How do heavy-element abundances in H II regions change with distance from the centre of the Milky Way Galaxy?

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H II region Centre of the Orion Nebula (M42). Astronomers have identified some 700 young stars in this 2.5-light-year-wide area. They have also detected over 150 protoplanetary disks, or proplyds, which are believed to be embryonic solar systems that will eventually form planets. These stars and proplyds generate most of the nebula's light. This picture is a mosaic combining 45 images taken by the Hubble Space Telescope.

In the Milky Way Galaxy, the abundance of heavy elements within H II regions exhibits a distinct gradient relative to the distance from the galactic centre.

As one moves inward toward the centre of the Galaxy, the concentration of heavy elements increases. Specifically, at a distance of 12,000 light-years inward from the local position, the abundances of heavy elements are approximately 50 percent higher than those found locally. Conversely, the ratio of heavy elements to hydrogen decreases as one moves outward from the centre of the Galaxy, a trend that has also been observed in other spiral galaxies.12