newsflash: most of missing universe found

Some 90% of the visible universe appeared to be missing. We finally found the right tools to see it...





The universe as we know it is mostly empty, with light years separating most stars and great voids stretching for millions of light years between large galaxies. But there was also a major chunk of the universe missing, a chunk to the tune of 90% which physics said should be there and yet, no telescope could track it down. That is until the ESO’s giant telescope array in the Atacama desert of Chile flexed its 8.2 meter mirrors and found the swaths of missing galaxies about 10 billion light years away just by using a different wavelength. The problem was the gas composing the galaxies in question. Instead of just letting the light escape, it was absorbing the emissions for which astronomers look: the Lyman alpha lines generated when electrons shed some energy, emitting ultraviolet light in the process. When the first surveys of galaxies emitting Lyman alpha lines began, they were based on the idea that ionized hydrogen gas from new stars should be shining bright with a certain frequency of ultraviolet light and found that it was indeed the case. For just 10% of the galaxies they saw…

However, giant chunks of the universe don’t just go missing for no good reason, at least not as far as science is concerned. The problem was that survey teams before were looking for a hydrogen transition line between an electron’s second and first quantum states, or as the electrons were essentially grounding themselves. In the successful attempt to find the missing galaxies, astronomers looked for the Hα line, one energetic order higher. The light they observed came from electrons moving from their third energetic state to its second with quantum energies of approximately 1.9 electron volts from a very well studied area of the sky in which a swath of never before seen galaxies would be very obvious. When the sky lit up with galactic archipelagos, it was a pretty safe bet that the missing galaxies weren’t really missing or hidden behind some space-time manifold, but were out in plain sight. All we had to do was look with a different eye…

See: Hayes, M., et. al., (2010). Escape of five per cent of Lyman-α photons from high-redshift star-forming galaxies Nature, 464 (7288), 562–565 DOI: 10.1038/nature08881