File: 6 October 2026 · Source date: September 23, 2026 · NASA Hubble
Why might the same event appear again?
NASA is viewing gravitationally lensed images of Supernova Athena behind the MACS J0417 cluster. Because the mass of the cluster warps space-time, light from the supernova can take different paths. When path lengths and gravitational delays are different, images of the same explosion may reach us at different times.
The promise of measurement
Examining the reemergence time and the lens model together may provide an independent method of testing the expansion rate of the universe. But NASA's announcement describes a monitoring program and forecast; A new and precise Hubble constant does not yet explain the result.
Why is the model needed?
To interpret the delay, the distribution of visible and invisible mass in the galaxy cluster is modeled. The same data may give different limits with different model assumptions. Therefore, the image, delay and mass model must be evaluated together.
discussion question
If two independent methods measure the same cosmological quantity differently, would you examine the data, the model, or the uncertainty calculation first? Justify your ranking.
Resources and further reading
NASA Hubble — Lensed supernova and the 200,000th orbit ↗Share your answer
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