The Star is a family of US solid-propellant rocket motors originally developed by Thiokol and used by many space propulsion and launch vehicle stages. They are used almost exclusively as an upper stage, often as an apogee kick motor. The number designations refer to the approximate diameter of the fuel casing in inches.
Three Star 37 stages, and one Star 48 stage, were launched on solar escape trajectories; fast enough to leave the Sun's orbit and out into interstellar space, where barring the low chance of colliding with debris, they will travel past other stars in the Milky Way galaxy and survive potentially intact for millions of years.