{"id":9958,"date":"2026-06-22T20:39:06","date_gmt":"2026-06-23T00:39:06","guid":{"rendered":"https:\/\/spaceandplanetarynewswire.com\/?p=9958"},"modified":"2026-06-22T20:39:06","modified_gmt":"2026-06-23T00:39:06","slug":"third-times-the-charm-for-a-row-of-faint-galaxies-without-dark-matter","status":"publish","type":"post","link":"https:\/\/spaceandplanetarynewswire.com\/?p=9958","title":{"rendered":"Third Time\u2019s the Charm for a Row of Faint Galaxies Without Dark Matter"},"content":{"rendered":"<p>Astronomers have followed a faint, cosmic trail\u00a0of gas\u00a0to a third galaxy that\u00a0has\u00a0no\u00a0dark matter.<\/p>\n<figure style=\"width: 1260px\" class=\"wp-caption alignnone\"><img decoding=\"async\" class=\"size-medium lazyload\" data-src=\"https:\/\/news.yale.edu\/sites\/default\/files\/styles\/horizontal_topper_image\/public\/2026-06\/YN_DF9-drak-galaxy.jpg?h=fcf25457&amp;itok=vQmodIqy\" width=\"1260\" height=\"840\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 1260px; --smush-placeholder-aspect-ratio: 1260\/840;\" \/><figcaption class=\"wp-caption-text\">The inset image shows Hubble Space Telescope imaging of DF9, the third \u201cgalaxy without dark matter\u201d along a trail of galaxies (Keim et al. 2026). The background shows the full trail of galaxies, including the first two galaxies without dark matter, DF2 and DF4. (DECaLS)<\/figcaption><\/figure>\n<p>In a\u00a0<u><a href=\"https:\/\/nam12.safelinks.protection.outlook.com\/?url=https%3A%2F%2Fiopscience.iop.org%2Farticle%2F10.3847%2F1538-4357%2Fae6b8d&amp;data=05%7C02%7Cmolly.freeman%40yale.edu%7Ccaef9a389f334740e8bc08decbc4d1b6%7Cdd8cbebb21394df8b4114e3e87abeb5c%7C0%7C0%7C639172243341895617%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&amp;sdata=67XKOUo5nyKBqT1bWZ2iybBieOjTAxF516oJEb0%2FLwU%3D&amp;reserved=0\">new study<\/a><\/u>\u00a0in The Astrophysical Journal, a team of\u00a0Yale\u00a0astronomers\u00a0reports\u00a0on a dwarf galaxy\u00a0located45 million light-years from Earth\u00a0\u2014\u00a0called\u00a0NGC 1052-DF9\u00a0\u2014 that appears to have\u00a0formed in a\u00a0straight line with\u00a0nine\u00a0other galaxies.<\/p>\n<p>Two of those other galaxies,\u00a0DF2 and DF4, were previously shown to\u00a0lack dark matter \u2014 an invisible, theorized\u00a0material that gives shape to the universe and is thought by most astronomers to be essential to galaxy formation.<\/p>\n<p>Now, DF9\u00a0has\u00a0joined the no-dark-matter\u00a0club.<\/p>\n<p>\u201cA line of galaxies\u00a0lacking dark matter has never been seen before,\u201d\u00a0said Michael Keim, a\u00a0Ph.D. student in astrophysics\u00a0in\u00a0Yale\u2019s\u00a0Graduate School of Arts and Sciences\u00a0and first author of the new study.\u00a0\u201cThe discoveryprovides some of the strongest evidence yet that these galaxies formed through an extreme and previously unseen process and offers a rare new window into the nature of dark matter itself.\u201d<\/p>\n<div style=\"width: 640px;\" class=\"wp-video\"><video class=\"wp-video-shortcode\" id=\"video-9958-1\" width=\"640\" height=\"360\" preload=\"metadata\" controls=\"controls\"><source type=\"video\/mp4\" src=\"https:\/\/news.yale.edu\/sites\/default\/files\/2026-06\/DF9-6.mp4?_=1\" \/><\/video><\/div>\n<h6>Artist&#8217;s animation depicting the formation of DF9. Researchers propose that a collision separated gas from dark matter, allowing a new galaxy to form from ordinary matter alone. DF9 lies alongside two other dark matter-free galaxies, DF2 and DF4, suggesting that all three are part of the same narrow chain of faint, diffuse galaxies stretching across space.<\/h6>\n<p>Keim\u2019s advisor,\u00a0Yale astronomer Pieter van Dokkum, led the\u00a0original\u00a0studies\u00a0that\u00a0analyzed DF2 and DF4, using data from the\u00a0Hubble Space\u00a0Telescope.\u00a0Van Dokkum,\u00a0the Sol Goldman Family Professor of Astronomy and\u00a0professor\u00a0of\u00a0physics\u00a0in Yale\u2019s Faculty of Arts and Sciences,\u00a0is co-author of the new study.