There are a number of planetary objects proposed in religion, astrology, ufology and pseudoscience whose existence is not supported by scientific evidence.
Kolob
Kolob is a star or planet described in the Book of Abraham, a sacred text in many traditions of the Latter Day Saint movement. Kolob is also mentioned in a Latter-day Saint hymn. The Book of Abraham refers to Kolob as a "star", however, it also refers to several planets as stars, and Kolob is commonly viewed as a planet by Latter Day Saints today.
Kolob is described as the heavenly body closest to the throne of God. Joseph Smith also claimed it "signified" the first creation.
Lilith
Lilith is a fictitious invisible moon of Earth, supposedly about the same mass as the Earth's Moon, proposed in 1918 by astrologer Walter Gorn Old, who called himself Sepharial. Sepharial applied the name Lilith from medieval Jewish legend, where she is described as the first wife of Adam. Sepharial claimed that Lilith was the same second moon that scientist Georg Waltemath claimed to have discovered twenty years earlier, but which had never been confirmed. Sepharial also claimed to be the first person in history to observe Waltemath's moon as it crossed the Sun, and rationalized that it was too dark to be otherwise visually detected.
Sepharial's comments ignored the fact that Waltemath's proposed moon had already been discredited by the scientific community at the turn of the century.
There are many readily apparent holes in the arguments supporting Lilith's existence, and its existence is believed only by fringe groups; astrologers now generally use the name for the position of the actual Moon's apogee.
In modern astrology
In present-day astrology, the name Lilith or Black Moon Lilith is usually given to a point on the horoscope of the actual Moon's apogee. When considered as a point, this Lilith is sometimes defined as the second focus of the ellipse described by the Moon's orbit; the Earth is the first focus, and the apogee lies in the same approximate direction as the focus. It takes 8 years and 10 months for this point to complete a circuit through the zodiac tracking the apsidal precession.
Planets proposed by L. Ron Hubbard
L. Ron Hubbard, the founder of Scientology, proposed as part of his cosmology a Galactic Confederacy which consisted of 26 stars and 76 planets including Earth, which was then known as "Teegeeack". One planet in the Scientology doctrine is known as Helatrobus.
Ummo
Ummo or Ummoism is a decades-long series of claims that aliens from the planet Ummo were communicating with people on the Earth. Most Ummo information was in the form of detailed documents and letters sent to various esoteric groups or UFO enthusiasts. The Ummo affair was subject to much mainstream attention in France and Spain during the 1960s through the 1970s, and a degree of interest remains regarding the subject. Consensus is that Ummoism was an elaborate hoax. The culprit (or culprits) is unknown, but a José Luis Jordán Peña has claimed responsibility for instigating Ummoism. However, there are still a few small groups of devotees, such as "a strange Bolivian cult called the Daughters of Ummo".
Jacques Vallée has said that the author(s) of the Ummo documents might be a real-world analogue of the fictional creators of Borges' "Tlön, Uqbar, Orbis Tertius". Historian Mike Dash writes that Ummoism began on February 6, 1966, in Madrid. On that day, Jordán Peña claimed to have had a close encounter of the first kind when he saw "an enormous circular object with three legs and, on its underside, a curious symbol: three vertical lines joined by a horizontal bar. The two exterior lines curved outward at the edges, which made the pictogram resemble the alchemical sign for the planet Uranus." (Dash, 299) Peña's report generated a fair amount of excitement, but it was only the beginning. Not long afterwards, a Madrid author of a UFO book received several photographs in an anonymous mailing. The photos were of a craft similar to the one reported by Peña, and bearing the same symbol. Within a few weeks, "a leading Spanish contactee named Fernando Sesma Manzano became involved when he began receiving lengthy, typewritten documents which purported to come from a spacefaring race called the Ummites." (Dash, 299)