What is a quark star?
Outer crust A quark star would have an outer crust, potentially made up of densely packed neutrons like those found in a neutron star.
Slightly smaller than a neutron star A quark star would be slightly smaller than a neutron star, which tend to be between 10 and 20km (6.2 and 12.4 miles) in radius.
No inner core Unlike a neutron star, a quark star would not have an inner core of protons, electrons and so on, it would only have quark matter inside.
Free quarks Inside a quark star, the quarks would be free compared to inside a neutron star, where they are confined as neutrons.