First pictures from Euclid satellite reveal billions of orphan stars

Thursday, 23 May 2024

The first scientific pictures from the Euclid satellite mission have revealed more than 1,500 billion orphan stars scattered throughout the Perseus cluster of galaxies.

Led by astronomers from the University of Nottingham, this discovery sheds light on the origins of these celestial wanderers.

The Perseus cluster, located 240 million light-years away from Earth, is one of the Universe's most massive structures, boasting thousands of galaxies. However, amidst this cosmic ensemble, the Euclid satellite captured faint ghostly light - the orphan stars - drifting between the cluster's galaxies.

Stars naturally form within galaxies, so the presence of orphan stars outside these structures raised intriguing questions about their origins.

We were surprised by our ability to see so far into the outer regions of the cluster and discern the subtle colours of this light. This light can help us map dark matter if we understand where the intracluster stars came from. By studying their colours, luminosity, and configurations, we found they originated from small galaxies.
Professor Nina Hatch, School of Physics and Astronomy and project lead

The orphan stars are characterised by their bluish hue and clustered arrangement. Based on these distinctive features the astronomers involved in the study suggest that the stars were torn from the outskirts of galaxies and from the complete disruption of smaller cluster galaxies, known as dwarfs.

After being torn from their parent galaxies, the orphaned stars were expected to orbit around the largest galaxy within the cluster. However, this study revealed a surprising finding: the orphan stars instead circled a point between the two most luminous galaxies in the cluster.

Image shows: Captured by the Euclid satellite, depicts the Perseus cluster of galaxies bathed in a gentle, soft blue light emanating from orphan stars. These orphan stars are dispersed throughout the cluster, extending up to 2 million light-years from its centre. The cluster galaxies stand out as luminous elliptical shapes against the dark expanse of space Credits: ESA/Euclid/Euclid Consortium/NASA, image processing by M. Montes (IAC) and J.-C. Cuillandre (CEA Paris-Saclay)

Dr Jesse Golden-Marx, a Nottingham astronomer involved in the study, commented, "This novel observation suggests that the massive Perseus cluster may have recently undergone a merger with another group of galaxies. This recent merger could have induced a gravitational disturbance, causing either the most massive galaxy or the orphan stars to deviate from their expected orbits, thus resulting in the observed misalignment."

Dr Matthias Kluge, from the Max-Planck institute for Extraterrestrial Physics in Munich, Germany, stated: "This diffuse light is more than 100,000 times fainter than the darkest night sky on Earth. But it is spread over such a large volume that when we add it all up, it accounts for about 20% of the luminosity of the entire cluster."

ESA's Euclid mission is designed to explore the composition and evolution of the dark Universe. The space telescope will create a great map of the large-scale structure of the Universe across space and time by observing billions of galaxies out to 10 billion light-years, across more than a third of the sky. Euclid will explore how the Universe has expanded and how structure has formed over cosmic history, revealing more about the role of gravity and the nature of dark energy and dark matter.

Dr Mireia Montes, an astronomer from the Institute of Astrophysics on the Canary Islands involved in the study said, “This work was only possible thanks to Euclid’s sensitivity and sharpness”. Euclid’s revolutionary design means that it can take images with similar sharpness as the Hubble Space Telescope, but covering an area that is 175 times larger.


Story credits

More information is available from Professor Nina Hatch on

This research has been submitted to the journal of Astronomy and Astrophysics and is published on the preprint website

For more information about the Euclid mission in the UK visit:

About the Leverhulme Trust

Since its foundation in 1925, the Leverhulme Trust has provided grants and scholarships for research and education, funding research projects, fellowships, studentships, bursaries and prizes; it operates across all academic disciplines, the intention being to support talented individuals as they realise their personal vision in research and professional training. Today, it is one of the largest all-subject providers of research funding in the UK, distributing approximately £120 million a year. / @LeverhulmeTrust

Jane Icke - Media Relations Manager Science
Phone: 0115 7486462

Notes to editors:

About the University of Nottingham

Ranked 32 in Europe and 16th in the UK by the QS World University Rankings: Europe 2024, the University of Nottingham is a founding member of the Russell Group of research-intensive universities. Studying at the University of Nottingham is a life-changing experience, and we pride ourselves on unlocking the potential of our students. We have a pioneering spirit, expressed in the vision of our founder Sir Jesse Boot, which has seen us lead the way in establishing campuses in China and Malaysia - part of a globally connected network of education, research and industrial engagement.

Nottingham was crowned Sports University of the Year by The Times and Sunday Times Good University Guide 2024 – the third time it has been given the honour since 2018 – and by the Daily Mail University Guide 2024.

The university is among the best universities in the UK for the strength of our research, positioned seventh for research power in the UK according to REF 2021. The birthplace of discoveries such as MRI and ibuprofen, our innovations transform lives and tackle global problems such as sustainable food supplies, ending modern slavery, developing greener transport, and reducing reliance on fossil fuels.

The university is a major employer and industry partner - locally and globally - and our graduates are the second most targeted by the UK's top employers, according to The Graduate Market in 2022 report by High Fliers Research.

We lead the Universities for Nottingham initiative, in partnership with Nottingham Trent University, a pioneering collaboration between the city’s two world-class institutions to improve levels of prosperity, opportunity, sustainability, health and wellbeing for residents in the city and region we are proud to call home.

More news…

Media Relations - External Relations

The University of Nottingham
YANG Fujia Building
Jubilee Campus
Wollaton Road
Nottingham, NG8 1BB

telephone: +44 (0) 115 951 5798