{"id":5873,"date":"2017-03-28T10:49:50","date_gmt":"2017-03-28T10:49:50","guid":{"rendered":"https:\/\/blogs.nature.com\/aviewfromthebridge\/?p=5873"},"modified":"2017-03-28T18:22:52","modified_gmt":"2017-03-28T18:22:52","slug":"imaging-black-holes","status":"publish","type":"post","link":"https:\/\/blogs.nature.com\/aviewfromthebridge\/2017\/03\/28\/imaging-black-holes\/","title":{"rendered":"Imaging and imagining black holes"},"content":{"rendered":"<h3><em>Posted on behalf of Davide Castelvecchi<\/em><\/h3>\n<p><iframe loading=\"lazy\" title=\"\u00c0 QUOI ressemble vraiment un Trou Noir ? (Simulation scientifique)\" width=\"584\" height=\"438\" src=\"https:\/\/www.youtube.com\/embed\/5Oqop50ltrM?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe><\/p>\n<p>Until several years ago, most cinematic and artistic depictions of black holes \u2014 including many in the pages of <em>Nature \u2014 <\/em>failed to match the known facts<strong>.<\/strong> A black hole (the remnant of a runaway gravitational collapse) often looked like a <a href=\"https:\/\/www.nature.com\/news\/astrophysics-fire-in-the-hole-1.12726\">space whirlpool<\/a>, or perhaps a simple black sphere representing the event horizon \u2014 the surface that constitutes a point of no return for anything that falls inside. This would be pictured either <a href=\"https:\/\/www.nature.com\/news\/did-a-hyper-black-hole-spawn-the-universe-1.13743\">against a background of stars<\/a>, or <a href=\"https:\/\/www.nature.com\/news\/young-black-hole-had-monstrous-growth-spurt-1.16989\">surrounded by an \u2018accretion disk\u2019<\/a>. (Think Saturn\u2019s rings, but made of superheated plasma and spiralling in at close to the speed of light.)<\/p>\n<p><a href=\"https:\/\/www.nature.com\/nature\/journal\/v515\/n7526\/full\/515196a.html\">Thanks in part to physicist Kip Thorne\u2019s involvement<\/a>,Christopher Nolan\u2019s 2014 film <em>Interstellar<\/em> was the first one to show what you would actually see if you were to fly near a black hole (<a href=\"https:\/\/www.nature.com\/news\/the-quantum-source-of-space-time-1.18797\">see image here<\/a>). And <a href=\"https:\/\/www.nature.com\/news\/how-to-hunt-for-a-black-hole-with-a-telescope-the-size-of-earth-1.21693\">as I wrote last week in <em>Nature<\/em><\/a>, an ambitious radio astronomy project now aims at taking the first snapshot of an actual black hole. In other words, a real-life picture of <em>Interstellar<\/em>\u2019s black hole Gargantua, if a highly pixelated one.<\/p>\n<p>Between accurate art and actual observation, it might finally begin to sink into our collective imagination just how weird these objects must look<strong>.<\/strong> Gravitational lensing, a consequence of Albert Einstein\u2019s theory of gravity, makes light rays curve around a black hole \u2014 some light rays do so multiple times. This means that ironically, even though a black hole forever hides what has fallen into it, it cannot hide anything that lies behind it. In particular, if there is an accretion disk, gravitational lensing produces multiple images of it, which appear to wrap around the black disk of the event horizon like a halo (see the <a href=\"https:\/\/www.nature.com\/news\/how-to-hunt-for-a-black-hole-with-a-telescope-the-size-of-earth-1.21693#\/dark\">infographic<\/a> accompanying my article).<\/p>\n<div id=\"attachment_5999\" style=\"width: 970px\" class=\"wp-caption aligncenter\"><a class=\"wpn-image-link\" href=\"https:\/\/blogs.nature.com\/aviewfromthebridge\/files\/2017\/03\/pm4b.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-5999\" class=\"size-full wp-image-5999 wpn-image\" title=\"pm4b\" src=\"https:\/\/blogs.nature.com\/aviewfromthebridge\/files\/2017\/03\/pm4b.jpg\" alt=\"A black hole cannot hide another object (in this case another black hole) that passes directly behind it. Instead, the object in the background will appear like a ring surrounding the one in the foreground.\" width=\"960\" height=\"768\" srcset=\"https:\/\/blogs.nature.com\/aviewfromthebridge\/files\/2017\/03\/pm4b.jpg 960w, https:\/\/blogs.nature.com\/aviewfromthebridge\/files\/2017\/03\/pm4b-300x240.jpg 300w\" sizes=\"auto, (max-width: 960px) 100vw, 960px\" \/><\/a><p id=\"caption-attachment-5999\" class=\"wp-caption-text\">A black hole cannot hide another object (in this case another black hole) that passes directly behind it. Instead, the object in the background will appear like a ring surrounding the one in the foreground.