Astronomers from the College of Literature, Science and the Arts at the University of Michigan have discovered that the Milky Way's gas halo not only spins but is doing so at a dizzying speed.
It was earlier presumed that the galaxy's disk was the only one spinning while the hot gas reservoir surrounding it stayed in place. In a study published in the Astrophysical Journal, however, the astronomers showed that the hot gas halo is not only also spinning, but it's doing so at a speed similar to the disk's.
The NASA-funded study used archival data from the XMM-Newton, a telescope by the European Space Agency (ESA). Motion creates a shift in light's wavelength and the astronomers used this shift, measuring them to show the halo spinning in the same direction as the Milky Way's disk at about 400,000 mph. The disk moves at 540,000 mph.
"The rotation of the hot halo is an incredible clue to how the Milky Way formed. It tells us that this hot atmosphere is the original source of a lot of the matter in the disk," said Edmund Hodges-Kluck, assistant research scientist for the study.
Now that astronomers know about the rotation, the discovery can be used to explore how the Milky Way was formed, and eventually what will happen to it.
According to the New World Atlas of Artificial Night Sky Brightness, a third of the world can no longer see the Milky Way from where they are, including 80 percent of North America. Western Europe is one of the parts of the globe most heavily affected by light pollution, but Spain, Scotland, Sweden, Norway and Austria are still dark enough to view the galaxy.
The most light-polluted skies belong to South Korea, Italy and Saudi Arabia, while the darkest skies were observed over Germany and India.
Fortunately, unlike other forms of pollution, light pollution is reversible. According to the International Dark-Sky Association (IDA), light pollution can be reduced by using energy-efficient light bulbs and drawing blinds at night to keep interior light from seeping out.
The organization also urges people to only use light when necessary, switching off lights when not in use or installing motion detectors and timers to avoid unnecessary use of artificial lights. Communities can also experiment with technologies like full cutoff lighting, which helps prevent light flashing up into the sky.
Light pollution makes it difficult to observe the skies, but it also affects human health by interfering with the body's circadian rhythm and contributing to sleep problems.
