Modern astronomers break the sky into 88 designated star groups known as constellations. Here’s a quick breakdown of the five largest.Constellations are typically measured in square degrees of the night sky; for comparison, a full moon covers about 0.2 square degrees.HydraMeasuring at 1,303 square degrees, Hydra is the largest of the modern constellations. It’s visible in the northern hemisphere from January to May, but it’s best seen in the Southern Hemisphere.HydraIt’s a string of nearly 20 main stars, and its brightest star, Alphard (also known as Alpha Hydrae), is about 177 light-years away from our sun. In artistic depictions, Hydra is typically represented as a serpent.VirgoVirgo covers 1,294 square degrees. Its brightest star, Spica, is about 260 light-years from Earth, and it’s roughly 2,300 times brighter than our sun.VirgoVirgo is visible from around the world. In the Southern Hemisphere, it’s most visible in the fall and winter, and in the Northern Hemisphere, it’s most visible in spring and summer.Ursa MajorUrsa Major means “great bear" or “larger she-bear†in Latin. It occupies 1,280 square degrees and includes the Big Dipper. The Big Dipper is an seven-star asterism, which is a pattern of stars with no officially recognized boundaries; Ursa Major, the constellation it’s part of, is comprised of about 20 stars.Ursa MajorThe Big Dipper is one of the most well-known asterisms in the night sky. In the United States, it’s represented as a ladle, but in other cultures, its shape represents other items such as a plow, bull’s thigh, or a wagon.The brightest star in Ursa Major is Alioth (the middle star of the dipper’s handle), which is about 82 light-years from Earth. The constellation’s second-brightest star, Dubhe, is about 2 percent less luminous than Alioth.CetusSometimes called “the Whale,†Cetus stretches over 1,231 square degrees. The brightest of these is Beta Ceti, which is 96.3 light-years from Earth. As a whole, Cetus is a fairly dim constellation, and it’s most visible in the Northern Hemisphere in November.CetusCetus gets its name from a misshapen sea monster in Greek mythology, which was sent by Poseidon to consume Andromeda. It’s also depicted as a whale-like creature with various heads attached to its body.HerculesHercules occupies 1,225 square degrees. It’s often represented as a human body—the body of Hercules, or Heracles, of Greco-Roman mythology.HerculesFour bright stars make up the “torso" of this body: Pi, Eta, Zeta, and Epsilon Herculis. Hercules is visible in both the Northern and Southern hemispheres. In the Northern Hemisphere, it’s most visible from April through November.The brightest star in the constellation is Kornephoros (also called Beta Herculis). It is about 139 light-years from Earth.