An international research team, including Marcin Wesołowski, D.Sc., Associate Professor at the University of Rzeszów, from the Institute of Physical Sciences, University of Rzeszów, has published findings that provide new insights into the mechanisms responsible for cometary outbursts. The study, entitled "Long-term Outburst Activity of Comet 17P/Holmes and Constraints on Ejecta Size Distributions," has been published in the prestigious Monthly Notices of the Royal Astronomical Society (MNRAS), one of the world's leading journals in astronomy and astrophysics.

The publication is the result of a successful international collaboration involving researchers from leading European institutions specializing in Solar System studies, the dynamics of small bodies, and meteor science.

 The research focused on comet 17P/Holmes, renowned for one of the most spectacular cometary outbursts ever recorded in modern astronomy. In 2007, the comet experienced an unexpected outburst, brightening by an extraordinary Δm = –14 magnitudes within just 42 hours. The resulting gas-and-dust coma expanded to a size exceeding the diameter of the Sun, making it the largest object in the Solar System visible to the naked eye at the time. The research team investigated variations in the comet's brightness associated with its outburst activity over the period 1892–2021. By combining historical records with modern observational data, the researchers were able to determine the size distribution of particles ejected during these events and estimate their total number and mass. The results demonstrate that the brightness of a cometary outburst is governed primarily by the number of particles released and their size distribution, rather than solely by the total mass of the ejected material. These findings provide important new insights into cometary physics and the processes responsible for the formation of meteoroid streams and interplanetary dust. They also enable the development of more realistic models of the evolution of dust clouds produced by cometary outbursts, thereby improving both theoretical studies and the interpretation of future astronomical observations.

The publication in Monthly Notices of the Royal Astronomical Society further confirms the high scientific quality of the research. For decades, MNRAS has ranked among the world's most influential journals in astronomy, publishing groundbreaking studies in cosmology, astrophysics, and Solar System science.

The article also exemplifies the growing internationalization of research conducted at the Institute of Physical Sciences, University of Rzeszów. By bringing together expertise from researchers representing different countries and scientific disciplines, the collaboration enabled a comprehensive analysis of more than a century of observations of comet 17P/Holmes and established new constraints on the properties of material ejected during cometary outbursts. The findings contribute to a deeper understanding of the processes shaping the Solar System's dust environment and represent an important step forward in studies of the evolution of small bodies in the Solar System.

Publication:
Maria Gritsevich, Marcin Wesołowski, Josep M. Trigo-Rodríguez, Alberto J. Castro-Tirado, Jorma Ryske, Markku Nissinen, Peter Carson, Long-term outburst activity of comet 17P/Holmes and constraints on ejecta size distributions, Monthly Notices of the Royal Astronomical Society, Volume 549, Issue 2, June 2026, stag571, DOI: 10.1093/mnras/stag571