Our home spiral arm in the Milky Way is less wimpy than thought | New Scientist
https://www.newscientist.com/...456-our-home-spiral-arm-in-the-milky-way-is-less-wimpy-than-thought/
It’s tricky to map an entire galaxy when you live in one of its arms. But astronomers have made the clearest map yet of the Milky Way –
and it turns out that the arm that hosts our solar system is even bigger than previously thought.
The idea that the Milky Way is a spiral was first proposed more than 150 years ago, but we only started identifying its limbs in the 1950s.
Details about the galaxy’s exact structure are still hotly debated, such as the number of arms, their length and the size of the bar of hot
gas and dust that stretches across its middle.
The star-filled arms are densely packed with gas and dust, where new stars are born. That dust can obscure stars we use to measure distances,
complicating the mapping process.
Two of the arms, called Perseus and Scutum-Centaurus, are larger and filled with more stars, while the Sagittarius and Outer arms have fewer
stars but just as much gas. The solar system has been thought to lie in a structure called the Orion Spur, or Local Arm, which is smaller
than the nearby Perseus Arm.