The galaxy, observed through the James Webb Space Telescope (NASA/ESA), was forming when the universe was only half its current age
UGR astronomer Daniel Espada was recently involved in research that observed more than 40 individual stars in a galaxy nearly 6.5 billion light-years from Earth. Espada was part of a large team of astronomers and scientists from various scientific institutions around the world who used the James Webb Space Telescope (JWST), operated by NASA and the European Space Agency (ESA), to observe a galaxy nearly 6.5 billion light-years from Earth. In this galaxy, the team identified a large number of individual stars, visible thanks to an effect known as gravitational lensing and the powerful light-collecting capabilities of the JWST. The discovery marks a record-breaking achievement, as it involves the largest number of individual stars ever detected in the distant universe. It also opens up new possibilities for studying very distant stars and offers a way to explore one of the universe’s greatest mysteries: dark matter.
Daniel Espada is a member of the MAGNIF project, an international JWST collaboration designed to study very distant galaxies, which provided some of the JWST data used in the research. Espada was also involved in the scientific interpretation of the results and contributed to developing the article.
All galaxies, including our Milky Way, are made up of tens of billions of stars. In nearby galaxies, such as the Milky Way and the Andromeda, astronomers can observe each star individually due to their proximity. However, in galaxies billions of light-years away, stars cannot be distinguished from each other and their light must travel enormous distances before reaching us. Observing individual stars in these distant galaxies has long been a challenge for studying galactic formation in detail.
Recent advances in astronomy have made this possible through the use of gravitational lenses, a natural magnification effect caused by the strong gravitational fields of massive objects. As Albert Einstein’s theory of relativity predicted, these gravitational lenses can amplify the light of distant stars by factors of hundreds or even thousands, making them detectable with sensitive instruments like the JWST. The first discovery of such individual stars in distant galaxies occurred in 2018, leading to subsequent publications. However, these findings were generally limited to one or two stars per galaxy. To study stellar populations in a statistically meaningful way, many more observations of individual stars are needed.
The research team focused on a galaxy behind a cluster called Abell 370. This galaxy, nicknamed the Dragon Arc, is a huge, elongated spiral galaxy owing to the strong gravitational lensing effect of Abell 370. In December 2022 and 2023, the JWST captured two images of the Dragon Arc. In these images, astronomers counted 44 individual stars whose brightness changed over time due to variations in the gravitational lensing landscape. The discovery demonstrates, for the first time, that it is possible to study large numbers of individual stars in a distant galaxy.
The research team carefully analysed the colours of each of the stars and found that many are red supergiants, similar to Betelgeuse, in the final stages of their life cycle. This contrasts with earlier discoveries, which predominantly identified blue supergiants, including Rigel and Deneb. This difference in stellar types highlights the unique power of JWST observations at infrared wavelengths, which can detect stars at lower temperatures.
Future JWST observations of Abell 370 may capture more magnified stars in the Dragon Arc galaxy. The team plans to observe the Dragon Arc at more wavelengths to identify more stars and investigate their properties in greater detail. This would lead to a more detailed study of hundreds of stars in distant galaxies. Moreover, observations of individual stars could provide insight into the structure of gravitational lenses and could even shed light on the elusive nature of dark matter. The team is currently analysing the findings to prepare for these promising future applications.
Link to original article: Identification of more than 40 gravitationally magnified stars in a galaxy at redshift 0.725. Nature Astronomy
Authors: Yoshinobu Fudamoto, Fengwu Sun, Jose M. Diego, Liang Dai, Masamune Oguri, Adi Zitrin, Erik Zackrisson, Mathilde Jauzac, David J. Lagattuta, Eiichi Egami, Edoardo Iani, Rogier A. Windhorst, Katsuya T. Abe, Franz Erik Bauer, Fuyan Bian, Rachana Bhatawdekar, Thomas J. Broadhurst, Zheng Cai, Chian-Chou Chen, Wenlei Chen, Seth H. Cohen, Christopher J. Conselice, Daniel Espada, Nicholas Foo, Brenda L. Frye, Seiji Fujimoto, Lukas J. Furtak, Miriam Golubchik, Tiger Yu-Yang Hsiao, Jean-Baptiste Jolly, Hiroki Kawai, Patrick L. Kelly, Anton M. Koekemoer, Kotaro Kohno, Vasily Kokorev, Mingyu Li, Zihao Li, Xiaojing Lin, Georgios E. Magdis, Ashish K. Meena, Anna Niemiec, Armin Nabizadeh, Johan Richard, Charles L. Steinhardt, Yunjing Wu, Yongda Zhu, Siwei Zou
With the final observation of the distant galaxy cluster Abell 370 — some five billion light-years away — the Frontier Fields programme came to an end. Abell 370 is one of the very first galaxy clusters in which astronomers observed the phenomenon of gravitational lensing, the warping of spacetime by the cluster’s gravitational field that distorts the light from galaxies lying far behind it. This manifests as arcs and streaks in the picture, which are the stretched images of background galaxies.
Contacto:
Daniel Espada – despada@ugr.es – 958243305
