Percival Lowell: Pioneer of Pluto and Planetary Astronomy

Percival Lowell was a trailblazing American astronomer whose dedication to uncovering a planet beyond Neptune profoundly influenced modern astronomy. Born in 1855 into the distinguished Lowell family of Massachusetts, he cultivated an early passion for science and exploration. This enthusiasm led him to establish the Lowell Observatory in Flagstaff, Arizona, in 1894, an institution that remains vital to astronomical research today.

Lowell's obsession with a hypothetical ninth planet, which he termed "Planet X," arose from perceived anomalies in the orbits of Uranus and Neptune. These irregularities suggested the gravitational influence of an unseen celestial body. Lowell poured his energy into the meticulous observation of planetary motions, pioneering mathematical calculations and predictive models to locate this elusive planet. Despite the limitations of early 20th-century technology, his efforts yielded a rich archive of astronomical data.

Though Lowell passed away in 1916, his work inspired subsequent generations of astronomers. His vision bore fruit in 1930 when Clyde Tombaugh, a young assistant at the Lowell Observatory, identified Pluto. Using a custom-built blink comparator and photographic plates, techniques championed by Lowell, Tombaugh pinpointed the distant object that would come to be known as the ninth planet. This discovery not only vindicated Lowell's hypothesis but also marked a historic milestone in astronomy.

However, Pluto's status as a planet has evolved since its discovery. In 2006, the International Astronomical Union redefined the criteria for planetary classification, relegating Pluto to the status of a "dwarf planet." While this decision sparked debate, it underscored the dynamic and ever-evolving nature of science, reflecting new understandings of the solar system. Importantly, Lowell’s work remains foundational, influencing ongoing explorations into trans-Neptunian objects and the broader Kuiper Belt, where Pluto resides.

Today, Percival Lowell’s legacy is celebrated not only for the discovery of Pluto but also for his visionary contributions to the field of planetary astronomy. The observatory he founded continues to thrive as a hub of discovery and innovation, perpetuating his spirit of inquiry. Lowell’s relentless pursuit of knowledge serves as a testament to the enduring impact of curiosity and determination in unraveling the mysteries of the universe.
Percival Lowell: Pioneer of Pluto and Planetary Astronomy

Oort Cloud Discovery

The Oort cloud, also referred to as the Öpik-Oort cloud, constitutes a spherical layer composed of icy objects encircling the Sun, our star. Positioned at a distance ranging from approximately 2,000 to 100,000 astronomical units (AU) away from the Sun, it extends well beyond the Kuiper Belt and even the Sun's magnetic field, existing within what is technically considered interstellar space.

In 1932, Estonian astronomer Ernest J. Öpik put forth the notion of a remote reservoir of comets, arguing that the relatively rapid burning out of comets passing through the inner solar system necessitated a constant source of "fresh" comets to replenish the comet supply.

The discovery of the Oort cloud took place in 1950, when Dutch astronomer Jan Hendrik Oort identified it not through direct telescopic observations but rather via a theoretical analysis of long-period comets—those with orbital periods surpassing 200 years. These long-period comets can follow various orbits, including eccentric ellipses, parabolas, and even modest hyperbolas.

Professor Oort, widely recognized as one of the most eminent astronomers of the 20th century, excelled both as an observer and a theorist. He proposed the existence of a vast cloud comprising possibly 100 million comets surrounding our Solar System. Through his study of long-period comet orbits, Oort observed that many of them seemed to originate from a region much farther out than the orbit of Pluto.

Recently, astronomers Pedro Bernardinelli and Gary Bernstein made a captivating discovery of a celestial object named 2014 UN271. This object orbits the Sun and extends into the Oort cloud. Their finding emerged from a study of archival images collected during the Dark Energy Survey conducted between 2014 and 2018.
Oort Cloud Discovery

The works of al-Kashi

Ghiyath aI-DIn Jamshid al-Kashi, an eminent Iranian mathematician and astrono­mer of the 15th century, left his birthplace Kashan for Samarkand in A.D. 1421 and joined the scientific circle of Ulugh Beg.

He is a scientist at an observatory and learning center established in Samarkand by the prince Ulugh Beg, a grandson of the Mongol conqueror Tamerlane.

