Wednesday, May 19, 2021

Discovering the Galactic center

The Milky Way Galaxy is our home. It is a spiral barred galaxy with a mass around one trillion solar masses. Its stellar disk is around 185,000 light years across and around 1,000 light years thick. The dark matter halo of the Milky Way, could be up 10 times greater than its disk size (across). 

Our Solar system is located in the Orion-Cygnus arm, at a distance of around 27,000 light years and it needs 225-250 million years to complete one orbit.

Due to dust along the line of sight, the centre of the Milky Way is not easy to study at visible, ultraviolet, and low-energy X-rays. Thus, radio, sub-millimetre, infrared, high-energy X-rays, and gamma rays observations are required. 

Sagittarius A is an intense radio source that characterizes the galactic centre. It hosts a massive compact object. This is attributed to a supermassive black hole with a mass around 4.5 million times the mass of the Sun.

Image: Compass/scale annotated image of the Milky Way Galaxy. The image was created using X-ray data from Chandra X-ray Observatory (blue), optical data from the Hubble Space Telescope (yellow), and infrared data from Spitzer Space Telescope (red). The Arches Cluster is the densest star-cluster of our Galaxy and it is located at a distance of only 100 light years from the Galactic centre. It hosts numerous supermassive stars. The Pistol star is a blue supermassive star in the Quintuplet cluster. The Arched Filaments are a large-scale feature of the Galactic centre, located at a distance of around 100 light years from Sagittarius A. It is believed that they are the edges of molecular clouds that are ionized. Finally, 1E 1743.1-2843 it is believed that it is a low mass X-ray binary that consists of a neutron star and a normal star.

Image Credit: NASA, ESA, SSC, CXC and STScI

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