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<TITLE>Two Planetary Talks this Week: Youdin and Holman</TITLE>
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<P><B><FONT FACE="Arial">MONDAY, NOVEMBER 28</FONT></B>
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<P><FONT FACE="Arial">12:30 pm: </FONT><A HREF="http://www.cfa.harvard.edu/ssp/today.shtml"><U><FONT COLOR="#0000FF" FACE="Arial">Solar, Stellar and Planetary Sciences Division Seminar</FONT></U></A><FONT FACE="Arial">. "The Formation of Planetesimals," Dr. Andrew Youdin, Princeton University. Pratt Conference Room. </FONT></P>
<P><I><FONT FACE="Arial">Abstract:</FONT></I><FONT FACE="Arial"> The formation of planetesimals, the first generation of solids greater than a kilometer, will be addressed. Purely collisional growth of planetesimals from mm-sized grains faces several fundamental obstacles. As an appealing alternative, collective instabilities driven by self-gravity might gather small solids. Stirring by turbulence is thought to prevent such gravitational instabilities (GI). We show that when dissipation by gas drag is taken into account, GI persists even in the presence of moderately strong turbulence. Dissipative GI produces growth times and wavelengths longer than traditional dynamical collapse. Applications to meteorites from the asteroid belt and mm-wave observations will be discussed. </FONT></P>
<P><A HREF="http://www.cfa.harvard.edu/cfa/calendar/latest.html"><U><FONT COLOR="#0000FF" FACE="Arial">http://www.cfa.harvard.edu/cfa/calendar/latest.html</FONT></U></A>
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<P><B><FONT FACE="Arial">THURSDAY, DECEMBER 1</FONT></B><FONT FACE="Arial"> </FONT>
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<P><FONT FACE="Arial">4:00 pm: </FONT><A HREF="http://www.cfa.harvard.edu/colloquia/latest.html"><U><FONT COLOR="#0000FF" FACE="Arial">Colloquium</FONT></U></A><FONT FACE="Arial">. "The Use of Transit Timing to Detect Extrasolar Planets," Dr. Matthew Holman, CfA. Preceded by tea at 3:30 pm. Phillips Auditorium. </FONT></P>
<P><A HREF="http://www.cfa.harvard.edu/colloquia/latest.html"><U><FONT COLOR="#0000FF" FACE="Arial">http://www.cfa.harvard.edu/colloquia/latest.html</FONT></U></A>
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