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Stories, updates, insights, and original analysis from The Planetary Society.

Analyzing Signals in Real Time

Candidate signals sent in by users around the world will be quickly analyzed and compared to existing signals.

Pluto: The Discovery of a Planet

To mark the 75th anniversary of the discovery of the planet Pluto, The Planetary Society presents to its readers the remarkable story of the discovery.

The Discovery of a Planet, Part 6: From Pluto to Sedna

74 years after Clyde Tombaugh discovered Pluto as a faint dot on a pair of photographic plates, a modern group of astronomers made another remarkable discovery. On March 15, 2004, Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale announced the discovery of Sedna – the furthest object ever detected in the Solar System.

The Discovery of a Planet, Part 5: The Aftermath

The discovery of Planet X was announced to the world on March 13, 1930, which marked the anniversary of William Herschel’s discovery of Uranus in 1781 as well as Percival Lowell’s birthday. The observatory’s communiqué emphasized that the discovery was no coincidence, but the vindication of Lowell’s predictions made years before.

The Discovery of a Planet, Part 4: Clyde's Search

Since his teenage years Clyde Tombaugh had been an avid amateur astronomer and a gifted telescope builder. Based on instructions contained in an article from a boy’s Sunday school paper, he built a series of telescopes of increasing power and quality on the family farm.

The Discovery of a Planet, Part 3: Planet X

The discovery of Neptune accounted for nearly all the unexplained motions of the outer planets of the Solar System. Nevertheless, several astronomers insisted that some unexplained residual motions remained, pointing to the presence of a ninth planet beyond the orbit of Neptune.

The Discovery of a Planet, Part 2: Out of the Six-Planet World

Since humans first set their eyes to the stars, they noticed that a few of these bright objects behaved differently from the others. Whereas all the stars moved together, revolving around the Earth once every 24 hours, five appeared to move within the firmament among the other stars. Accordingly, they were named “planets,” meaning “wanderers” in Greek.

The Discovery of a Planet, Part 1: The Blinking Image

February 18, 1930, was a cloudy day at the Lowell Observatory, on top of Mars Hill in Flagstaff, Arizona. 22 year old Clyde Tombaugh was hard at work, peering through the lens of an ancient-looking brass-colored device. The instrument, known as a “blink comparator,” mounted two large photographic plates.

Mars Exploration Rovers Update: Spirit Too Finds Traces of Water

Four days after scientists announced that rocks examined by the rover Opportunity in Meridiani Planum were once soaked with water, Opportunity's twin Spirit made some headline news of its own. In a press conference this morning at the Jet Propulsion laboratory in Pasadena, Dr. Ray Arvidson, Deputy Principal Investigator for the rovers, announced that Spirit had discovered the telltale signs that some amount water had once been present in Gusev Crater as well.

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