The HR 4796A, Fomalhaut, & HD 32297 Narrow Planet-Building Ring Systems. Lisse, Sitko, Marengo+ AJ 154, 182L (2017) Keck/NIRSPEC 2.1 µm HR 4796A GPi 2 µm Perrin+ 2015 Fomalhaut MacGregor+ 2017 HD 32297 Currie+ 2012 A0.5V, Age ~ 10 Myr L* ~23 LSun MRing > 0.9 Mearth RRing ~ 75 AU TRing ~ 100 K No Circumstellar gas A2V, Age ~ 400 Myr L* ~ 17 LSun MRing ~ 3 Mearth RRing ~ 130 AU Tring ~ 80 K CO gas from Comets A4V, Age ~ 30 Myr L* ~ 15 LSun MRing > 1.1 Mearth RRing ~ 110 AU Tring ~ 80 K CO gas from Comets

Near-IR Disk Survey (NIRDS) 60+ Systems Observed, 100+ hrs, 0.8 – 5.0 µm R = 1000 - 2000, ~1% Precision Spectroscopy from the 3m NASA/IRTF/SpeX Instrument atop Mauna Kea, Hawai‘i.

Lisse, Sitko, Marengo+, AJ 2017 HR4796A Stands Out as Having an Red Excess Spectrum GPI 2um, Perrin et al. 2015   Lisse, Sitko, Marengo+, AJ 2017

HR4796A Ring Reflectivity 3.2-3.5 µm Organics? Tholins? 2.3 µm CO? HR 4796A 2 µm Polarized GPI, Perrin et al. 2015   3.2-3.5 µm Organics? Tholins? 2.3 µm CO? HK "Flattening"

Only Active Solar System Comets at T ≥ 100K Are This Red 67P/C-G Quirico et al. 2015 COMET NUCLEI 124P/Mrkos C/LONEOS 2001 OG108 67P/C-G 2.39 um Absorption? KUIPER BELT 19P/Borrelly Small End 5145 Pholus H2O Ice? H2O Ice 5145 Pholus 67P/C-G CENTAURS & TROJANS 624 Hektor 10199 Chariklo 2060 Chiron H2O Ice Jewitt & Luu 2004

How Do We Know the HR4796A Ring is Full of Burnt Out Comet Material? The Only Outer Solar System Objects as Red as the HR4796A Ring are Evolved Comet Nuclei The Run of Brightness Around the Ring Can Be Modeled by Comet Dust Scattering The Temperature of the Ring Dust is 100K, Where Comets Become Active in our Solar System and Lose Their Ices No Comet-Produced Gas is Seen in the System by ALMA, as Predicted

Excess No Excess HD 32297’s Ring is Not Red!

By Contrast, the Fomalhaut and HD 32297 Rings are Full of Icy Comets The Run of Brightness Around the Ring Can Be Modeled by Comet Dust Scattering The Temperature of the Ring Dust is 70-80K, Where Comets are Inactive and Stable in our Solar System The Ring Dust is Blue and Icy Low Amounts of CO Comet-Produced Gas is Seen in these Systems by ALMA, as We Predicted

X What is HR4796A Doing? What are Fomalhaut and HD 32297 Doing? Red dust w/ no circumstellar gas ring => Thick localized dust cloud creation from burnt-out comets Multi-Earth scale ring mass Very narrow, confined ring in 10Myr system! => Multiple sheparding co-orbiting bodies Recipe for Carbon-rich SuperEarth formation What are Fomalhaut and HD 32297 Doing? Blue/grey dust ring containing cometary CO => Thick localized dust cloud creation from icy comets Multi-Earth scale ring mass Very narrow, confined ring! => Multiple sheparding co-orbiting bodies Recipe for Gas-poor mini-Neptune formation

Backup Slides

Older YSOs & Transition Disks Easily Detectable From NIR Flat Continua + CO Emission Lisse+ 2018 <= “Flat” Continuum => CO (2-0) CO (1-0)

Exo-Asteroids: Warm Dust in Debris Disks ~125 Myr Data = Red, Green, Blue Model Photosphere = Yellow, Black ~80 Myr > 2 Gyr ~12 Myr ~10 Myr 10-100* Myr ~12 Myr Dore+2016, Lisse+2018