Signs of the Zodiac & the Planets in their Exaltations
The signs of the zodiac are shown in the innermost wheel. Their traditional planetary exaltations occupy the next and the "modern" planets occupy the outermost wheel. A planet is said to be exalted when placed in the sign of its greatest power and influence, like a visiting dignitary in a foreign court.
The seven traditional planets are visible with the unaided eye and have been known since ancient times. The outer (transpersonal) planets are only visible with a powerful telescope.
Uranus was discovered in 1781, Neptune in 1846, Pluto in 1930.
The Dragon's Head (north lunar node aka Rahu) and Dragon's Tail (south lunar node aka Ketu) are traditional power points in the horoscope, which are given planetary strength.