AWhat changed
After four images of supernova Refsdal were observed in 2014 behind galaxy cluster MACS J1149.5+2223, five modeling teams used existing imaging and spectroscopy to construct seven lens models and predicted an additional image. Hubble observations on 11 December 2015 revealed a new source at the predicted location, interpreted as that fifth image. Its early brightness and timing allowed a blind comparison with prior lens-model predictions. A later blinded analysis of the extended light curves reported an SX–S1 delay of 376.0 days with a 16th–84th percentile interval of approximately −5.5 to +5.6 days, using a weighted combination of four fitting methods.
Scientific scope
After four images of supernova Refsdal were observed in 2014 behind galaxy cluster MACS J1149.5+2223, five modeling teams used existing imaging and spectroscopy to construct seven lens models and predicted an additional image. Hubble observations on 11 December 2015 revealed a new source at the predicted location, interpreted as that fifth image. Its early brightness and timing allowed a blind comparison with prior lens-model predictions. A later blinded analysis of the extended light curves reported an SX–S1 delay of 376.0 days with a 16th–84th percentile interval of approximately −5.5 to +5.6 days, using a weighted combination of four fitting methods. This is a later image of the same explosion, not a new explosion. The seven forecasts share observational inputs and are not seven independent confirmations. In the October 2015 forecast most models predicted the peak in the first quarter of 2016; the December detection is an appearance, not the date of the peak. The early light curve constrains time delay and magnification jointly; full light-curve fitting and systematic errors including mass-sheet degeneracy and line-of-sight structure remained open. The pre-observation forecast and subsequent observation have distinct source-specific bylines. The later delay and its uncertainty depend on light-curve models, simulation-calibrated method weights and microlensing assumptions; a companion Hubble-constant inference is a separate analysis. In the v1 corner-plot figure, some short-delay labels differ from the primary delay table and figure; those values need reconciliation and are not exported.
Evidence
The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. This is a later image of the same explosion, not a new explosion. The seven forecasts share observational inputs and are not seven independent confirmations. In the October 2015 forecast most models predicted the peak in the first quarter of 2016; the December detection is an appearance, not the date of the peak. The early light curve constrains time delay and magnification jointly; full light-curve fitting and systematic errors including mass-sheet degeneracy and line-of-sight structure remained open. The pre-observation forecast and subsequent observation have distinct source-specific bylines. The later delay and its uncertainty depend on light-curve models, simulation-calibrated method weights and microlensing assumptions; a companion Hubble-constant inference is a separate analysis. In the v1 corner-plot figure, some short-delay labels differ from the primary delay table and figure; those values need reconciliation and are not exported.
Contributors
- The named authors in the research record · SCIENCE: These are the listed authors of the cited contribution sources. Paper authorship does not quantify individual effort. An incomplete list is explicitly marked; same names are not automatically merged.
- Déjà Vu All Over Again: The Reappearance of Supernova Refsdal
- Refsdal meets Popper: comparing predictions of the re-appearance of the multiply imaged supernova behind MACSJ1149.5+2223
- The Magnificent Five Images of Supernova Refsdal: Time Delay and Magnification Measurements
Provisional WRS assessment, edition 2026-10-28.1. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.
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