<\/p>\n
JWST unveils most intricate map yet of cosmic dark matter<\/p>\n
Astronomers puzzled out minuscule distortions in images of faraway galaxies taken by JWST in order to chart the invisible<\/p>\n
Containing nearly 800,000 galaxies, this image from NASA\u2019s James Webb Space Telescope (JWST) is overlaid with a map of dark matter, represented in blue. Researchers used JWST data to find the invisible substance via its gravitational influence on regular matter.<\/p>\n
It\u2019s an open secret in astronomy that, practically wherever the James Webb Space Telescope (JWST) looks in the sky, a vast, clump-filled mist fills its view. But luckily for everyone marveling at JWST\u2019s crisp snapshots of faraway galaxies, this dense haze is totally invisible.<\/p>\n
That lightless, see-through murk is dark matter. Think of dark matter as scaffolding for all the luminous, normal stuff out there\u2014with the former outweighing the latter five times over\u2014like a gravitational glue that holds everything else together. But scientists have no idea what this \u201cglue\u201d is made of and have yet to detect it directly; they have only inferred its presence through subtle but unmistakable clues. For something so integral to all we see, it\u2019s astonishingly hidden from our cosmic view.<\/p>\n
Now astronomers have traced dark matter\u2019s ghostly contours in the foreground of one of JWST\u2019s deep-sky images. They\u2019ve turned a survey of the Cosmic Evolution Survey (COSMOS) field\u2014one of the sky\u2019s best-studied patches\u2014into the most finely detailed dark matter map in existence. With it, they hope to learn more about how galaxies depend on its presence. A study reporting the results appears today in Nature Astronomy.<\/p>\n
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\u201cWe can see the influence of gravity on galaxy formation,\u201d says Diana Scognamiglio, a postdoctoral fellow at NASA\u2019s Jet Propulsion Laboratory, who co-led the study. \u201cIt\u2019s a way to trace, really, the backbone of the universe.\u201d<\/p>\n
Gaze upon any JWST image of some faraway galaxy. What you really see is where each ray of light hit JWST\u2019s optics during observations. The image essentially traces each ray back to its source within a targeted galaxy.<\/p>\n
But that ray\u2019s journey from the galaxy to JWST isn\u2019t really a straight line. On its voyage through intergalactic space, that light traverses countless clumps of dark matter. Each clump slightly warps the spacetime around it, altering the light ray\u2019s path much like a glass lens.<\/p>\n
That warping distorts the image in the same way that wearing someone else\u2019s glasses blurs your sight. For JWST\u2019s images, this effect is imperceptible to the eye, which is why it\u2019s called \u201cweak gravitational lensing.\u201d But the images encode all the dark matter between the far-off object and the telescope.<\/p>\n
No one knew how to decode this warping, however, until around the start of the third millennium. \u201cPeople were saying that there\u2019s absolutely no way you can measure a 1 percent distortion with everything else going on,\u201d says Catherine Heymans, a professor of astrophysics at the University of Edinburgh and Scotland\u2019s astronomer royal. Heymans and her peers proved them wrong, launching the field of \u201cweak lensing\u201d that has since shed more light on dark matter.<\/p>\n
Heymans helped build the first dark matter map of the COSMOS field using JWST\u2019s predecessor, the Hubble Space Telescope. \u201cIt was a really pioneering work,\u201d Scognamiglio says.<\/p>\n
Two decades later Scognamiglio\u2019s team of cosmic cartographers has updated that map using the heaps more galaxies JWST\u2019s images contain. \u201cIt\u2019s super exciting just because of the sheer number of galaxies and that they can use,\u201d says Zoltan Haiman, an astrophysicist at Columbia University. The new map spans an area on the sky only twice as big as the full moon\u2014a quarter of the original\u2019s size\u2014but it\u2019s far more detailed, pinpointing blobs of dark matter that are too small for Hubble to discern.<\/p>\n
And JWST\u2019s larger, more sensitive optics can collect light from farther out in the universe\u2014and thus further back in cosmic time. So it can see weak lensing caused by dark matter clumps from 10 billion or 11 billion years ago, when the universe was most prodigiously forming stars and galaxies. Studying these clumps\u2014which likely host clusters of adolescent galaxies\u2014is a rare chance to learn more about what dark matter\u2019s role was in that epoch, called \u201ccosmic noon,\u201d and how the universe has evolved ever since. Next the team wants to infer the various distances of the structures that the researchers have glimpsed and to use them to make the map more dynamic and three-dimensional.<\/p>\n
For now, the map as is puts one of the universe\u2019s most elusive sculptors starkly in view. \u201cBefore we only had dark matter simulations, and I always wanted to be able to see it,\u201d Heyman says. \u201cWhat I love about weak lensing is: it allows us to see the invisible.\u201d<\/p>\n
In the coming years, astronomers\u2019 dark matter maps will be massively extended\u2014though with less fine-grained detail. Weak lensing is part of the stated mission of newer space telescopes such as the European Space Agency\u2019s Euclid, already in orbit, and NASA\u2019s Nancy Grace Roman Space Telescope, scheduled for launch this year. Ground-based projects such as the Dark Energy Survey, which released a new trove of data last week, and the Vera C. Rubin Observatory also use weak lensing to study the universe\u2019s expansion.<\/p>\n
A generation after the trailblazing Hubble dark matter map, Scognamiglio is proud to help extend its legacy. \u201cI like this continuity,\u201d she says. \u201cI hope that, 20 years from now, my student will be able to make an even better map.\u201d<\/p>\n
Joseph Howlett is a staff reporter at Scientific American covering physics, math, astronomy and more. He was previously a math staff writer at Quanta Magazine, and holds a Ph.D. in particle physics from Columbia University.<\/p>\n
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David M. Ewalt,\u00a0Editor in Chief, Scientific American<\/p>\n","protected":false},"excerpt":{"rendered":" JWST unveils most intricate map yet of cosmic dark matter Astronomers puzzled out minuscule distortions in images…\n","protected":false},"author":2,"featured_media":307775,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[271],"tags":[18,19,17,452,133],"class_list":{"0":"post-307774","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-eire","9":"tag-ie","10":"tag-ireland","11":"tag-physics","12":"tag-science"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/115972064119763992","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/307774","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=307774"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/307774\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/307775"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=307774"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=307774"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=307774"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}