Credit: ESA/Hubble & NASA, M. Hayes
Visible as a small, sparkling hook in the dark sky, this beautiful
object is known as J082354.96+280621.6, or J082354.96 for short. It is a
starburst galaxy, so named because of the incredibly (and unusually)
high rate of star formation occurring within it.
One way in which astronomers probe the nature and structure of
galaxies like this is by observing the behaviour of their dust and gas
components; in particular, the Lyman-alpha emission.
This occurs when electrons within a hydrogen atom fall from a higher
energy level to a lower one, emitting light as they do so. This emission
is interesting because this light leaves its host galaxy only after
extensive scattering in the nearby gas — meaning that this light can be
used as a pretty direct probe of what a galaxy is made up of.
The study of this Lyman-alpha emission is common in very distant galaxies, but now a study named LARS (Lyman Alpha Reference Sample)
[1] is investigating the same effect in galaxies that are closer by.
Astronomers chose fourteen galaxies, including this one, and used
spectroscopy and imaging to see what was happening within them. They
found that these Lyman-alpha photons can travel much further if a galaxy
has less dust — meaning that we can use this emission to infer how
dusty the source galaxy is.
The LARS study relies heavily on the high resolving power of Hubble.
When Hubble is decommissioned, no telescope will be able to make
observations like this in the far ultraviolet part of the spectrum —
meaning that small, glittering galaxies imaged and probed by studies
like LARS may give us some of the most detailed data we have to work
with for some time to come.
Notes
[1] Hayes, Östlin et al., The Lyman Alpha Reference Sample: extended Lyman alpha halos produced at low dust content, The Astrophysical Journal, 2013.
Source: ESA/HUBBLE - Space Telescope
