The Lifetime of

Dust Disks

Lynne Hillenbrand. . . . . . . . . . .

Caltech

Star and planet formation/evolution

Cloud collapse

104 yr

Planetary system

109 yr

105 yr

100 AU

107 yr

Tstar (K)

Lstar

Main sequence

8,000 5,000

10

1

2,000

Disk/wind

Planet building

[Beckwith & Sargent 1996]

Before/during/afterprotostellar collapse

[Alves, Lada, Lada]

[B68]

[Padgett et al.]

[McCaughrean et al.; Stauffer et al.]

[04302+2247]

[ONC “proplyd”]

Not so much later: Debris disks

What is the difference between “primordial” and “debris” disks?

Primordial Debris

[Dullemond and Pontoppidian]

Spitzer legacy science:The formation and evolution of planetary systems

• Birth of planetary embryos:

Characterize transition from

primordial to debris dust disks.

• Growth of gas giant planets:

Constrain time scale for gas

disk dissipation.

• Mature solar system evolution:

Examine diversity of planetary

systems based on debris disks.

PO

ST A

CC

RE

TIO

ND

EB

RIS

DIK

S

ice

gian

t for

mat

ion

3 Myr – 3 Gyr

Evolution of our own dust disk in time

Model spectral energy distribution

Is our solar system

common

or

u n i q u e ?

[D. Backman]

Circumstellar disk and SED

In an observed SED, each wavelength traces a distinct temperature, and different temperatures correspond to different radii in disk (cooler at larger radii).

NIR MID FIR sub-m

0.1 1.0 10.0 – 40.0 100 AU

Temperature

1 10 100

Young (< 30 Myr) disks

NIR – MID

0.1 – <1.0 AU

A Spitzer instrument to detect these disks: IRAC (3.6 m, 4.5 m, 8.0 m)

Warm disks

MIR FIR

10.0 – 40.0

A Spitzer instrument to detect these disks: IRS (10 – 35 m)

Cold outer disks

FIR

~20 – 100 AU

A Spitzer Instrument to detectthese disks: MIPS (24 – 160 m)

Constraints on planet-formation time scales

Inner disk dissipationData suggest <3–10 Myr as maximum accretion disk lifetime. Typical lifetime for material at <0.1 AU is <3 Myr.

Mid-disk dissipationMaximum disk lifetime for terrestrial planet material at 1 AU is also <10 Myr. Compare with meteoritic evidence suggesting Earth formed in <10 Myr with moon-forming impact occurring at 30 Myr.

Outer disk dissipation and re-generationPrimordial disk lifetimes as yet unconstrained. Debris disk lifetimes consistent with expectations from self-sustaining collisional cascade.