Summer Triangle (Winter in the south hemisphere)
Lyra - 天琴座The Lyre
Lyra, the Harp, is a small constellation with a very recognizable shape. It is one of the few constellations that actually resembles the object for which it is named. Lyra is located between Hercules 武仙座 and Cygnus 天鵝座, and is best seen from May through November.
Lyra includes the brilliant star Vega 織女星, one of the brightest stars in the Northern Hemisphere's summer skies. Below Vega is a parallelogram formed by four third magnitude stars.
History and Mythology
The constellation Lyra represents the instrument that was said to be used by Orpheus 奧菲斯. This mythical instrument is said to have been created by the Greek god Hermes赫密士when he came upon a turtle. The god is said to have hollowed out its shell and drawn strings across it, creating the first lyre. Mercury then traded the instrument to Apollo, the sun god, when he was caught stealing Apollo's cattle.
The tale of the Lyre then passes to Orpheus. Apollo became entranced by the songs of the great musician Orpheus and gave him the instrument so that Orpheus could accompany his words. Orpheus is said to have been so grateful for the instrument that he would often seek a high mountain before sunrise, to greet the sun god with his music as he rose in the morning.
Orpheus' most renowned tale is one of the greatest Greek myths. The love story began with Orpheus' marriage to the nymph Eurydice歐律狄刻. One day Satyr薩堤爾, smitten by Eurydice's beauty, chased her through the forest to take her for his own. While fleeing Satyr's pursuit, Eurydice stepped on a nest of vipers and was bitten on the heel. Thus poisoned, the nymph dies. When Orpheus came upon the body of his beloved, he is said to have sung songs so mournful that the muses and gods were brought to tears. Orpheus was so bereft at the loss of his love that he undertook to journey to the underworld and beg for her return to the land of the living. Upon his arrival in the land of the dead, he beseeched Hades 哈得斯 with mournful music. Thus he was the only human ever to warm the hearts of the lords of the underworld. Hades agreed to let Orpheus take Eurydice from the underworld, on condition that during the return trip, he would never turn to look back at the ghost of his wife. The musician readily agreed, and began leading the spirit of his wife through the dark corridors of the underworld with his music. But, as Orpheus and Eurydice neared the end of their long journey back to the land of the living, Orpheus became unnerved by the silence of being followed by a ghost. So, in great worry that she was not really there, he turned around, only to see the spirit of his wife pulled back into the underworld for eternity.
Alpha Lyrae, the harp star, is commonly known as Vega 織女星. This name comes from an Arabic word "waqi," meaning "vulture." In ancient Egypt and India, the constellation Lyra was represented as a vulture.
Alpha Lyrae is a brilliant, blue-white star 25 light-years away, and it is the 5th brightest star in the sky. It is three times larger than our Sun, and 60 times more luminous. Vega was the first star to be photographed in the 1850's. It was also one of the first stars discovered to have a disk of proto-planetary dust orbiting around it, by the IRAS satellite in 1983. This discovery was inspiration for Vega's role as the home to an extraterrestrial civilization in the famous science fiction movie Contact.
Around 10,000 BCE, Vega was the North Pole Star. It will be the pole star again in AD 14,500.
Vega is only 25.3 light years away, making it one of the closer stars to Earth. Being nearby, Vega has an angular movement of a degree every 11,000 years. Vega will become the brightest star in the sky in around 210,000 years for about 270,000 years.
Vega has served as the baseline for calibrating the photometric brightness scale.
Vega織女星, Deneb 天津四 in Cygnus 天鵝座, and Altair 牛郎星in Aquila 天鷹座 form the Summer Triangle.
Beta Lyrae is traditionally named Sheliak, which is Arabic for "tortoise" or "harp." Located 880 light-years away, it is the prototype for the class of eclipsing binaries whose components are so close together that they deform each other by their mutual gravitation. Beta Lyrae's apparent magnitude changes from 3.4 to 4.6 over a period of 12.9 days.
Clusters, Nebulae, and Galaxies
The most famous deep sky object in Lyra is M 57, the Ring Nebula環狀星雲. It lies midway between the two lower stars in the parallelogram of Lyra. It is a ninth magnitude planetary nebula which looks like a smoke ring or a pale donut. For a good view, use a 4-inch or larger telescope at a magnification of 200x.
The Ring Nebula is often regarded as the prototype of all planetary nebulae. These objects are the remains of sunlike stars which have blown away their outer envelopes, leaving planet-sized white dwarfs at their centers. The distance to M 57 is not very well known; estimates range from 1400 to 4100 light-years. The current estimate is 2300 light-years, making its physical size about one light-year in diameter.