are consistent; among adults, the prevalence of allergic sensitization decreases with increasing age. A birth cohort effect has been discussed as a reason for this pattern, i.e., subjects born more recently has been growing up under conditions that may increase the development of allergic sensitization.
In a recent article in The Journal of Allergy and Clinical Immunology (JACI), Warm et al have in a longitudinal setting evaluated the natural process of allergic sensitization among adults. They used data from a random sample of the general population who was examined in 1995 and followed up in 2005. The cohort was interviewed and skin prick testing with ten common allergens was performed. The same methods were used in 1995 and at the follow up. However, at the follow-up in 2005 also specific IgE was measured. The high participation rate, 555 (93% of invited) participated at the follow-up, supports the validity of their results.
The researchers analyzed the prevalence of allergic sensitization, measured as a positive skin prick test or presence of elevated specific IgE, and found a significant association to age. The prevalence was highest in young adults and decreased with increasing age. In analyses of the longitudinal course they revealed a low incidence (5%) and a high remission (32%) of allergic sensitization over the 10 years. Remission was highest among older subjects. Interestingly, in this cohort of adults, they found that having had furred animals at home during childhood was negatively related to specific IgE.
The authors explain that the low incidence and high remission of allergic sensitization in adulthood causes the decreasing prevalence by age. They thus argue that the low prevalence of allergic sensitization among the elderly found in cross-sectional studies is an effect of normal aging and not primarily a birth cohort effect.
The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.


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The Foundry team have been hard at work, announcing three new releases in as many days. There are some new cool features added to MARI to improve its 3D texture painting capability, and NUKE has loads of feature enhancements and fixes worth checking out. Here is a summary of what you can expect from the new releases:
- The latest version of Mari incorporates Python 2.6.5 with an integrated script editor and more examples of real production tasks. Check out what's new in Mari 2.1 here.
- NUKE and NUKEX 6.1v4 is a maintenance release with an updated Furnacore and a significantly faster multi-view EXR. Check out the full update in the release notes.
- NUKE and NUKEX 6.2v2 has several bug fixes and Quicktime codecs are now configurable. More info can be found here.
There is also a new Foundry Vimeo channel with NUKE customer demos and NUKE tutorials for you to check out.
All new versions are free to customers on a valid maintenance. If you want to give NUKE or MARI a try yourself, get in touch for a free trial.
There will be a more detailed look at the new MARI features in the coming days, where Simon will share his thoughts on the new version, so stay tuned.


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From American Power (Steidl, 2009)
To see what is in front of one's nose needs a constant struggle.
—George Orwell
In Cheshire, Ohio, I watched backhoes crush whole houses into kindling in less than an hour. The destruction was so fast and easy, I had to remind myself these were real homes, not a child's cardboard constructions. At the local pizza shop, I photographed a newspaper that pictured a white clapboard house in front of a power plant; across the house's roof in black marker the shop owner had written "GONE."
It was the fall of 2003 and I had been hired to photograph a town in the process of being erased. The American Electric Power Company had paid residents of Cheshire a lump sum to leave, never come back, and never complain in the media or in court if they became sick from environmental contaminates spewed out of the AEP plant. The company was buying itself a lawsuit-free future. Back in New York, I could not get Cheshire out of my mind.
It was my visit with Beulah Hern that had made the deepest impression on me. Boots, as she called herself, was in her eighties and refused to sell her home. American Electric Power, she said, was harassing her for holding out, so she had taken her security in hand. Boots showed me two surveillance cameras installed at her window under a ruffled curtain. On top of her wooden television cabinet sat a video monitor. This enabled her to watch her favorite T.V. programs and simultaneously monitor her backyard for suspicious activity. Here I was in the home of a genteel elderly woman who could have been my grandmother, except that this grandma had taken extreme measures to protect herself. Her security set-up unnerved me. It mirrored the coal plant's security. Surveillance was everywhere in the tiny town of Cheshire. Boots sat down in her easy chair and watched me as I photographed her video cameras. "Would you like to see my gun?" she said, and from the side pouch of the chair, where I expected to find copies of Readers Digest and the Farmers Almanac, Boots pulled out a handgun. Sensing my alarm, she kindly unloaded it.
Six months later, in the spring of 2004, I began to make pictures of the production and consumption of energy in the United States. I wanted to photograph the relationship between American society and the American landscape, and energy was the linchpin; this much I had gleaned from Cheshire. Energy—how it was made, how it got used, and the ramifications of both—would therefore be my focus. For the next five years, I traveled the country making photographs at or near energy production sites: coal, oil, natural gas, nuclear, hydroelectric, fuel cell, wind, and solar. It was a strange kind of tourism: energy tourism. Everything I photographed related to energy, even if the link was not always obvious or simple. The electric chair in the Moundsville State Penitentiary, for instance, might appear incongruous to this series. Yet, aside from being an icon of electrical power usage, the chair presses the question: for what exactly are we importing all of this oil, burning all of this dirty coal, and drilling into our oceans and our national parks?
In my studio hung a giant map of the United States stuck with color-coded push-pins: red for coal, blue for nuclear, green for wind, yellow for "been there," and so on. My studio manager, Ryan Spencer, and I would plot my next trip while staring at the map. Before I could leave, dozens of queries went out to corporate public relations, plant managers, government bureaus, people living off the grid or stewing up bio-diesel, congressional aids, and cheap motels. The point of all that careful planning, though, was to set myself up for the unexpected. Having a clear plan was a ruse to launch me into the world and into the work. Much of the time, my favorite pictures were the result of serendipity.
Hurricane Katrina threw a painfully resonant wrench into my well-laid plans. I had already plotted a trip to Louisiana to photograph the offshore oil platforms and refineries along the Gulf Coast when the storm hit. Six weeks after the initial devastation, I went to see the rigs and what remained of the coastline. Even before this hurricane, scientists had connected the dots between energy production, climate change, and an increase in deadly weather. Katrina was the ultimate symbol of how we, as a society, had failed; how our rapacious, "supersize-me" culture had led to catastrophe. The oil platform I photographed on Dauphine Island in Alabama was an unmoored mangle of bent and broken steel. It brought to mind a great prehistoric creature that has finally been crushed by something greater.
I traveled numerous times to photograph the repercussions of westward expansionism on the landscape. Mountains, rivers, and deserts there supported dams, power plants, highways, oil wells, and the occasional solar or wind farm. Human-kind's technical prowess had etched itself into nature's grandeur. But settlers did not expect that their American Dream of material ease would ultimately require more energy than the land could give. The Hoover Dam, for instance, a supreme feat of hydro-engineering in the 1930s, has now become an emblem of nature's depletion. Looking at my photograph of the dam, it is hard not to be impressed by society's taming of the untameable: the harnessing of water to foster the growth of the American West. Pride is evident in the dam's magnificent architecture. But this depiction of human triumph also shows Lake Mead's diminishing waterline, known as "the bathtub ring." The ring is a result of a ten-year drought, as well as the siphoning off of water to nearby Las Vegas for luxury hotels and golf courses. Water itself has become more valuable than the electricity it can produce.
The wounds I discovered in the American landscape made me reconsider my own sense of entitlement and the American heritage of Manifest Destiny. These pictures question the human conquest of nature at any cost. Might we, as Americans, consider our obligation to nature and one another, not only our individual rights?
One right to which I cling, however, is the right to photograph in public space. Security and surveillance continually interfered with this right, and inadvertently influenced my pictures. There was a new sense of vulnerability in the U.S. after 9/11 and I expected to be questioned now and then. But I resented the systematic harassment I faced while I worked on American Power. Law enforcement officials more than once ran me out of town when I had done nothing remotely criminal. The result was that from 2003 to 2008—a span that coincided with the Bush era—most of where I went in the United States to work, I went in fear. This was because my intentions ran counter to corporate interests, which had Homeland Security to back them up. I wanted to make the topic of energy more transparent, while big energy companies and their governmental counterparts shrouded themselves in secrecy.
