YSOs: Young Stellar Objects Provide evidence for planet-forming nebular disks around stars Dusty...
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Transcript of YSOs: Young Stellar Objects Provide evidence for planet-forming nebular disks around stars Dusty...
YSOs: Young Stellar Objects
Provide evidence for planet-formingnebular disks around stars
Dusty cocoon surrounding YSO
Different types of YSOs:
1) IR stars2) Proplyds3) Herbig-Haro objects4) T-Tauri stars5) Beta Pictoris systems
Range from protostarsto newly-formed stars
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
visible light image IR light image mosaic
IR stars in Orion
IR star DC303.8-14.2
visible light (700 nm),showing dust
IR light (1.65 um), showingring of warmed dust aroundembedded IR star
IR light (2.17 um), showing inner clumps(shocked gas?)
Proplyds: protoplanetary disks
• dusty cocoons seen around YSOs• first seen clearly in the Orion Nebula
Proplyd with evidence for infalling matter (nebular disk shocks)
Disk ~800 AU across
Pattern of methanolemission can be explainedby clumpy accretion ontosurface of disk
Herbig-HaroObjects:
• YSOs withdisks & bipolaroutflows
Bipolar jet
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 Hayashitrack (4-7) and Main Sequence trend(grey band)
http://www.go.ednet.ns.ca/~larry/stars/prtostar.html
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)
colors represent light intensities
waves in disk probably caused by interaction with planets
Dust disk around Beta Pictoris seen edge on