The Milky Way is our home, but since we are in it, it may be the most unfamiliar 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, including 4 main spiral arms, namely: Swan Arm (or outer arm, Rectangle Arm), Shield-Southern Cross Arm, Sagittarius Arm, Perseus Arm, the interstellar matter in the Milky Way and Hundreds of billions of stars are distributed on 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 in the Sagittarius arm branch-Orion’s arm. superior.
▲ The spiral arms of the Milky Way. (Source: Dragons flight & Surachit (English version), Zanhsieh (zh-hant translation)., 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 goal of the Gaia satellite is to study the positions and trajectories of more than 1 billion stars and uncover the details of the structure of the Milky Way.
Another method is to observe specific 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 distances of many young stars in the nebula to help us confirm that the Milky Way has 4 The main spiral arm.
Now a new study combines the observation data of the Gaia satellite and the Spitzer telescope to focus on the analysis of the overall distribution of the Sagittarius Nebula and stars. The former includes four famous nebulae: the Eagle Nebula (where the Pillar of Creation is located), the Omega Nebula, and the Three In the Split Nebula and the Lagoon Nebula, it was discovered that although the main arm elevation angle was about 12 degrees as in the past, there was a regional elevation angle of 60 degrees, that is, a structure almost perpendicular to the original spiral arm appeared, with a length of about 3,000 lights. year.
▲ A broken arm appears on the arm of the horse. (Source: NASA)
In addition to the peculiar protruding angle, hundreds of thousands of stars in the broken arm seem to move at the same speed and direction, indicating that the stars there may be formed at about the same time and are affected by the same gravitational force, that is, there is a local external force that removes these nebulae from Another long straight line was drawn from the centaur’s arm.
The research team does not yet know what caused these stars to break away from their original spiral arms. As we observe more closely, it may be more likely to find similar spiral arms. The new paper was published in Astronomy and Astrophysics.
(Source of the first image: NASA)
Further reading:
