Scientists Simulate the Birthplaces of Planetary Systems
on the NCCS Discover Supercomputer


This collection shows 30 Hubble Space Telescope images of embryonic planetary systems — called protoplanetary disks — in the Orion Nebula. New simulations at the NASA Center for Climate Simulation (NCCS) show how protoplanetary disks like these evolve over 10 billion years. Image collection by NASA/ESA and L. Ricci (ESO).

Harnessing the NASA Center for Climate Simulation (NCCS), scientists from the National Science Foundation’s NOIRLab, Center for Astrophysics | Harvard & Smithsonian, and University of Utah simulated the evolution of cosmic disks of dust and rocks — the birthplaces of planetary systems.

“By studying how these disks evolve from young protoplanetary disks to older debris disks, we hope to learn about our own origins, that is, the history of the solar system, and how its story of planet formation and evolution compares to that of other stars,” said Joan Najita, Astronomer and Head of Scientific Staff for User Support, NOIRLab.

Najita was lead author on the study with co-authors and longtime collaborators Scott Kenyon, Senior Astrophysicist, Center for Astrophysics; and Ben Bromley, Professor and Associate Chair, Physics and Astronomy, University of Utah. Their study appears in a recent issue of The Astrophysical Journal.

Study co-authors were (left to right) Joan Najita, National Science Foundation’s NOIRLab; Scott Kenyon, Center for Astrophysics | Harvard & Smithsonian; and Ben Bromley, University of Utah.

Observational evidence for disks comes in several different wavelengths from instruments both in space and on Earth. These include optical-wavelength observations from the Hubble Space Telescope (for example, see the image collection that opens this story); infrared-wavelength observations from the Infrared Astronomical Satellite (IRAS); and millimeter-wavelength observations from the Atacama Large Millimeter Array (ALMA). As these observations show, disks play important roles in the formation of both stars and planets.

“Stars are born surrounded by disks, and much of the mass that ends up in the star first spirals through the disk before reaching the stellar photosphere,” Bromley explained. “But not all of the disk material reaches the star; some of the gas and dust in the disk may form planets instead.”

Impact: The study illustrates how combining calculations of disk evolution with observed debris disk demographics enables scientists to infer the pathways by which protoplanetary disks evolve into debris disks and how the solar system fits into this cosmic evolutionary picture.


Protoplanetary disks can be as large as several hundred Astronomical Units, stretching several hundred times the distance between the Earth and the Sun, which is 150 million kilometers, or 93 million miles. To follow the evolution of these massive structures over 10 billion years, the researchers designed complex simulations using Bromley and Kenyon’s Orchestra computer code.

Orchestra solves mathematical equations to derive the time evolution of the size and velocity distributions of solid bodies within the disks. Using Orchestra, the scientists ran 110 simulations of protoplanetary disks with varying initial conditions on the NCCS Discover supercomputer. The simulations consumed 24,000 CPU-days.

The NCCS-hosted simulations show that protoplanetary disks of centimeter-sized pebbles and 100-kilometer-sized planetesimal rocks can evolve into planets and debris disks. The planets range in size from Pluto to several times the mass of Earth. Moreover, the time evolution of the dust emission in the debris disks matches observations from NASA’s Spitzer Space Telescope (infrared wavelength) and the Herschel Space Observatory (far infrared and submillimeter wavelengths).


Protoplanetary disks have two distinct life histories (above) depending on their initial size and makeup, as shown by simulations run at NCCS and compared to observations from NASA’s Spitzer Space Telescope (below, left) and the Herschel Space Observatory (below, right). Top illustration by Najita, Kenyon, and Bromley; Spitzer conceptual image by NASA/JPL-Caltech; Herschel conceptual image by ESA/NASA/JPL-Caltech.


“Access to the NASA Discover system allowed us to perform the large number of simulations required to understand how the time evolution of the dust emission depends on the initial conditions,” Kenyon said. “Discover gave us a complete picture of the evolution instead of the glimpse possible using computers at our home institutions.”

One surprising result was that the initial ratio of the pebble mass to the total disk mass made a significant difference in the evolution of the dust emission. “As this ratio grew from zero to 0.1 or so, the behavior of the dust emission looked more and more like the observations,” Kenyon said. “Once the ratio exceeded 0.1, most of the calculations resembled the observations. In principle, we might be able to derive this ratio from observations, but we do not have quite enough data yet."

In the more immediate future, the researchers want to extend their disk simulations backwards in time to study the effects of gas, which disperses after the first 10 million years of disk evolution. The scientists plan to add extra physics to the Orchestra code so that future simulations can evolve the solids and the gas together.

The diagram shows four pathways for protoplanetary disks to produce cold debris disks around solar-type stars at three points in time:

  • 1 Myr – 1 million years
  • 100 Myr – 100 million years
  • 1 Gyr – 1 billion years

At 1 Myr, Bright Stalwarts and Early Flares have bright rings of solids at 40 Astronomical Units or farther from the center. Steady Glows have low masses of solids in rings far from the centet that are undetectable with current observational instruments. Debris rings in Late Bloomers have much lower dust luminosity than Steady Glows and are also undetectable.

At 100 Myr, Bright Stalwarts and Early Flares have bright debris disks. Steady Glows and Late Bloomers still have undetectable debris rings.

At 1 Gyr, the debris rings in Bright Stalwarts, Steady Glows, and Late Bloomers are bright and readily observable. Early Flares have undetectable amounts of debris in rings.

Diagram adapted from Najita, Kenyon, and Bromley, 2022.


Related Link


Jarrett Cohen, NASA Goddard Space Flight Center
April 29, 2022