Extreme magnification of a star at redshift 1.5 by a galaxy-cluster lens
  Galaxy-cluster gravitational lenses can magnify background galaxies by a
total factor of up to ~50. Here we report an image of an individual star at
redshift z=1.49 (dubbed "MACS J1149 Lensed Star 1 (LS1)") magnified by >2000. A
separate image, detected briefly 0.26 arcseconds from LS1, is likely a
counterimage of the first star demagnified for multiple years by a >~3
solar-mass object in the cluster. For reasonable assumptions about the lensing
system, microlensing fluctuations in the stars' light curves can yield evidence
about the mass function of intracluster stars and compact objects, including
binary fractions and specific stellar evolution and supernova models.
Dark-matter subhalos or massive compact objects may help to account for the two
images' long-term brightness ratio.
