The Sad Sunset Of Planets That No Longer Exist.

Planets that don't exist anymore Just like any good story, the tale of our solar system is filled with characters who exited the stage early, or whose existence has faded into the mists of hypotheses and legends. In this case, we're talking about celestial objects, moons that were spotted and then never seen again, planets that might have only been imagined but were considered as real as the ones we know today, if only for a moment or even centuries. This is also astronomy and the quest for truth, even if most of these stories have turned into a maze of dead ends over the years. How many planets are in the solar system today? Eight. Well, it might surprise you, but there was a time when the solar system boasted many more planets. For many years after their initial discovery, asteroids were considered full-fledged planets, despite numerous uncertainties. Here's an example. An English book written in dialogue form for Teaching Astronomy to Children, First Steps to Astronomy and Geography, London, 1828, includes the following question and answer, clearly reflecting the planetary status of these new arrivals. Herschel was the provisional name for Uranus, discovered by William Herschel in 1781. How many planets were there then? There are 11. Mercury, Venus, Earth, Mars, Vesta, Juno, Ceres, Pallas, Jupiter, Saturn, and Herschel. That was in 1828. The list included only the first four, but the number was set to increase. By the end of 1850, astronomers had found a total of 13 new objects, all classified as planets. This belief was supported by the fact that the new arrivals all orbited between Mars and Jupiter, where the so-called Titus-Bode Law predicted a planet should be. Despite this, as early as May 13, 1802, Herschel had already communicated to the Royal Society his intention not to consider the two newly discovered objects, Ceres and Pallas, as planets, but simply as asteroids, because no matter how much they were magnified through a telescope, they stubbornly maintained a star-like, point-like appearance. Herschel's decision irritated Piazzi, the discoverer of Ceres, but within a few decades it became the majority view among astronomers. From 1861, the Astronomische Nachrichten Astronomical News, the most authoritative journal of the time, began using the subcategory claimed planet, minor planet, in its index. By 1866, the Paris Observatory did the same with all Petit Planète, except for the first four discovered, which continued to be considered planets until 1868. The Greenwich Observatory held out until the beginning of the century, continuing to publish asteroid affirmatities in the section Observations of the Sun, the Moon and the Planets. This practice was abandoned only in 1907, by which time more than 600 small planets had been discovered. Think about it, for the most famous astronomical observatory of the time, until 1906, the solar system contained more than 600 planets. But what caused the uncertainty in understanding the true nature of these particular objects? After all, Uranus had been recognized as a planet just a couple of months after its discovery. What prevented a quick decision in the same way? Today we know that the main challenge in determining whether these objects were planets was their extremely small apparent size. For instance, Ceres, with its diameter of nearly a thousand kilometers, only subtends about 0.7 arcseconds even at opposition. Additionally, the technical equipment available at the time was quite inadequate. This led to some imaginative estimates of their diameter, ranging from the exaggerations of German astronomer Johann Schroeder who estimated Ceres at 2,613 km, Pallas at 3,380 km and Juno at 2,290 km to Herschel's underestimation which placed Ceres at no more than 250 km. The extreme uncertainty is also reflected in the scientific publications of the time, which sometimes adopted one view or the other and occasionally reported both. However, by the end of the 19th century, a more reliable method emerged. Between 1894 and 1895, American astronomer Edward Bernard made the first measurements of the diameters of Ceres, Pallas, Juno and Vesta using a wire micrometer on both the 36-inch Lick refractor and the 40-inch Yerkes refractor. The values he obtained, Ceres 830 km, Pallas 550 km, Juno 195 km and Vesta 420 km, were much more closer to reality and were considered definitive for over half a century. These measurements helped bring some order to the chaos, ending the frightening vision of a solar system populated by thousands of planets. Enter Vulcan. This was an era of great observational campaigns. Astronomers were trying to inventory our cosmic home, and around the same time that asteroids were losing their battle to maintain planetary status, the discovery of a new planet was being celebrated. Here's how it happened. At the time of Neptune's discovery in 1846, thanks to his calculations, French astronomer Le Verrier was also monitoring a second planet, Mercury. In this case, too, the perturbation calculations didn't add up. Observations clearly indicated that Mercury's perihelion was subject to precession, but calculations considering the influences of other solar system bodies couldn't account for the observed motion. There were a few arcseconds for which no explanation could be found. Le Verrier was convinced that, once again, the gravitational influence of an unseen object was at play, or rather an object hidden in plain sight. The new planet capable of perturbing Mercury's motion could have escaped detection due to its orbit being much closer to the Sun than any other planet. Confident in his belief, on September 12, 1859, Le Verrier announced to the French Academy of Sciences the existence