from the world's big
These cities are the hubs of Africa’s economic boom
South Africa is no longer the only place on the continent that has urban wealth clusters
- The wealth of Africans is projected to grow by a third over the next decade
- The continent's wealth is agglomerating in a number of urban clusters, in the south, east and west
- Wealth is collected in a few other places - isolated capitals and mini-clusters stretching from Morocco down to Angola
Over the past decade, 19,000 Africans have become dollar millionaires. Africa's combined wealth has grown by 13% - 3% just in the last year alone. The combined individual wealth of all Africans is $2.3 trillion today – by the end of 2027, it will have increased by a third to $3.1 trillion. Clearly, it's boom time in Africa.
This map offers a revealing perspective on the wealth of the continent. The African subsoil may be resource-rich in many places, but as elsewhere in the world, it's in the great urban centres that money accumulates. And people too: by 2100, 13 of the world's 20 biggest megacities will be in Africa.
South Africa still boasts the main concentration of wealth in Africa, but no longer the only one.Image: Visual Capitalist
And this overview of Africa's richest cities, based on the The AfrAsia Bank Africa Wealth Report 2018, indicates where clusters of wealthy cities are developing across the continent, as well as showing a few more isolated locations of money aggregation.
- Long the most developed nation on the continent, South Africa – with four of Africa's ten richest cities – continues to be the economic engine of Africa's southern half. With a total GDP of $722 billion, South Africa as a whole continues to be the continent's wealthiest country, but on a per-capita basis it comes second after the tiny island nation of Mauritius ($32,700).
- The East African economy is dominated by a string of wealthy cities, from Uganda's capital Kampala via Nairobi and Mombasa in Kenya to Dar es Salaam, Tanzania's biggest city.
- In West Africa, a similar transnational conglomeration runs from Abidjan in Ivory Coast over Ghana's Accra to Lagos and Abidjan in Nigeria.
- In Morocco, Casablanca's wealth is flanked by that of Tangier and Marrakesh. In Egypt, Cairo dwarfs but not completely outshines Alexandria.
- The 'isolates', in descending order, are four capitals: Luanda (Angola), Addis Ababa (Ethiopia), Windhoek (Namibia) and Lusaka (Zambia).
Here are Africa's 10 wealthiest cities:
1. Johannesburg (South Africa): $276 billion
Jo'burg city centre.
Image: Brand South Africa
Fittingly, Africa's richest city was built on gold – on the Witwatersrand Gold Rush of 1886, to be exact. It's the commercial capital of South Africa and the wider region.
2. Cape Town (South Africa): $155 billion
View of Cape Town's City Bowl from Lion's Head, with Signal Hill and Cape Flats in the distance
Image: Martin Power, CC BY-SA 3.0
The city with Africa's highest prime residential rates, at around $6,100 per square metre (similar to DC or Berlin) also is an important hub for financial services, retail and tourism.
3. Cairo (Egypt): $140 billion
Rooftops of Cairo
Image: Luc Legay, CC BY-SA 2.0
Real estate, financial services and construction are some of the key sectors in this city of 9 million, the biggest metropolis in the Middle East.
4. Lagos (Nigeria): $108 billion
The Golden Plaza in Ikoyi, Lagos. On the left the Falomo Bridge to Victoria Island
Image: Ulf Ryttgens, CC BY-SA 1.0
It may no longer be the country's capital, Lagos still is the gateway for 80% of Nigeria's exports – and the centre of the burgeoning film industry, a.k.a. Nollywood. At 21 million inhabitants (2016 est.), it's Africa's largest metropolis, as well as one of the world's fastest-growing cities.
5. Durban (South Africa): $55 billion
Indian Ocean beach at Durban
Image: Brand South Africa
Subtropical Durban is South Africa's third-biggest city (after Johannesburg and Cape Town), second-biggest manufacturing hub and biggest port, as well as a major tourist destination. Durban's Gateway Theatre of Shopping is Africa's biggest mall. It has 12,000 parking slots, 390 stores, 90 restaurants, more than a dozen movie theatres (including an IMAX theatre), a skate park designed by Tony Hawk, and the highest fountain in Africa.
6. Nairobi (Kenya): $54 billion
Image: © Sam Stearman
Kenya's capital and largest city (metro area: 7 million) Nairobi is also known as the Green City in the Sun. Founded in 1899 by the British as a rail depot, the city today is home to thousands of Kenyan businesses, as well as the Nairobi Securities Exchange, Africa's 4th-largest stock exchange; and regional hub for hundreds of multinationals.
