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The Planet Vulcan

A small and very hot place, the Planet Vulcan was believed to exist in a very close orbit around the Sun. The Planet Vulcan in question is not to be confused with where Mr Spock came from, although that's also known as the Planet Vulcan. Indeed, we're talking about a planet which is mentioned in some books, documented as actually existing in the known physical universe. For example in "Everything Within", that helpful and delightfully oldfashioned encyclopaedic volume which you see on grandparents' bookshelves, there's a list of planets which includes Neptune, (but no Pluto as the book was written before that particular item was discovered), and there it is, Planet Vulcan, inside the orbit of Mercury. So whereas Planet Mercury has a year of 88 days, the Planet Vulcan has a year of 28 days.

It would be a very inhospitable place. Besides being fiercely hot being so close to the Sun, it would also be subject to severe radiation, and possibly severe tidal forces (like on Io, which orbits rather close to Jupiter).

Anyway, the Planet Vulcan. Does it exist? It's printed in a book, so surely it does? And, if it does exist, why has it been dropped from respectable scientific works about astronomy? Has it been "hushed up"? Besides, although astronomers had problems with it, astrologers found it quite useful, and made various predictions about people's lives based on the Planet Vulcan's orbital period of 28 days, and the phase of it, etc. Incidentally, just because a planet doesn't exist, it doesn't mean it ceases to have relevance in astrology. Astrology is a mystical art, whereas Astronomy is science. So, for astronomers, it makes a big difference whether something exists or not.

If the Planet Vulcan existed, scientists would want to send spacecraft there. The craft would be small, neat, and fireproof. A probe would go into solar orbit, rendezvous with the planet, and try to make a soft landing with its springy tungsten feet touching down on the surface, and then the webcam inside the craft would peer out though a solid diamond window at the flaming hot landscape and send back pictures to Earth, where the pictures and story would be on the news briefly, behind all the supposedly important stuff such as some minor celebrity doing something untactful, politicians making a mess of things as usual, and the ongoing wars between various arrogant tribes with sophisticated weapons and very little commonsense.

The sad news for any such proposed interplanetary mission to the Planet Vulcan is that the place does not exist. There is no Planet Vulcan. (There are plenty of other places to explore, though!)

Now hang on a bit, you can't just state "The Planet Vulcan does not exist". These things have to be backed up with evidence and reason, and we live in a world of science, not belief. In the case of Vulcan, a while ago some quite clever people believed the planet existed, and now it's no longer in the books, so what's happened?

Let's compare the situation with a similar one, PLUTO. Before 1936, Neptune was the last planet on the list, and there was no Pluto. However, measurements of the positions of Uranus and Neptune suggested that they might be having their orbits augmented by something else out there, such as another planet. This situation got turned into "A PLANET" after something was discovered. Even so, "Planet Pluto" as it was termed then, didn't look big enough to move the somewhat larger Neptune and Uranus much. Later still, it was found that the "Planet Pluto" was two objects, Pluto and Charon, and their co-orbit made the initial estimates of the size of the "Planet Pluto" to have been too big. It would have been like seeing two lights at night in the distant road ahead and guessing it was a car, and later discovering it was two bicycles.

So, the best-guess regarding Pluto was initially that it was a large planet, then later (on observation) reckoning it to be a smaller planet, and then later (with better telescopes) finding it to be two even smaller objects. More about the Pluto contentious stuff here.

With Vulcan, there had been observations of objects going around the sun every 28 days or so, but that happens to fit rather well with the rotational period of the Sun itself, and sunspots on the surface going around, etc. Also, if there'd been a Planet Vulcan, it would have been subject to the same sort of things as the Planet Mercury, and as time went on and observations became better and the physics became better understood, the Planet Vulcan's estimated size and position got so small and so close to the sun that it could not possibly exist. If you'd like to read more about the details, there's a book on it, In Search of Planet Vulcan which makes it much clearer.

If you came to this page hoping to find some planetary exploration, take heart in the fact that there is (at the time of writing) a spacecraft on its way to Pluto, which, (regardless of whether it's defined as a planet or not), exists, and it will soon be visited. That should be fun! See New Horizons. Also, there was a remarkably good landing on Titan, which is one of the worlds orbiting the Planet Saturn. There's a variety of interplanetary exploration going on, if you know where to look for it. It can't actually be "hushed up", and in practice it's just hidden by there being lots of waffle on the news.

Also, have you ever heard of Ceres? That's a minor planet that actually exists, and yet is generally ignored.

Other vaguely relevant stuff at this site: How Orbits work, some basic astronomy, the risks of Earth on a Collision Course with Asteroid ("minor planets" is a scary phrase).

Also see the continuing Fuss about Pluto