The height of my security troubles came in the fall of 2004 when I returned to the Ohio River Valley. In Raymond City, West Virginia, more hamlet than city, a stranger proudly invited me into her backyard to, as she put it, "appreciate a better view of the cooling towers." A bench sat on the riverbank facing the Amos coal power plant. I imagined warm summer evenings when residents would drink a cold beer there and enjoy the view of the massive stacks as they belched toxic emissions into the sky above the Kanawha River.
In neighboring Poca, I set up my camera on a public sidewalk and twenty minutes later the flashing lights of a four-wheel police cruiser came towards me. A sheriff stepped out and shouted orders at me. As she ran a check on our driver's licenses, another four-wheeler pulled up. Another sheriff got out and asked to search my car: "You don't have a dead body in there, do you?" I handed him my rental keys, and watched him rummage through my belongings, nervous that he might light strike a sheet of exposed film. He returned with a stack of 4×5 black and white Polaroids as evidence against me. The Deputy and State Police had to be called now, he said, because I'd been photographing the power plant without authorization. I wanted to point out to him that I had been standing on public property, that I had been at a great distance from the plant, and that I also photographed an empty chair on the river's edge. But this was one of those times when you know that any comment you offer—however sensible—will make a bad situation worse.
Thirty minutes later, an unmarked car arrived. A middle-aged man in a suit and tie stepped out and flashed his I.D.: FBI. "You know," he said, "if you were Muslim, you'd be cuffed and taken in for questioning." Another unmarked vehicle pulled up, making the final count six vehicles and six law-enforcement officers. Passers-by must have thought there had been a murder.
I was becoming less sure that this would end with a laugh and apology on their part. Six officers huddled to discuss my fate. Five minutes later, the FBI agent returned to scold me: "you can't just go pointing your camera at these infrastructures anymore. Times are changing. Why didn't you tell me that you've been questioned for this kind of thing before?"
It was true—I had already gone through many interrogations by then. One resulted from a call the police had received in Shippingport, Pennsylvania reporting a man on Main Street carrying a missile launcher. The missile launcher was my tripod. A police officer escorted me out of town, explaining that the power company I was photographing didn't allow pictures. I had broken no law, however, having attempted to photograph a coal stack from a public street in the center of town. Apparently, Shippingport police now enforced corporate instead of Constitutional law. I was witnessing the Patriot Act in action.
On a later trip to West Virginia, a public relations officer at the Amos Coal Power Plant welcomed me warmly and allowed me to make pictures inside the facility. I was shocked. It turned out he was a photography buff and had a copy of one of my books. His cooperation was an exception. The cops and FBI let me go after the nearly two-hour interrogation in Poca, but henceforth I worked with a discomforting urgency, sensing Big Brother at my heels. At one point, I consulted my attorney, hoping I could find a legal argument to use against the next officers who would lawlessly eject me. "Don't get arrested at all costs," he counseled, less than reassuringly. "You don't want to end up in some small town jail that won't be easy to get out of."
Energy's symbiosis with politics was a given, so it made sense to visit my nation's capitol. Ironically, I photographed a nuclear warhead at the Department of Energy headquarters and a solar array at the Pentagon. Energy production is now a major concern of our military command, which is sponsoring several progressive renewable energy projects. I had expected an alternative energy display in the lobby of the Department of Energy, which is, after all, charged with overseeing domestic energy production, research, and conservation. Instead, the DOE lobby displayed a nuclear missile—a vestige of the Department's predecessor, the Atomic Energy Commission, which began in 1946 to grapple with the dangers of the recently unleashed nuclear bomb. I couldn't help think it was time to change the DOE lobby display.
With energy politics in mind, I also went to both political conventions in the late summer of 2008. The Republicans were holding theirs at the Xcel Energy Center; and the Democrats were boasting a "Green" event sponsored by the so-called "clean coal" industry. I nosed around the prison-like metal fencing that surrounded the hall in Denver, but never gained access. Neither did I get into the Xcel Center in St. Paul. I had tried hard for each, and with good connections. But I was not a photojournalist who would promote the events in the news, which made me unnecessary and a potential liability. By this time, I was used to getting rejected from official venues. This project was, in part, about not getting in. What I saw on the outside, though, was less predictable and more intriguing to me than the choreographed hoopla inside the halls. I made a picture of the Fox News electronic billboard outside the Xcel Center, which showed the approach of Hurricane Gustav. Gustav halted the RNC proceedings for a day and brought back horrible, and, for many politicians, embarrassing memories of their response to Katrina.
Between Denver and St. Paul, I photographed the energy landscape of the Midwest. I visited a strip mine in the Powder River Basin of Northeastern Wyoming, where coal's purported cleanliness eluded my camera, which I had to wipe laboriously to remove the soot after the shoot. Three months later, in amazement, I watched a Christmas time television ad run by the coal industry, in which several chunks of coal with cute blinking eyes cheerily sang:
Frosty the Coalman is a jolly happy soul,
He's abundant here in America and he helps our economy roll.
Frosty the Coalman's getting cleaner every day,
He's affordable and adorable and helps workers keep their pay.
There must have been some magic in clean coal technology,
For when they looked for pollutants there were nearly none to see . . .
Should we believe this ad made by an industry that stands to make billions if we do? Or listen to Nobel prize-winning energy expert Al Gore, who says clean coal is "imaginary."
In one of the strangest, most optimistic pictures here, a young inventor spins blue-white threads of electricity, as vivid as Zeus's thunderbolt, from a Tesla Coil. The Coil itself, invented in 1891, is a source of cheap, high voltage ignition. It is no answer to our energy dilemma, to be sure, but one of Mr. Lowrey's experiments may eventually lead to one. This electrical DJ embodies, for me, the grassroots ingenuity that has historically improved American lives.
About a year into making this series of pictures, I realized that power was like a Russian nesting doll. Each time I opened one kind of power, I found another kind inside. When I opened electrical power, I discovered political power; when I opened political power, I discovered corporate power; within corporate was consumer; within consumer was civic; within civic was religious, and so on, one type of power enabling the next. I began making these pictures with the idea that an artist lives outside the nesting doll, and simply opens and examines it. But now—while America teeters between collapse and transformation—I see it differently: as an artist, I sit outside, but also within, exerting my own power.
When I photograph, I do not consciously think about politics. But it was inevitable that the grim reality of American power circa 2003–2008 would find its way into my work. I could not ignore the security excesses, corporate avarice, and environmental indifference I encountered. I have tried to convey in these pictures the beauty and terror of early 21st century America, as it clings to past comforts and gropes for a more sensible future.
—Mitch Epstein, New York City, 2009
Copyright 2009 Mitch Epstein


text: Maria Yuryevna Sharapova is a former World No. 1 Russian professional tennis player and three time Grand Slam singles champion. As of 31 August 2009, she is ranked World No. 31. When Sharapova was seven, she and her father moved from their life of poverty in Russia to the United States, to enroll in the Nick Bollettieri Tennis Academy. After rising rapidly through the junior and professional ranks... Full Article At Wikipedia.org


text:
When Emmy nominations were announced, the Minnesota-based series was one of the big winners.
Hollywood loves "Fargo." The Minnesota-based drama garnered 18 Emmy nominations Thursday, second only to "Game of Thrones" with 19 nods.
Billy Bob Thornton, Martin Freeman, Colin Hanks and newcomer Allison Tolman all were recognized for their performances.
Part of the reason for the high count is that the FX project chose to compete in the miniseries category, which kept it from going head to head with heavily hyped "Breaking Bad" and "True Detective."
