In a first, astronomers watch a black hole’s corona disappear, then reappear
A colliding star may have triggered the drastic transformation.
It seems the universe has an odd sense of humor. While a crown-encrusted virus has run roughshod over the world, another entirely different corona about 100 million light years from Earth has mysteriously disappeared.
For the first time, astronomers at MIT and elsewhere have watched as a supermassive black hole's own corona, the ultrabright, billion-degree ring of high-energy particles that encircles a black hole's event horizon, was abruptly destroyed.
The cause of this dramatic transformation is unclear, though the researchers guess that the source of the calamity may have been a star caught in the black hole's gravitational pull. Like a pebble tossed into a gearbox, the star may have ricocheted through the black hole's disk of swirling material, causing everything in the vicinity, including the corona's high-energy particles, to suddenly plummet into the black hole.
The result, as the astronomers observed, was a precipitous and surprising drop in the black hole's brightness, by a factor of 10,000, in under just one year.
"We expect that luminosity changes this big should vary on timescales of many thousands to millions of years," says Erin Kara, assistant professor of physics at MIT. "But in this object, we saw it change by 10,000 over a year, and it even changed by a factor of 100 in eight hours, which is just totally unheard of and really mind-boggling."
Following the corona's disappearance, astronomers continued to watch as the black hole began to slowly pull together material from its outer edges to reform its swirling accretion disk, which in turn began to spin up high-energy X-rays close to the black hole's event horizon. In this way, in just a few months, the black hole was able to generate a new corona, almost back to its original luminosity.
"This seems to be the first time we've ever seen a corona first of all disappear, but then also rebuild itself, and we're watching this in real-time," Kara says. "This will be really important to understanding how a black hole's corona is heated and powered in the first place."
Kara and her co-authors, including lead author Claudio Ricci of Universidad Diego Portales in Santiago, Chile, have published their findings today in Astrophysical Journal Letters. Co-authors from MIT include Ron Remillard, and Dheeraj Pasham.
A nimble washing machine
In March 2018, an unexpected burst lit up the view of ASSASN, the All-Sky Automated Survey for Super-Novae, that surveys the entire night sky for supernova activity. The survey recorded a flash from 1ES 1927+654, an active galactic nucleus, or AGN, that is a type of supermassive black hole with higher-than-normal brightness at the center of a galaxy. ASSASN observed that the object's brightness jumped to about 40 times its normal luminosity.
"This was an AGN that we sort of knew about, but it wasn't very special," Kara says. "Then they noticed that this run-of-the-mill AGN became suddenly bright, which got our attention, and we started pointing lots of other telescopes in lots of other wavelengths to look at it."
The team used multiple telescopes to observe the black hole in the X-ray, optical, and ultraviolet wave bands. Most of these telescopes were pointed at the the black hole periodically, for example recording observations for an entire day, every six months. The team also watched the black hole daily with NASA's NICER, a much smaller X-ray telescope, that is installed aboard the International Space Station, with detectors developed and built by researchers at MIT.
"NICER is great because it's so nimble," Kara says. "It's this little washing machine bouncing around the ISS, and it can collect a ton of X-ray photons. Every day, NICER could take a quick little look at this AGN, then go off and do something else."
With frequent observations, the researchers were able to catch the black hole as it precipitously dropped in brightness, in virtually all the wave bands they measured, and especially in the high-energy X-ray band — an observation that signaled that the black hole's corona had completely and suddenly vaporized.
"After ASSASN saw it go through this huge crazy outburst, we watched as the corona disappeared," Kara recalls. "It became undetectable, which we have never seen before."
A jolting flash
Physicists are unsure exactly what causes a corona to form, but they believe it has something to do with the configuration of magnetic field lines that run through a black hole's accretion disk. At the outer regions of a black hole's swirling disk of material, magnetic field lines are more or less in a straightforward configuration. Closer in, and especially near the event horizon, material circles with more energy, in a way that may cause magnetic field lines to twist and break, then reconnect. This tangle of magnetic energy could spin up particles swirling close to the black hole, to the level of high-energy X-rays, forming the crown-like corona that encircles the black hole.
Kara and her colleagues believe that if a wayward star was indeed the culprit in the corona's disappearance, it would have first been shredded apart by the black hole's gravitational pull, scattering stellar debris across the accretion disk. This may have caused the temporary flash in brightness that ASSASN captured. This "tidal disruption," as astronomers call such a jolting event, would have triggered much of the material in the disk to suddenly fall into the black hole. It also might have thrown the disk's magnetic field lines out of whack in a way that it could no longer generate and support a high-energy corona.
