Zusammenfassung
Galaxy-cluster gravitational lenses can magnify background galaxies by a
factor of up to ~50. An individual well-aligned background star, however, could
potentially become much more highly magnified. Here we report an image of a
star (dubbed "MACS J1149 Lensed Star 1 (LS1)") at redshift z=1.49 magnified by
>2000. We measure fluctuations in the star's flux arising from microlensing by
intracluster stars and compact objects, whose effective Einstein radii should
become exaggerated by a factor of ~100 by the cluster's potential. LS1's light
curve is sensitive to the mass function of intracluster stars and compact
objects and provides evidence about binary fractions as well as specific
stellar evolution and supernova models, and against a high abundance of ~30
solar-mass primordial black holes. A second event, separated by 0.26" from LS1,
likely corresponds to LS1's counterimage demagnified for multiple years by a ~3
solar-mass object in the cluster. Additional monitoring should test the
hypothesis that dark matter consists of extremely light bosons.
Nutzer