Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is the fifth largest of the modern constellations.
See also: List of stars in Hercules
Hercules has no first magnitude stars.
Mu Herculis is 27.4 light years from Earth. The solar apex, i.e., the point on the sky which marks the direction that the Sun is moving in its orbit around the center of the Milky Way, is located within Hercules, close to Vega in neighboring Lyra.
Eleven stars in Hercules are known to be orbited by extrasolar planets. These planets were discovered one in 1996, two in 2005, two in 2006, four in 2007, one in 2009, and one in 2010.
- 14 Herculis has one confirmed and one unconfirmed planet. The planet 14 Herculis b had the longest period (4.9 years) and widest orbit (2.8 AU) at the time of discovery. The planet 14 Herculis c orbits much further out with very low eccentricity.
- HD 164922 has the first long period Saturian planet discovered. The mass is 0.36 MJ and semimajor axis of 2.11 AU.
- HD 147506 has the most massive transiting planet HAT-P-2b at the time of discovery. The mass is 8.65 MJ.
- HD 155358 has two planets around the lowest metallicity planet-harboring star (21% Sun). Both planets orbit in mild eccentricities.
- GSC 03089-00929 has a short transiting planet TrES-3. The period was 31 hours and undergoing orbital decay.
- HD 156668 has a 4.15 Earth mass planet, which is the second lightest planet detected by radial velocity.
Hercules contains two of the most awesome globular clusters: M13, the brightest globular cluster in the northern hemisphere (containing 300,000 stars), and M92. It also contains the nearly spherical planetary nebula Abell 39. M13 lies between the stars η Her and ζ Her; it is dim, but may be detected by the non-aided eye on a very clear night.