If the world’s combined space fleet was in a school classroom together, NASA’s Voyager probes would be those annoying kids who constantly show up the the rest of the class with perfect assignments, extra credit homework and general overachievement.
Like Spirit and Opportunity – the equally keen Mars rovers who continued to work for years after they could have quit – the twin Voyagers just keep on turning in new science reports, three decades after their launch. As if discovering Jupiter’s faint ring system, Neptune’s Great Dark Spot, active volcanoes on Io, giant magnetic bubbles and, oh, a little something called entering the heliosheath wasn’t enough, the Voyagers have now allowed scientists to detect the long sought-after Lyman-alpha emission from our galaxy.
According to the experts at Sky & Telescope:
Lyman-alpha is a specific ultraviolet wavelength (121.6 nm, to be exact) emitted when a hydrogen atom’s electron drops down one orbital energy level to the ground state. Until now, astronomers hadn’t detected Lyman-alpha emission from the Milky Way, because of the interference caused by emission created when solar Lyman-alpha photons are scattered by neutral hydrogen atoms in the solar system. Astronomers have detected plenty of Lyman-alpha emission in far-away galaxies, but that’s because the light from those galaxies is redshifted to wavelengths where solar-system interference isn’t a problem.
Because of the Voyagers’ distance from earth (17,933,379,913km and counting), researchers were able to draw on data from their ultraviolet spectrometers to identify a band of Lyman-alpha radiation along the plane of the Milky Way, consistent with star formation. We should learn even more post-2015, when NASA’s New Horizons probe and its fancy spectrometer pass beyond Pluto to give us another view back from the depths of deep space.
And the overachievement continues: NASA just announced that Voyager has entered “a new region between our solar system and interstellar space.” How far can they go?