Vulcan

This article is not about the planet from which Mr. Spock comes.

Hypothetical planet, Vulcan, from an 1846 lithograph.

It's not rocket science, it's...
Astronomy

The Final Frontier

* Gliese 581c
* Brown dwarf
* Sun
* Geocentrism
* Cosmoquest Forum
* Alternative cosmology
* Eclipse
* Hanns Hörbiger
* Andromeda Galaxy
* Moon
* Earth
* Expanding universe

The abyss stares back

* Galileo Galilei
* Arthur C. Clarke
* Neil deGrasse Tyson
* Jason Lisle
* Tycho Brahe

v \- t \- e

Vulcan is a hypothetical planet that was thought to orbit the Sun in an orbit inner to Mercury before the 20th century, named after the Roman god of the same name equivalent to the Greek Hephaestus.

## Contents

* 1 Theory and observations
* 2 Enter Einstein
* 3 Today
* 4 References

## Theory and observations[edit]

Claims about objects seen transiting in front of the Sun have existed since the invention of the telescope, back in the 17th century[1] and reaching a maximum in the 19th century,[2][3][3] even if most if not all of them are more than likely to have been just reports of the observations of sunspots if they were real at all.

Theories about an innermost planet to Mercury began circulating in that century[4] and were followed by observations that hoped to spot the planet when it passed in front of the Sun, given that seeing it after sunset or before dawn would be very difficult or outright impossible with it lost the Sun's glare.[4] All of them, of course, came up empty or were impossible to replicate, suggesting that if the planet existed at all it would be very small and would orbit close to the Sun, as otherwise it would have been detected before—either transiting in front of the Sun or during a solar eclipse, as such closeness to the Sun means a lot of solar irradiation such that that it would have been quite bright, especially in the case of a large planet.

## Enter Einstein[edit]

Anomalies in Mercury's orbit that models of the latter failed to account for, causing astronomers to think the gravity of planet(s) orbiting closer to the Sun were responsible, were a mystery until 1915, when Einstein's Theory of Relativity showed they were caused by space-time being warped by the Sun, matching almost exactly the observations done in the previous century,[5] with such prediction being confirmed during the solar eclipse of May 29, 1919 catapulting Einstein to fame and Vulcan's existence being no longer needed.[6]

## Today[edit]

Earth-based searches have been supplemented by observations from space using telescopes such as SOHO, to spacecraft ~~that have boldly gone where no spacecraft has gone before~~ positioned within Mercury's orbit, such as NASA's Parker Solar Probe, that have not only failed to find such a planet, but also revealed that the space within Mercury's orbit is devoid of bodies of significant size, with a proposed population of asteroids that would be there as an alternative to the existence of such planet having also failed to materialize, besides the occasional comet or asteroid.

Many other star systems contain planets (sometimes very comfortably) within a radius equivalent to Mercury's orbit. Whether this is simply an observational bias (as such kind of planetary systems are easier to detect with our current technology), or the lack of them in our Solar System is actually a feature ~~and not a bug~~ is a mystery.

The name "Vulcan" being still today reserved for a planet that turned out not to exist is the reason why he is the only Olympian not to have an object in the solar system named after him.

## References[edit]

1. ↑ Drobyshevskii, E. M. (1992). "Impact Avalanche Ejection of Silicates from Mercury and the Evolution of the Mercury / Venus System". Soviet Astr. 36 (4): 436–443\. Bibcode:1992SvA....36..436D.436-443&rft.date=1992&rft_id=info:bibcode/1992SvA....36..436D&rft.aulast=Drobyshevskii&rft.aufirst=E.+M.&rfr_id=info:sid/rationalwiki.org:Vulcan" class="Z3988">
2. ↑ Blake, William (1796). "The Monthly magazine. v.45 (1818)". Monthly Magazine and Critical Register of Books. Retrieved 2017-07-04.
3. ↑ 3.0 3.1 Elger, T.G.E. (May 4, 1869). "The Supposed New Planet Vulcan". Astronomical Register. 7: 164. Bibcode:1869AReg....7..164E.
4. ↑ 4.0 4.1 ,Baum, Richard P.; Sheehan, William (August 2003). In Search of Planet Vulcan: The Ghost in Newton's Clockwork. New York: Basic Books. ISBN 0738208892.
5. ↑ Kurt Larson, Jan 2, 1860: The Discovery of Planet Vulcan, oddsalon.com
6. ↑ David Baron (2017). American Eclipse. Liveright. ISBN 9781631490163.