Milky way diameter: 40 kpc (120,000 light years) Microlensing planets: 5 kpc Kepler planets: 2 kpc Imaged planets: 0.2 kpc Credit: Exoplanet app Planet detection remains difficult at large distances, and characterization even more so
Why studying protoplanetary disks is important for understanding habitability Planet formation laboratory – ground truth for our ideas about how planets form and habitability develops Understanding formation process allows us to extrapolate to the rest of the galaxy/universe
Overview of what we do and dont know about protoplanetary disks Current studies of development of Goldilocks properties: – Location – Planet size and type – Chemistry
Composed of gas and (opaque) dust, Few 100 AU in size CO velocity in HD 163296 (ALMA) de Gregorio-Monsalvo et al. 2013 Opaque disks in Orion (Hubble) 1800 AU
Small (but evolved) dust, consistent with olivine composition Spitzer spectra of Si-O stretch Chondrule from American Museum of Natural History meteorite collection Kessler-Silacci et al. 2006 Data Models
Small (but evolved) dust, consistent with olivine composition Chondrule from American Museum of Natural History meteorite collection Spitzer spectra of Si-O stretch Kessler-Silacci et al. 2006 Data Models
Protoplanetary disks are ubiquitous* Kraus & Ireland, 2011 *around sun-like stars in nearby star-forming regions
Protoplanetary disks last a few Myr Kraus & Ireland, 2011
Masses are consistent with Minimum Mass Solar Nebula, or slightly lower Ophiuchus data from Andrews et al. 2007
Masses are consistent with Minimum Mass Solar Nebula, or slightly lower Ophiuchus data from Andrews et al. 2007 small
Planet size and location: Snow lines and disk dispersal Chemistry: Chemical inventories of planet forming regions Active research related to habitability
What processes determine planetary size and location?
Gas giants Terrestrial planets What processes determine planetary size and location?
Gas giants Terrestrial planets The snow line – an increase in solid surface density
What is the expected location of the snow line?
Gas giants Terrestrial planets The snow line Habitable zone
Multi-wavelength observations of water vapor measure snow line locations ice line K. Pontoppidan
First measured locations of snow lines in disks Meijerink+ 2009 Zhang+ 2013
First measured locations of snow lines in disks Meijerink+ 2009 Zhang+ 2013 See poster by Sandra Blevins for an update!
Gas giants Terrestrial planets Ice giants (super Earths?) Planet type affected by disk dispersal
Dispersal of disk gas also affects planet migration Snapshot of disk surface density with planet undergoing migration P. Armitage 1 10 100 # of planets Orbital Period [days] Hot Jupiters
How do disks evolve/disperse? Disk winds Blandford & Payne 1982 Pudritz & Norman 1983 Cartoon inspired by Bai et al. 2013 B wind accretion
Molecular emission lineshapes and images – evidence for disk winds? Pontoppidan+ 2009; also Bast+ 2011 Flux Velocity ALMA CO velocity field Salyk+ in prep Brown+ 2013 Vibrational CO
How do disks evolve/disperse? Photoevaporative winds wind FUV EUV X-ray
How do disks evolve/disperse? Photoevaporative winds wind FUV EUV X-ray ? Main open question: How quickly do disks dissipate at each disk radius?
Observations of photoevaporation tracers measure location and mass-loss [Ne II] emission from two disks + models Pascucci & Sterzik 2009
Chemistry: Chemical inventories of planet forming regions
Solar data from Grevesse et al. 2010 Chondrite data from Allegre et al. 2001 CI chondrite abundances vs. solar abundances (R ~ 4 AU)
Earth abundances vs. solar abundances (R = 1 AU) Solar data from Grevesse et al. 2010 Chondrite data from Allegre et al. 2001
N 2, HCN, NH 3, organics ? CO, CO 2, organics, graphite? Earth abundances vs. solar abundances (R = 1 AU) Solar data from Grevesse et al. 2010 Chondrite data from Allegre et al. 2001
What is the correct chemical pathway? Inheritance or reset? Maximum reset Maximum Inheritance
Resemblance between cometary and cloud ice compositions = an inheritance assumption Data from Mumma & Charnley 2011 (and references therein) Cometary abundance % relative to water Cloud abundance % relative to water
Evidence for reset in the solar system: CAIs and chondrules Chondrule Calcium Aluminum-rich Inclusion (CAI) Thin sections from the American Museum of Natural History meteorite collection
Carr & Najita 2008 Also, Salyk+ 2008 The study of chemistry in inner disks was enabled by the Spitzer InfraRed Spectrograph (IRS)
O,C,N inventory in inner disks is being measured Pontoppidan+ 2014 O C N Fraction
Evidence for reset in disks: O,C,N inventory different from birth cloud Salyk et al. 2011; Öberg et al. 2011
Evidence for reset in disks: Variability in disk chemistry Banzatti et al. 2012 See poster by Andrea Banzatti
Current: Partial chemical inventory, evidence for reset Yet to come: Chemical differences between disks, and as a function of radius
Basic protoplanetary disk properties have been characterized Studies of development of Goldilocks properties ongoing: – Location – Planet size and type – Chemistry Conclusions Measuring snow lines Observing disk evolution/dispersal Chemical inventory in planet-forming regions, evidence for reset, details yet to come Questions about observing disks?