This week in astronomy I first learned about the differences between asterisms and constellations. The former is simply an arbitrary group of stars, while the latter means “a group of stars.” “Con” means together, and “stellar” means “of or pertaining to stars,” combined to make constellation, a group of stars. I learned that a constellation is technically a region of the sky, and that the sky is divided into 88 of these regions. I also learned about the diurnal motion of the earth’s axis, causing the asterisms to rise in the east and to set in the west. In addition, because the earth orbits around the sun on a yearly basis, different asterisms are visible at different times on the earth. For example, such asterisms as Leo, Virgo, and Cancer are some of the most prominent of the springtime.
I also learned of some well-known constellations, including Ursa Major, or The Great Bear. This constellation contains the Big Dipper, a famous asterism with a long handle that makes it look like a “dipper” for water. This asterism is important because it allows you to be able to find the Polaris star, or the North Star, by following the line made by the ladle of the Big Dipper. This can help you figure out where north is.
A galaxy, I learned, is a massive group of stars, planets, dark matter, and all of the empty space among them, all bound together by the galactic center of the galaxy. Each galaxy contains billions or even trillions of stars. The earth is in the Milky Way galaxy, so named because of the milky color caused by the stars. Of the some 500,000,000,000 galaxies in the universe, many billions of them are not observable without special equipment.
A final topic of note which I shall mention from this week’s astronomy lessons was the subject of black holes. A black hole is a “region of spacetime exhibiting gravitational acceleration so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.” Basically, a black hole can swallow everything around it, including light. These extremely powerful objects often form when a star runs out of fuel, causing the stars, which are commonly much larger than the earth, to condense to very great extremes, causing the force which becomes a black hole.
Thank you for reading!