via Nasa.
Lyman Alpha blobs are enormous concentrations of hydrogen gas that are emitting light at the wavelength known as Lyman Alpha. Dozens of blobs, each hundreds of thousands of light years across and at a distance equivalent to when the Universe was a mere two billion years old, are known to dot the skies, but where do these giants come from?
Nasa studied 29 lyman alpha blobs with a series of different telescopes, both on the Earth and in space. The Earth bound Japanese telescope Subaru, located in Hawaii, took images of the blobs themselves. In the image below, these are shown in yellow. The Hubble and Spitzer space telescopes took images of galaxies in the area – Hubble’s optical data are in white, Spitzer’s infrared data are in red. Finally the Chandra space telescope took some x-ray images that are likely to trace high energy events such as accretion around black holes. These are coloured blue.
Credits: Left panel: X-ray (NASA/CXC/Durham Univ./D.Alexander et al.); Optical (NASA/ESA/STScI/IoA/S.Chapman et al.); Lyman-alpha Optical (NAOJ/ Subaru/Tohoku Univ./T.Hayashino et al.); Infrared (NASA/JPL-Caltech/ Durham Univ./J.Geach et al.); Right, Illustration: NASA/CXC/M.Weiss
At an age of around two billion years, some of the earliest galaxies were formed through gravitational collapse. The massive amount of hydrogen available after the big bang fell into clumps. As it did so, the release of gravitational potential energy created heat, which can then be emitted as radiation. However, the stuff seen in the picture blob isn’t doing that. At a later stage, hydrogen has fallen into the galaxy, allowing the creation and relatively swift destruction of massive stars, which in turn provides black holes. The central back hole of the galaxy then starts to grow in size, accreting material as it does so. This generates heat and radiation that then pushes hydrogen out, heating it once again. This is the stage at which the vast sheets of hydrogen glow so brightly they that they can be seen from Earth.