(134340) Pluto - SpeedyLook encyclopedia

History

Discovered

Pluto was discovered in 1930 at the time of the search for a celestial body making it possible to explain the orbital disturbances of Neptune, assumption suggested by Percival Lowell as being the Planet X.

Having made fortune in the businesses, Lowell is made build in 1894 a observatory with more than 2,000 meters of altitude in the Arizona and begins the research of a ninth planet beyond Neptune. He thinks of following the same method as that which had led to discovered the latter by studying its orbit, but the precision of the instruments of the time not making it possible to measure in a precise way the orbital anomalies, he must be folded back on those of Uranus. Its planet (baptized “X”) would be located at 47.5 ua, would have one period 327 years and a mass of two fifths of that of Neptune. In 1905, it launches a first three photographic year campaign, but this one does not give anything conclusive, in particular, as it was shown thereafter, because this program was focused on the ecliptic and that the tilted orbit strongly of Pluto at that time placed it apart from the field of the photographs. Lowell does not lower the arms for as much and decides to redouble efforts, in particular when he sees appearing a competitor: William Pickering. This one announces in 1908 the presence of a planet which it names “0” of two terrestrial masses, at a distance from 52 ua and one period 373 years. In 1911, Lowell acquires of a machine intended for the photographic analysis enabling him to compare the stereotypes much more quickly (two series of photographs are taken at a few days of interval to locate the possible movement of a star) and starts a new series of photographs. A new failure which will carry out it to ignore its planet X.

Percival Lowell dies in 1916 but leaves in its will what continue research without worrying about the money problems, although problems of heritage with his wife end up reducing the budget of the observatory. However ten years later, the observatory requires a new instrument. Abott Lawrence Lowell, the brother of Percival Lowell, agrees to give ten thousand dollars for the construction of a telescope of 13 inches that Clyde W. Tombaugh will be charged to control for this heavy task which is the meticulous cartography of the sky, with the research of the planet X. Tombaugh reorganizes its scheme of work and proceeds to three catches instead of two in order to increase the chances to perceive the movement of planet. The third series of stereotypes ends on January 29th, 1930 and begins the analysis of the photographic plates then. The February 18th at 4 p.m., it notices a point of magnitude +15 to move from one plate to another on two photographs taken January 23rd and 29th. The team of the Lowell observatory, after having taken other photographs allowing to confirm the discovery, telegraphs the news with the Harvard College Observatory on March 13rd, 1930.

The planet is named at the same time in reference to the Roman god of the hells and Percival Lowell whose initial ones form the first two letters of Pluto. Its initial forms the symbol of Pluto (♇). The name was suggested by Venetia Burney, an eleven year old young girl of Oxford, in England.

Many observatories are then put to observe this new planet, in order to determine its orbit most precisely possible. While retrogressing, Pluton is retroactively observed on photographic plates going up until 1909.

Pluto and planet X

The discovery of Pluto east in the beginning related to the systematic search for a planet allowing to explain the disturbances observed in the orbits of Uranus and Neptune, but the doubt is very quickly thrown on the fact that Pluton is the Planet X that Percival Lowell sought.

At that time, Pluto east so remote that its diameter cannot be given with precision, but its weak luminosity and its absence of apparent disc let predict a rather small, comparable body cuts with the telluric planets of it already known, probably larger than Mercure but not more than Mars, one thinks at the time. It thus becomes quickly clear that Pluton cannot be the source of the disturbances in the orbits of Neptune and Uranus, and the astronomers are brought to imagine that many other bodies similar to Pluton can orbit around the Sun beyond Neptune. One thinks whereas the solar system could be made up of several zones gathering the celestial bodies by families, telluric Planet, giant planet, “ultra-neptunian objects” will make it possible to solve many problems as for the mass and the size of Pluto. That made it possible to still re-examine with the fall the mass of the system Pluton/Charon, weaker even as the minimal estimates provided by the opponents to the theory of the specular reflection (which consequently was completely invalidated). The astronomers are of agreement today to give to Pluton a diameter quite lower than that of the the Moon, with only one fraction of its mass, in agreement with its composition (of the ice mainly). In the Years 1970, calculations of the trajectories of the probes Voyager showed that Neptune had a mass lower than the preceding assumptions, and by taking account of this new measurement, the divergences in the movements of the Uranus planets and Neptune become negligible in front of the uncertainty of measurement related to the precision of the instruments.

Planet statute

Towards the end of the 20th century, the statute of Planet of Pluto is more and more often called in question.

On the one hand, of very many bodies are discovered which have an orbit very close to that of Pluto, and are like it in resonance 2:3 with Neptune. Approximately 150 objects of this type, known under the name of Plutino S, were listed in February 2006, which tends to show that Pluton is the largest representative of a vast family of more or less massive bodies.