of a new planet, which he had already named Vulcan. Just as with Neptune 13 years earlier, it was now a matter of waiting for observational confirmation of this new arrival. The wait lasted only a few months. In December of that same year, Le Verrier received a letter from Edmond Lescarbeau, a doctor from the town of Augere, and an amateur astronomer. The doctor recounted how, during an observation of the Sun's surface on March 26, he had clearly seen a small, perfectly circular dark spot transit across the disc. You can imagine the urgency with which Le Verrier rushed from Paris to Augere to get detailed information about this observation. Despite some initial disappointment at seeing Lescarbeau's rudimentary instruments, Le Verrier was convinced of his sincerity and used the observational data from that transit to calculate Vulcan's orbital parameters. According to Le Verrier, the new planet had a diameter of about 1600 km, was 21.5 million km from the Sun, had an orbital period of 19 days and 18 hours, and a mass one-seventeenth that of Mercury. Le Verrier quickly realized that such a small mass couldn't account for the observed perturbation, but this wasn't a valid reason to doubt the existence of this small object. Theoretical analysis alone couldn't determine whether the perturbation of Mercury's perihelion was due to a single object or a belt of small objects. On July 18, 1860, there was an opportunity to settle the matter. A total solar eclipse, the most observed in history, the first to use photographic plates, and the first to see a massive coronal mass ejection, occurred in nearby Spain. This was the perfect chance to catch the hypothetical small planet near the occulted solar disk. Le Verrier mobilized all the major observational astronomers of the time to find Vulcan, but no one saw anything, though this wasn't considered definitive proof against its existence. Four years after Les Garbeau's report, another observational evidence came from W. Loomis, an amateur astronomer from Manchester. He reported seeing a dark spot on the solar disk moving rapidly during observations on March 20, 1862. Its movement was too fast to be a sunspot, and its shape was circular with well-defined edges. Calculations based on this transit provided results very similar to those already defined by Le Verrier, further confirming that Vulcan wasn't just an illusion. Another piece of evidence in favor of Vulcan and Le Verrier came from a German astronomer who reported seeing a circular spot transit the sun's disk on April 4, 1875, an observation confirmed by Greenwich and Madrid. The surprising thing about this sighting was that Le Verrier's calculations predicted a transit of Vulcan for April 3 of that same year. This renewed the success of mathematical prediction, just like with Neptune. Not everyone shared the general excitement, as there were observational data suggesting that things were far from clear. For example, Les Garbeau's observations were strongly contested by a French astronomer named Emmanuel Lié. Lié claimed to have observed the solar disk during the same period when Les Garbeau reported Vulcan's transit, but despite using a much powerful telescope, he saw nothing unusual. He suggested that what Les Garbeau saw was not a large planet near the sun, but a small asteroid passing close to Earth and coincidentally projected onto the solar disk. Thus, the story dragged on for decades, with recurring confirmations and denials. Throughout all this, Le Verrier maintained an unwavering belief in Vulcan's existence and in Newtonian mechanics, and his conviction of having discovered the new planet stayed with him until his death on September 23, 1877, at the age of 66. Le Verrier's death did not end the search for observational confirmation of Vulcan's existence, nor did it quell the controversies that ignited scientific discussions worldwide. Another excellent opportunity to explore the vicinity of the sun for potential planets was on the horizon. On July 29, 1878, less than a year after Le Verrier's death, a total solar eclipse was expected to be visible in the United States. Emerging American astronomers decided it was finally time to settle the mystery of Vulcan once and for all. Lewis Swift and James Watson, two American astronomers, Swift is known for the comet, observed the eclipse from two different locations, and both claimed to have spotted objects not listed on their star charts. This time, it couldn't have been a mistake, and the prestigious journal Nature published the official announcement. However, some things didn't add up, and other astronomers were quick to point this out. Firstly, Swift and Watson's data were incompatible. Watson claimed to have found two intramercurial planets, while Swift reported seeing only one, but in a different position from either Watson's planets. Additionally, neither Watson's nor Swift's Vulcan matched Le Verrier's and Les Garbeau's Vulcan. This meant there were now four intramercurial objects, making the discovery even more incredible. The more likely alternative was that Swift and Watson had made some errors due to haste and limited time. Once again, the matter slipped into controversy. Fortunately, another extremely favorable eclipse was just around the corner. On May 17, 1882, Egypt would experience 5 minutes and 33 seconds of totality, compared to the 2 minutes and 40 seconds of 1878. Expectations for confirmation were high, but they were disappointed. Accurate observations revealed nothing unusual near the Sun, except for the unexpected sight of a large comet, previously unnoticed, shining near the eclipsed solar disk. Similar results were obtained during subsequent eclipses. In the 1901, 1905, and 1908 eclipses, the newly introduced