The Vera C. Rubin Observatory, even before beginning full science operations, has captured an unprecedented image of a massive stellar stream trailing behind the galaxy Messier 61 (M61). This discovery, revealed in June, demonstrates the observatory’s unique ability to detect faint, low-surface-brightness structures previously hidden from view. The stream stretches roughly 50 kiloparsecs (163,000 light-years) – comparable to the diameter of our Milky Way – making it one of the longest known stellar streams.
Discovery Details
The stellar stream was found in a deep-field image of the Virgo cluster, the closest major galaxy cluster to our own. M61, a well-studied barred spiral galaxy, appears to be the source of this structure. The stream consists of stars torn apart by M61’s gravity, likely remnants of a dwarf galaxy consumed by the larger spiral.
Significance of the Discovery
This finding is significant for several reasons:
- Galactic Cannibalism: The stream provides further evidence that large galaxies grow by consuming smaller ones. This process, known as galactic cannibalism, is thought to be a common mechanism in the universe.
- Starburst Trigger: The breakup of the dwarf galaxy may have triggered a starburst in M61, a period of rapid star formation that began around 10 million years ago. This connection between galactic mergers and star formation is a key area of research in astrophysics.
- Observational Breakthrough: The discovery highlights the power of the Rubin Observatory’s advanced imaging capabilities. Its ability to detect faint structures opens up new avenues for studying galactic evolution.
Comparison to the Sagittarius Stream
The newly discovered stream bears similarities to the Sagittarius Stream, a long, looping structure that encircles the Milky Way. The Sagittarius Stream originated from the Sagittarius Dwarf Elliptical Galaxy, which has been gradually disrupted by the Milky Way’s gravity. Both streams demonstrate how tidal forces can stretch and distort galaxies over time.
Future Implications
The Rubin Observatory is embarking on its 10-year Legacy Survey of Space and Time (LSST), which will create a high-definition time-lapse record of the universe. This survey is expected to reveal many more hidden structures around galaxies, providing a wealth of data for astronomers studying galactic evolution.
The authors of the study, uploaded to arXiv on October 28, wrote that this discovery is just the beginning. They expect to find “a treasure trove of substructures” around other galaxies with future Rubin data. This suggests that galactic cannibalism may be even more common than previously thought, and that the universe is filled with the remnants of past mergers
