Photons struggle to escape distant galaxies
http://www.ras.org.uk/...truggle-to-escape-distant-galaxies-creates-giant-halos-of-scattered-photons
Astronomers led by David Sobral and Jorryt Matthee, of the Universities of Lancaster in the UK and Leiden in the Netherlands, have discovered giant halos
around early Milky Way type galaxies, made of photons (elementary particles of light) that have struggled to escape them. The team reports its findings
in the journal Monthly Notices of the Royal Astronomical Society.
In order to understand how our own Milky Way galaxy formed and evolved, astronomers rely on observing distant galaxies. As their light takes billions of
years to reach us, telescopes can be used as time machines, as long as we have a clear indicator to pinpoint the distance to the objects being observed.
As with closer galaxies, stars and planets, astronomers use the technique of spectroscopy to analyse their light, dispersing it into a spectrum.
Scientists then look for characteristic features (spectral lines) that tell them about properties including the composition, temperature and movement of
the object. With the most distant galaxies, only one spectral feature typically stands out, the so-called Lyman-alpha line associated with hydrogen gas.
