Discovery of Neptune

The first six planets have been observed since ancient times. The 7th planet, Uranus, was discovered by the English astronomer William Hershel in 1781.

The 8th planet was discovered 65 year later. Neptune discovery is rather impressive example of the power of the scientific method. Modern studies of Galileo’s notebooks show that he saw Neptune on December 24, 1612, and again on January 28, 1613 but he plotted it as star in the background of drawing Jupiter.

In October 1845, young English astronomer John Couch Adams going through a laborious and difficult calculation computed the orbit of the undiscovered planet. He sent his prediction to the Astronomer Royal, Sir George Airy, who passed it on to an observer who began a painstaking search of the area star by star. Adams predicted position was almost as good, off by less than 1.5°.

Meanwhile, the French astronomer Urbain Jan Leverrier made the same calculation and sent his prediction position of the planet to Johann Galle at the Berlin Observatory.

Galle received Leverrier’s prediction on the afternoon of September 23, 1846 and after searching for 30 minutes that evening, found Neptune. Neptune was nearly the exact size, in appearance, as predicted by Leverrier and was less than 1° from the position predicted for it by Leverrier.

Little was known about Neptune before the Voyager 2 spacecraft swept past it in 1989. Voyager 2 passed only 4900 km above Neptune’s cloud tops, closer than any spacecraft has ever come to one of the Jovian planets.
Discovery of Neptune

Planet of Mars: History of discovery

For thousands of years it was only a blood red dot among the starry host. The name Egyptians gave to Mars was Har decher, ‘The Red One’.

Egyptians already aware of Mars having a backward or retrograde motion at times by giving another name Sekded-ef-em-khekhet (The One Moving Backwards). The Babylonians referred to its as Nergal, the Star of Death, and the Greeks too associated it with warfare and bloodshed. 

Astronomers carefully charted the motion of Mars across the sky even before the advent of the telescope in 1609.

By 1610, Galileo reported that Mars can show a gibbous phase, which subsequent observers verified.

In 1659, Christiaan Huygens sketched the dark triangular feature now known as Syrtis Major. From his observations, Huygens concluded that the rotation period of Mars is about 24 hours. The exact Martian days is 24 hours 37 minutes 22.6 seconds.

Major advances in understanding of Mars began in 1830 during a close approach between Mars and Earth, The first complete map of Mars was derived from observations during this time and published in 1840.

Mars and Earth very close in 1877 resulting in a surge of new discoveries. Principal among these was the discovery of Mars’ two small moons, Phobos and Deimos by Asaph Hall.

NASA began its attempt to reach Mars in the early 1960s, achieving incredible technological success on 14-15 July 1965 when spacecraft Mariner IV passed by the planet at a distance of 9600 km and snapped some the first blurry close-up pictures of the Martian surface, reveling its true nature.
Planet of Mars: History of discovery