space Cosmic Scale

A comet exploded in 2007 and briefly created a dust cloud that was actually bigger than the Sun.

March 19, 2026

Original Paper

Long-term outburst activity of comet 17P/Holmes and constraints on ejecta size distributions

Maria Gritsevich, Marcin Wesołowski, Josep M. Trigo-Rodríguez, Alberto J. Castro-Tirado, Jorma Ryske, Markku Nissinen, Peter Carson

arXiv · 2603.17130

The Takeaway

In 2007, Comet Holmes unexpectedly brightened by half a million times in just two days, becoming the largest object in the solar system to the naked eye. This research analyzes the outburst to explain how a tiny frozen rock could undergo such a violent 'mega-outburst' and eject enough mass to rival the scale of a star.

From the abstract

A quantitative understanding of cometary outbursts requires robust constraints on the size distribution of ejected particles, which governs outburst dynamics and underpins estimates of released gas and dust. In the absence of direct measurements of particle sizes, assumptions about the size distribution play a central role in modelling dust-trail formation, their dynamical evolution and observability, and the potential production of meteor showers following encounters with Earth. We analyse brig