This last point is a potentially important one for understanding how coronas first form. Depending on the mass of a black hole, there is a certain radius within which a star will most certainly be pulled in by a black hole's gravity.
"What that tells us is that, if all the action is happening within that tidal disruption radius, that means the magnetic field configuration that's supporting the corona must be within that radius," Kara says. "Which means that, for any normal corona, the magnetic fields within that radius are what's responsible for creating a corona."
The researchers calculated that if a star indeed was the cause of the black hole's missing corona, and if a corona were to form in a supermassive black hole of similar size, it would do so within a radius of about 4 light minutes — a distance that roughly translates to about 75 million kilometers from the black hole's center.
"With the caveat that this event happened from a stellar tidal disruption, this would be some of the strictest constraints we have on where the corona must exist," Kara says.
The corona has since reformed, lighting up in high-energy X-rays which the team was also able to observe. It's not as bright as it once was, but the researchers are continuing to monitor it, though less frequently, to see what more this system has in store.
"We want to keep an eye on it," Kara says. "It's still in this unusual high-flux state, and maybe it'll do something crazy again, so we don't want to miss that."
This research was funded, in part, by NASA.
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"Nothing but naked people: fat ones, thin ones, old, young…"
"The Yellow Sands", 1888, John Reinhard Weguelin; source: Wikimedia Commons<h3>Naked revolution</h3><p>Yet long before anyone knew about beach fashion, naturism was trendy. Bathing naked in the sea was going on in England as early as 1840. However, during the reign of Queen Victoria, this pleasure was outlawed. But it popped up again among the conservative Germans. In 1898, the first Naturist Club was founded in Essen and in 1900 the Wandering Birds group (<em>Wandervögel</em>) was scouring the country for uninhabited places and naked sunbathing. In the same year, Heinrich Pudor wrote <em>The C</em><em>ult of </em><em>the </em><em>Nud</em><em>e</em>, winning the hearts of contemporary supporters of naturism.</p><p>In the 1920s, on the back of this, members of the Movement for Natural Healing (<em>Naturheilbewegung</em>) organized naked sunbathing for the improvement of health. Persuaded by Pudor's theory of the healing properties of the sun and wind, which could be absorbed through the skin, they launched the naked revolution.</p><p>Pudor's book became the naturists' manifesto and soon after, not far from Hamburg, the Free Body Culture (<em>Freikörperkultur</em>, or FKK) movement was founded. This spread through other German centres and brought together thousands of people. The FKK still operates under the same name today.</p><p>The cult of the naked body even wrote itself into the ideology of fascist Germany, which advocated a pure, Aryan race. But in 1933, Hermann Göring issued an order that defined nudity as "the greatest threat to the German soul" and, with that, criminalized naturist organizations. But this wasn't the end of the movement. The naturists went underground, continuing their activities under the guise of improving physical fitness.</p><p>In 1936, the idea was even floated of having a naturist display to open the Berlin Olympic Games. It was quickly dropped. Despite this, in 1939 the naturists managed to organize their own Games in the Swiss village of Thielle.</p>
Would you ever have sex with a robot?
- In 2016, "Harmony", the world's first AI sex robot was designed by a tech firm called Realbotix.
- According to 2020 survey data, more than one in five Americans (22 percent) say they would consider having sex with a robot. This is an increase from a survey conducted in 2017.
- Robots (and robotic tech) already play a vital role in speeding up manufacturing, packaging, and processing across various industries.