7. Luanda (Angola): $49 billion
View of Luanda's harbour, with the Restinga peninsula in the background
Image: OneVillage Initiative, CC BY-SA 2.0
Luanda is the biggest city, major port and capital of Angola – and its metro area is home to one in three Angolans. While the majority of Luandans live in poverty, the booming oil and gas industry has created huge wealth for a minority (as well as a boom in banking and building). Luanda is one of the world's most expensive cities for ex-pats, in part because of high import tariffs imposed to help pay for diversifying the economy.
8. Pretoria (South Africa): $48 billion
Pretoria's central business district, seen from Muckleneuk Hill
Image: Petrus Potgieter/public domain
The administrative capital of South Africa and the hub of the wider Tshwane metro area, Pretoria is also a centre for academia and R&D, as well as commerce and industry, including metalworks to car factories.
9. Casablanca (Morocco): $42 billion
Dawn over Casablanca
Image: Achalhikarim, CC BY-SA 4.0
Officially ad-Dar al-Bayda in Arabic but informally known as Kaza, Casablanca is the largest city in the entire Maghreb region (metro area: 7 million), and its economic hub. It is important both as port city and financial centre. Major Moroccan and multinational companies are headquartered here rather than in the political capital Rabat.
10. Accra (Ghana): $38 billion
Independence Arch in Accra
A merger of coastal settlements around British, Dutch and Danish coastal forts, Accra in 1957 became the capital of sub-Saharan Africa's first independent nation. Today, it is a centre for manufacturing, marketing, finance, insurance, and transportation.
Over the next decade, the AfrAsia Bank's report expects growth to remain strong in South Africa, Angola, Morocco, Egypt, Ivory Coast, Tanzania and Nigeria – not coincidentally countries hosting many of the hubs shown on this map.
But the strongest growth projections apply to some of the smaller countries in Africa: Uganda, Rwanda, Ghana and Mauritius.
Strange Maps #941
Got a strange map? Let me know at firstname.lastname@example.org.
If you don't practice accountability at work you're letting the formula for success slip right through your hands.
- What is accountability? It's a tool for improving performance and, once its potential is thoroughly understood, it can be leveraged at scale in any team or organization.
- In this lesson for leaders, managers, and individuals, Shideh Sedgh Bina, a founding partner of Insigniam and the editor-in-chief of IQ Insigniam Quarterly, explains why it is so crucial to success.
- Learn to recognize the mindset of accountable versus unaccountable people, then use Shideh's guided exercise as a template for your next post-project accountability analysis—whether that project was a success or it fell short, it's equally important to do the reckoning.
Iranian Tolkien scholar finds intriguing parallels between subcontinental geography and famous map of Middle-earth
- J.R.R. Tolkien himself hinted that his stories are set in a really ancient version of Europe.
- But a fantasy realm can be inspired by a variety of places; and perhaps so is Tolkien's world.
- These intriguing similarities with Asian topography show that it may be time to 'decolonise' Middle-earth.
Mental decolonisation<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzQzMDM0OS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY1MDU4Mjg3N30.pKS1PLxKYeJ6WDPAcleg7NCxzDn7Pddcg9rSJaul6no/img.png?width=980" id="56ee5" class="rm-shortcode" data-rm-shortcode-id="1d2ba98946accd12f7e0070c8d10154d" data-rm-shortcode-name="rebelmouse-image" alt="Menu page for Arda.ir, the website of the Persian Tolkien Society." />
Menu page for Arda.ir, the website of the Persian Tolkien Society.
Image: Arda.ir<p>Where on earth was Middle-earth? Based on a few hints by Tolkien himself, we've always sort-of assumed that his stories of <em>The Hobbit</em> and <em>Lord of the Rings</em> were centered on Europe, but so long ago that the shape of the coasts and the land has changed. </p><p>But perhaps that's too easy, too euro-centric an assumption; perhaps, like so many other things these days, Tolkien's fantasy realm too is in dire need of mental decolonisation.</p><p>And here's an excellent occasion: an Iranian tolkienologist has found intriguing hints that the writer based some of Middle-earth's topography on mountains, rivers and islands located in and near present-day Pakistan. </p><p>As mentioned in a previous article – recently reposted on the <a href="https://www.facebook.com/VeryStrangeMaps" target="_blank">Strange Maps Facebook page</a> on the occasion of the death of Ian Holm – Tolkien admitted that "The Shire is based on rural England, and not on any other country in the world;" and that "the action of the story takes place in the North-West of 'Middle-earth', equivalent in latitude to the coastlands of Europe and the north shores of the Mediterranean."<br></p>
Non-European topography<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzQzMDM1MC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY1NTQ4MzcyMX0.891LPW42L78fdrwUhXdgOab7cbhs3YOqZK4ukIQx-Rw/img.png?width=980" id="6741c" class="rm-shortcode" data-rm-shortcode-id="f0e720018e3f9f7bec4260fe7151816e" data-rm-shortcode-name="rebelmouse-image" alt="If you look at it like that, yes: that does resemble Mordor..." />
If you look at it like that, yes: that does resemble Mordor...