photographic technique was applied to the investigation, but the results were always disappointingly negative. Commenting on the results of his work, Charles Perrine, the astronomer from the Lake Observatory who conducted this photographic research, was categorical. It was impossible for an object larger than 40 km in diameter to exist within Mercury's orbit. End of story and end of the planet Vulcan. The phantom moon of Venus It's well known that Mercury and Venus are the only two planets in the solar system without satellites. Yet another striking example of a discovered and then forgotten celestial body involves the centuries-long debate over Venus' supposed satellite. In 1672, Giovanni Domenico Cassini, one of the most important astronomers of the time, noticed a bright spot near Venus, but decided not to reveal his observation. In 1686, he saw the object again and noted it in his diary. He estimated that the object was about one-fourth the diameter of Venus and showed the same phase as Venus. In the following decades, the object was also seen by many other astronomers, including James Short in 1740, Andreas Meyer in 1759, and Joseph-Louis Lagrange in 1761. However, many others who pointed their instruments at the same night swore they saw nothing. A long controversy ensued, and what better occasion than a transit of Venus across the Sun to decide who was right? The event occurred on June 6, 1761, and from India, amateur astronomer Abraham Shuton reported clearly seeing Venus' disk accompanied by a smaller dark spot. However, no one else was able to validate the sighting. Finally, in 1766, the director of the Vienna Observatory, Maximilian Hell, published a treatise arguing that all observations of the satellite were nothing more than optical illusions. The image of Venus, he explained, is so bright that it creates a smaller secondary image next to the original. This seemed to put the matter to rest, but in the 19th century, the topic resurfaced. Some astronomers in Belgium, the Netherlands, and Denmark questioned whether the likes of Cassini, Short, and Lagrange, who were highly skilled professionals, could have made such a glaring mistake as Hell's study suggested. To explain the observations, some hypotheses were formulated. The first involved the possibility that unknown asteroids were in Venus' field of view. However, subsequent calculations showed that this hypothesis had no basis. The only asteroid that could have been near Venus was Vesta, but it was never in the right position during the mentioned observations. Even extending the investigation to the positions of the first 100 numbered asteroids, none would have appeared in Venus' field on the right days and within one degree of the planet. The hypothesis of Venus' moon was definitively dismissed in 1877 by another Belgian astronomer, Paul Strubant. In a lengthy study published by the Belgian Academy of Sciences, he examined all previous observations and found plausible explanations for each. The scientific community welcomed his critical synthesis with enthusiasm. In August 1888, during a speech on the progress of astronomy, the then president of the Société Astronomique de France, Camille Flammarion, stated, The issue of Venus' anti-magnetic satellite has been definitively clarified by Mr. Strubant. Where it wasn't an optical illusion, it was found that in the remaining 33 well-documented sightings, the presence of a fixed star couldn't account for the observed positions. Thus, after more than two centuries, a quest that had captivated astronomers across Europe was finally laid to rest. Not even the sighting by the great Bernard, who saw a seventh magnitude object near Venus on August 13, 1892, could revive it. History repeats with Pluto and Eris You might think these are all things of the past, but it's impossible to forget that a similar story of changing status from planet to asteroid happened in our own time with the incredible demotion of Pluto to the rank of dwarf planet. And for the same convoluted reason, to avoid dealing with an overwhelming population of planets. If today the solar system has only 8 planets instead of 9, it's because of Eris. The name given by astronomers was fitting, Eris, the goddess of discord. When discovered in 2003, Eris showed that beyond Neptune's orbit, there are a significant number of dwarf planets as large as or even larger than Pluto. Should we then expand the number of planets in our solar system to include all of Pluto's smaller and larger siblings? That seems too much. So, in 2006, the International Astronomical Union made the historic decision to reclassify Pluto as a dwarf planet like Eris, reducing the number of official planets in the solar system to 8. This fear was unjustified, though, since the discovery of Eris wasn't followed by dozens of similarly sized objects, as happened in the early 19th century in the main asteroid belt. And so, with a single stroke, the 9th and 10th planets of the solar system were erased from history. This wasn't a painless disappearance of hypothetical planets or merely imagined celestial bodies. This wound is real, and it hurts a lot. We'll stop here, although there are many more stories to tell, starting with Theia, the planetary body that must have collided with our planet 4.5 billion years ago to create the Moon, to the moons of the gas giants, observed and then lost forever, and the 5th planet, once thought to be the progenitor of all asteroids. Not to mention the latest fantasy, that of a 9th planet, which without the demotion of Pluto and Eris would have been called the 11th planet. That of Michael Brown's team, the discoverer of Eris and the main culprit for Pluto's disappearance, has been haunting for a long time. Paradoxical, isn't it?