Vulcan (hypothetical planet)

Volcano (or Vulcan ) is the name of a hypothetical planet inside the orbit of Mercury, which was adopted earlier to explain the perihelion of Mercury completely. When the perihelion of Mercury could be explained by the general theory of relativity, the volcanic hypothesis lost its necessity and at the same time their meaning.

The hypothesis

In the 19th century it was found at web observations of Mercury that its actual orbit deviates from the form of a Keplerian ellipse. While each track circulation shifts the perihelion of Mercury ( perihelion ). This deviation was determined to a size of 574 " ( seconds of arc ) per 100 years and could use the Newtonian law of gravitation by the interference of the other planets largely be explained. The error could be reduced to 43 " per century. Even if this amount is very small, the result is inconsistent with the celestial mechanics by Isaac Newton. Only with the general theory of relativity by Albert Einstein, this effect of the perihelion is sufficiently explained.

The existence of a planet inside the orbit of Mercury was postulated in 1859 by the French mathematician and astronomer Urbain Le Verrier to explain this deviation. In a lecture on January 2, 1860 in Paris, he took with good reason, his guess. 1846 had already calculated the trajectory of the time still undiscovered planet Neptune through observation of perturbations of Uranus Le Verrier. A short time later, Johann Gottfried Galle discovered the planet just one degree of the predicted position away. Against this historical background appeared for Le Verrier the existence of volcanic plausible, and many astronomers around the world were trying to find him.

Searching for Vulkan

Observations of an object within the orbit of Mercury is very difficult because the telescope must be directed at a point which is very close to the Sun, where the sky is never black. In addition, an error in the alignment of the telescope optics and cause serious damage, irreversible eye damage if an observer. The extreme brightness can also cause reflections in the optics that confuse the observer and let him see objects that do not exist.

Over half a century astronomers were trying to track the hypothetical planet Vulcan, especially during solar eclipses. There were numerous false alarms and confusion, or optically neighboring stars were held for the planet looking for. So it was among other things the asteroid researcher James Craig Watson.

When Le Verrier died in 1877, he was still convinced that they have found volcano. With his death, the search went to the planet fiction back strong, as most astronomers whose existence after years of fruitless search is now doubted. The 123 -fold asteroid explorer Johann Palisa tried again at a Tahiti expedition in 1883.

Another former explanation for the anomalies of Mercury's orbit postulated a flattening of the sun, which was not demonstrated a sufficient degree.

Since Einstein in 1916 published his General Theory of Relativity and the perihelion of Mercury has almost completely explained by the effect of the sun on the surrounding spatial structure, the hypothesis of volcano is indeed superfluous, but some researchers postulate now in its place a thin asteroid belt from so-called Vulkanoiden. Possible preferred train areas of potential asteroids were calculated at 0.18 and 0.15 AU distance from the Sun.

For a brief resurgence of the volcanic hypothesis it came to 1970, when some researchers thought they had during the total solar eclipse observed in that year faint objects near the sun. The American astronomer Henry Courteen, a professor at Dowling College in Oakdale (USA), believed to have is substantial evidence for such a so-called intramerkuriellen planet found. According to his calculations, the volcano should rotate at a large semi-major axis of 14.4 million miles, the Sun in about 11 days time and have a diameter between 300 and 800 kilometers. Remarkably, this mean solar distance of 0.096 astronomical units left fit in very well with the Titius - Bode series when the factor -1 used for volcano ( 0.4 0.3 × -1 = 0.1 AE). In the observed objects it has possibly acted to faint comet, similar to the later, which could be observed close to the Sun and are plunged in some cases even in it.

Volcano transit

As a volcano is called the transit observed from Earth hypothetical Gone Pull volcano in front of the solar disk, which would occur very frequently at such a planet in the solar neighborhood. Especially in the 18th and 19th centuries, there have been reports of such observations.

It was never clarified what looked pass the time before the sun disk, the observer. While it is likely to have acted in some cases to errors in optics, but at least one case from the 18th century known companies listed on the two observers at different places the parading of an unknown object from the sun.

This could well have been an asteroid. However, to date no asteroids transit from the sun has been registered. Sunspots can in any case be excluded, as they require over 10 days of one side of the sun to the other and in the 18th century were already known.

Volcano in the science fiction

The name Vulcan was also used by science fiction writers, some of which are fictional planet outside our solar system:

In the universe of the Star Trek movies and television series, there is a Planet Vulcan, but in a different solar system. It is located about 16 light-years away from Earth and orbits the star Keid. See also: Vulcan.

The Sten Chronicles by Allan Cole and Chris Bunch volcano is an artificial planet. Volcano was originally an industrial space station, which grew by adding new manufacturing facilities more and more, and thereby assumed planet-like proportions.

The volcanic theory inspired some authors (for example, Nikolai von Michalewsky ) to revive the Pythagorean idea of ​​a Counter-Earth, a planet in the same orbit around the Sun as the Earth, but it constantly opposes in conjunction.