YSOs: Young Stellar Objects

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

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IR stars in Orion
visible light image
IR light image mosaic
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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?)
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• Proplyds protoplanetary disks
• dusty cocoons seen around YSOs
• first seen clearly in the Orion Nebula

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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
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• Herbig-Haro
• Objects
• YSOs with
• disks bipolar
• outflows

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Bipolar jet
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• 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.ht
ml
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• 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)

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