Osteopenia refers to bone density that is lower than normal peak density but not low enough to be classified as osteoporosis. Bone density is a measurement of how dense and strong the bones are. If your bone density is low compared to normal peak density, you are said to have osteopenia.steopenia refers to bone density that is lower than normal peak density but not low enough to be classified as osteoporosis. Bone density is a measurement of how dense and strong the bones are. If your bone density is low compared to normal peak density, you are said to have osteopenia.
The Milky Way is the second-largest galaxy in the Local Group, with its stellar disk approximately 100,000 ly (30 kpc) in diameter, and, on average, approximately 1,000 ly (0.3 kpc) thick.
The Andromeda Galaxy (M31) is a spiral galaxy and the most massive galaxy in our Local Group of galaxies. Our Local Group of galaxies is made up of roughly 46 galaxies, most of which are not as large or even close to the size as the Andromeda Galaxy, making it the biggest, baddest and most awesomest galaxy in our Local Group.