Researchers have uncovered a growing black hole heading toward a merger in the early universe

After analyzing infrared images captured by the James Webb Space Telescope (JWST), an international team of researchers has discovered multiple massive black holes approximately 12.5 to 12.8 billion years ago, actively building up with surrounding matter and growing rapidly, some of them even on the path to merging, reports a new study published on August 31 in the Publications of the Astronomical Society of Japan.

By continuing the search for these black hole mergers using the image analysis method developed in this study and statistically measuring the proportion of massive black holes that form close pairs, researchers could find out the role that black hole mergers played in black hole growth in their early evolutionary stages.

Researchers agree there is a supermassive black hole at the center of every galaxy in today's universe, with a mass ranging from millions to billions of times of the Sun. These black holes have masses that are orders of magnitudes larger than ordinary black holes, but how they came to be this large is still unknown.

JWST, which has been operational since 2022, has identified several new types of objects in the far universe that are very small and have a characteristic red color. Named Little Red Dots (LRD), researchers think that these objects are black holes collecting matter around it and growing rapidly (Figure 2).

A black hole merging with another black hole could explain why the black holes are growing rapidly, but until now no one had been able to surely identify two LRDs approaching one another. However, conventional methods may have been the problem. In the case of two LRDs very close together, current methods could have mistakenly treated them as a complex, single object.

A team of researchers led by The University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI) graduate student Takumi Tanaka, and including Professor John Silverman, analyzed high-resolution infrared images taken by the JWST, and rather than rely solely on the overall brightness and color of objects as researchers had done up to now, the team developed a new pixel-by-pixel color selection method that examines the color of each individual pixel in the image.

By fine-tuning conventional methods, they searched for LRDs appearing as a single object that could in fact be two black holes on the path to merging with one another.

As a result, the researchers uncovered four sets of dual LRDs, where each LRD was extremely close to the other, in the universe between 12.5 to 12.8 billion years ago (Figure 1). The distance between the two celestial bodies ranged from a few thousand to a few tens of thousand light-years, which is a distance much smaller than the 100,000 light-year length of our Milky Way galaxy.

To make sure the two LRDs were in fact close to one another, and not at different distances so to only appear aligned by observers on Earth, the researchers calculated the probability of such close pairs appearing by chance based on the number and distribution of LRDs in the area. What they found was that it was unlikely all four pairs only appeared close, suggesting that LRDs could cluster strongly on a scale of several thousand light years (Figure 3).

Mergers are thought to be one of the mechanisms that transport large amounts of gas towards the center of galaxies, stimulating matter towards the black hole at the center. The results in this study could indicate that galaxy mergers are linked to rapidly growing black holes in the early universe. If each LRD contains a growing black hole, the black holes themselves might eventually merge as well. If true, these mergers could be detected by future gravitational-wave observatories.

The next step for the researchers will be to analyze the dual LRDs even further, and improve their new method by using it on a bigger sample.

https://www.ipmu.jp/en/20260831-LRD

Journal: Publications of the Astronomical Society of Japan
Paper title: Hidden in Pixels. I. Discovery of dual “little red dots” indicates
excess clustering on kilo-parsec scales
Authors: Takumi S. TANAKA (1,2,3), John D. SILVERMAN (1,2,3,4), Kazuhiro SHIMASAKU (2,5), Junya ARITA (2), Hollis B. AKINS (6), Feige WANG (7), Kohei INAYOSHI (8), Xuheng DING (9 ), Masafusa ONOUE (10,1,8), Zhaoxuan LIU (1,2,3), Caitlin M. CASEY (11,6,12), Erini LAMBRIDES (13), Vasily KOKOREV (6,14), Shuowen JIN (12,15), Andreas L. FAISST (16), Jianwei LYU (17), Jan-Torge SCHINDLER (18), Yunjing WU (1 ), Nicole DRAKOS (19), Yue SHEN (20,21), Junyao LI (20), Mingyang ZHUANG (20), Qinyue FEI (22,23), Kei ITO (12,15), Wei Leong TEE (17), Weizhe LIU (刘伟哲)(24), Wenke REN (25,26), Tomokazu KIYOTA (27,28), Zi-Jian LI (29,30), Suin MATSUI (2), Makoto ANDO (28,31), Shun HATANO (32), Michiko S. FUJII (2), Jeyhan S. KARTALTEPE (33), Anton M. KOEKEMOER (34), Daizhong LIU (35), Henry Joy MCCRACKEN (36), Jason RHODES (37), Brant E. ROBERTSON (38), Maximilien FRANCO (39,6), Koki KAKIICHI (12,40), Jinyi YANG (41), Romain A. MEYER (42), Irham T. ANDIKA (43,44), Aidan P. CLOONAN (45), Xiaohui FAN (24), Ghassem GOZALIASL (46,47), Santosh HARISH (48), Christopher C. HAYWARD (49), Marc HUERTAS-COMPANY (49,50,51,52,53), Darshan KAKKAD (34,54), Tomoya KINUGAWA (55,56,5), Mingyu LI (57), Namrata ROY (4), Marko SHUNTOV (12,40), Margherita TALIA (58,59), Sune TOFT (12,40), Aswin P. VIJAYAN (12,15), Yiyang ZHANG (9)