But that shrewd move shouldn't take away from "Fargo"'s brilliance, that makes it a runaway favorite to beat out "American Horror Story: Coven," "Bonnie & Clyde," "Luther," "The White Queen" and — in one of the morning's most delightful surprises — "Treme."
There were more stunners, most of them positive.
Most pundits expected season one of Netflix's "Orange is the New Black" to make a mark, but it exceeded expectations with 12 nominations, more than any other comedy, including "Modern Family" and "Veep."
Netflix also had reason to cheer for Ricky Gervais, who may have scored the day's biggest upset by securing a spot in the category of best comedic actor for his role in the woefully underappreciated "Derek." In all, Netflix picked up 31 nominations, more than the Fox network and all but two cable channels, HBO and FX.
HBO had a total of 99 nominations, largely because of the overwhelming support of "The Normal Heart" and "True Detective." But let's also give a hand to "Silicon Valley," which managed to pick up five nominations, including one for outstanding comedy.
And then there are the heavyweight fights.
The most anticipated battle will take place in the category of lead actor in a drama, as Bryan Cranston, in his final season of "Breaking Bad," takes on Matthew McConaughey for his withering performance in "True Detective." If McConaughey pulls off a victory, he will be the first male actor to win an Oscar and an Emmy in the same year.
Also keep an eye on "Modern Family." It may not be as hip as the competition, which includes "Orange is the New Black" and "Louie," but it's a longtime Emmy favorite, and a win for outstanding comedy will make it five in a row, an accomplishment previously achieved only by "Frasier."
There was one major sour note: For the second year, Tatiana Maslany was overlooked for playing a variety of clones in "Orphan Black." Just how many characters does she have to play to finally get some Emmy love?
The awards will be handed out on Aug. 25, a Monday, to avoid competing against "Sunday Night Football" and "The MTV Video Awards." Seth Meyer hosts.
Neal Justin • 612-673-7431


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EUGENE, Ore. — Scientists from around Oregon and other Western states will be in Eugene this weekend to discuss climate change. The keynote topic will center on a study looking at how it will affect the state.
Three University of Oregon professors will give us a glimpse into what the future holds for Oregon as carbon dioxide continues to steadily rise in the atmosphere.
According to the study, the state is projected to warm up by 7 to 9 degrees in the next 85 years, but we won't experience extreme heat and extensive loss of land due to rising sea levels.
Oregon is also projected to be wetter by 2 to 9 inches. Seasonal droughts may still be in the future, but researchers say we're expected to face them in late winter and summer.
Even with all these potential changes, researchers say Oregon will fare relatively well during ongoing climate change when compared with surrounding states.
If you would like to learn more about the study, you can attend the panel Saturday at the University of Oregon. Click here for more information.


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Kirilenko turned down a $10 million dollar player option in Minnesota to come play for the Nets at the $3.18 taxpayer's midlevel exception. It may seem odd that Kirilenko would take such a pay cut, but even more that the Nets were able to afford him despite having inked Kevin Garnett and Paul Pierce.
One NBA Owner told Yahoo Sports,
Let's see if the league has any credibility. It's not about stopping them, it's about punishing them if they're doing so.After thorough investigation on the topic, it was concluded that there was nothing wrong with the signing.
If there was one team that wanted this issue investigate, it was probably the Knicks, considering considering that their rivals were moving forward. It's odd that a player like Kirilenko would take that much of a pay cut, but when you have the chance to win a title, nothing should be out of the equation.
Follow @NetsTakeOver


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Mediterranean Fig
The scent begins with a top note of green apple, strawberry, melon and fig. The heart is a fresh green floral with lily, rosewood jasmine and violet. The base is a rich woody bouquet with oak moss and velvety cashmere.
This fragrance oil is infused with natural essential oils.
Suggested Colors: Brown, Butterscotch, GreenSee our complete list of candle making dyes.
Soy Performance | |
Usage | Candles & Bath/Body |
Flashpoint | 212 °F |
Phthalate Free | No |
Diffuser Base Compatible | Yes; up to 25% |
Customer Reviews
Submitted On 2014-09-10 Kendall
One of my favorites! Great cold and hot throw!!! Smells beautiful and rich! I love burning this candle! Used 4627 Comfort Blend
Submitted On 2014-05-10 Lena C
When I first smelled this out of the bottle I got hit with melon big time, and was kinda disappointed. A day or two after I poured (used 464) still only melon :( after a week of curing the cold throw totally changed, now it smells amazing! Don't be disappointed by the immediate scent. Haven't burned these guys yet so not sure about hot throw, but I would definitely recommend a long cure time.
Submitted On 2014-04-10 Ang
This is definitely a winner and a must add to any candle line. I agree with some other reviewers- not sure what a Meditteranean Fig smells like, but I love this candle. Has nice woodsy-floral notes with fruity underneath (subtle). A very sophisticated scent- would be great if you were having guests over for dinner. Great for any time of year. I used 1 oz/lb in GB 464.
Submitted On 2014-03-07 Carlos C.
This scent is a winner in my book for sure! Not sure what Mediterranean Fig smells like but I know this FO smells damn good! It has a slight earthiness to it but not overpowering though, it's a great blend, and the notes really come together well. This scent is very strong too which I really love about it. I used a 4 percent FO load in a 10 ounce candle and the hot throw was nice and strong. Can easily fill a large area. This scent kinda reminds me of Oakmoss and Amber, another great scent, but they are indeed different and both amazing scents. Great job CS!
Submitted On 2013-10-03 DT
Very nice fig scent (used soy wax), as others have mentioned. Not too heavy. The cold throw was a bit weak, but the hot throw was fantastic, which surprised me. Definitely a keeper--will buy this again.
Submitted On 2013-09-06 K.Elizabeth
A truely beautiful sophisticated fig fragrance.They really managed to capture the fig in this one. I agree w/the others a "higher end" fragrance like Oakmoss & Amber. This would be a great fragrance category "sophisticated/high end fragrances."
Submitted On 2011-02-05 Tomara Carter
Everyone loves this and with good reason. It is a dead on dupe of Trapp candles. It is wonderful in parasoy tarts and cp soap. Behaves beautifully and scent stays true.
Submitted On 2011-01-24 ARStudio
This has gotten a lot of good reviews. Nice throw in GB 464, a good scent for many different tastes. Unique and classy. :)
Submitted On 2009-03-29 jennifer
I got this as a free sample and will be ordering more. This is the new addition to my candle line.
Submitted On 2008-11-20 Sue Shattuck
this is great ! very fresh most excellent for my diffuser reeds ! i totally love it, its a clean but happy scent ........ 5 *****
Submitted On 2008-09-19 Christine G
I put this into HP soap and it was perfect with the rustic look. The scent was pretty strong at first but mellowed out as I let the soap age. Really nice earthy scent with a hint of fruit, just a touch though.


