Colloquium: The Fiery Seeds of Planet Formation

Date: January 27, 2017
Time: 3:00 pm – 4:15 pm

Location: Exploratory Hall L003 (Google map)

Featured Speaker:
Joel Green
Space Telescope Science Institute

Abstract:
When a new planetary system forms around a young star, we usually think of the process as a gradual (thousands to millions of years) buildup of material from tiny dust grains to planetessimals.  But is the process of star and planet formation a slow and steady one, or are there bumps in the road to planet construction? Does this leave a measurable signature that we could find if it happened here in our own Solar System 4.6 billion year ago?

In 1936, the young star FU Orionis (FU Ori) became 100 times brighter in only a few short months. FU Ori was undergoing a “burst” of accretion from its own planet-forming disk cascading onto the star itself — and nearly 20 Jupiter masses of gas have accreted in during the past 80 years. This sustained flow is a large fraction of the entire measureable disk mass (both gas and dust) surrounding FU Ori. What changes did this increased brightness wreak upon FU Ori’s disk, and what implications would it have for any planets that might have formed or form later? Unlike most observed young stars, FU Ori and its (~ 10) brethren with similar behavior show no evidence of crystalline dust grains like forsterite (peridot), and the temperatures at ~ 1 AU distance would have risen to a scalding 1000 degrees Kelvin. Thus we would expect significant chemical changes that could lead to long term grain segregation, grain processing and circulation. By comparing with a 12 year previous Spitzer/IRS study, we used SOFIA/FORCAST to investigate both the instantaneous changes in the disk of FU Ori, and observe the evolution of the disk through the burst.  We present  the first multi-epoch infrared spectroscopic study of an FUor, as it appeared in 2004 and 2016, and see what changes the fading heat has left on disk chemistry.

The James Webb Space Telescope (JWST), NASA’s next great observatory launching in October 2018, will be a perfect tool to follow the evolution of disks like FU Ori.  A hundred times more sensitive than Spitzer, with 50 times the spatial resolution, JWST will revolutionize our understanding of planet formation. How will we maintain the prestige and cultural impact of Hubble as the torch passes to Webb?  And can they work together even more directly, in 3D?

Refreshments will be served.