Hercules (constellation)
The constellation Hercules appears in the second-century catalog of astronomer Ptolemy as one of 48 original constellations. Modern astronomy recognizes it today among 88 official groupings. Its name derives from Roman mythology, adapting the Greek hero Heracles. Babylonian star lore may have influenced its shape through a figure called the Standing Gods. Gavin White suggests this ancient form resembled a man with a serpent body instead of legs. The Greek poet Aratus described the figure simply as On His Knees around the first century BCE. He noted that no man could clearly read what task the Phantom was bent upon. Later writers like Hyginus connected the stars to various myths including Theseus lifting a stone at Troezen. Aeschylus wrote about Hercules fighting Ligurians until his weapons broke and he fell to his knees. Jupiter then placed him among the stars using stones thrown by the gods. Phoenician tradition linked the pattern to their sun god who slew a dragon. Chinese astronomers placed these stars within two enclosures: the Purple Forbidden enclosure and the Heavenly Market enclosure.
Eugène Delporte defined the official boundaries of Hercules in 1930 using a polygon of 32 segments. The constellation covers 1225.1 square degrees representing 2.970% of the night sky. It ranks fifth largest among all modern constellations. Its three-letter abbreviation Her was adopted by the International Astronomical Union in 1922. Right ascension coordinates for its borders lie between specific values while declination ranges from +3.67° to +51.32°. Mid-northern latitudes offer best viewing from mid-spring until early autumn. The constellation culminates at midnight on June 13. The solar apex marks the direction of open motion relative to the Local Standard of Rest inside this region. Coordinates place it near right ascension and declination points. The north pole of the supergalactic coordinate system also resides here. Neighboring constellations include Draco to the north and Boötes to the west. Serpens Caput lies to the southwest while Aquila borders the southern edge. Sagitta, Vulpecula, and Lyra form the eastern boundary.
Alpha Herculis traditionally bears the name Rasalgethi meaning the kneeler's head. This triple star system sits 359 light-years from Earth. Its primary component is an irregular variable star with magnitude fluctuating between 4 and 3. The diameter spans roughly 400 times that of our sun. A spectroscopic binary orbits the primary every 3600 years appearing blue-green at magnitude 5.6. Beta Herculis known as Kornephoros means club-bearer. It shines brightest in the constellation at magnitude 2.8 and lies 148 light-years away. Delta Herculis A forms a double star divisible by small amateur telescopes. Gamma Herculis presents another optical pair separated widely enough for observation. Zeta Herculis becomes resolvable in medium-aperture scopes as components widen toward peak separation in 2025. Mu Herculis sits just 27.4 light-years from Earth near Omicron Herculis. The solar apex narrowly figures between Hercules' left elbow and Vega in neighboring Lyra. Several dimmer variable stars exist including 30 Herculis which cycles through a three-month period. 68 Herculis operates as a Beta Lyrae-type eclipsing binary with a two-day cycle.
Fifteen stars within Hercules host known extrasolar planets. 14 Herculis possesses two planets where b holds the longest period of 4.9 years. Its orbit spans 2.8 AU while c orbits much further out with low eccentricity. Planet c was discovered in 2005 but confirmed only in 2021. HD 149026 contains a transiting hot Jupiter planet. HD 154345 hosts a long-period planet spanning 4.18 AU over 9.095 years. HD 164922 held the first long-period Saturn-like planet found with mass at 0.36 MJ. HD 147506 contained the most massive transiting planet HAT-P-2b measuring 8.65 MJ when discovered. HD 155358 surrounds the lowest metallicity star harboring planets at 21% Sun. GSC 03089-00929 features short transiting planet TrES-3b completing an orbit every 31 hours. Gliese 649 holds a saturnian planet around its red dwarf star. HD 156668 contains an Earth-mass planet weighing four times our own. TOI-561 possesses four or possibly five planets including ultra-short period TOI-561 b.
M13 stands as the brightest globular cluster visible in the northern hemisphere. It lies between stars eta Herculis and zeta Herculis detectable by unaided eyes on clear nights. The cluster spans more than 100 light-years physically containing over 300,000 stars. Its apparent diameter exceeds 0.25 degrees half the size of the full moon. M92 measures magnitude 6.4 sitting 26,000 light-years from Earth. This Shapley class IV cluster shows high concentration with a very clear nucleus. At 14 billion years old it remains the oldest known globular cluster. NGC 6229 appears dimmer at magnitude 9.4 located 100,000 light-years away. NGC 6210 forms a planetary nebula appearing blue-green elliptical through telescopes larger than 75 mm. AT2018cow represents a large astronomical explosion detected on the 16th of June 2018. Astronomers worldwide generated significant interest regarding this event tentatively named Supernova 2018cow. The Hercules Cluster Abell 2151 contains multiple galaxies within its boundaries.
Hercules A stands as the brightest radio source in the constellation. An elliptical galaxy sits 2.1 billion light-years distant hosting a supermassive black hole. That black hole weighs 2.5-billion-solar-mass creating radio jets extending one-and-a-half million light-years. Another bright radio source includes quasar 3C 345 whose jet appears to move faster than light speed. The Hercules, Corona Borealis Great Wall exists within this region of space. It ranks as the largest structure currently known in the universe. These massive formations demonstrate the scale of cosmic architecture beyond individual stars. Observations reveal complex interactions between galactic clusters and surrounding voids. Radio emissions provide critical data about energy distribution across vast distances. Scientists continue mapping these structures to understand universal expansion patterns.
Common questions
When was the constellation Hercules first cataloged by Ptolemy?
The constellation Hercules appears in the second-century catalog of astronomer Ptolemy as one of 48 original constellations. Modern astronomy recognizes it today among 88 official groupings.
Who defined the official boundaries of Hercules and when did this occur?
Eugène Delporte defined the official boundaries of Hercules in 1930 using a polygon of 32 segments. The constellation covers 1225.1 square degrees representing 2.970% of the night sky.
What is the distance to Alpha Herculis from Earth?
Alpha Herculis traditionally bears the name Rasalgethi meaning the kneeler's head. This triple star system sits 359 light-years from Earth.
How many stars within Hercules host known extrasolar planets?
Fifteen stars within Hercules host known extrasolar planets. HD 149026 contains a transiting hot Jupiter planet while HD 154345 hosts a long-period planet spanning 4.18 AU over 9.095 years.
When was Supernova 2018cow detected by astronomers worldwide?
AT2018cow represents a large astronomical explosion detected on the 16th of June 2018. Astronomers worldwide generated significant interest regarding this event tentatively named Supernova 2018cow.