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From Wikipedia, the free encyclopedia - View original article
Observation data Epoch J2000.0 Equinox J2000.0 | |
Constellation | Orion |
Pronunciation | /ˈbiːtəldʒuːz/, /ˈbɛtəldʒuːz/[1] or /ˈbiːtəldʒuːs/[2] |
Right ascension | 05h 55m 10.3053s[3] |
Declination | +07° 24′ 25.426″[3] |
Characteristics | |
Spectral type | M2Iab[3] |
Apparent magnitude (V) | 0.42 (0.3 to 1.2)[3][4] |
Apparent magnitude (J) | -2.99 ± 0.10[3] |
U−B color index | 2.06[5] |
B−V color index | 1.85[5] |
Variable type | SR c (semi-regular)[3] |
Astrometry | |
Radial velocity (Rv) | +21.91[3] km/s |
Proper motion (μ) | RA: 24.95 ± 0.08[6] mas/yr Dec.: 9.56 ± 0.15[6] mas/yr |
Parallax (π) | 5.07 ± 1.10[6] mas |
Distance | 643 ± 146[6] ly (197 ± 45[6] pc) |
Absolute magnitude (MV) | −5.85[6] |
Details | |
Mass | 7.7–20[7] M☉ |
Radius | 950–1200[7][8] R☉ |
Luminosity | 90,000-150,000[7][9][10] L☉ |
Surface gravity (log g) | -0.5[11] cgs |
Temperature | 3,140–3,641[7][12][13] K |
Metallicity | 0.05 Fe/H[14] |
Rotation | 5 km/s[13] |
Age | ~7.3×106[15] years |
Other designations | |
Database references | |
SIMBAD | data |
Observation data Epoch J2000.0 Equinox J2000.0 | |
Constellation | Orion |
Pronunciation | /ˈbiːtəldʒuːz/, /ˈbɛtəldʒuːz/[1] or /ˈbiːtəldʒuːs/[2] |
Right ascension | 05h 55m 10.3053s[3] |
Declination | +07° 24′ 25.426″[3] |
Characteristics | |
Spectral type | M2Iab[3] |
Apparent magnitude (V) | 0.42 (0.3 to 1.2)[3][4] |
Apparent magnitude (J) | -2.99 ± 0.10[3] |
U−B color index | 2.06[5] |
B−V color index | 1.85[5] |
Variable type | SR c (semi-regular)[3] |
Astrometry | |
Radial velocity (Rv) | +21.91[3] km/s |
Proper motion (μ) | RA: 24.95 ± 0.08[6] mas/yr Dec.: 9.56 ± 0.15[6] mas/yr |
Parallax (π) | 5.07 ± 1.10[6] mas |
Distance | 643 ± 146[6] ly (197 ± 45[6] pc) |
Absolute magnitude (MV) | −5.85[6] |
Details | |
Mass | 7.7–20[7] M☉ |
Radius | 950–1200[7][8] R☉ |
Luminosity | 90,000-150,000[7][9][10] L☉ |
Surface gravity (log g) | -0.5[11] cgs |
Temperature | 3,140–3,641[7][12][13] K |
Metallicity | 0.05 Fe/H[14] |
Rotation | 5 km/s[13] |
Age | ~7.3×106[15] years |
Other designations | |
Database references | |
SIMBAD | data |
Coordinates: 05h 55m 10.3053s, +07° 24′ 25.426″
Betelgeuse (/ˈbiːtəldʒuːz/, /ˈbɛtəldʒuːz/[1] or /ˈbiːtəldʒuːs/[2]), also known by its Bayer designation Alpha Orionis (shortened to α Orionis or α Ori), is the ninth-brightest star in the night sky and second-brightest in the constellation of Orion. Distinctly reddish, it is a semiregular variable star whose apparent magnitude varies between 0.2 and 1.2, the widest range of any first-magnitude star. Betelgeuse is one of three stars that make up the Winter Triangle, and it marks the center of the Winter Hexagon. The star's name is derived from the Arabic يد الجوزاء Yad al-Jauzā', meaning "the hand of Orion". The Arabic character for Y was misread as B by medieval translators, creating the initial B in Betelgeuse.
The star is classified as a red supergiant of spectral type M2Iab and is one of the largest and most luminous observable stars. If Betelgeuse were at the center of the Solar System, its surface would extend past the asteroid belt, possibly to the orbit of Jupiter and beyond, wholly engulfing Mercury, Venus, Earth and Mars. Estimates of its mass are poorly constrained, but range from 5 to 30 times that of the Sun. Its distance from Earth was estimated in 2008 at 640 light-years, yielding a mean absolute magnitude of about −6.02. 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 crimson runaway has been observed moving through the interstellar medium at a supersonic speed of 30 km/s, creating a bow shock over 4 light-years wide. Currently in a late stage of stellar evolution, the supergiant is expected to proceed through its life cycle before exploding as a type II supernova within the next million years. An observation by the Herschel Space Observatory in January 2013 revealed that the star's winds are crashing against the surrounding interstellar medium.[16]
In 1920, Betelgeuse became the second star (after the Sun) to have the angular size of its photosphere measured. Since then, researchers have used telescopes with different technical parameters to measure the stellar giant, often with conflicting results. Studies since 1990 have produced an angular diameter (apparent size) ranging from 0.043 to 0.056 arcseconds, an incongruity largely caused by the star's tendency to periodically change shape. Due to limb darkening, variability, and angular diameters that vary with wavelength, many of the star's properties are not yet known with any certainty. Adding to these challenges, the surface of Betelgeuse is obscured by a complex, asymmetric envelope roughly 250 times the size of the star, caused by colossal mass loss.
Betelgeuse and its red coloration have been noted since antiquity; the classical astronomer Ptolemy described its color as ὑπόκιρρος (hypókirros), a term that was later described by a translator of Ulugh Beg's Zij-i Sultani as rubedo, Latin for "ruddiness".[17][18] 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.[19] By contrast, three centuries before Ptolemy, Chinese astronomers observed Betelgeuse as having a yellow coloration, suggesting that the star may have spent time as a yellow supergiant around the beginning of the common era,[20] a possibility given current research into the complex circumstellar environment of these stars.[21]
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.[22] 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.[4][23] This variability in brightness may explain why Johann Bayer, with the publication of his Uranometria in 1603, designated the star alpha as it may have rivaled the usually brighter Rigel (beta).[24] From Arctic latitudes, Betelgeuse's red colour and higher location in the sky than Rigel meant the Inuit regarded it as brighter, and one local name was Ulluriajjuaq "large star".[25]
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".[26] However, limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements.
The 1950s and 1960s saw two developments that would impact 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.[27][28] 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.[27]
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.[29][30] 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,[31][32][33] causing them to suspect the presence of huge gas bubbles resulting from convection.[34] 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.[35] The technique contributed some of the most accurate measurements of Betelgeuse while revealing bright spots on the star's photosphere.[36][37][38] 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.[39][40]
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.[41] Because ultraviolet light is absorbed by the Earth's atmosphere, observations at these wavelengths are best performed by space telescopes.[42] Like earlier pictures, this image contained a bright patch indicating a region in the southwestern quadrant 2,000 K hotter than the stellar surface.[43] 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°.[44]
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.[26][45] 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, numerous interferometric studies in the near-infrared made at the Paranal Observatory in Chile argue for much tighter diameters. On 9 June 2009, Nobel Laureate Charles Townes announced that the star had shrunk by 15% since 1993 at an increasing rate without a significant diminution in magnitude.[46][47] Subsequent observations suggest that the apparent contraction may be due to shell activity in the star's extended atmosphere.[48]
In addition to the discussion of 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 giants are major contributors, yet the mechanics of stellar mass loss remain a mystery.[49] 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 being ejected from the star into the surrounding atmosphere with distances approximating 30 AU.[13][15] 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.[46]
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 giant 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 70º and 80º south latitude.
The apparent magnitude of Betelgeuse is listed in the astronomical database SIMBAD at 0.42, making it on average the eighth brightest star in the celestial sphere excluding the Sun. Because Betelgeuse is a variable star whose brightness ranges between 0.2 and 1.2, there are periods when it will surpass Procyon to become the seventh brightest star. Occasionally it can even outshine Rigel and become the sixth brightest star, as the latter star, with a nominal apparent magnitude of 0.12, has been reported to fluctuate slightly in brightness, by 0.03 to 0.3 magnitudes.[50] At its faintest, Betelgeuse will fall behind Deneb as the 19th brightest star and compete with Mimosa for the 20th position.
