Astronomers have just discovered a stellar stream as long as the Milky Way

Since June 2025, the Vera C. Rubin Observatory has found many galaxies, some of which have never been studied before. And recently, astronomers have discovered a stellar stream measuring about 163,000 light-years in the galaxy Messier 61.

It is in a study published on arXiv that this discovery was mentioned, and it is surprising. It must be said that M61, which is about 47 million light-years from Earth, has already been studied by astronomers, but this stellar stream has never been observed before. 

Regarding the origin of this structure, many questions remain unanswered. But according to the authors of this study, it appears that due to its gravity, M61 may have shredded a dwarf galaxy several billion years ago. This would have given birth to many stars, which then scattered around this galaxy. However, the size of this stellar stream is colossal, and it could have been caused by an extremely violent collision.

But while this discovery is incredible, new observations will be conducted in the coming weeks and months, as the authors of this study point out: 

"It is remarkable that the stream went long unnoticed around a Messier galaxy. We expect a treasure trove of substructures to be unveiled around other galaxies with future Rubin data.” 

Thus, new surprises could appear, allowing us to better understand the galaxies and the world around us.