{credit}Alain Riazuelo\/Institut d\u2019Astrophysique de Paris{\/credit}<\/p><\/div>\n<p>Theoretical physicist John Wheeler <a href=\"https:\/\/www.sciencenews.org\/blog\/context\/50-years-later-it%E2%80%99s-hard-say-who-named-black-holes\">famously made the term \u2018black hole\u2019 official<\/a> in 1967 to describe the phenomenon. Fewer realise that around a decade after that, an astrophysicist accurately portrayed a black hole, as Thorne relates in his splendid companion book to the film, <a href=\"https:\/\/www.nature.com\/nature\/journal\/v515\/n7526\/full\/515196a.html\"><em>The Science of <\/em>Interstellar<\/a>. In 1978 at the <a href=\"https:\/\/www.obspm.fr\/-observatoire-de-paris-.html?lang=en\">Paris Observatory<\/a>, Jean-Pierre Luminet became the first to make a detailed computer calculation of a black hole\u2019s appearance. He did so, he told me<strong>, <\/strong>by programming a (by then already obsolete) 1960s IBM 7040 computer, using punch cards.<\/p>\n<p>Because Luminet had no way to print out the resulting image or visualize it on a screen, he used the data to draw an image by hand, putting individual dots of India ink onto a photographic negative. He published it that year in the French magazine <em>La Recherche<\/em>, and then with more detailed technical results <a href=\"https:\/\/adsabs.harvard.edu\/full\/1979A%26A....75..228L\">in the journal <em>Astronomy and Astrophysics<\/em> in 1979<\/a>. (On his blog, Luminet <a href=\"https:\/\/blogs.futura-sciences.com\/e-luminet\/2015\/01\/20\/black-hole-illuminations-13-back-basics\/\">explains<\/a> how calculating the appearances of black holes is technically similar to understanding the optics of glories, atmospheric phenomena similar to rainbows.)<\/p>\n<p>Given that Gargantua is an accurate simulation using twenty-first-century knowledge and computing, it is uncanny to see how Luminet\u2019s hand-drawn picture made from a punch-card computer\u2019s data already had all the crucial ingredients. In fact, in one respect it was even more accurate. In Luminet\u2019s image, one side of the accretion disk (the one rotating towards the observer) looks much brighter than the other \u2014 a consequence of its extreme speeds. As Thorne notes in his book, the <em>Interstellar<\/em> team considered including this effect in their renderings, but director Christopher Nolan decided it would be too confusing for viewers. This was possibly the only aspect in which the Gargantua sequence strayed from scientific accuracy.<\/p>\n<div id=\"attachment_5881\" style=\"width: 740px\" class=\"wp-caption aligncenter\"><a class=\"wpn-image-link\" href=\"https:\/\/blogs.nature.com\/aviewfromthebridge\/files\/2017\/03\/Luminet-image.png\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-5881\" class=\"size-full wp-image-5881 wpn-image\" title=\"Luminet image\" src=\"https:\/\/blogs.nature.com\/aviewfromthebridge\/files\/2017\/03\/Luminet-image.png\" alt=\"The first accurate image of the appearance of a black hole (India ink on Canson negative paper).\" width=\"730\" height=\"385\" srcset=\"https:\/\/blogs.nature.com\/aviewfromthebridge\/files\/2017\/03\/Luminet-image.png 730w, https:\/\/blogs.nature.com\/aviewfromthebridge\/files\/2017\/03\/Luminet-image-300x158.png 300w\" sizes=\"auto, (max-width: 730px) 100vw, 730px\" \/><\/a><p id=\"caption-attachment-5881\" class=\"wp-caption-text\">The first accurate image of the appearance of a black hole (India ink on Canson negative paper).{credit}Jean-Pierre Luminet{\/credit}<\/p><\/div>\n<p>That realism was a long time coming. From the 1970s at least, most popular-science renderings of black holes lacked the effects of gravitational lensing. \u201cI was a little bit upset to see that in many popular magazines, they more or less systematically used artistic views with no scientific accuracy at all,\u201d Luminet recalls. Starting in the late 1960s, science-fiction had also battened onto black holes, but under an intriguing array of names. A 1967 <a href=\"https:\/\/en.wikipedia.org\/wiki\/Tomorrow_Is_Yesterday\"><em>Star Trek<\/em> episode<\/a> had a \u2018black star\u2019. A 1975 episode in another TV series, <em>Space: 1999,<\/em> involved a \u2018black sun\u2019. Films, too, began to feature black holes, including\u00a0 Disney\u2019s 1979 <em>The Black Hole<\/em>.<\/p>\n<p>Meanwhile, the rise of powerful computers in the decades after Luminet\u2019s efforts meant researchers made ever more realistic simulations, and began to craft colour animations. In the early 1990s, the late astrophysicist Jean-Alain Marck, also at the Paris Observatory, created the animation at the top of this piece, which Luminet later used in the documentary <em>Infinitely Curved<\/em>. Even more spectacular animations were created by Alain Riazuelo at the <a href=\"https:\/\/www.iap.fr\/?langue=en\">Paris Institute of Astrophysics<\/a> and by Andrew Hamilton at the University of Colorado in Boulder. (Hamilton also rendered what happens when you fall inside a black hole.)