The Birth of Stars and Planets in the Orion Nebula

K. Smith

(STScI)

Orion (the hunter)

Why Orion?

• Closest massive star forming region (450pc)

(there are closer low mass star forming regions)

• Relatively young (1Myr)

• Now believed that our Sun started life in such an environment

Giant molecular clouds

Found throughout galactic plane

Are the sites of star formation

Dame et al

Star formation…

Stars form in clusters and groups

NGC 346, SMC

Pleiades

NGC 1850, LMC

Orion + CO

Barnard loop

Rosette Nebula

Orion and surroundings in the visibleNGC 1741

NGC 2022

Witch Head Nebula

IRAS 100 micron image

…and in the far-infrared

Stellar density in Taurus vs. Orion

14.6´ × 15.1´ @140pc = 0.59pc ×0.61pc

7´ × 7´ @450pc = 0.91pc ×0.91pc

Massive stars• Disperse the cloud• Ionise the gas• May disrupt low mass

star disks• Burn out quickly

Hot stars, ionized gas

and dusty nebulae trace

star formation

NGC2024

Horsehead

NGC1976M42

NGC1977

Massive stars• Disperse the cloud• Ionise the gas• May disrupt low mass

star disks• Burn out quickly

Low mass stars• Have disks and accrete

material for several million years

• Launch jets• Form planetary

systems

The current paradigm (Low Mass Objects)

Cloud collapse

104 yr

Disk/wind

105 yr

Planetary system

109 yr107 yr

Low-mass binary

HH 30

Sargent & Beckwith 1987, Ap. J., 323, 294.

13CO 2-1 4.4-5.8 km s-1

1000

AU

HL TauXZ Tau

HH 305000 AU

Mundt et al. 1990, A&A, 232, 37.

SII 6717 Å 3.5m Calar Alto

Disk / jet “standard” model

e.g. Lin et al, 1994, Ap. J., 435, 821.

Ray et al. 1996, Ap. J., 468, L103.

HST images of disks provided "proof"

Disks in the IR (NICMOS/HST)

HK Tau B

C. Koresko, Ap.J.Lett. 1998

Adaptive optics on Keck

Jets

Jets from binaries

Treasury program

104 HST orbits, parallel ACS +WFPC2 +NIC3• ACS: B (420s), V (385s), I (385s), z (385s), Ha (340s)• WFPC-2: U (2400s), B (80s), I (10s), Ha (400s)• NIC-3: J (5256s), H (4192s)

2 Orientations• 100° (35 orbits, Fall 2004) • 280° (69 orbits, Spring 2005)

Precise tiling pattern allows for full coverage with ACS and WFPC2

PI : M. Robberto

Mapping strategy

Mapping strategy

Fall campaign on 2-Mass

On ESO Optical Image On 2MASS JHK Color

Mapping strategy

MotivationApart from pretty picture, what do we learn?

IMF - the distribution of masses

HR diagram - test models of stellar evolution

Reaction of disks to different environments

Binary properties

For every massive star (>10Msol)…

there are many hundreds of lower mass stars

Hillenbrand & Carpenter, 2000

The HR diagram

Hillenbrand 1997

PSF subtraction reveals close binary companions

Companion is 0.45" from the primary, flux ratio ~6 mag I band

Original images, visits 49, 4a, 4c final drizzled

Disks in the Orion environment

114-426: giant dark silhouette disk

IR emission from Disks

Chiang & Goldreich 1997, Ap. J., 490, 368.

Superheated surfacelayer with small grainsproduces infrared.

“Black” interior producesmillimeter-wave emission.

The cluster core

The core region

Proplyds

400 AU2000 AU

Section of the Orion Nebula

114-426183-405

206-446 182-413

O’Dell & Wen 1992, Ap.J., 387, 229; McCaughrean & O’Dell 1996, AJ, 108, 1382.

Disk evaporationDisk evaporation

6 – 13.6 eV UV photons

Disk evaporationDisk evaporation

6 – 13.6 eV UV photons

Disk evaporationDisk evaporation

6 – 13.6 eV UV photons

Disk evaporationDisk evaporation

6 – 13.6 eV UV photons

Disk evaporationDisk evaporation

6 – 13.6 eV UV photons> 13.6 eV photons

Disk evaporationDisk evaporation

6 – 13.6 eV UV photons> 13.6 eV photons

Disk evaporationDisk evaporation

6 – 13.6 eV UV photons> 13.6 eV photons

Stellar wind

Disk evaporationDisk evaporation

6 – 13.6 eV UV photons> 13.6 eV photons6 – 13.6 eV UV photons> 13.6 eV photons

Stellar wind

Disk evaporationDisk evaporation

Disks are evaporated by FUV photons

Animation showing HH502 motion between Aug 2002

and Nov 2004 (2.25 yr)

To sum up…

The treasury programme is the widest and deepest survey yet made of the Orion nebula cluster

The main goals;

Determine the IMF for low mass stars in Orion

Obtain a precise HR diagram to test models

Observe disks in a ‘hostile’ environment - believed to be similar to the birth environment of the Sun