Astronomers have found that the explosive conversion of a neutron star into a quark star (namely, a Quark-Nova) has the right properties to explain the super-luminous supernovae SN2006gy, SN2005gj and SN2005ap. Denis Leahy and Rachid Ouyed of the University of Calgary in Canada presented their results this week at at the American Astronomical Society meeting in St. Louis, Missouri.

Their results are of special interest for two reasons: astronomers previously did not have a satisfactory explanation for super-luminous supernovae; and this provides supporting evidence for the existence of quark stars- a manifestation of a new state of matter.

The objects of study are the three most luminous supernova ever observed. SN2006gy was in the galaxy NGC1260 at a distance from earth of 240 million light-years; SN2005gj and SN2005ap occurred in more distant galaxies.

They were observed at Lick Observatory for SN2006gy (Smith et al, 2008), at Mount Palomar for SN2005gj (Aldering et al 2006) , and at McDonald Observatory for SN2005ap (Quimby et al 2008). They produced 100 times more light energy than normal supernova and are a challenge to explain.

We study the properties of quark stars, which have been proposed to exist but are not yet been confirmed. The most compact solid objects in the universe known to exist are neutron stars: 16 miles across and about 1.5 times as massive as our Sun.

Neutron stars are made up of neutrons tightly packed together and produced by collapse of the core of a massive star at the end of its life, which also produces a supernova explosion. Quark stars are even more dense: the same mass but only 12 miles across.

Quark stars may be produced when the density inside a neutron star becomes high enough. In that case the neutrons dissolve into quarks, and also release much energy- enough to power an explosion similar to the original explosion which formed the neutron star.

Super-luminous supernova can be the result of the second explosion (the Quark-Nova), which converts the neutron star into a quark star. The first explosion which made the neutron star, would be not noticed since the known super-luminous supernovae have occurred so far away from Earth.

The shock wave from the second explosion takes a few weeks to heat up the gas ejected by the first explosion. As a result, the gas is very large (a hundred times the Sun-Earth distance) when it is heated and produces a bright long lived supernovae.

There are alternate models for such super-luminous supernovae, so observations of more of these events are needed to confirm our model.