Image: Mohammad Reza Kamali, reproduced with kind permission<p>Extrapolating from the location of the Shire in Middle-earth and from other clues dropped by Tolkien, geophysics and geology professor Peter Bird matched the geography of Middle-earth with that of Europe (more about that in the <a href="https://bigthink.com/strange-maps/121-where-on-earth-was-middle-earth?utm_medium=Social&utm_source=Facebook&fbclid=IwAR0ZFYK1EXrf4J3B3X5_U4hSAgidgBs24ZNTYV9QEFbz2qI34OA_DpZsn70#Echobox=1592583835" target="_blank">aforementioned article</a>).</p><p>However, seeing Middle-earth as a mere palimpsest for present-day Europe is to place an undue limit on the imagination of its creator. As Tolkien also said about the shape of his world: "(It) was devised 'dramatically' rather than geologically or paleontologically."</p><p>In other words, certain parts of Middle-earth may very well have been inspired by other places than European ones. It is telling that it took a non-European connoisseur of Tolkien's topography to find some examples. <br></p>
"Seen that map before"<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzQzMDM1MS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY1MTQ3Njc3NH0.azDO1_NWm9q9FwMpmqBOV2troOX0ajAXS4lP2bLstJI/img.png?width=980" id="1b193" class="rm-shortcode" data-rm-shortcode-id="565b62df93cef8936c8f348cdb059db8" data-rm-shortcode-name="rebelmouse-image" alt="\u200bThe Indus river is a prominent geographical feature of Pakistan. Its course is similar to that of the Anduin, the Great River of Middle-earth." />
The Indus river is a prominent geographical feature of Pakistan. Its course is similar to that of the Anduin, the Great River of Middle-earth.
Image: Mohammad Reza Kamali, reproduced with kind permission<p>In an article published on <a href="https://arda.ir/" target="_blank">Arda.ir</a>, the web page for the Persian Tolkien Society, Mohammad Reza Kamali writes that during several years of cartographic study, "I found that maybe there are real lands (that) could have inspired Professor Tolkien, and some of them are not in Europe."</p><p>Around 2012, Mr Kamali's eye stopped when it came across a Google Map of Central Asia that showed the mountain chain of the Himalayas, the peaks of the Pamirs bunched together in an almost circular area, and the huge, flat oval of the Takla Makan desert, bounded to the north by the Tian-Shan mountains. </p><p>"I had seen that map before," he writes. "This is of course Mordor, the land of Sauron and the dark powers of Middle-earth, where Frodo and Sam destroy the One Ring." </p><p>In <a href="http://lotrproject.com/map" target="_blank">Tolkien's world</a>, the Himalayas transform into Ephel Duath, the Mountains of Shadow; and the Tian Shan into Ered Lithui, the Ash Mountains. And the circle-shaped Pamirs "are the same shape and in exactly the same corner as the Udûn of Mordor, where Frodo and Sam originally tried getting into Mordor, via the Black Gate."<br></p>
Similar shapes<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzQzMDM1Mi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxMDQyODMzNX0.KHrY7rDCNNaKKJQz-xn431APM2TqxGPCaMsqNvBe1xA/img.jpg?width=980" id="7a9fa" class="rm-shortcode" data-rm-shortcode-id="642e135455b2067ac4425e6984bcc697" data-rm-shortcode-name="rebelmouse-image" alt="A U.S. Marine Corps CH-46 Sea Knight helicopter flies near the Tarbela Dam in Pakistan's Khyber-Pakhtunkhwa province, Aug. 27, 2010. Defense Department officials announced Aug. 30, 2010, the deployment of 18 helicopters to Pakistan from the 16th Combat Aviation Brigade, based at Fort Wainwright, Alaska." />
A US Marine Corps helicopter flying over the Tarbela Dam on the Indus river in Pakistan. At its center: a former river island which may have been the inspiration for Cair Andros, a ship-shaped island in Middle-earth's Anduin river.
Image: Paul Duncan (USMC), public domain<p>Mulling over these similarities, Mr Kamali became convinced that Tolkien's map work was heavily inspired by Asia. Looking further, he found more evidence. Consider Anduin, the Great River of Middle-earth, in whose waters the One Ring was lost for more than two thousand years. </p><p>On Tolkien's map, the Anduin bends toward the sea in a shape similar to that of another great river: the Indus, which runs the length of Pakistan. Like the Anduin, it flows to the west of a major mountain chain. A prominent feature of the Anduin is the river island of Cair Andros, just north of Osgiliath. Its name means 'Ship of Long Foam', a reference to its long and narrow shape, and the sharpness of its rocks, which split the waters of the Anduin like a prow. <br></p><p>Mr Kamali is not entirely sure, but proposes that Tolkien may have been inspired by a similar-shaped island in the Indus. Now integrated into the Tarbela Dam, which was inaugurated in 1976, it would still have been a separate island in the 1930s and 40s, when Tolkien dreamed up his map.</p>
Kutch as Tolfalas Island<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzQzMDM1NC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYwOTU5NjcyNn0.869W8iiowQb9_T3laFKOUe5o5UMXuMlSITb1VxRlC2g/img.png?width=980" id="9c49e" class="rm-shortcode" data-rm-shortcode-id="0d1e386474d99b19a50b740112ad199f" data-rm-shortcode-name="rebelmouse-image" alt="During the rainy season, the coastal region of Kutch, near the mouth of the Indus, turns into an island that resembles Tolfalas Island, near the mouth of the Anduin." />
During the rainy season, the coastal region of Kutch, near the mouth of the Indus, turns into an island that resembles Tolfalas Island, near the mouth of the Anduin.
Image: Mohammad Reza Kamali, reproduced with kind permission<p>Turning our eyes to the mouth of the Anduin and Indus, we see another pair of islands, and Mr Kamali is more certain about the real one having inspired the fictional one. The fictional one is Tolfalas Island, the largest island in Belfalas Bay. <br></p><p>At first glance, it doesn't seem to have a real-life counterpart near where the Indus joins the Arabian Sea. But take a look at the coastal part of the Indian state of Gujarat. It is known as <em>Kutch</em>, a name which apparently refers to its alternately wet and dry states. In the rainy season, the shallow wetlands flood and Kutch becomes an island – the biggest island in the Gulf of Kutch, and not too dissimilar to Tolfalas Island. </p>
General knowledge<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzQzMDM1NS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyMDIwODkyOH0.aInJedv3tiQo1LmW-M6D5LV699oeWNltxeYcVKWwtF0/img.jpg?width=980" id="9bc6e" class="rm-shortcode" data-rm-shortcode-id="01d97d3941f9ba732b4df35c3aedd977" data-rm-shortcode-name="rebelmouse-image" alt="British Indian Empire 1909 Imperial Gazetteer of India" />
1909 map showing British India in pink (direct British control) and yellow (princely states). Circled: Kutch, clearly recognisable as an island.
Image: Edinburgh Geographical Institute; J. G. Bartholomew and Sons, public domain<p>But are these similarities really more than coincidences? Why would Tolkien, who was based in Cambridge and steeped in English lore and Germanic mythology, turn to the Indian subcontinent for topographical inspiration? Perhaps because cartographic knowledge of that part of the world was far more general in Britain then than it is now. Until the late 1940s, the countries we know today as India and Pakistan were part of the British Empire. Detailed maps of the region would have been standard fare for British atlases. </p><p>Mr Kamali is convinced that the topographical features on Tolkien's map of Middle-earth are not mere fantasy, but derive from actual places in our world, and were 'riddled' onto the map. In that case, we may look forward to more discoveries of Tolkien's real-world inspiration. <br></p>
From Frodingham to Frodo<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzQzMDM1Ni9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTU5NzgzMzE2OH0.uMd43VxS9WQSWr1Z0IQ-UxIhBYkERhxTU7hoPvNachk/img.jpg?width=980" id="05037" class="rm-shortcode" data-rm-shortcode-id="753c410e12164cb59f27e56bcc743e1b" data-rm-shortcode-name="rebelmouse-image" alt="Image based on a photograph of J. R. R. Tolkien in army uniform (taken in 1916, when Tolkien was aged 24). This image is a digitally modified version with cut-out contours, added gradient "shadow" around the contours, and noise reduction." />
J.R.R. Tolkien in 1916, when he was 24. Around that time, he was stationed near the village of Frodingham, which may have given him the inspiration for the name of the main protagonist in Lord of the Rings.