<\/p>\n<p>During his\u00a0doctoral work\u00a0with van\u00a0Dokkum,\u00a0Keim\u00a0found DF9\u00a0\u2014\u00a0which had been\u00a0misidentified as a supermassive black hole \u2014\u00a0and\u00a0proposed a thorough analysis\u00a0with\u00a0W.M.\u00a0Keck\u00a0Observatory\u2019s\u00a0Cosmic Web Imager,\u00a0in Hawaii,\u00a0which is designed specifically to\u00a0study\u00a0faint starlight\u00a0such as the light emitted by DF9.<\/p>\n<p>The researchers\u00a0measured the motions of stars within\u00a0DF9 to\u00a0determine\u00a0its\u00a0mass. They\u00a0found that\u00a0DF9 has the mass of 100 million suns\u00a0\u2014\u00a0which is\u00a0consistent with the\u00a0expected\u00a0amount of visible matter\u00a0in a galaxy of its size\u00a0\u2014 and nothing else.\u00a0If DF9 also had the expected amount of dark matter, its mass would be\u00a0equal tomore than 10 billion suns.<\/p>\n<p>DF9\u2019s lack of dark matter strongly suggests that\u00a0DF2, DF4, and DF9 formed together in the same violent event, such as a high-speed collision between galaxies, Keim said.\u00a0In this\u00a0scenario,\u00a0the collision would have\u00a0separated\u00a0out\u00a0gas from the galaxies\u2019 dark matter\u00a0\u2014 and that gas went on to form new galaxies in a linear trail.<\/p>\n<p>\u201cUp until now it was\u00a0assumed galaxies formed within\u00a0pools of dark matter called \u2018halos,\u2019\u201d Keim said.\u00a0\u201cThis system shows that\u00a0stars and galaxies can form outside of dark matter\u00a0\u2018halos\u2019 in\u00a0extreme events\u00a0and indicates that\u00a0dark matter is a physical substance\u00a0that can act\u00a0independently of normal matter or gas, challenging alternative theories that dark matter is gravity.\u201d<\/p>\n<p>In this regard, the new study\u00a0reaffirms van Dokkum\u2019s original work on DF2 and DF4, which\u00a0also suggested that\u00a0dark\u00a0matter is a\u00a0separate material.<\/p>\n<p>The researchers\u00a0are now conducting follow-up observations with other telescopes\u00a0\u2014 including the\u00a0new Mothra telescope co-founded by van\u00a0Dokkum\u00a0and University of Toronto astronomer Roberto Abraham \u2014\u00a0to search for any gas\u00a0that was left behind after the\u00a0initial\u00a0galaxy collision.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Astronomers have followed a faint, cosmic trail\u00a0of gas\u00a0to a third galaxy that\u00a0has\u00a0no\u00a0dark matter. In a\u00a0new study\u00a0in The Astrophysical Journal, a team of\u00a0Yale\u00a0astronomers\u00a0reports\u00a0on a dwarf galaxy\u00a0located45 million light-years from Earth\u00a0\u2014\u00a0called\u00a0NGC 1052-DF9\u00a0\u2014 that appears to have\u00a0formed in a\u00a0straight line with\u00a0nine\u00a0other galaxies. Two of those other galaxies,\u00a0DF2 and DF4, were previously shown to\u00a0lack dark matter \u2014 an invisible,&hellip;<\/p>\n","protected":false},"author":71,"featured_media":9959,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"fifu_image_url":"https:\/\/news.yale.edu\/sites\/default\/files\/styles\/horizontal_topper_image\/public\/2026-06\/YN_DF9-drak-galaxy.jpg?h=fcf25457&itok=vQmodIqy","fifu_image_alt":"","footnotes":""},"categories":[216],"tags":[],"class_list":["post-9958","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-discovery"],"_links":{"self":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/9958","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/users\/71"}],"replies":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=9958"}],"version-history":[{"count":1,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/9958\/revisions"}],"predecessor-version":[{"id":9960,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/9958\/revisions\/9960"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/media\/9959"}],"wp:attachment":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=9958"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=9958"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=9958"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}