Formation of Brown Dwarfs and Protoplanetary Discs in a Star Cluster

The following movies and still images were created from calculations performed on the UKAFF supercomputer showing the collapse of a gas cloud to form a cluster of stars, some surrounded by protoplanetary discs.

The first movie shows the full evolution of the system.
Available formats:
AVI for Windows or Unix (57.1MB, high-quality)

Simulation & visualisation by Matthew Bate, University of Exeter.

Shorter clip showing the details of the formation of stars and protoplanetary discs.
Available formats:
AVI for Windows or Unix (3.9MB, high-quality)

Simulation & visualisation by Matthew Bate, University of Exeter.

Still images

Click on the images below for a larger version

Clouds of interstellar gas are seen to be very turbulent with supersonic motions. We begin with such a gas cloud, just over 1 light-year across, and containing 50 times the mass of the Sun.

As the calculation proceeds, the turbulent motions in the cloud form shock waves that slowly damp the supersonic motions.

When enough energy has been lost in some regions of the simulation, gravity can pull the gas together to form a dense "core".

The gas within this core continues to collapse, forms filamentary strutures, and breaks up to form very low-mass protostars with about 10 times the mass of Jupiter.

Some of the remaining gas falls in around these protostars forming protoplanetary discs and building up the mass of the protostars. The first protostars to form in this simulation form a binary, although others form later on their own.

The discs of gas that form around the protostars contain a lot of mass and gravity can also form protostars to form within these discs. For example, around the first binary, 3 objects form. The orbits of these objects are unstable and they are quickly ejected from the binary. Because they are ejected from the dense gas just after they are formed they are unable to increase their masses by attracting the residual gas and they become brown dwarfs with masses of 10-40 times that of Jupiter. Many of the other objects are able to attact enough gas that they become proper stars. The most massive star in this calculation has about the same mass as our Sun.

As the stars and brown dwarfs form, their gravity tends to pull them together into a close group. They then undergo a series of close interactions before the group breaks up and the stars fly out of the cloud and into the rest of the galaxy. During these close interactions many of the large discs (4-10 times the size of our solar system) are destroyed. However, some discs survive and would be expected to form planets, towards the top-left of this image for example.

Another large protoplanetary disc develops as further star formation begins in the filaments.