Proxima Centauri

Turn away from Neptune and look towards the Physics Building, 450 metres away. You are now looking inward through our Solar System, towards the Sun—our own star. In the sky above you, around a thousand other stars are visible to the naked eye. That is only a tiny fraction of all the stars that exist out there.

Our nearest stellar neighbour is called Proxima Centauri. It lies just over 4 light-years away. Proxima is part of the triple-star system Alpha Centauri, in the constellation Centaurus in the southern sky. The other two stars, Alpha Centauri A and B, appear as a single star when seen from Earth. Together, they form the third-brightest star in the night sky. Proxima, by contrast, is a red dwarf star. It is much smaller and fainter than A and B, and cannot be seen without a telescope.

The orbits within this triple-star system mean that Proxima is currently the star closest to Earth. In fact, we now know that this small star has at least three planets of its own in orbit around it, one of which is a rocky planet about the size of Earth. At the scale of The Planet Field, Proxima would be a glowing red sphere just under 2 cm in diameter. By comparison, the Sun has a diameter of 14 cm in this model.

But where should we place Proxima Centauri? Clearly, it would have to be far beyond the campus. Perhaps at the Oslo Opera House? Or all the way down in Sarpsborg? In fact, we would have to go considerably farther still. The small glowing red sphere would need to be placed near the Canary Islands—more than 4,000 km away.