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CATEGORIES:Exoplanet Seminars
SUMMARY:Chemistry and evolution of the oldest white dwarf 
 planetary systems - Mark Hollands (Warwick)
DTSTART;TZID=Europe/London:20161102T160000
DTEND;TZID=Europe/London:20161102T170000
UID:TALK67928AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/67928
DESCRIPTION:Almost all main-sequence stars\, including the Sun
 \, will eventually become white dwarfs.\nDuring th
 e giant-stages of the stellar evolution\, planetar
 y objects within about 1 AU will be engulfed\,\nwh
 ile those further out will survive to the white dw
 arf stage.\nRocky-planetesimals (i.e. asteroids/mi
 nor planets) that are accreted onto the central de
 generate-star\,\nlead to white dwarf atmospheres e
 nriched with metals\, rather than the pure hydroge
 n/helium\ncomposition expected from gravitational 
 settling of elements.\nThe spectra of these "metal
 -polluted" white dwarfs therefore provide a unique
  tool\nfor analysing the bulk compositions of rock
 y material outside of the Solar-system.\n\nUsing S
 DSS spectra\, we have identified 231 white dwarfs 
 that are both old (cooling ages 1--8 Gyr)\,\nand h
 ave atmospheres rich in metallic elements. Abundan
 ce analyses of the spectra\nreveal wide ranging co
 mpositions from crust-like to core-like\,\nwith th
 e most extreme cases indicating highly differentia
 ted planetesimals.\nAdditionally\, the old ages of
  the systems we identify have allowed us to probe\
 nremnant planetary system evolution.\nWe find comp
 elling evidence that white dwarfs deplete their pl
 anetesimal reservoirs on a\n~1 Gyr e-folding times
 cale\, an effect not seen in other studies which h
 ave predominantly\nfocussed on much younger white 
 dwarfs.
LOCATION:Martin Ryle Seminar Room\, Kavli Institute
CONTACT:Ed Gillen
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