{"id":802659,"date":"2026-10-14T20:14:08","date_gmt":"2026-10-14T20:14:08","guid":{"rendered":"https:\/\/www.newsbeep.com\/uk\/802659\/"},"modified":"2026-10-14T20:14:08","modified_gmt":"2026-10-14T20:14:08","slug":"triplet-of-ghostly-galaxies-hints-at-what-dark-matter-is-and-isnt","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/uk\/802659\/","title":{"rendered":"Triplet of \u2018Ghostly\u2019 Galaxies Hints at What Dark Matter Is \u2014 and Isn\u2019t"},"content":{"rendered":"

About 65 million light-years from Earth, three galaxies don\u2019t look quite right. They aren\u2019t whirlpools bursting with light, but pallid objects dimly illuminated by a smattering of stars. \u201cThey have this ghostly appearance,\u201d said Michael Keim<\/a>, an astrophysicist at Yale University. And this isn\u2019t even the weirdest thing about them.<\/p>\n

Dark matter is the invisible glue that keeps the largest structures in the cosmos together. It draws ordinary, visible matter toward it, allowing stars to form and keeping the stelliferous limbs of galaxies from flying off. \u201cAlmost all galaxies are dominated by dark matter,\u201d said Shyam Balaji<\/a>, a theoretical physicist at King\u2019s College London.<\/p>\n

But these three diffuse galaxies, known as DF2, DF4, and DF9, have left astronomers stunned. After using a suite of telescopes to estimate their masses \u2014 using the motions of their stars as a proxy \u2014 the researchers found that all three have little dark matter. Instead, a pittance of ordinary matter alone must have forged their small selection of stars. How could these rule-breaking galaxies have formed?<\/p>\n

A paper<\/a> published in June 2026 in The Astrophysical Journal offers a potential solution. Once upon a time, two regular galaxies collided. Their ordinary matter \u2014 their gas and dust \u2014 swirled about and got clumped up. But the dark matter passed right through and continued on, like a specter passing through a wall. The cosmic pileup left behind three new galaxies, each bereft of dark matter, each left to struggle to form a new batch of stars.<\/p>\n

It\u2019s a convincing explanation for many experts \u2014 one that, crucially, may tell us something about the mystery of dark matter.<\/p>\n

Is there a way of evolving the galaxies without dark matter in the first place? Our understanding says no.<\/p>\n

Chamkaur Ghag, University College London<\/p>\n

Some scientists have suggested that dark matter, which has yet to be directly detected, may not exist. Instead, they propose that a tweak to our understanding of the gravitational force might explain various features of the universe.<\/p>\n

These bizarre galaxies pour cold water on that idea. \u201cWhat this is showing is that dark matter is \u2026 not just a modification of gravity,\u201d said Keim, who is an author of the new study. If you segregate ordinary matter from dark matter, you\u2019d expect that the dark matter\u2013lacking galaxies would struggle to form stars \u2014 and that\u2019s what DF2, DF4, and DF9 show.<\/p>\n

That suggests, as many have suspected for some time, that dark matter is a physical thing. \u201cThe absence of dark matter is, in a way, some evidence of dark matter, which is ironic,\u201d Balaji said.<\/p>\n

Dark Ghosts<\/p>\n

What, exactly, is dark matter? Ever since it was formally proposed by the astronomer Fritz Zwicky in the 1930s \u2014 and built upon in the 1970s by the astronomer Vera Rubin \u2014 cosmologists and astrophysicists have been putting forward their best candidates. Could it be a stealthy type of neutrino<\/a>? Might it be so-called weakly interacting massive particles, or WIMPs<\/a>? Some have even opined that it could be primordial black holes<\/a> as small as individual atoms and as old as the universe itself.<\/p>\n

\u201cWe don\u2019t know which dark matter candidate is the right one,\u201d said Daniel Whiteson<\/a>, a particle physicist at the University of California, Irvine. Whatever it is, it has yet to be detected. But \u201cthere\u2019s a lot of independent lines of evidence that dark matter is matter.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"About 65 million light-years from Earth, three galaxies don\u2019t look quite right. They aren\u2019t whirlpools bursting with light,…\n","protected":false},"author":2,"featured_media":802660,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[59,90,56,54,55],"class_list":["post-802659","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-gb","tag-science","tag-uk","tag-united-kingdom","tag-unitedkingdom"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/802659","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/comments?post=802659"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/802659\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media\/802660"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media?parent=802659"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/categories?post=802659"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/tags?post=802659"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}