The Milky Way is our home, but since we are in it, it may be the least familiar galaxy in terms of observation. Recently, astronomers discovered for the first time in the Milky Way that the spiral arms of Sagittarius were broken, disrupting the seemingly uniform flow of the Milky Way.

The Milky Way is a beautiful spiral galaxy, which includes 4 main spiral arms, namely: Swan Arm (or Outer Arm, Rectangular Arm), Southern Shield-Cross Arm, Sagittarius Arm, Perseus Arm, the interstellar matter in the Way. Milky Way and Hundreds of Billions of stars are distributed in the arms of these galaxies, but the spiral structure of the Milky Way has not been fully determined, and the spiral arms often branch, merge, and twist. For example, our solar system is located on the Sagittarius branch arm – the upper arm of Orion.

▲ The spiral arms of the Milky Way. (Source:Dragonflight and Surachit (English version), Zanhsieh (translation from zh-hant)., CC BY-SA 3.0, via Wikimedia Commons）

One of the methods used by astronomers to map the Milky Way is to measure the positions and distances of thousands of stars. For example, the main objective of the Gaia satellite is to study the positions and trajectories of more than one billion stars and discover the details of the structure of the Milky Way.

Another method is to observe certain objects in the Milky Way, such as the nebula that is usually located in the spiral arms of the galaxy with a large amount of gas and dust. The Spitzer Infrared Space Telescope measures the distance of many young stars in the nebula to help us confirm that the Milky Way has 4 main spiral arms.

Now, a new study combines observational data from the Gaia satellite and the Spitzer telescope to focus on analyzing the general distribution of the Sagittarius Nebula and the stars. The first includes four famous nebulae: the Eagle Nebula (where the Pillar of Creation is located), the Omega Nebula and the Three in the Divided Nebula and the Lagoon Nebula, it was found that although the elevation angle of the main arm was approximately 12 degrees as in the past, there was a regional elevation angle of 60 degrees, that is, a structure appeared almost perpendicular to the original spiral arm, with a length of about 3,000 lights. year.

▲ A broken arm appears on the horse’s arm. (Source:POT）

In addition to the peculiar protruding angle, hundreds of thousands of stars in the broken arm appear to move at the same speed and direction, indicating that the stars there may form at roughly the same time and are affected by the same gravitational force, which is That is, there is a local external force that removes these nebulae from another long straight line being drawn from the centaur’s arm.

The research team does not yet know what caused these stars to separate from their original spiral arms. If we look closer, we are more likely to find similar spiral arms.New treatyPosted in Astronomy and Astrophysics.

(Source of the first image:POT）

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