My Science School

When we learn about the solar system, we are introduced to a class of objects called asteroids. Most of these asteroids exist in the main asteroid belt that lies between Mars and Jupiter. While this much is common knowledge these days, the existence of this asteroid belt wasn't even known a little over 200 years back.

Pallas, third largest asteroid in the asteroid belt and the second such object to be discovered, by the German astronomer and physician Wilhelm Olbers on March 28, 1802, following the discovery of Ceres the year before. It is named after Pallas Athena, the Greek goddess of wisdom. A.s. Ganesh takes a look at the third largest asteroid in the asteroid belt……..

Late in the 18th Century, German astronomers Johann Daniel Titius and Johann Elert Bode arrived at a mathematical expression now known as Titius-Bode law. These calculations not only predicted the positions of the planets then known, but also suggested possible positions of others.

The search begins

When the discovery of Uranus in 1781 corresponded to that predicted by this law, there was a sense of anticipation as the law suggested another between Mars and Jupiter. Among the group of astronomers hunting down the missing planet was Wilhelm Olbers, a German physician who did his astronomical work by setting up his own house for the purpose.

Ceres, which was discovered by Italian astronomer Giuseppe Piazzi in January 1801, was believed to be the missing planet and was tracked down for a while before it went behind the sun. It was Carl Friedrich Gauss, a young mathematician who later became a good friend of Olbers, who devised a way to find out the orbit of an object using limited observations.

Olbers applied Gauss' method and observed Ceres later in 1801. He continued this exercise on an everyday basis and discovered a similar object on March 28, 1802. Named after the Greek goddess of wisdom Pallas Athena, 2 Pallas (number based on order of discovery) can even be considered the first asteroid to be discovered as 1 Ceres was classified as a dwarf planet in 2006.

Remnants of a planet?

Apart from being the second such object to be discovered in what we now know as the asteroid belt, Pallas is also the third largest asteroid in the region. The discovery of Ceres and Pallas, along with Juno and Vesta over the next few years, led to the idea that asteroids are remnants of an actual planet. Even though this is no longer accepted, the idea that asteroids are pieces of the missing planet predicted by the Titius-Bode law endured for a long time.

While little was known about Pallas for over 200 years, a study in the past few years revealed that this asteroid has a violent, cratered past. In order to analyse Pallas' shape and surface in detail, scientists used the Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) imager on the Very Large Telescope in the Atacama Desert of northern Chile.

Pockmarked surface

 Researchers were able to capture 11 images of the asteroid's surface. Using these images along with their own simulations, the scientists were able to tell that there were numerous craters ranging from 30 to 120 km wide on Pallas surface and that its appearance could even resemble that of a golf ball.

Even though the orbital eccentricity of Pallas is moderate, its orbital inclination is unusually large. This means that Pallas' orbit is highly inclined with respect to the plane of the asteroid belt and the asteroid is therefore rather inaccessible to spacecraft. Plenty still remains unknown about this asteroid and even though missions are planned, Pallas is for now the largest asteroid that hasn't been visited by a spacecraft yet.

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William H. Wollaston discovered Palladium in 1803. He experimented on the residues left after dissolving platinum in aqua regia. He successfully isolated palladium by heating palladium cyanide to produce palladium metal. But Wollaston decided to announce his discovery in an unconventional manner. He gave a quantity of the metal for sale to a mineral dealer in London, and posted handbills describing the property of the new metal, anonymously.

Many doubts came up with this peculiar way of announcement, and Richard Chenevix, a renowned chemist of the time stated that palladium was just an alloy of platinum and mercury. In response to that, Wollaston announced a reward of twenty guineas to anyone who could produce the metal artificially. Nobody claimed the money. In 1805, Wollaston made a speech before the Royal Society of London about the properties of palladium and how to isolate it. He revealed he was the discoverer of the metal at the end of the speech. He explained that he remained anonymous to use the time to study and reveal more properties of the metal.

Palladium is named after an asteroid called ‘Pallas’, which refers to the Greek goddess of wisdom.

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English chemist William H. Wollaston discovered rhodium in 1803 while he was experimenting on a platinum ore in Peru. Hippolyte- Victor Collet- Descotils alerted Wollaston about the chance of a new element as he believed that the red colour of some platinum salts was due to the presence of an unidentified metal.

To find out this new metal, Wollaston, dissolved crude platinum in aqua regia, which is a concentrated solution of hydrochloric and nitric acids. After that he precipitated platinum by dissolving the solution in ammonium chloride. But there was no new element.

Further experiments produced a deep red powder, sodium rhodium chloride. When this compound was treated with zinc, it gave a black and flaky precipitate of rhodium. Wollaston named the element rhodium based on the Greek word ‘rhodon’, which means rose.

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Technetium is the first artificially produced element. Dmitri Mendeleev, the Russian chemist who created the periodic table, is the first person to predict the existence of technetium, atomic number 43. But he called it eka-manganese. Three scientists: lda Take, Walter Noddack, and Otto Berg examined some platinum ores and columbite minerals in hopes of discovering eka-manganese and rhenium, atomic number 75.

They published the X-ray analysis of their experiment and claimed that they found 2 new elements. Element 43 was named as masurium by them. But their findings were disregarded by the scientific community then. After three years, their finding of rhenium, element 75, was approved but masurium was not.

Carlo Perrier and Emilio Segre were credited with the discovery of technetium at the University of Palermo in Italy in 1937.

It is the first element that was created synthetically. Technetium was derived from the Greek word ‘technetos’, which means artificial. Technetium is a silver grey metal that is rare. It gets damaged slowly in moist air.

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The mineral molybdenite (molybdenum sulphide) was often mistaken for graphite or lead ore until 1778. This soft black mineral was analyzed by German chemist Carl Scheele, who discovered that it was neither of these substances, and that it was a totally new element. But Scheele did not have a suitable furnace to reduce the mineral to a metal. As a result, it took a few more years until it was actually identified. Although Scheele made a number of chemical discoveries such as oxygen, the credit was always given to someone else because he couldn’t come to a final analysis. As a result, he later became known as “hard luck Scheele”.

For many years, scientists continued to assume that molybdenite had a new element, but they could not reduce the mineral to the metal and isolate it. Later, Peter Jacob Hjelm, a Swedish chemist, ground molybdic acid with carbon in linseed oil to form a paste. Then he allowed this paste to be in close contact with carbon and the molybdenite. This mixture was then heated in a closed crucible to produce the metal. He named it molybdenum (atomic number 42) after the Greek word “molybdos”, which means lead. According to the Royal Society of Chemistry, this new element was announced in the autumn of 1781.

Molybdenum has silvery-white appearance and it is ductile and highly resistant to corrosion. It also has one of the highest melting points of all pure elements. Only tantalum and tungsten have higher melting points than molybdenum. This element is also a micronutrient that is essential for life.

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Niobium, atomic number 41, was discovered by Charles Hatchett, an English scientist in 1801. It was recognised in an ore sent to England from the American colonies, more than a century earlier by John Winthrop the Younger, who was the first governor of the state of Connecticut. The ore was called columbite and Hatchett named this element columbium (symbol Cb).

Later, in 1846, a German chemist named Henrich Rose independently discovered the element and named it niobium. This metal was first isolated by Christian Blomstrand, a Swedish scientist, in 1864.

Internationally, the name niobium was adopted in 1950. Niobium is a shiny, white, ductile metal. Due to its many properties, niobium is used in many areas of research and in creating magnets. One of the strongest superconducting magnets in the world makes use of niobium alloy wires such as niobium-tin and niobium-titanium.

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The discovery of yttrium (atomic number 39) began in 1787 when Carl Arrhenius found a mineral that resembled coal in a quartz mine near Ytterby of Sweden. Arrhenius named this black mineral ‘ytterbite’ based on Ytterby, where it was found.

In Finland, Johan Gadolin received a sample of ytterbite from Arrhenius. He carried out a detailed analysis of it in 1794 and found that it contained an unknown earth metal. The new metal was named yttrium. His results were confirmed by Anders Ekeberg, a Swedish chemist in 1797.

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Strontium, atomic number 38, was recognized as a new element in 1790. A mineral sample from a lead mine near Strontian in Scotland (after which the element is named) was analysed by Adair Crawford, leading to this discovery. Until then, the scientific community thought that strontium and barium were the same element. Scientists had only discovered barium’s existence by then. It was initially called strontianite (strontium carbonate). Strontium was first isolated by Sir Humphry Davy in 1808 while working in London. He used electrolysis to isolate it.

Strontium is very common in nature and is the 15th most abundant element in the planet’s crust. Physically, strontium is a soft, silvery metal. It is used to block X-rays emitted by TV picture tubes. It causes paint to glow in the dark and is responsible for the bright red colours in fireworks. Strontium is also vital in understanding the origin of the species as anthropologists study the levels of strontium ions in fossils to determine the geographic origins of ancient humans and animals. The compound strontium chloride is used in toothpaste to help people with sensitive teeth. Strontium oxide also improves the quality of pottery glazes.

Natural strontium is harmless, but one of its isotopes, Sr-90, is a very dangerous by-product of nuclear fallout. The world’s most accurate atomic clock is based on strontium atoms.

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Rubidium, atomic number 37, was discovered in 1861. It was discovered in Heidelberg in Germany by Robert Bunsen and Gustav Kirchhoff using spectroscopy. This method was invented and developed by the pair in the previous two years. At the heart of the spectroscope there is a glass prism, which splits the light coming from a flame into a spectrum. This is very similar to how raindrops can split sunlight into a rainbow.

When different salts were placed in the flame of the recently invented Bunsen burner, Bunsen and Kirchhoff saw coloured lines in all the spectra they saw. What was more exciting was that they discovered that these coloured lines were unique to the substance that was burnt. They concluded that the lines in a spectrum were a way of finger-printing an element.

In 1861, the duo began studying the mineral lepidolite (a lithium, potassium and aluminium silicate). This mineral was found in Saxony, Germany. Bunsen and Kirchoff used hydrochloroplatanic acid to isolate potassium chloroplatinate from the mineral. In potassium chloroplatinate that was isolated, they found another salt. This salt produced a spectrum containing many new lines when it was placed in the Bunsen burner. Two of the lines that were produced were particularly outstanding. It was a new element. They named this new element rubidium (and the symbol Rb) from the Latin word rubidius, which refers to the darkest red colour.

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In 1825, a salt maker sent a sample of salt spring waters from Bad Kreuznach, a German town, asking chemist Justus von Liebig for an analysis. This sample had a very high amount of bromine in it, and Liebig had isolated it too. But he considered the substance as a compound of iodine and chlorine. Had he not taken it lightly, Liebig would have been the discoverer of bromine.

The next person in the story of bromine’s discovery is Carl Loewig, who discovered it while he was still a chemistry student at Heidelberg University in Germany. Loewig’s hometown was Bad Kreuznach, the same place from where Liebig had received the sample. Loewig took water from a salt spring in his hometown and added chlorine to it. He then shook the solution with ether and found that a red-brown substance dissolved in the ether. Loewig evaporated the ether to find bromine, a red-brown liquid.

Loewig’s professor at Heidelberg University asked him to prepare more of this substance for testing. But this took him a year, and by that time, in 1826, another person named Antoine Balard had discovered bromine and took the credit. Balard took brine (evaporated sea water in which salts have been concentrated) and crystallized salt from it. After that, he took the remaining liquid and mixed it with chlorine. Later, this solution was distilled, which left behind a dark red liquid-bromine.

Balard published his results in 1826, which provided evidence to the discovery. Since he was the first to publish, he came to be known as bromine’s discoverer.

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Krypton was discovered by William Ramsay and Morris Travers in residue left from evaporating nearly all the components of liquid air. Within weeks, the duo had detected two other noble gases: neon and xenon. To honour their scientific spirit, King Edward VII made Ramsay a Knight Commander of the Order of the Bath in 1902. William Ramsay also received the Nobel Prize for Chemistry in 1904. It was awarded in recognition of his contributions in the discovery of the noble gases and for the determination of their places in the periodic table. Ramsay was also responsible for adding an entire new group to the periodic table. The only noble gas that he didn’t discover was radon.

Krypton is widely used today. It is employed in flashes for high-speed photography, in fluorescent lights along with argon, and in making neon signs that have a greenish-yellow light. (Neon alone glows red only).

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