Bounty Ended with 50 reputation awarded by Mrigank Pawagi occurred Jul 30 '18 at 0:54 2 added 618 characters in body edited Jul 23 '18 at 15:57 enumaris 3,62511 gold badge66 silver badges2121 bronze badges Since you don't provide an actual speed, I can only give an order of magnitude type estimate for you. A particle is said to become "relativistic" if it's kinetic energy becomes comparable (or greater than) its rest mass-energy $$mc^2$$. Particles in thermal equilibrium have kinetic energies of order $$kT$$ where $$k$$ is the Boltzmann constant and $$T$$ is the temperature. This gives us, for matter of mass $$m$$ the temperature at which the individual particles would become relativistic at a temperature of $$T\approx mc^2/k$$. If $$m$$ is the electron mass (the electrons in the matter will go relativistic first), this corresponds to temperatures of order $$10^{10}K$$. If $$m$$ is an atomic mass unit, this corresponds to temperatures of order $$10^{13}K$$. For a particle which has kinetic energy equal to the rest mass, the gamma factor would be $$\gamma=2$$ which corresponds to a velocity of $$\sqrt{3}c/2\approx .87c.$$ EDIT (per user request): Only the most massive of stars will ever achieve temperatures close to these (and even then, only in their cores). And those stars will run into pair production instabilities due to the spontaneous production of electron-positron pairs in their cores from the high energy gamma radiation around. As an isolated object (i.e. not massive like a star), an object of this temperature wouldn't be bound in any way. One would have to design apparatus to contain such an object. It would look essentially like a very hot plasma. (Since that's exactly what this object would be - a very hot plasma) Since you don't provide an actual speed, I can only give an order of magnitude type estimate for you. A particle is said to become "relativistic" if it's kinetic energy becomes comparable (or greater than) its rest mass-energy $$mc^2$$. Particles in thermal equilibrium have kinetic energies of order $$kT$$ where $$k$$ is the Boltzmann constant and $$T$$ is the temperature. This gives us, for matter of mass $$m$$ the temperature at which the individual particles would become relativistic at a temperature of $$T\approx mc^2/k$$. If $$m$$ is the electron mass (the electrons in the matter will go relativistic first), this corresponds to temperatures of order $$10^{10}K$$. If $$m$$ is an atomic mass unit, this corresponds to temperatures of order $$10^{13}K$$. For a particle which has kinetic energy equal to the rest mass, the gamma factor would be $$\gamma=2$$ which corresponds to a velocity of $$\sqrt{3}c/2\approx .87c.$$ Since you don't provide an actual speed, I can only give an order of magnitude type estimate for you. A particle is said to become "relativistic" if it's kinetic energy becomes comparable (or greater than) its rest mass-energy $$mc^2$$. Particles in thermal equilibrium have kinetic energies of order $$kT$$ where $$k$$ is the Boltzmann constant and $$T$$ is the temperature. This gives us, for matter of mass $$m$$ the temperature at which the individual particles would become relativistic at a temperature of $$T\approx mc^2/k$$. If $$m$$ is the electron mass (the electrons in the matter will go relativistic first), this corresponds to temperatures of order $$10^{10}K$$. If $$m$$ is an atomic mass unit, this corresponds to temperatures of order $$10^{13}K$$. For a particle which has kinetic energy equal to the rest mass, the gamma factor would be $$\gamma=2$$ which corresponds to a velocity of $$\sqrt{3}c/2\approx .87c.$$ EDIT (per user request): Only the most massive of stars will ever achieve temperatures close to these (and even then, only in their cores). And those stars will run into pair production instabilities due to the spontaneous production of electron-positron pairs in their cores from the high energy gamma radiation around. As an isolated object (i.e. not massive like a star), an object of this temperature wouldn't be bound in any way. One would have to design apparatus to contain such an object. It would look essentially like a very hot plasma. (Since that's exactly what this object would be - a very hot plasma) 1 answered Jul 20 '18 at 16:46 enumaris 3,62511 gold badge66 silver badges2121 bronze badges Since you don't provide an actual speed, I can only give an order of magnitude type estimate for you. A particle is said to become "relativistic" if it's kinetic energy becomes comparable (or greater than) its rest mass-energy $$mc^2$$. Particles in thermal equilibrium have kinetic energies of order $$kT$$ where $$k$$ is the Boltzmann constant and $$T$$ is the temperature. This gives us, for matter of mass $$m$$ the temperature at which the individual particles would become relativistic at a temperature of $$T\approx mc^2/k$$. If $$m$$ is the electron mass (the electrons in the matter will go relativistic first), this corresponds to temperatures of order $$10^{10}K$$. If $$m$$ is an atomic mass unit, this corresponds to temperatures of order $$10^{13}K$$. For a particle which has kinetic energy equal to the rest mass, the gamma factor would be $$\gamma=2$$ which corresponds to a velocity of $$\sqrt{3}c/2\approx .87c.$$