{"id":5429,"date":"2026-05-14T12:57:14","date_gmt":"2026-05-14T03:57:14","guid":{"rendered":"https:\/\/sci.nao.ac.jp\/main\/?p=5429"},"modified":"2026-05-14T12:57:14","modified_gmt":"2026-05-14T03:57:14","slug":"hightlight20260514","status":"publish","type":"post","link":"https:\/\/sci.nao.ac.jp\/main\/en\/highlights-en\/hightlight20260514","title":{"rendered":"Astronomers Find Most Chemically Primitive Galaxy in Early Universe"},"content":{"rendered":"\n
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Revealing the Nature of the Ultra-Faint Galaxy LAP1-B through a giant \u201cgravitational lens.\u201d A 3 color image created from data taken with the Near-Infrared Camera (NIRCam) on the James Webb Space Telescope (JWST). Because the stars in this galaxy are extremely faint and few in number, the galaxy is invisible in the background image taken by NIRCam, but another instrument, the Near-Infrared Spectrograph (NIRSpec) was able to detect chemical signatures. A visualization (not an actual image) of the NIRSpec velocity and distribution data is shown in the inset for oxygen (green) and two different excitation states of hydrogen (blue and red). (Credit: NASA, ESA, CSA & K. Nakajima et al., Nature)\u00a0\u00a0Image (703KB)<\/a><\/figcaption><\/figure>\n\n\n\n

An international team of astronomers has used the James Webb Space Telescope (JWST) and a natural phenomenon known as gravitational lensing to achieve a definitive characterization of LAP1-B, an ultra-faint galaxy from 13 billion years ago. Expanding upon initial detections, this new study revealed a record-breaking low oxygen abundance \u2013 merely 1\/240th that of the Sun. This chemically primitive state, coupled with an elevated carbon-to-oxygen ratio and a dominant dark matter halo, suggests that LAP1-B is the long-sought \u201cancestor\u201d of the mysterious fossil galaxies found near our Milky Way Galaxy today.<\/p>\n\n\n\n

Just after the Big Bang, contained only light elements like hydrogen and helium. The heavier elements, such as oxygen and carbon, were forged much later inside the hearts of the very first stars. For decades, astronomers have tried to find the moment these \u201cfirst-generation stars\u201d began scattering heavier elements across the cosmos. However, the earliest galaxies hosting such young, primordial stars are so small and faint that seeing their chemical makeup was considered nearly impossible \u2013 until now.<\/p>\n\n\n\n

A research team led by Kimihiko Nakajima of Kanazawa University and including Masami Ouchi at the National Astronomical Observatory of Japan (NAOJ) and the University of Tokyo focused on a tiny, ultra-faint galaxy named LAP1-B. Its light was magnified 100 times by a phenomenon called \u201cgravitational lensing,\u201d where the gravity of a massive galaxy cluster acts like a natural giant telescope lens in space. By staring at this spot for over 30 hours with JWST, the team determined that the galaxy\u2019s oxygen abundance is roughly 1\/240th that of the Sun. \u201cI was instantly thrilled by the extreme lack of oxygen,\u201d says Nakajima. \u201cFinding a galaxy in such a primitive state is astonishing. It\u2019s a chemical signature that clearly indicates a primordial galaxy caught in the moments shortly after its formation.\u201d<\/p>\n\n\n\n

Beyond its primitive nature, the galaxy exhibited a high carbon-to-oxygen abundance ratio. This unique ratio of elements aligns closely with theoretical predictions for the material dispersed by the explosions of the universe\u2019s first-generation stars.<\/p>\n\n\n\n

The team also discovered that LAP1-B is incredibly lightweight \u2013 less than 3,300 times the mass of the Sun \u2013 implying that most of the galaxy consists of invisible dark matter. This feature, together with its unique chemical makeup, makes it a near-perfect match for the \u201cUltra-Faint Dwarf galaxies (UFDs)\u201d found near our Milky Way Galaxy today, which are extremely dim, small, and contain very few stars.<\/p>\n\n\n\n

\u201cUFDs are not only the faintest galaxies; they are composed of ancient stars over 12 billion years old and are often described as \u2018fossils of the Universe,\u2019\u201d explains Ouchi. \u201cAstronomers suspected they might be the remains of the Universe\u2019s earliest galaxies because they lack heavy elements, but astronomers never had a direct link \u2013 until we found LAP1-B.\u201d<\/p>\n\n\n\n

Ouchi continues: \u201cIt is a profound surprise to find that LAP1-B looks exactly like the \u2018ancestor\u2019 we had only imagined in theories. This helps us solve the mystery of why these cosmic fossils have survived in their current form to the present day.\u201d<\/p>\n\n\n\n

This discovery establishes a new way to map the birth of elements and the formation of the Universe\u2019s oldest structures. Moving forward, the team will use JWST to search for even more primitive objects, aiming to find the very first galaxies ever formed.<\/p>\n\n\n\n

Researcher(s) Involved in this Release<\/h3>\n\n\n\n

Kimihiko Nakajima (Kanazawa University)
Masami Ouchi (National Astronomical Observatory of Japan \/ University of Tokyo)<\/p>\n\n\n\n

Coordinated Release Organization(s)<\/h3>\n\n\n\n

Kanazawa University
National Astronomical Observatory of Japan, NINS
Institute for Cosmic Ray Research, The University of Tokyo<\/p>\n\n\n\n

Paper(s)<\/h3>\n\n\n\n

K. Nakajima et al. \u201cAn ultra-faint, chemically primitive galaxy forming in the reionization era\u201d, in Nature, DOI: 10.1038\/s41586-026-10374-1 <\/a><\/p>\n\n\n\n

Related Link(s)<\/h3>\n\n\n\n

The Most Chemically Primitive Galaxy in the Early Universe: Clues to the Mysterious Origins of Ultra-Faint Dwarfs (Institute for Cosmic Ray Research, the University of Tokyo)\u00a0<\/a><\/a><\/p>\n\n\n\n

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An international team of astronomers has used the James Webb Space Telescope (JWST) and a natural phenomenon k […]<\/p>\n","protected":false},"author":89,"featured_media":5418,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"cybocfi_hide_featured_image":"yes","_locale":"en_US","_original_post":"https:\/\/sci.nao.ac.jp\/main\/?p=5417","footnotes":""},"categories":[23],"tags":[],"class_list":["post-5429","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-highlights-en","en-US"],"_links":{"self":[{"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/posts\/5429","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/users\/89"}],"replies":[{"embeddable":true,"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/comments?post=5429"}],"version-history":[{"count":1,"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/posts\/5429\/revisions"}],"predecessor-version":[{"id":5430,"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/posts\/5429\/revisions\/5430"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/media\/5418"}],"wp:attachment":[{"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/media?parent=5429"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/categories?post=5429"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sci.nao.ac.jp\/main\/wp-json\/wp\/v2\/tags?post=5429"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}