Science - USA (2020-09-04)

suggesting that this disk region is susceptible

to disk tearing ( 16 ).

We used the observational constraints on

the orbital parameters of the GW Orionis sys-

tem as input for simulations using smoothed

particle hydrodynamics (SPH) and radiative

transfer. We parameterized the initial disk

with the observed total dust mass ( 24 ) and

adopted the measured stellar orbits and outer

disk orientation ( 16 ). After a few thousand

years, the gravitational torque from the mis-

aligned triple-star system breaks the disk apart

into several distinct planes. An eccentric ring

forms with a radius of ~40 au, which precesses

around the inner multiple system with a pre-

cession period of ~8000 years. A snapshot of

this simulation is shown in Fig. 4. The size of

Krauset al.,Science 369 , 1233–1238 (2020) 4 September 2020 3of5

Fig. 2. Scattered light model used to determine

the eccentricity and three-dimensional orienta-

tion of ring R3 and the geometry of the disk

warp.(A) Diagram of the three-dimensional orienta-

tion of the disk components in the model ( 16 ).

(B) Orientation of the orbits in the hierarchical triple-

star system, with the stellar positions at the time of

our imaging measurements indicated (same as in

Fig. 1). The coordinate system is centered on the center

of mass of the system. The white grid indicates the

observed plane of the sky (right ascension RA and

declination Dec), and thezaxis points toward the

observer, represented by the eye symbol in (A).

(C) Synthetic image computed ( 16 ) from the scattered

light model, convolved to match the resolution of the

observation. The position of the scattered light

features from Fig. 1, C and D, are indicated.

Fig. 3. Interactive three-

dimensional model of the

GW Ori system.The model

can be zoomed and rotated in

Adobe Reader to display the

disk geometry. Thexandy

axes correspond to the

directions of Dec (north) and

RA (east), respectively, and

thezaxis points toward Earth.

Zooming in shows the triple

star orbits (GW Ori A, blue;

GW Ori B, orange; and GW Ori

C, black).

RESEARCH | REPORT