The difference comes from what each telescope can see. Roman will observe near-infrared light, which cosmic expansion stretches from distant events into longer wavelengths; the report says it is optimized for tidal disruption event light that has traveled 8 billion to 11 billion years to reach us. Rubin will scan broad areas in visible light, limiting it to closer events. [S1]
A tidal disruption event occurs when a lighter supermassive black hole tears apart and consumes a star. The resulting beacon can brighten over a couple of weeks and then fade. By counting these events across redshift, astronomers could constrain the population of million-solar-mass black holes and test competing origin scenarios: lighter “seeds” formed from massive stars, or heavier seeds formed through processes such as direct gas-cloud collapse. [S1]
These figures are research-team forecasts based on simulations, not detections: the report says Roman may find up to 100 events per year, while Rubin may detect thousands to tens of thousands. Roman’s smaller predicted tally is aimed at a different slice of cosmic history—one the researchers consider especially useful for distinguishing black-hole origins. [S1]
Source documents
- NASA’s Roman Telescope Will Spot Distant Black Holes That Shred Starshttps://www.nasa.gov/missions/roman-space-telescope/nasas-roman-telescope-will-spot-distant-black-holes-that-shred-stars/