<\/p>\n<p><iframe loading=\"lazy\" title=\"A Journey into a Black Hole\" width=\"584\" height=\"329\" src=\"https:\/\/www.youtube.com\/embed\/eI9CvipHl_c?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe><\/p>\n<p>However, none of these outreach efforts had the same impact as <em>Interstellar<\/em>. The film has begun to affect the way artists represent black holes, says Eug\u00e9nie von Tunzelmann, who led the 200-strong team of computer-graphics experts at London-based company <a href=\"https:\/\/www.dneg.com\/\">Double Negative<\/a>, which created the special effects<strong>. <\/strong>Stylized icons now often look like a strip crossing a circle \u2013 suggestive of the accretion disk and its lensed image. \u201cThe first thing that comes to mind when people say \u2018black hole\u2019 might have changed.\u201d<\/p>\n<p>Even in relatively inaccurate sci-fi representations, black holes still provided inspiration for young minds \u2013 including for many kids who grew up to become researchers and perhaps work on projects such as <a href=\"https:\/\/www.eventhorizontelescope.org\/\">the Event Horizon Telescope<\/a> (EHT), the radio astronomy project that plans to image real black holes<strong>.<\/strong> \u201cA lot of scientists, and maybe especially astronomers, always carry that little flame within them,\u201d says Sheperd Doeleman, an astrophysicist at Harvard University in Cambridge, Massachusetts, who helms the EHT. \u201cIt really gets you thinking about what\u2019s possible.\u201d<\/p>\n<p><strong>Davide Castelvecchi is senior physical sciences reporter at <em>Nature<\/em>. He tweets at @dcastelvecchi.<\/strong><\/p>\n<p><strong><em>Notes on the animations:<\/em><\/strong><\/p>\n<p><em>Colour Animation of a Black Hole with Accretion Disk<\/em> (top): this shows the gravitational lensing around the event horizon (Jean-Alain Marck; from the documentary <em>Infinitely Curved<\/em>).<\/p>\n<p><em>A Journey into a Black Hole <\/em>(bottom): a simulation of what an observer would see while falling into a black hole (Andrew Hamilton).<\/p>\n<p>&nbsp;<\/p>\n<p><strong>For\u00a0<em>Nature<\/em>\u2019s full coverage of science in culture, visit www.nature.com\/news\/booksandarts.<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Until several years ago, most cinematic and artistic depictions of black holes \u2014 including many in the pages of Nature \u2014 failed to match the known facts. A black hole (the remnant of a runaway gravitational collapse) often looked like a space whirlpool, or perhaps a simple black sphere representing the event horizon \u2014 the surface that constitutes a point of no return for anything that falls inside. This would be pictured either against a background of stars, or surrounded by an \u2018accretion disk\u2019. (Think Saturn\u2019s rings, but made of superheated plasma and spiralling in at close to the speed of light.)&nbsp; <a href=\"https:\/\/blogs.nature.com\/aviewfromthebridge\/2017\/03\/28\/imaging-black-holes#more-5873\" class=\"more-link\"> &hellip; Read more<\/a> <a href=\"https:\/\/blogs.nature.com\/aviewfromthebridge\/2017\/03\/28\/imaging-black-holes\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":3353,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7,37,1390391],"tags":[],"class_list":["post-5873","post","type-post","status-publish","format-standard","hentry","category-arts","category-astronomy","category-astrophysics"],"_links":{"self":[{"href":"https:\/\/blogs.nature.com\/aviewfromthebridge\/wp-json\/wp\/v2\/posts\/5873","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.nature.com\/aviewfromthebridge\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.nature.com\/aviewfromthebridge\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.nature.com\/aviewfromthebridge\/wp-json\/wp\/v2\/users\/3353"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.nature.com\/aviewfromthebridge\/wp-json\/wp\/v2\/comments?post=5873"}],"version-history":[{"count":0,"href":"https:\/\/blogs.nature.com\/aviewfromthebridge\/wp-json\/wp\/v2\/posts\/5873\/revisions"}],"wp:attachment":[{"href":"https:\/\/blogs.nature.com\/aviewfromthebridge\/wp-json\/wp\/v2\/media?parent=5873"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.nature.com\/aviewfromthebridge\/wp-json\/wp\/v2\/categories?post=5873"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.nature.com\/aviewfromthebridge\/wp-json\/wp\/v2\/tags?post=5873"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}