 Spica is a blue star and the fifteenth brightest star in the nighttime sky. It's a close binary system whose components orbit each other every four days. Myra is a very high proper motion red star that is shedding an enormous tail of material. The tail stretches a startling thirteen light years across the sky. It has released enough material over the past thirty thousand years to seed at least three thousand earth-sized planets. Polaris is our current day north star. For it lies less than one degree from the north celestial pole. It is a double star system with one being a supergiant. The supergiant is a classic Siphiid variable star. Siphiids are a critically important kind of star for our distance ladder. I'll talk more about them in a minute when we come to Delta Siphi, the first Siphiid star completely analyzed. Antares is a bright red star, the sixteenth brightest star in the nighttime sky. The size of Antares has been calculated using its parallax and angular diameter. His radius is 822 times larger than our sun's.