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. 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.[52] 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 sky.[23]
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.[6] 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 1,300 ly.[6]
Before the publication of the Hipparcos Catalogue (1997), there were two conflicting parallax measurements for Betelgeuse. The first was the Yale University Observatory (1991) with a published parallax of π = 9.8 ± 4.7 mas, yielding a distance of roughly 102 pc or 330 ly.[53] 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—almost twice the Yale estimate.[54] Given this uncertainty, researchers were adopting a wide range of distance estimates, leading to significant variances in the calculation of the star's attributes.[6]
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.[55] However, later evaluation of the Hipparcos parallax measurements for variable stars like Betelgeuse found that the uncertainty of these measurements had been underestimated.[56] In 2007, Floor van Leeuwen improved upon the Hipparcos parallax, producing a new figure of π = 6.55 ± 0.83, hence a much tighter error factor yielding a distance of roughly 152 ± 20 pc or 520 ± 73 ly.[57]
In 2008, Graham Harper and colleagues, using the Very Large Array (VLA), produced a radio solution of π = 5.07 ± 1.10 mas, equaling a distance of 197 ± 45 pc or 643 ± 146 ly.[6] As 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.[6] The European Space Agency's current Gaia mission may not improve over the measurements of Betelgeuse by the earlier Hipparcos mission because it is brighter than the approximately V=6 saturation limit of the mission's instruments.[58]
Betelgeuse is classified as a semiregular variable star of subgroup SRc; these are pulsating red supergiants with low-amplitude variations and periods of stable brightness.[4] Different hypotheses have been put forward to explain Betelgeuse's pulsations and their rhythm—which result in an absolute magnitude oscillation from −5.27 and −6.27.[note 1] Established theories of stellar structure suggest that the outer layers of this supergiant gradually expand and contract, causing the surface area (photosphere) to alternately increase and decrease, and the temperature to rise and fall—thereby eliciting the measured cadence in the star's brightness between its dimmest magnitude of 1.2, seen as early as 1927, and its brightest of 0.2, seen in 1933 and 1942. A red supergiant like Betelgeuse will pulsate this way because its stellar atmosphere is unstable. As the star contracts, it absorbs more and more of the energy that passes through it, causing the atmosphere to heat up and expand. Conversely, as the star expands, its atmosphere becomes less dense, allowing the energy to escape and the atmosphere to cool, thus initiating a new contraction phase.[4] Calculating the star's pulsations and modeling its periodicity have been difficult, as it appears there are several cycles interlaced. As discussed in papers by Stebbins and Sanford in the 1930s, there are short-term variations of around 150 to 300 days that modulate a regular cyclic variation with a period of roughly 5.7 years.[59][60]
The supergiant consistently displays irregular photometric, polarimetric and spectroscopic variations, phenomena pointing to complex activity on the star's surface and its extended atmosphere.[36] In marked contrast to most giant stars that are typically long-period variables with reasonably regular periods, red giants are generally semiregular or irregular with pulsating characteristics. Martin Schwarzschild in 1975 attributed these brightness fluctuations to the changing granulation pattern formed by a few giant convection cells covering the surface of these stars.[40][61] For the Sun, these convection cells, known as solar granules, represent the foremost mode of heat transfer—hence those convective elements dominate the brightness variations in the solar photosphere.[40] The typical diameter for a solar granule is about 2,000 km (a surface area roughly the size of India), with an average depth of 700 km. With a surface of roughly 6 trillion km2, there are about 2 million such granules on the Sun's photosphere, and this large number produces a relatively constant flux.[62] By contrast, Schwarzschild argues that stars like Betelgeuse may only have a dozen granules with diameters of 180 million km or more dominating the surface of the star with depths of about 60 million km, which, due to the low temperatures and extremely low density found in red giant envelopes, result in convective inefficiency. Consequently, if only a third of these convective cells are visible at any one time, the variations in their observable light emission may result in the recorded irregular brightness variations of the overall light from the star.[40]
The hypothesis that gigantic convection cells dominate the surface of red giants and supergiants remains accepted by the astronomical community. When the Hubble Space Telescope captured its first direct image of Betelgeuse in 1995 revealing a mysterious hot spot, astronomers attributed it to convection.[63] Two years later, astronomers observed intricate asymmetries in the brightness distribution of the star, revealing at least three bright spots, the magnitude of which was "consistent with convective surface hotspots."[37] In 2000, another team of astronomers, led by Alex Lobel of the Harvard–Smithsonian Center for Astrophysics, noted that Betelgeuse exhibits raging storms of hot and cold gas in its turbulent atmosphere. The team surmised that large areas of the star's photosphere bulge out in different directions at times, ejecting long plumes of warm gas into the cold dust envelope. Another explanation is the occurrence of shock waves caused by warm gas traversing cooler regions of the star.[60][64] Observing the atmosphere of Betelgeuse over a period of five years between 1998 and 2003 with the Space Telescope Imaging Spectrograph aboard Hubble, the team likened the rise and fall of convection cells in the chromosphere to the blobs in a lava lamp.[64]
On 13 December 1920, Betelgeuse became the first star outside the Solar System to have the angular size of its photosphere measured.[26] 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".[26][47] Since then, other studies have produced angular diameters that range from 0.042 to 0.069 arcseconds.[30][45][65] 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.[note 2] 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.
The precise diameter has been hard to define for several reasons:
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.[68] 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.[69] It was this methodology that identified the hotspots on Betelgeuse in the 1990s.[70] Other technological breakthroughs include adaptive optics,[71] space observatories like Hipparcos, Hubble and Spitzer,[41][72] and the Astronomical Multi-BEam Recombiner (AMBER), which combines the beams of three telescopes simultaneously, allowing researchers to achieve milliarcsecond spatial resolution.[73][74]
Which part of the electromagnetic spectrum—the visible, near-infrared (NIR) or mid-infrared (MIR)—produces the most accurate angular measurement is still debated.[note 2] In 1996, Manfred Bester, working with the ISI in the mid-infrared, led a team at the Space Sciences Laboratory (SSL) at U.C. Berkeley to produce a solution, showing Betelgeuse with 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.[45] Also included was a theoretical allowance for limb darkening, yielding a diameter of 55.2 ± 0.5 mas. The Bester estimate equates to a radius of roughly 5.6 AU or 1,200 R☉, assuming the 2008 Harper distance of 197.0 ± 45 pc,[9][10] 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.[75][76]
A team of astronomers working in the near-infrared and led by Guy Perrin of the Observatoire de Paris produced a 2004 document arguing that the more accurate photospheric measurement was 43.33 ± 0.04 mas.[66] 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.[66]
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.[78][79] In 2011, Keiichi Ohnaka and colleagues from the Max Planck Institute for Radio Astronomy produced a third estimate in the near-infrared corroborating Perrin's numbers, this time showing a limb-darkened disk diameter of 42.49 ± 0.06 mas.[80] 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☉.[10][81]
Central to this discussion is another paper published in 2009 by the Berkeley team, led by Charles Townes, reporting 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.[47][82] 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.[47] 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.[83]
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.[48] 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. Betelgeuse is now considered to be in third place, although R Doradus, being much closer to Earth at about 200 ly, has a diameter roughly one-third that of Betelgeuse.[84]
Betelgeuse is a very large, luminous and cool star classified as a red supergiant of M2Iab class. 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;[3] the "Iab" suffix luminosity class indicates that it is an intermediate luminous supergiant. Uncertainties regarding the star's surface temperature, angular diameter and distance, make it difficult to achieve a precise measurement of Betelgeuse's luminosity. Research from 2012 gives Betelgeuse an average luminosity of 120,000 ± 30,000 L☉,[7] assuming a median temperature of 3,300 K and a radius of 1,200 R☉.[10] However, because most of the star's radiation is in the near infrared, the human eye cannot perceive the star's intrinsic brightness. Since 1943, the spectrum of Betelgeuse has served as one of the stable anchor points by which other stars are classified.[85]
The mass of Betelgeuse has never been measured because it has no known companion.[86] A mass estimate is only possible using theoretical modeling, a situation which has produced mass estimates ranging from 5 to 30 M☉ in the 2000s.[87][88] Smith and colleagues calculated that Betelgeuse began its life as a star of 15 to 20 M⊙, based on a photospheric measurement of 5.6 AU or 1,200 R⊙.[9] However, a novel method of determining the supergiant's mass was proposed in 2011 by Hilding Neilson and colleagues, arguing for a 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⊙.[86] How the debate will be resolved is still open—at least until a companion is identified allowing for a direct calculation of stellar mass.
