1. YSOs: Young Stellar Objects Provide evidence for planet-forming nebular disks around stars Dusty cocoon surrounding YSO

2. Different types of YSOs: 1) IR stars 2) Proplyds 3) Herbig-Haro objects 4) T-Tauri stars 5) Beta Pictoris systems Range from protostars to newly-formed stars

3. IR stars: infrared protostars show excess emission in IR compared to visible wavelengths explained by dust cocoons surrounding protostar these cocoons obscure the visible light from the central star-like object, but are warmed by that visible light and so radiate in the IR

4. visible light imageIR light image mosaic IR stars in Orion

5. IR star DC303.8-14.2 visible light (700 nm), showing dust IR light (1.65 um), showing ring of warmed dust around embedded IR star IR light (2.17 um), showing inner clumps (shocked gas?)

6. Proplyds: protoplanetary disks dusty cocoons seen around YSOs first seen clearly in the Orion Nebula

7. Proplyd with evidence for infalling matter (nebular disk shocks) Disk ~800 AU across Pattern of methanol emission can be explained by clumpy accretion onto surface of disk

8. Herbig-Haro Objects: YSOs with disks & bipolar outflows

9. Bipolar jet

10. T-Tauri star: catchall term for many types of YSOs YSO has not yet ignited H; it follows Hayashi track in luminosity & temperature YSO can show evidence for rapid rotation, strong magnetic field, strong stellar winds, short-lived brightness spikes (FU-Orionis outbursts), excess IR emission H-R diagram showing Hayashi track (4-7) and Main Sequence trend (grey band) http://www.go.ednet.ns.ca/~larry/stars/prtostar.html

11. Beta Pictoris-type system: newly-formed star that still has a surrounding dust disk YSO has achieved H to He fusion and falls on Main Sequence trend dust disk soon to be destroyed, either by: stellar winds (material blown out of system) or movement to star (e.g., via Poynting-Robertson effect)

12. colors represent light intensities waves in disk probably caused by interaction with planets Dust disk around Beta Pictoris seen edge on