Dr Cavecchi runs computer simulations of the Type I Bursts that
take place on neutron stars.
The neutron stars are fascinating objects that result from the
explosion of massive stars, the so called supernovae. What is left of
the core of the original star collapses to form a new object, the
neutron star, which encloses the mass of almost two suns within 10 Km;
the approximate size of a small city.
Due to their high mass in such a small volume, the density of matter
near the centre of the neutron stars exceed even the density found in
the nuclei of atoms on Earth. The physics governing this state of
matter is not well understood and is the subject of theoretical and
experimental work.
The neutron stars offer a great opportunity to study the behaviour of
this matter, but the centres of the stars cannot be observed directly
and we have to reply on other proxies. The Type I Bursts are
thermonuclear explosion on the surface of neutron stars that strip
matter from a companion star. They produce extremely bright X-ray
flashes that makes them ideal to observe the neutron stars.
Dr Cavecchi runs magnetohydrodynamical simulations of these
explosions, trying to understand how the nuclear flame propagates on
the surface of the star. With precise models of the flame propagation,
it is possible to construct synthetic images of the bursts that, once
compared to the observed ones, can inform us about the properties of
the star where they burn. In this way, we can shed light on the
mysterious behaviour of matter in the centre of the neutron stars.
During this action, Dr. Cavecchi showed how to reconcile the theory of
nuclear burning with the observed frequency of ignition of Type I Bursts.
He also showed how the subsequent flame propagates. Contrary to our
previous picture, the flame does not develop with an orderly front: the latter
breaks down into small vortices which make the flame proceed up to 10 times
faster. These vortices may also hold the key to explain the lightcurves during
the cooling phase of the bursts.
