Welcome to the mostpolluted place in the galaxy
If you thought that choking carbon emissions were a problem specific to the more industrial areas of modern-day Earth, you’d be wrong. The eerie glow you see in this image, taken from NASA’s GLIMPSE360 (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) survey, is caused by a giant cloud of polycyclic aromatic hydrocarbons (PAHs). These hydrogen and carbon compounds are more commonly found on Earth in the soot caused by dirty vehicle exhausts and open fireplaces.
Here, they’ve been coloured green so that their glow can be more easily observed by scientists in infrared light. The image is a composite of data taken from the Two-Micron All-Sky Survey (2MASS) and Spitzer, whose liquid helium coolant ran dry in May 2009, at which point it started its ‘warm’ mission with its two remaining infrared detector arrays, operating at 3.6 and 4.5 microns.
In the centre right of this image is GL490, a young star around 3,000 light years from Earth in the constellation Camelopardalis, the ‘Giraffe’. The streaks in the upper left quadrant are thought to be caused by the magnetic field surrounding the star, lining up dust grains in the cloud into more orderly lanes.
This kind of gas is produced by the new, massive stars that are forming in this region; at this stage in the stellar life cycle they are hard to spot, so scientists look for these globular outflows to allow them to zero in on a particular region of space and find these stars.