Lecturer: Dr. Yossi Shvartzvald Affiliation: Tel Aviv University Abstract: The discovery of thousands of extrasolar planets ranks among the most exciting scientific developments of the past decade. Among the techniques currently used to discover extrasolar planets, microlensing has some unique capabilities. It is the most sensitive technique to detect planets beyond the "snowline", where gas and ice giants are likely to form. Over the past four years, we have carried out a "second generation" microlensing survey, combining OGLE, MOA, and the Wise observatory. I will present a statistical analysis for the first four seasons of the survey. Over 15% of the events that were observed by all three sites showed a deviation from a single-lens microlensing, and for ~1/4 of those the anomaly might be explained by a planetary companion. By accounting for our detection efficiency, we find a ~40% planetary system abundance. Moreover, we find that Neptunes-mass planets are ~4 times more common than Jupiter-mass planets. The companion to host-mass ratio distribution shows a deficit at q~0.01, dividing the distribution into two populations, analogous to the binary and planet populations that are divided by the ``brown dwarf desert'' seen in radial-velocity surveys. Additional details of the upcoming Astrophysics' seminars can be found on the following link. ‏האירוע הזה כולל שיחת וידאו ב-Google Hangouts. הצטרף: https://hangouts.google.com/hangouts/_/mail.huji.ac.il/astrophysics?hceid=bWFpbC5odWppLmFjLmlsX2c0czhydDlpcmhwZzRvdGNybWIzZGFqcjdvQGdyb3VwLmNhbGVuZGFyLmdvb2dsZS5jb20.mtan3c0j7odjfik7tbhhkc359s&hs=121