With current propulsion technology only able to move spacecraft at 0.005% of the speed of light, a one-way trip to the star system nearest our Sun, Alpha Centauri, would take 80,000 years to travel the four light-years to our nearest stellar neighbors, according to Sidney Perkowitz, Candler Professor of Physics Emeritus at Emory University.
Starting with the development of a rocket engine that can reach high velocity, humans are not short of initiative, but, as Perkowitz describes, even with engines based on photon-powered sails or nuclear fusion, we are still a long way from reaching the speed of light.
Some theoretical models offer intruiging options, such as Miguel Alcibierre's idea to contract space–time in front of a spaceship and expand space–time behind it to create a bubble that would propel the spacecraft at any speed without violating special relativity.
Focusing on this example, Perkowitz explained that the maths is impeccable but that the model requires negative mass, which, to the best of our knowledge, doesn't exist: "With the exploration of the solar system by the US space agency NASA and others well under way, and with the discovery of hundreds of exoplanets orbiting distant stars, it may be time to contemplate the next great jump outwards."
Of the three stars in the Alpha Centauri system, the dimmest -- called Proxima Centauri -- is actually the nearest star. The bright stars Alpha Centauri A and B form a close binary as they are separated by only 23 times the Earth- Sun distance - slightly greater than the distance between Uranus and the Sun.
The Alpha Centauri system is not visible in much of the northern hemisphere. Alpha Centauri A, also known as Rigil Kentaurus, is the brightest star in the constellation of Centaurus and is the fourth brightest star in the night sky. Sirius is the brightest even thought it is more than twice as far away.
By an exciting coincidence, Alpha Centauri A is the same type of star as our Sun, causing many to speculate that it might contain planets that harbor life.
Indeed, yesterday European astronomers announced that they have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope atESO’s La Silla Observatory in Chile. Alpha Centauri A is the brightest component, Alpha Centauri B is the slightly fainter second star and Alpha Centauri C is the much fainter Proxima Centauri. Proxima Centauri is slightly closer to Earth than A or B and hence is formally the closest star.