You'll Go Loop-I For This Picture
The European Space Agency (ESA) has released a dazzling picture of the Loop I – that mysterious and enormous “bubble” of interstellar gas which exists in the Orion Arm of the Milky Way galaxy. The picture was captured by ESA’s Plank satellite. The dotted area represents the relative size of the bubble compared to the view of the entire sky. Here are the details courtesy of the ESA website:
Fifty years ago, astronomers discovered a mystery. They called it Loop I. Today, we still have not fully resolved the mystery of how this giant celestial structure formed but we do now have the best image of it, thanks to ESA’s Planck satellite.
Loop I is a nearly circular formation that covers one third of the sky. In reality, it is probably a spherical ‘bubble’ that stretches to more than 100º across, making it wider than 200 full Moons. Its absolute size, however, is extremely uncertain because astronomers do not know how close it is to us: estimates to the centre of the bubble vary from 400 light-years to 25 000 light-years.
What they do know is that the structure shows up in many different wavelengths, from radio waves to gamma rays. Planck sees Loop I in microwaves. This image’s colours reflect the polarisation – the direction in which the microwaves are oscillating.
You can read the ESA’s full description here.