If you accept conventional views of the Milky Way, humans live in a sort of cosmic cul-de-sac: our star is in the Orion Arm (aka Local Arm), a small spur sitting in between the much larger Sagittarius and Perseus arms. A team of international researchers might just shake up that sense of place, however. They’ve published a study indicating that our arm is much, much larger than once thought. Instead, it incorporates a large arm that extends almost all the way to the Perseus Arm, and another long spur that branches between the Orion and Sagittarius arms. It’s now believed to be about 25,000 light years long, or several times longer than expected.
The findings come after discovering several Orion Arm masers, or bright spots of radio emissions frequently caused by gas. Compare them to a readily available source of light on Earth (here, the light from a handheld red laser) and you can gauge their relative distance and speed.
It won’t surprise you to hear that verifying this data could be difficult. The study relied on the northern hemisphere’s Very Long Baseline Array of telescopes, and you’d need info from the southern hemisphere to form a more complete view. It’s not as if you can fly above the galaxy to get a better look, either. Even so, what’s here is enough to suggest that our segment of the Milky Way isn’t just a tiny offshoot, and that we don’t know as much about our galactic home as we think we do.