From homemade dildos to Harmony, the AI sex robot<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="3f7451615568e74c6a839f04329c9902"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/-cN8sJz50Ng?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p><em>"...amid an economic crisis, with restaurants and retailers closing their doors and larger companies laying off and furloughing employees, the sex tech industry is booming."</em><br></p><p>A Bustle <a href="https://www.bustle.com/wellness/the-sex-tech-industry-is-booming-amid-economic-crisis-22819801" target="_blank" rel="noopener noreferrer">article</a> published in April 2020, weeks after COVID-19 was declared a pandemic, explored the drastic boost in the sex tech industry. According to the research, <a href="https://www.dameproducts.com/" target="_blank" rel="noopener noreferrer">Dame Products</a> (a popular sex toy retailer) experienced a 30 percent increase in sales between the months of February to April, and popular sexual wellness brand <a href="https://unboundbabes.com/?utm_source=%7Bsource%7D&utm_medium=%7Bmedium%7D&utm_keyword=unbound%20babes&utm_matchtype=e&device=c&utm_campaign=%7Bcampaign%7D&utm_adgroup=%7Badgroup%7D&gclid=CjwKCAjw1v_0BRAkEiwALFkj5qYbdEwANUjCdRkCeVZ2HZzHjcGmpYbsOXYcMcNneLc2nySvrbaalBoChEsQAvD_BwE" target="_blank" rel="noopener noreferrer">Unbound</a> reported selling twice as many toys as normal in this period.</p><p>While the new coronavirus was crashing the economy in other ways, the sex tech industry was one of the few that actually saw improvements, likely due to people all over the world being advised, encouraged, and in some instances forced to stay at home.</p><p>Something similar happened in 2008, <a href="https://www.villagevoice.com/2010/08/23/the-great-recession-is-a-turn-on-for-the-sex-toy-industry/" target="_blank" rel="noopener noreferrer">during the recession</a>: the sex toy industry was one of the only industries at the time that didn't gravely suffer. </p><p><strong>The evolution of sex tech from stone dildos to artificial intelligence.</strong></p><p><a href="https://sofiagray.com/what-is-the-history-of-sex-toys-from-stone-to-silicone-and-beyond/" target="_blank" rel="noopener noreferrer">The history of sex toys</a> is quite interesting. A 28,000-year-old siltstone dildo was uncovered in Germany in 2005. Luxury bronze dildos have also been found in China that are at least 2,000 years old.</p><p>Aside from various materials being shaped into dildos, there has always been an interest in how to advance sex technology, even before it involved actual technology at all.</p><ul><li>The 1700s: Steam-powered vibrators (such as the Manipulator).</li><li>The 1800s—1900s: The invention of the first electric vibrator (the Pulsoson) and "beauty tools" being used for sexual satisfaction (such as the Polar Cub massager)</li><li>The 1920s—1940s: The introduction of hand-held massagers (the Andis Vibrator) and compact devices (such as the Oster Stim-U-Lax)</li><li>The 1940s—1960s: Japan introduced the "Cadillac of Vibrators" (The Hitachi Magic Wand), which eventually made it's way to America.</li><li>1965: The invention of silicone, which most modern sex toys are made of.</li><li>The 1980s—1990s: The invention of the rabbit-style vibrator, made more popular with one of the first showings of a sex toy on television ("Sex and the City"). </li><li>The 2000s: Visual porn website Pornhub launched and sex toys became increasingly popular. Erotic literature also became more common and popular, with "50 Shades of Grey" and others like it. </li><li>The 2010s and beyond: Sex toys and technology start to blend, and the world's first internet-controlled sex toy was launched in 2010 by Lovense.</li></ul><p>In 2016, "Harmony", <a href="https://www.youtube.com/watch?v=-cN8sJz50Ng" target="_blank" rel="noopener noreferrer">the world's first AI sex robot</a> was designed by a tech firm called Realbotix. </p>
From television shows to real-life applications, artificial intelligence (AI) is becoming more and more popular in all areas of human life.
Credit: Willyam Bradberry on Shutterstock<p>In 2020, more than one in five Americans (22 percent) say they would consider having sex with a robot. <a href="https://today.yougov.com/topics/science/articles-reports/2020/03/19/2020-both-men-and-women-are-more-likely-consider-h" target="_blank" rel="noopener noreferrer">YouGov conducted a study</a> in February 2020 that compared results from a similar study from 2017.<br></p><p>According to the results, 6 percent more people in 2020 are comfortable with the idea of having sex with a robot than in 2017.</p><p>YouGov points out that the increase in consideration is particularly significant among American adults between the ages of 18-34 years old. Additionally, how people feel about having sex with a robot has also changed. In 2020, 27 percent of Americans said they would consider it cheating if they had a partner who had sex with a robot during the relationship, compared to the 32 percent reported in 2017.</p><p><strong>"If you had a partner who had sex with a robot, would you consider it cheating?"</strong></p><p>The results from this interesting study also reveal that many people (42 percent) believe having sex with a robot is safer than having sex with a human stranger.</p><p>Robots (and robotic tech) already play a vital role in speeding up manufacturing, packaging, and processing across various industries. From television shows to real-life applications, artificial intelligence is becoming more and more popular in all areas of human life.</p><p>According to YouGov, "a <a href="https://www.bloomberg.com/news/articles/2019-07-12/amazon-plans-high-end-echo-ramps-up-work-on-alexa-home-robot" target="_blank">Bloomberg</a> report outlining Amazon's plans for an Alexa-powered robot that follows and helps you around the home may redefine how these machines service humans in the near future." </p>