"Refsdal" meets Popper: comparing predictions of the re-appearance of
  the multiply imaged supernova behind MACSJ1149.5+2223
  Supernova "Refsdal," multiply imaged by cluster MACSJ1149.5+2223, represents
a rare opportunity to make a true blind test of model predictions in
extragalactic astronomy, on a time scale that is short compared to a human
lifetime. In order to take advantage of this event, we produced seven
gravitational lens models with five independent methods, based on Hubble Space
Telescope (HST) Hubble Frontier Field images, along with extensive
spectroscopic follow-up observations by HST, the Very Large and the Keck
Telescopes. We compare the model predictions and show that they agree
reasonably well with the measured time delays and magnification ratios between
the known images, even though these quantities were not used as input. This
agreement is encouraging, considering that the models only provide statistical
uncertainties, and do not include additional sources of uncertainties such as
structure along the line of sight, cosmology, and the mass sheet degeneracy. We
then present the model predictions for the other appearances of SN "Refsdal." A
future image will reach its peak in the first half of 2016, while another image
appeared between 1994 and 2004. The past image would have been too faint to be
detected in existing archival images. The future image should be approximately
one third as bright as the brightest known image (i.e., H_AB~25.7 mag at peak
and H_AB~26.7 mag six months before peak), and thus detectable in single-orbit
HST images. We will find out soon whether our predictions are correct.