Due to its variability and the presence of hotspots, the photospheric temperature of Betelgeuse is uncertain. Studies since 2001 report temperatures ranging from 3,140[7] to 3,641 K[66] with a median of about 3,300K.[7][12][13] The star is also a slow rotator and the most recent velocity recorded was 5 km/s.[13] Depending on its photospheric radius, it could take the star from 25 to 32 years to turn on its axis—much slower than Antares, which has a rotational velocity of 20 km/s.[89]
In 2002, astronomers using computer simulations speculated that Betelgeuse might exhibit 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.[90] 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.[91]
The kinematics of Betelgeuse are complex. The age of Class M supergiants with an initial mass of 20 is roughly 10 million years.[6][92] Given its motion, a corresponding projection back in time would take 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 to the ONC between 389 and 414 parsecs. Consequently, it is likely that Betelgeuse has not always had its current motion through space and has changed course at one time or another, possibly the result of a nearby stellar explosion.[6][93]
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 from molecular clouds observed in Orion,[94] but has evolved rapidly due to its high mass.[6]
Like many young stars in Orion whose mass is greater than 10 , 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 probably exhausted the hydrogen in its core—unlike its OB cousins born about the same time—causing it 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 producing enough radiation to unfurl its outer envelopes of hydrogen and helium. Its mass and luminosity are such that the star will eventually fuse higher elements through neon, magnesium, sodium, and silicon all the way to iron, at which point it will probably collapse and explode as a type II supernova.[60][95]
As an early M-type supergiant, Betelgeuse is one of the largest, most luminous and yet one of the most ethereal stars known. A radius of 5.5 AU is roughly 1,180 times the radius of the Sun—able to contain over 2 quadrillion Earths (2.15 × 1015) or more than 1.6 billion (1.65 × 109) Suns. That is the equivalent of Betelgeuse being a football stadium like Wembley Stadium in London with the Earth a tiny pearl, 1 millimeter in diameter, orbiting a Sun the size of a mango.[note 3] Moreover, observations from 2009 of Betelgeuse exhibiting a 15% contraction in angular diameter would equate to a shortening of the star's radius from about 5.5 to 4.6 AU, assuming that the photosphere is a perfect sphere. A reduction of this magnitude would correspond to a diminution in photospheric volume of about 41%.[note 4]
Not only is the photosphere enormous, but the star is surrounded by a complex circumstellar environment where light could take over three years to escape.[96] In the outer reaches of the photosphere, the density is extremely low. Yet the mass of the star is believed to be no more than 20 M☉, with mass loss estimates projected at one to two Suns since birth.[9][95] Consequently, the average density is less than twelve parts per billion (1.119 × 10−8) that of the Sun. Such star matter is so tenuous that Betelgeuse has often been called a "red-hot vacuum".[4][23]
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.[15] 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.[97] However, the physical mechanism is not well understood.[81] 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.[40] 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.[81] In 2001, Graham Harper estimated a stellar wind at 0.03 M☉ every 10,000 years,[12] but research since 2009 has provided evidence of episodic mass loss making any total figure for Betelgeuse uncertain.[15][98] 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.[21]
As a result of work done by Pierre Kervella and his team at the Paris observatory, astronomers may be close to solving this mystery. They noticed a large plume of gas extending outward at least six times the stellar radius indicating that Betelgeuse is not shedding matter evenly in all directions.[13][15] 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, Kervella noted, were large-scale convection cells or polar mass loss, possibly due to rotation.[13] Probing deeper with ESO's AMBER, Keiichi Ohnaka and colleagues observed that the gas in the supergiant's extended atmosphere is 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.[15][98]
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.[78]
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.[78][99] 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.
Extending for several radii (~10–40 AU) about the photosphere exists another cooler region known as an asymmetric gaseous envelope. 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.[78][100]
Radio-telescope images taken in 1998 confirm that Betelgeuse has a highly complex atmosphere,[101] with a temperature of 3,450 ± 850K—similar to that recorded on the star's surface but much lower than surrounding gas in the same region.[101][102] The VLA images also show this lower-temperature gas progressively cool 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."[101] 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.[78]
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.[103] 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 5,500K.[63][78] 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.[103] The observations have conclusively demonstrated that the warm chromospheric plasma spatially overlaps and coexists with cool gas in Betelgeuse's gaseous envelope as well as with the dust in its circumstellar dust shells (see below).[78][103]
The first attestation of a dust shell surrounding Betelgeuse was put forth by Sutton and colleagues, who noted in 1977 that dust shells around mature stars often emit large amounts of radiation in excess of the photospheric contribution. Using heterodyne interferometry, they concluded that the red supergiant emits most of its excess beyond 12 stellar radii or roughly the distance of the Kuiper belt at 50 to 60 AU, depending on the assumed stellar radius.[31][78] 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.[106][107] These studies point out that the dust environment surrounding Betelgeuse is not static. In 1994, Danchi et al. reported that Betelgeuse undergoes sporadic dust production involving decades of activity followed by inactivity. In 1997, a group of astronomers led by Chris Skinner noticed significant changes in the dust shell's morphology in one year, suggesting that the shell is asymmetrically illuminated by a stellar radiation field strongly affected by the existence of photospheric hotspots.[106] The 1984 report of a giant asymmetric dust shell 1 pc (206,265 AU) from the star has not been corroborated by recent studies, although another report 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 journeys.[96][108]
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.[109] 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 (~1400 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.