Image: public domain<p>Here's one example of tolkienography - if that's what we can call the effect of actual geography on this particular writer's imagination - which I gleaned myself, some years ago in East Yorkshire. A local historian told me that Tolkien had been stationed in the area during the First World War, and had apparently stored away some local place names for later use. The name Frodo, he said, derived from a town where he had attended a few dances – Frodingham, a village across the Humber in northern Lincolnshire, not far from Scunthorpe (<em>Scunto</em>? We dodged a bullet there). </p><p>Whether that story is entirely true or not is beside the point. As fantasy fans know, any grail quest is ultimately about the quest, not the grail. In fact, to quote Mr Kamali, the treasure is important only because it's well hidden, "by a clever professor who enjoys riddles."</p><p><em>Unless otherwise indicated, illustrations are from Mr Kamali's <a href="https://arda.ir/the-tale-of-the-annotated-map-and-tolkien-hidden-riddles/?fbclid=IwAR3RmtU0ZdyzQGlK-iCsUjho4LA2W279fwO9dt8vv90FX2IeO3zrfMuMToU" target="_blank">article</a> on <a href="https://arda.ir/" target="_blank">Arda.ir</a>, reproduced with kind permission. </em><br></p><p><strong>Strange Maps #1036</strong></p><p><em>Got a strange map? Let me know at </em><a href="mailto:email@example.com">firstname.lastname@example.org</a><em>.</em></p>
The ocean's largest shark relies on vision more than previously believed.
- Japanese researchers discovered that the whale shark has "tiny teeth"—dermal denticles—protecting its eyes from abrasion.
- They also found the shark is able to retract its eyeball into the eye socket.
- Their research confirms that this giant fish relies on vision more than previously believed.
A. Anterior view of the whale shark, showing the locations of the eye (arrows). Note that whale shark eye is well projected from the orbit. Photo was taken in the sea near Saint Helena Island. B. Close-up view of the left eye of a captive whale shark (Specimen A).<p>Considering their dietary habits, vision was not thought be that important for whale sharks. This species is unique for not having any sort of eyelid or protective mechanism—until now, that is. Not only do dermal denticles protect their vision, the team, led by Taketeru Tomita, discovered that whale sharks have another trick:</p><p style="margin-left: 20px;">"We also demonstrate that the whale shark has a strong ability to retract the eyeball into the eye socket."</p><p>The researchers studied these massive sharks in an aquarium, offering them a rare look at one of the ocean's largest fish (They also studied deceased sharks). The eye denticle is different from the rest of the scales covering their body: they are designed for abrasion resistance, not ocean stealth. </p><p style="margin-left: 20px;">"The covering of the eye surface with denticles in the whale shark is probably useful in reducing the risk of mechanical damage to the eye surface." </p><p>Despite their massive size, whale sharks have relatively small eyes, measuring less than 1 percent of their total length. Their brain's visual center is also relatively small. With this discovery, the researchers realized vision plays a more important role than previously assumed. </p><p style="margin-left: 20px;">"The highly protected features of the whale shark eye, in contrast to the traditional view, seems to suggest the importance of vision in this species. Interestingly, Martin showed that whale shark eyes actively track divers swimming 3–5 m away from the animal, suggesting that vision of the whale shark plays an important role in short-range perception." </p><p>While you likely won't bump into a whale shark while swimming just off the coast, this is yet another reminder of how species adapt to their environment. </p><p><span></span>--</p><p><em>Stay in touch with Derek on <a href="http://www.twitter.com/derekberes" target="_blank">Twitter</a>, <a href="https://www.facebook.com/DerekBeresdotcom" target="_blank">Facebook</a> and <a href="https://derekberes.substack.com/" target="_blank">Substack</a>. His next book is</em> "<em>Hero's Dose: The Case For Psychedelics in Ritual and Therapy."</em></p>
A gigantic star makes off during an eight-year gap in observations.
- The massive star in the Kinsman Dwarf Galaxy seems to have disappeared between 2011 and 2019.
- It's likely that it erupted, but could it have collapsed into a black hole without a supernova?
- Maybe it's still there, but much less luminous and/or covered by dust.