Author affiliations:
1 Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study,
The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
2 Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
3 Center for Data-Driven Discovery, Kavli IPMU (WPI), UTIAS, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
4 Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
5 Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
6 Department of Astronomy, The University of Texas at Austin, 2515 Speedway Boulevard Stop C1400, Austin, TX 78712, USA
7 Department of Astronomy, University of Michigan, 1085 S. University Avenue, Ann Arbor, MI 48109, USA
8 Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
9 School of Physics and Technology, Wuhan University, Wuhan 430072, China
10 Waseda Institute for Advanced Study (WIAS), Waseda University, 1-21-1, Nishi-Waseda, Shinjuku, Tokyo 169-0051, Japan;
Center for Data Science, Waseda University, 1-6-1, Nishi-Waseda, Shinjuku, Tokyo 169-0051, Japan
11 Department of Physics, University of California, Santa Barbara, Santa Barbara, CA 93109, USA
12 Cosmic Dawn Center (DAWN), Denmark
13 NASA-Goddard Space Flight Center, Code 662, Greenbelt, MD, 20771, USA
14 Kapteyn Astronomical Institute, University of Groningen, 9700 AV Groningen, The Netherlands
15 DTU Space, Technical University of Denmark, Elektrovej, Building 328, 2800, Kgs. Lyngby, Denmark
16 Caltech/IPAC, 1200 E. California Blvd. Pasadena, CA 91125, USA
17 Steward Observatory, University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721, USA
18 Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, D-21029 Hamburg, Germany
19 Department of Physics and Astronomy, University of Hawaii, Hilo, 200 W Kawili St., Hilo, HI 96720, USA
20 Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
21 National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
22 David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario, M5S 3H4, Canada
23 Department of Astronomy, School of Physics, Peking University, Beijing 100871, China
24 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
25 CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
26 School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, People’s Republic of China
27 Department of Astronomical Science, The Graduate University for Advanced Studies, SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan
28 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan
29 Chinese Academy of Sciences South America Center for Astronomy (CASSACA), National Astronomical Observatories of China (NAOC), CAS, 20A Datun Road, Beijing 100012, China
30 School of Astronomy and Space Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
31 Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582, Japan
32 Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), Osawa 2-21-1, Mitaka, Tokyo, 181-8588, Japan
33 Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623, USA
34 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
35 Purple Mountain Observatory, Chinese Academy of Sciences, 10 Yuanhua Road, Nanjing 210023, China
36 Institut d’Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université, 98 bis boulevard Arago, 75014 Paris, France
37 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91001, USA
38 Department of Astronomy and Astrophysics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
39 Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
40 Niels Bohr Institute, University of Copenhagen, Jagtvej 128, DK-2200 Copenhagen N, Denmark
41 Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109, USA
42 Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
43 Technical University of Munich, TUM School of Natural Sciences, Department of Physics, James-Franck-Str. 1, 85748 Garching, Germany
44 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
45 Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003, USA
46 Department of Computer Science, Aalto University, PO Box 15400, Espoo, FI-00 076, Finland
47 Department of Physics, Faculty of Science, University of Helsinki, 00014-Helsinki, Finland
48 Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY14623, USA
49 Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA
50 Instituto de Astrofísica de Canarias (IAC), La Laguna 38205, Spain
51 Observatoire de Paris, LERMA, PSL University, 61 avenue de l’Observatoire, 75014 Paris, France
52 Université Paris-Cité, 5 rue Thomas Mann, 75014 Paris, France
53 Universidad de La Laguna, Avda. Astrofísico Fco. Sanchez, La Laguna, Tenerife, Spain
54 Centre for Astrophysics Research, University of Hertfordshire, Hatfield, AL10 9AB, UK
55 Faculty of Engineering, Shinshu University, 4-17-1, Wakasato, Nagano-shi, Nagano 380-8553, Japan
56 Research Center for Aerospace System, Shinshu University, 4-17-1, Wakasato, Nagano-shi, Nagano 380-8553, Japan
57 Department of Astronomy, Tsinghua University, Beijing 100084, China
58 University of Bologna, Department of Physics and Astronomy (DIFA), Via Gobetti 93/2, I-40129, Bologna, Italy
59 INAF – Osservatorio di Astrofisica e Scienza dello Spazio, via Gobetti 93/3 - 40129, Bologna - Italy

DOI: 10.1093/pasj/psag092 (published August 31, 2026)
https://doi.org/10.1093/pasj/psag092
Paper abstract (Publications of the Astronomical Society of Japan)
https://academic.oup.com/pasj/advance-article/doi/10.1093/pasj/psag092/8770858
Pre-print (arXiv.org)
https://arxiv.org/pdf/2412.14246

Fichiers joints

Figure 3: Histogram of the angular separation between LRDs on the celestial sphere. Assuming a random distribution, the probability of finding two LRDs with the angular separation observed in this study would be extremely low. (Credit: Tanaka et al. 2026, PASJ)
Figure 2: A false-color, infrared image of a LRD taken by the JWST created using images filtered at wavelengths 1.5 µm, 2.8 µm, and 4.4 µm. The white line in the lower right corner shows the length for about 5000 light years. (Credit: COSMOS-Web / Tanaka)
Figure 1: False-color, infrared images from the JWST of dual LRDs created using images filtered at wavelengths 1.5 µm, 2.8 µm, and 4.4 µm. The white line in the lower right corner shows the length for about 5000 light years. (Credit: COSMOS-Web / Tanaka)

31/08/2026 Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo

Regions: Asia, Japan, Extraterrestrial, Sun, North America, United States

Keywords: Science, Space Science

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