Betelgeuse is travelling supersonically through the interstellar medium at a speed of 30 km per second (i.e. ~6.3 AU per year) creating a bow shock.[7][110] The shock is not created by the star, but its powerful stellar wind as it ejects vast amounts of gas into the interstellar medium at a rate of 17 km/s, heating up the material surrounding the star thereby making it visible in infrared light.[111] 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 1 parsec wide, assuming a distance of 643 light-years.[112]
3D hydrodynamic simulations of the bow shock made in 2012 indicate that it is very young—less than 30,000 years old—suggesting two possibilities: one, that Betelgeuse moved into a region of the interstellar medium with different properties recently or two, that Betelgeuse has undergone a significant transformation as its stellar wind has changed.[113] In their 2012 paper, Mohamed et al. propose that this phenomenon was caused by Betelgeuse transitioning from a blue supergiant (BSG) to a red supergiant (RSG). In the late evolutionary stage of a star like Betelgeuse, evidence suggests that 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."[7][114] 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 along its trajectory.[15]
The fate of Betelgeuse depends on its mass—a critical factor which is not well understood.[88] Since most investigators posit a mass greater than 10 M☉, the most likely scenario is that the supergiant will continue to burn and fuse elements until its core is iron, at which point Betelgeuse will explode as a type II supernova. During this event the core will collapse, leaving behind a neutron star remnant about 20 km in diameter.[24]
As of 2014, the most recent theoretical calculations suggest Betelgeuse has recently started core helium burning and that it will explode as a supernova after going through carbon burning, oxygen burning, neon burning, and silicon burning on its center within 100,000 years. The estimated age for the red supergiant, that is still ascending the red giant branch, would be between 8 and 8.5 million years and its mass 20 +5-3M☉.[116] Depending of its initial rotation speed while in the ZAMS, stellar evolution models for a star of that interval of mass suggest Betelgeuse may explode as red supergiant or become a luminous blue variable, or even a yellow hypergiant-like star before going supernova.[117] Its remmant would be a neutron star of around 1.5M ☉[116]
Betelgeuse is already old for its size class and is expected to explode relatively soon compared to its age.[15] Solving the riddle of mass-loss will be the key to knowing when a supernova may occur, an event expected in the next million years.[51][118][119] Supporting this hypothesis are unusual features that have been observed in the interstellar medium of the Orion Molecular Cloud Complex, which suggest that there have been multiple supernovae in the recent past.[93] Betelgeuse's suspected birthplace in the Orion OB1 Association is the probable location for such supernovae. Since the oldest subgroup in the association has an approximate age of 12 million years, the more massive stars likely had sufficient time to reach the end of their lifespan and explode already. Also, because runaway stars are believed to be caused by supernovae, 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.[93]
J. Craig Wheeler of the University of Texas at Austin predicts Betelgeuse's demise will emit 1046 joules of neutrinos, which will pass through the star's hydrogen envelope in around an hour, then travel at near light speed to reach the Solar System six centuries later—providing the first evidence of the cataclysm. The supernova could brighten over a two-week period to an apparent magnitude of −12,[120] outshining the Moon in the night sky and becoming easily visible in broad daylight.[15] It would remain at that intensity for two to three months before rapidly dimming.[120] Since its rotational axis is not pointed toward the Earth, Betelgeuse's supernova is unlikely to send a gamma ray burst in the direction of Earth large enough to damage ecosystems.[119] The flash of ultraviolet radiation from the explosion will likely be weaker than the ultraviolet output of the Sun. The year following the explosion, radioactive decay of cobalt to iron will dominate emission from the supernova remnant, and the resulting gamma rays will be blocked by the expanding envelope of hydrogen. If the neutron star remnant becomes a pulsar, it could produce gamma rays for thousands of years.[120]
Due to misunderstandings caused by the 2009 publication of the star's 15% contraction,[46][75] 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.[121][122] The timing and prevalence of these rumors have been linked to broader misconceptions of astronomy, particularly to doomsday predictions relating to the Mayan calendar.[123][124] In their 2012 study, physicists at the Space Sciences Laboratory point out that the apparent contraction in the star's diameter may be due to the complex dynamics in the star's surrounding nebula and not the star itself,[48] reconfirming that until we better understand the nature of mass loss, predicting the timing of a supernova will remain a challenge. The latest studies project a supernova in 100,000 years.[125]
Sten Odenwald has calculated the probable consequences on Earth of a Betelgeuse supernova.[126] Betelgeuse's apparent optical magnitude, -12, would be of the same order as the full moon. Optical radiation and other forms of radiation such as neutrinos reaching us 600 years after the explosion would not be significant to terrestrial life. However, a more significant consequence is the expanding particle shell which would accompany the supernova. With a velocity of around 10,000 km/s, the shell would reach the Solar System about 100,000 years after the visual supernova itself. This particle shell would carry approximately 10 M☉ of protons, producing a proton flux of about 140,000 protons per second per square centimeter—a small value compared to the 300 million protons/s/cm2 naturally occurring due to the solar wind. But due to its high velocity, the effective pressure of the Betelgeuse flux would be about 490 times as strong as the solar wind. This would collapse the Sun's magnetopause to perhaps less than the radius of Earth's orbit, rendering human exploration in the Solar System lethal, at least with current technology.
The shell would pass the Earth after a few decades. But Odenwald also points out that a plasma bubble inside the proton shell would consist of electrons and magnetic fields, causing x-ray emissions for tens of thousands years after the event. This "soft" radiation would not pass the Earth's atmosphere, but it would be of some concern for space travel.
In 1985, Margarita Karovska, in conjunction with other astrophysicists at the Harvard–Smithsonian Center for Astrophysics, announced the discovery of two close companions orbiting Betelgeuse. 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.[127][128]
In the years that followed no confirmation of Karovska's discovery was published. In 1992, a team of collaborators from the Cavendish Astrophysics Group questioned the finding. They published a paper noting that the brightness features on the surface of Betelgeuse appear to be "too bright to be associated with a passage of the suggested companions in front of the red giant." They also noticed that these features were fainter at 710 nanometers compared to 700 by a factor of 1.8, indicating that such features would have to reside within the molecular atmosphere of the star.[129] Despite this, that same year Karovska published a new paper reconfirming her team's exegesis, but also noting that there was a meaningful correlation between the calculated position angles of the orbiting companion and the reported asymmetries, suggesting a possible connection between the two.[130] Since then, researchers have turned their attention to analyzing the intricate dynamics of the star's extended atmosphere and little else has been published on the possibility of orbiting companions, although as Xavier Haubois and his team reiterate in 2009, the possibility of a close companion contributing to the overall flux has never been fully ruled out.[78] Dommanget's double star catalog (CCDM) lists at least four adjacent stars, all within three arcminutes of this stellar giant, yet aside from apparent magnitudes and position angles, little else is known.[131]
Betelgeuse has been known as Betelgeux,[1] and in German Beteigeuze[132] (according to Bode[133][134]). Betelgeux and Betelgeuze were used until the early 20th century, when the spelling Betelgeuse became universal.[135] There is no consensus for the correct pronunciation of the name,[136] and pronunciations for the star are as varied as its spellings:
There is uncertainty surrounding the first element of the name, rendered as "Bet-". However, "abet" or إبط is the Arabic word for "armpit",[138] which is where the star is in the Orion constellation. Betelgeuse is often mistranslated as "armpit of the central one".[139] 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,[140] and Italian Jesuit priest and astronomer Giovanni Battista Riccioli had called it Bectelgeuze or Bedalgeuze.[17] 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.[141] 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.[142] Other writers have since accepted Kunitzsch's explanation.[95]
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". Later, al-Jauzā' was also designated as the scientific Arabic name for Orion and for Gemini. 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.[142] The 17th-century English translator Edmund Chilmead gave it the name Ied Algeuze ("Orion's Hand"), from Christmannus.[17] 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",[17] as منكب الجوزاء Mankib al Jauzā'. In Persian, however, the name is اِبطالجوزا, derived from the Arabic ابط الجوزاء Ibţ al-Jauzā', "armpit of Orion".