A "very massive star" in the Kinman Dwarf galaxy caught the attention of astronomers in the early years of the 2000s: It seemed to be reaching a late-ish chapter in its life story and offered a rare chance to observe the death of a large star in a region low in metallicity. However, by the time scientists had the chance to turn the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Paranal, Chile back around to it in 2019 — it's not a slow-turner, just an in-demand device — it was utterly gone without a trace. But how?
The two leading theories about what happened are that either it's still there, still erupting its way through its death throes, with less luminosity and perhaps obscured by dust, or it just up and collapsed into a black hole without going through a supernova stage. "If true, this would be the first direct detection of such a monster star ending its life in this manner," says Andrew Allan of Trinity College Dublin, Ireland, leader of the observation team whose study is published in Monthly Notices of the Royal Astronomical Society.
Between astronomers' last look in 2011 and 2019 is a large enough interval of time for something to happen. Not that 2001 (when it was first observed) or 2019 have much meaning, since we're always watching the past out there and the Kinman Dwarf Galaxy is 75 million light years away. We often think of cosmic events as slow-moving phenomena because so often their follow-on effects are massive and unfold to us over time. But things happen just as fast big as small. The number of things that happened in the first 10 millionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang, for example, is insane.
In any event, the Kinsman Dwarf Galaxy, or PHL 293B, is far way, too far for astronomers to directly observe its stars. Their presence can be inferred from spectroscopic signatures — specifically, PHL 293B between 2001 and 2011 consistently featured strong signatures of hydrogen that indicated the presence of a massive "luminous blue variable" (LBV) star about 2.5 times more brilliant than our Sun. Astronomers suspect that some very large stars may spend their final years as LBVs.
Though LBVs are known to experience radical shifts in spectra and brightness, they reliably leave specific traces that help confirm their ongoing presence. In 2019 the hydrogen signatures, and such traces, were gone. Allan says, "It would be highly unusual for such a massive star to disappear without producing a bright supernova explosion."
The Kinsman Dwarf Galaxy, or PHL 293B, is one of the most metal-poor galaxies known. Explosive, massive, Wolf-Rayet stars are seldom seen in such environments — NASA refers to such stars as those that "live fast, die hard." Red supergiants are also rare to low Z environments. The now-missing star was looked to as a rare opportunity to observe a massive star's late stages in such an environment.
In August 2019, the team pointed the four eight-meter telescopes of ESO's ESPRESSO array simultaneously toward the LBV's former location: nothing. They also gave the VLT's X-shooter instrument a shot a few months later: also nothing.
Still pursuing the missing star, the scientists acquired access to older data for comparison to what they already felt they knew. "The ESO Science Archive Facility enabled us to find and use data of the same object obtained in 2002 and 2009," says Andrea Mehner, an ESO staff member who worked on the study. "The comparison of the 2002 high-resolution UVES spectra with our observations obtained in 2019 with ESO's newest high-resolution spectrograph ESPRESSO was especially revealing, from both an astronomical and an instrumentation point of view."
Examination of this data suggested that the LBV may have indeed been winding up to a grand final sometime after 2011.
Team member Jose Groh, also of Trinity College, says "We may have detected one of the most massive stars of the local Universe going gently into the night. Our discovery would not have been made without using the powerful ESO 8-meter telescopes, their unique instrumentation, and the prompt access to those capabilities following the recent agreement of Ireland to join ESO."
Combining the 2019 data with contemporaneous Hubble Space Telescope (HST) imagery leaves the authors of the reports with the sense that "the LBV was in an eruptive state at least between 2001 and 2011, which then ended, and may have been followed by a collapse into a massive BH without the production of an SN. This scenario is consistent with the available HST and ground-based photometry."
A star collapsing into a black hole without a supernova would be a rare event, and that argues against the idea. The paper also notes that we may simply have missed the star's supernova during the eight-year observation gap.
LBVs are known to be highly unstable, so the star dropping to a state of less luminosity or producing a dust cover would be much more in the realm of expected behavior.
Says the paper: "A combination of a slightly reduced luminosity and a thick dusty shell could result in the star being obscured. While the lack of variability between the 2009 and 2019 near-infrared continuum from our X-shooter spectra eliminates the possibility of formation of hot dust (⪆1500 K), mid-infrared observations are necessary to rule out a slowly expanding cooler dust shell."
The authors of the report are pretty confident the star experienced a dramatic eruption after 2011. Beyond that, though:
"Based on our observations and models, we suggest that PHL 293B hosted an LBV with an eruption that ended sometime after 2011. This could have been followed by
(1) a surviving star or
(2) a collapse of the LBV to a BH [black hole] without the production of a bright SN, but possibly with a weak transient."