arXiv:1706.10279astro-ph.GA
Extreme magnification of a star at redshift 1.5 by a galaxy-cluster lens
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Abstract
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.
This line from the article is wrong: > Over nine billion light-years away. With a redshift of z=1.49, the light from SN Refsdal was emitted 9.34 billion years ago, but the proper distance at the current time (a/k/a the co-moving distance) is 14.4 Gly due to the metric expansion…
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