Rho Persei

keystone in hercules

The Keystone

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The Keystone is an asterism formed by four relatively bright stars in the constellation Hercules: Pi, Eta, Zeta and Epsilon Herculis. The trapezoid-shaped pattern makes it easy for observers to identify the constellation and to find several well-known deep sky objects. On a clear night, the Keystone can be seen between the bright Vega, the brightest star in Lyra, and the stars of Corona Borealis, the Northern Crown. The asterism represents Hercules’ torso.
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Algol

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Algol, Beta Persei, is a bright multiple star located in Perseus. It is the second brightest star in the constellation, after Mirfak, Alpha Persei. The star is also known as Gorgona, Gorgonea Prima, Demon Star and El Ghoul. It lies at an approximate distance of 90 light years from Earth and has an apparent magnitude that varies between 2.12 and 3.4.
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