The discovery in 2005 of (136199) Éris, of a diameter and a mass slightly higher than that of Pluto, contributes to start again the debate. The diameter of Éris, which had initially been estimated at 3,600 km (it was then notably larger than Pluton) always currently remains (2006) of the same order of magnitude as that of Pluto, even if it were re-examined with fall (2,400 km ± 100 km). According to a study published in Science of June 14th, 2007, its mass would be higher than that of Pluto from approximately 27%. Many other bodies were also discovered at that time, such as, (90482) Orcus or (90377) Sedna, regularly announced as being it tenth planet of the solar system.

Certain scientists then propose to reclassify Pluton out of minor planet or Objet transneptunien. Others, like Brian Marsden of the Minor Planet Center , lean to allot the two statutes to him, because of the historical importance of its discovery. Marsden announces on February 3rd, 1999 that Pluton would be classified like: 10,000e object of the precisely counting catalog: 10,000 minor planets. The round number of: 10,000 would be allotted to Pluton in its honor for the “celebration” of this account reached.

It is interesting to note that, historically, the first four asteroids discovered ((1) Cérès, (2) Pallas, (3) Junon and (4) Vesta) were them also regarded as planets during several decades (their dimensions were not known with precision at the time). Certain astronomical texts of the beginning of the 19th century refer to eleven planets (including Uranus and the first four asteroids). The fifth asteroid ((5) Astrée) was discovered in 1845 little time before the discovery of Neptune, follow-up of several others in the following years. Although they are always called “minor planets”, they are not regarded today any more as “planets”.

The last word returning to the international astronomical Union, the organization coordinator of astronomy to the international level, in load of the denomination of the celestial bodies as well as theirs statute, this one, at the time of its XXVIe congress held on August 24th, 2006 in Czech Republic, decided at the end one week of debates to reclassify Pluton in dwarf Planet rather than Planet. The number of minor object 134340 to him was allotted on September 7th, 2006.

Nevertheless, following the vote, a petition having joined together in five days the signatures of more than 300 planetologists and astronomers mainly American was launched to challenge the scientific validity as well as the mode of adoption of this new definition and to invite to the reflection on another more suitable definition.

Exploration of Pluto

Pluto is a difficult objective for space exploration, because of the long distance separating it from the Ground and from its very low mass, and thus does not have until now summer visited by any Space probe, which explains the little of available data partly.

The probe Voyager 1 could possibly have reached it, but the exploration of Titan (the satellite of Saturn) and of the Saturn's rings was considered to be more important, resulting in a trajectory incompatible for an appointment with Pluton. There Voyager 2 could theoretically have also arrived, but the trajectory would have crossed the planet Neptune, and Charon thus appears motionless in the Plutonian sky.

Mass and dimensions

The diameter of Pluto east one of the physical parameters least well-known and most difficult to measure, and the primary source of uncertainty on the other derived parameters, such as the Density. Its very long distance combined with its small size make that it is impossible to solve with precision the disc of Pluto, and thus prevents “direct” measurements of its dimensions, that it is with the Space telescope Hubble or the terrestrial instruments equipped with optical adaptive. Current measurements being based on the Screening S of star by Pluto and screenings of Pluto by Charon do not agree exactly, and the explanations making it possible to explain these differences depend on the models used to analyze the data, in particular concerning the atmosphere of dwarf planet. The value and the margin of error generally retained of: 2,306±20 kilometers of diameter includes in fact the differences in result of the various methods of measurement and confirmed by another screening in 1988. When an object deprived of atmosphere passes in front of a star, this star of background disappears in a brutal way; in the case of Pluto, the luminosity of masked star gradually decreased. Evolution of this curve of luminosity, a mean atmosphere of 0.15 Pa was determined, that is to say approximately 1: 700,000e of that of the Earth. This atmosphere could exist only when the planet is with its Périhélie and to freeze when it moves away from the Sun.

In 2002, another stellar screening by Pluton was observed by several teams directed by Bruno Sicardy, Jim Elliot and Jay Pasachoff. In a surprising way, the atmospheric pressure was estimated at 0.30 Pa, although Pluton is further away from the Sun than in 1988 and thus colder. The assumption privileged at present is that the south pole of Pluto would have left the shade in 1987 for the first time since 120 years and that a surplus of nitrogen would then have sublimated southern polar icecap. This nitrogen excess should probably spend decades before condensing with the other pole.

Planetary system

Description

Charon

Other possible satellites

The observations carried out by the Space telescope Hubble placed limits as for the existence of additional satellites in the Plutonian system. With a probability of 90%, no moon of more than 12 km and a Albédo similar to that of Charon (that is to say 0,38) exists in a zone of 5 " around Pluto. For a darker albedo of 0,041, this limit is increased to 37 km. With a probability of 50%, this limit goes down to 8 km.

Possible rings

In an article published in the Natural review .

Appendices

Plutino
Belt of solar Kuiper
Eclipse on Pluto
Object transneptunien
Planet
(136199) Éris

External bonds

Astrofiles : Pluto
the solar system - isn't Pluto
Pourquoi Pluto any more one planet?
Pluto, dwarf planet (podcast)

Random links:

Congolese national radio-television | 1985 in science | David Bercuson | Two Harbors (Minnesota)