Download Different types of YSOs

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Transcript
Most meteorites formed in the earliest moments
of solar system history
Early solar system consisted of a planetary nebula-dust and gas surrounding protostar and early sun
Chondrites & components clearly formed in nebula.
Differentiated bodies too?
Chondrites & their components
Differentiated bodies
We see evidence for planet-forming
nebular disks around stars
These disks occur around Young
Stellar Objects (YSOs)
Dusty cocoon surrounding YSO
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
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
IR stars in Orion
visible light image
IR light image mosaic
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?)
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 methanol
emission can be explained
by clumpy accretion onto
surface of disk
Herbig-Haro
Objects:
• YSOs with
disks & bipolar
outflows
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 Hayashi
track (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)
• new idea: some Beta Pictoris-type dust disks may be
regenerated by collisions between planets
Dust disk around Beta Pictoris seen edge on
colors represent light intensities
waves in disk probably caused by interaction with planets