Other terms for Betelgeuse included the Persian Bašn "the Arm", and Coptic Klaria "an Armlet".[17] Bahu was its Sanskrit name, as part of a Hindu understanding of the constellation as a running antelope or stag.[17] In traditional Chinese astronomy, Betelgeuse was known as 参宿四 (Shēnxiùsì, the Fourth Star of the constellation of Three Stars)[144] 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.[145] 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.[146][147]
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".[148] A Hawaiian term for it was Kaulua-koko "brilliant red star".[149] The Lacandon people of Central America knew it as chäk tulix "red butterfly".[150]
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.[17] 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.[22]
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.[22] 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.[151] In South African mythology, Betelgeuse was perceived as a lion casting a predatory gaze toward the three zebras represented by Orion's Belt.[152]
A Sanskrit name for Betelgeuse was ãrdrã "the moist one", eponymous of the Ardra lunar mansion in Hindu astrology.[153] 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.[17] 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 am in late summer and autumn signified the time for village men to go to the fields and plough.[154] 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.[25]
The opposed locations of Orion and Scorpio, with their corresponding bright variable red stars Betelgeuse and Antares, were noted by ancient cultures around the world. The setting of Orion and rising of Scorpio signify the death of Orion by the scorpion. In China they signify brothers and rivals Shen and Shang.[22] 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.[155]
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. He added that they had received a suggestion the sequel be named Sanduleak-69 202 after the former star of SN 1987A.[135] In August Derleth's short story "The Dweller in the Darkness" set in H. P. Lovecraft's Cthulhu Mythos, Betelgeuse is the home of the "benign" Elder Gods.[156] The identity of the red star Borgil mentioned in Lord of the Rings was much debated; Aldebaran, Betelgeuse and the planet Mars were touted as candidates. Professor Kristine Larsen has concluded the evidence points to it being Aldebaran as it precedes Menelvagor (Orion).[157] Astronomy writer Robert Burnham, Jr. proposed the term padparadaschah which denotes a rare orange sapphire in India, for the star.[135] 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."[156] In the poetic work Betelguese, a Trip Through Hell by Jean Louis De Esque, hell is on Betelgeuse because De Esque believed that it was "a celestial pariah, an outcast, the largest of all known comets or outlawed suns in the universe."[158]
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.[159]
Article | Year1 | Telescope | # | Spectrum | λ (μm) | ∅ (mas)2 | Radii3 @ 197±45 pc | Notes |
Michelson[26] | 1920 | Mt-Wilson | 1 | Visible | 0.575 | 47.0 ± 4.7 | 3.2–6.3 AU | Limb darkened +17% = 55.0 |
Bonneau[30] | 1972 | Palomar | 8 | Visible | 0.422–0.719 | 52.0–69.0 | 3.6–9.2 AU | Strong correlation of ∅ with λ |
Balega[65] | 1978 | ESO | 3 | Visible | 0.405–0.715 | 45.0–67.0 | 3.1–8.6 AU | No correlation of ∅ with λ |
1979 | SAO | 4 | Visible | 0.575–0.773 | 50.0–62.0 | 3.5–8.0 AU | ||
Buscher[36] | 1989 | WHT | 4 | Visible | 0.633–0.710 | 54.0–61.0 | 4.0–7.9 AU | Discovered asymmetries/hotspots |
Wilson[129] | 1991 | WHT | 4 | Visible | 0.546–0.710 | 49.0–57.0 | 3.5–7.1 AU | Confirmation of hotspots |
Tuthill[39] | 1993 | WHT | 8 | Visible | 0.633–0.710 | 43.5–54.2 | 3.2–7.0 AU | Study of hotspots on 3 stars |
Gilliland[41] | 1995 | HST | UV | 0.24–0.27 | 104–112 | 10.3–11.1 | FWHM diameters | |
0.265–0.295 | 92–100 | 9.1–9.8 | ||||||
Weiner[45] | 1999 | ISI | 2 | MIR (N Band) | 11.150 | 54.7 ± 0.3 | 4.1–6.7 AU | Limb darkened = 55.2 ± 0.5 |
Perrin[66] | 1997 | IOTA | 7 | NIR (K Band) | 2.200 | 43.33 ± 0.04 | 3.3–5.2 AU | K&L Band,11.5μm data contrast |
Haubois[78] | 2005 | IOTA | 6 | NIR (H Band) | 1.650 | 44.28 ± 0.15‡ | 3.4–5.4 AU | Rosseland diameter 45.03 ± 0.12 |
Hernandez[79] | 2006 | VLTI | 2 | NIR (K Band) | 2.099–2.198 | 42:57 ± 0:02 | 3.2–5.2 AU | High precision AMBER results. |
Ohnaka[98] | 2008 | VLTI | 3 | NIR (K Band) | 2.280–2.310 | 43.19 ± 0.03 | 3.3–5.2 AU | Limb darkened 43.56 ± 0.06 |
Townes[47] | 1993 | ISI | 17 | MIR (N Band) | 11.150 | 56.00 ± 1.00 | 4.2–6.8 AU | Systematic study involving 17 measurements at the same wavelength from 1993 to 2009 |
2008 | ISI | MIR (N Band) | 11.150 | 47.00 ± 2.00 | 3.6–5.7 AU | |||
2009 | ISI | MIR (N Band) | 11.150 | 48.00 ± 1.00 | 3.6–5.8 AU | |||
Ohnaka[80] | 2011 | VLTI | 3 | NIR (K Band) | 2.280–2.310 | 42.05 ± 0.05 | 3.2–5.2 AU | Limb darkened 42.49 ± 0.06 |
Harper[6] | 2008 | VLA | Also noteworthy, Harper et al. in the conclusion of their paper make the following remark: "In a sense, the derived distance of 200 pc is a balance between the 131 pc (425 ly) Hipparcos distance and the radio which tends towards 250 pc (815 ly)"—hence establishing ± 815 ly as the outside distance for the star. |
1The final year of observations, unless otherwise noted. 2Uniform disk measurement, unless otherwise noted. 3Radii calculations use the same methodology as outlined in Note #2 below ‡Limb darkened measurement.
Extended content |
The analogy is based on the computation of certain ratios – specifically the diameter, radius and volume of the three celestial bodies in question, Betelgeuse, the Sun and Earth. Once these ratios are derived, the relative size of each as they relate to Wembley Stadium can be easily determined. The calculations begin with the formula for angular diameter as follows:
Extended content |
As pointed out in the Angular anomalies section, the observed contraction could be due to a shrinking of the star's radius or by other phenomena. Assuming the photosphere is spherical, calculating a reduction in volume begins with the formula for angular diameter as follows: Calculations for 1993 values:
Calculations for 2008 values:
The 0.047 arcsecond measurement was for a uniform disk. In the article Michelson notes that limb darkening would increase the angular diameter by about 17%, hence 0.055 arcseconds
The yellow/red "image" or "photo" of Betelgeuse commonly seen is not a picture of the red giant, but a mathematically generated image based on the photograph. The photograph was of much lower resolution: The entire Betelgeuse image fit within a 10x10 pixel area on the Hubble Space Telescopes Faint Object Camera. The images were oversampled by a factor of 5 with bicubic spline interpolation, then deconvolved.
Betelgeuse is a candidate to undergo a spectacular supernova explosion almost anytime in the next few thousand years.
Such a major single feature is distinctly different from scattered smaller regions of activity typically found on the Sun although the strong ultraviolet flux enhancement is characteristic of stellar magnetic activity. This inhomogeneity may be caused by a large scale convection cell or result from global pulsations and shock structures that heat the chromosphere."
Assuming a distance of 197 ± 45 pc, an angular distance of 43.33 ± 0.04 mas would equate to a radius of 4.3 AU or 920 R☉
Images of hotspots on the surface of Betelgeuse taken at visible and infra-red wavelengths using high resolution ground-based interferometers
Photograph showing three of the four enclosures which house 1.8 meter Auxiliary Telescopes (ATs) at the Paranal Observatory in the Atacama Desert region of Chile.
We derive a uniform-disk diameter of 42.05 ± 0.05 mas and a power-law-type limb-darkened disk diameter of 42.49 ± 0.06 mas and a limb-darkening parameter of (9.7 ± 0.5) × 10−2
The shrinkage corresponds to the star contracting by a distance equal to that between Venus and the Sun, researchers reported June 9 at an American Astronomical Society meeting and in the June 1 Astrophysical Journal Letters.
The mass of the star is unknown, but most investigators show a preference for a fairly large mass in the range of 10–20 M☉
In the article, Lobel et al. equate 1 arcsecond to approximately 40 stellar radii, a calculation which in 2004 likely assumed a Hipparcos distance of 131 pc (430 ly) and a photospheric diameter of 0.0552" from Weiner et al.
Noriega in 1997 estimated the size to be 0.8 parsecs, having assumed the earlier distance estimate of 400 ly. With a current distance estimate of 643 ly, the bow shock would measure ~1.28 parsecs or over 4 ly
Wikimedia Commons has media related to Betelgeuse. |


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