Providing answers about its curious supreme brightness, researchers say the superluminous supernova SN 2006gy - one of the brightest stellar explosions ever studied, and discovered in 2006 - gained its exceptional luster when a normal Type Ia explosion smashed into a surrounding shell of ejected stellar material. Superluminous supernovae (SNe) are as much as 100 times more luminous than normal SNe, far more than can be explained by standard astrophysical mechanisms. While several models have been proposed to explain these rare, brilliant transients, the origin of their energy and the nature of the stars that produce them remain unclear. Early observations of SN 2006gy - one of the first observed superluminous SNe - indicated that the transient was a Type IIn supernova. However, a little more than a year after the explosion, SN 2006gy produced an unusual spectrum with unidentified emission lines. No one had deciphered this mysterious spectrum. Through modeling of supernova spectral scenarios, Anders Jerkstrand and colleagues identified these lines as due to a large amount of iron. Using spectral and radiation hydrodynamic modeling, Jerkstrand et al. simulated various possible mechanisms that could have produced SN2006gy's unusual spectrum and brightness, featuring these iron lines. They found only one scenario consistent with the observations: a normal Type Ia supernova interacting with a dense shell of circumstellar material, probably ejected by the progenitor star roughly a century before the supernova explosion. Other superluminous SNe share similar properties with SN 2006gy and might also be caused by the same underlying mechanics.