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SUMMARY:Gaia wide binaries challenging a Newtonian prediction - Xavier Her
 nández (IA\, UNAM)
DTSTART:20190522T124500Z
DTEND:20190522T131500Z
UID:TALK122110@talks.cam.ac.uk
CONTACT:Catrina Diener
DESCRIPTION:Under Newtonian dynamics\, the relative motion of the componen
 ts of a binary star should follow a Keplerian scaling with separation. Onc
 e orientation effects and a distribution of ellipticities are accounted fo
 r\, dynamical evolution can be\nmodelled to include the effects of Galacti
 c tides and stellar mass perturbers\,\nover the lifetime of the solar neig
 hbourhood. This furnishes a prediction for the\nrelative velocity between 
 the components of a binary and their projected separation. Taking a carefu
 lly selected small sample of 81 solar neighbourhood wide binaries from the
  Hipparcos catalogue\, we identify these same stars in the recent Gaia DR2
 \, to test the prediction mentioned using the latest and most accurate ast
 rometry available. The results are consistent with the Newtonian predictio
 n for projected separations below 7000 AU\, but inconsistent with it at la
 rger separations\, where accelerations are expected to be lower than the c
 ritical $a_{0}=1.2 \\times 10^{-10} $ { m s$^{-2}$} value of MONDian gravi
 ty. This result challenges Newtonian gravity at low accelerations and show
 s the appearance of gravitational anomalies of the type usually attributed
  to dark matter at galactic scales\, now at much smaller stellar scales.
LOCATION:Sackler Lecture Theatre\, IoA
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