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Six Hypothetical Solar System Objects That Almost Certainly Do Not Exist

Would have been sweet and/or terrifying if they did, though.

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1. Neith

NASA-JPL/Caltech / Via

Neith was the name given to Venus’ moon—something that many astronomers claimed to have discovered back in the late 17th and early 18th centuries. Giovanni Cassini first proposed its existence in 1686 after he saw what appeared to be an object near Venus identical to one that he noted 14 years earlier.

After Cassini’s announcement, many other noted astronomers also recorded observations of a similar object. Scientists now reject its existence, and chalk most of the early sightings to stars that would have been visible in the vicinity of Venus at the time.

2. Phaeton

NASA-JPL/Caltech / Via

This planet was once thought to have existed between Mars and Jupiter billions of years in the past. The impressively named astronomer Heinrich Wilhelm Matthäus Olbers proposed that its destruction created the Asteroid Belt.

It almost certainly never existed, though. More widely accepted theories suggest that a planet in this region would never have been able to form in the first place, due to Jupiter's gravitational pull.

3. Vulcan


In the 19th century, Urbain Le Verrier imagined this hypothetical planet in between Mercury and the Sun to explain slight variations in Mercury's orbit that did not mesh with Newtonian physics.

Thanks to Einstein's General Relativity, we no longer have a need for this assuredly non-existent planet.

4. Planet X

NASA, ESA, and Adolf Schaller (for STScI) / Via

As originally proposed, Planet X existed beyond the orbit of Neptune. Its gravity, scientists hypothesized, caused what appeared to be anomalies in the orbits of Uranus and Neptune. Astronomers once considered Pluto to be a planet beyond Neptune, but it is too small to have caused any perturbations.

Now, Pluto is a considered a dwarf planet, and we don’t need Planet X to explain the orbits of Uranus and Neptune. NASA’s Voyager 2 spacecraft figured out that these supposed anomalies were all the result of a miscalculation of the Neptune’s mass!

Still the hunt for more dwarf planets beyond Neptune, and heck, maybe even a real planet, is still an active one.

5. Nemesis

NASA-JPL/Caltech / Via

In 1984, two paleontologists, David Raup and Jack Sepkoski, demonstrated what they thought to be a clear pattern in the geologic record—increases in biological extinction events every 26 million years. Astronomers regarded the pattern as a challenge to find some extraterrestrial cause for this apparent cycle.

One explanation was the existence of Nemesis, a companion star to the Sun. Nemesis was thought to be a brown dwarf—a stellar object not large enough to produce the nuclear reaction that powers brighter, more visible stars.

The idea was that its gravitational pull would disrupt comets in the Oort Cloud, increasing the number of impacts (which have likely caused at least one mass extinction) Earth experiences on a regular interval.

A number of problems with this theory have since come to light, including the fact that there may be no cycle to explain. Most damning, though, is the fact that, despite technological advances that could prove its existence, we haven’t yet found it.

6. Tyche

Adolf Schaller for NASA/STScI / Via

A group of astrophysicists proposed this hypothetical planet back in 1999. Tyche (named after Nemesis’ benevolent sister in Greek mythology), they argued, would lie deep within the Oort Cloud—the home to millions of icy comets. Tyche, they claimed, would explain why the orbits of many long-period comets don’t follow a trajectory predicted by existing comet theories. They imagined that Tyche’s gravitational pull disturbed the icy objects in this faraway region of our solar system.

An extremely thorough search by NASA's Wide-field Infrared Survey Experiment (WISE) suggests that the planet, as the astrophysicists defined it, is fairly unlikely.