Al-Kashi worked at many areas of science —astronomy, algebra and geometry. The first known scientific event in Al-Kashi’s life is his observation of an eclipse of the moon, made in Kashan on June 2, 1406. The day is precise, since Al-Kashi dated many of his works with the exact date on which they were completed.

In 1407, the scientist completed a work, named ‘Sullam Al-sama’. The full title of the work means The Stairway of Heaven, on Resolution of Difficulties Met by Predecessors in the Determination of Distances and Sizes (of the heavenly bodies).

In 1410-1411, he wrote Mukhtasar dar ilm-i hay’at-Compendium of the science of astronomy dedicated to Sultan Iskandar, one of the rulers of Timurid dynasty.

In 1413-1414, al-Kashi wrote Khaqani zij and dedicated it to Ulugh Beg. In the introduction of this book al-Kashi complains about living in poverty while working on mathematics and astronomy, and he says he could not have completed this work without Ulugh Beg’s support.

Kashi’s work “Nuzhat al-hada’iq’ completed in 1416, described an instrument ‘tabaq al-manatiq’ (equatorium) used for the determination ofthe position of the planets (longitude and latitude) on the ecliptic and a second instrument ‘lauh al-ittisalat’, used to compute the conjunctions of the planets.

On March 2, 1427, Al-Kashi completed a monumental book in Arabicon arithmetic called Mift ̄ah al-his ̄ab. His book Mift ̄ah al-his ̄ab (Key to Arithmetic) provides sufficient knowledge of mathematics for those who are working on astronomy, surveying, architecture, accounting and trading.

Al-Kashi provided accurate trigonometric tables. He also expressed the theorem in a suitable form for the modern usage. In French, the law of cosines in named theorem d'Al-Kashi after al-kashi unification of the exiting works on the subject.

All great discoveries of Al-Kashi were unknown in Europe and only in the 19th and 20thcenturies they were studied by the historians of science.
The works of al-Kashi

Distance to the sun discovered by Giovanni Cassini

Born in 1625, Giovanni Cassini was raised and educated in Italy. Invited by Louis XIV, Cassini moved to Paris in 1669 to head the brand-new Paris Observatory. With an improved, high powered telescope that he carefully shipped from Italy, Cassini continued a string of astronomical discoveries that made him one of the world’s most famous scientists. The discoveries include the rotation periods of Mars and Saturn, and the major gaps in the rings of Saturn - still called the Cassini gaps.

The solar distance had a priority in his research program there. Since the value suggested by the measurements in Bologna could have been influenced by variations in atmospheric refraction, it was important use some other method to prove, or disprove the longer Earth-Sun distance scale.

He made the first reasonably correct Earth-Sun distance measurement in 1672 via triangulation. As with triangulation measurement, Cassini first had to establish a base line. Since the orbit of Mars is outside that of Earth, Cassini knew that at some time, Mars would be in a position to provide a proper baseline; accordingly, Cassini decided to measure the Earth-Mars distance to use as his baseline.

He determined the parallax of Mars using observations he made in Paris and those made by Jean Richer in Cayenne, French Guiana. The distance to the sun has always been regarded as the most important and fundamental of all galactic measurements, Cassini’s 1672 measurements, however, was the first to accurately estimate that distance.
Distance to the sun discovered by Giovanni Cassini

Philosophy of science by Anaximander of Miletus

Anaximander (611-547 BC) was the student of Thales, a leader in the early development of the Ionian school of thought.

He continued his teacher’s search to discover the one source of all things, whether material or spiritual. Anaximander followed Thales in believing that everything in nature was composed of a single fundamental substance which he called the apeiron, the ‘boundless’, which is sometimes translated as ‘the infinite,’ meaning that it not defined or limited by having specific properties.

He was the first to have developed anything like cosmological system; he was also the first among the Greeks who draft a map and to construct a globe.

He offered a much more detailed picture of the world. Anaximander maintained that the earth was in the center of all things, suspended freely and without support, whereas Thales regarded it as resting on water.

According to Anaximander, there is no reason for earth to move in one direction or another, a concept known as the ‘principle of the lack of a sufficient reason’. The use of this principle by Anaximander is said to mark the boundary between mythology and science, which always requires an explanation in terms of a sufficient cause.

Diogenes Laertius recorded that Anaximander was the first to introduce to the Greeks the sundial or gnomon, with which to gauge time by day and to approximate the summer and winter solstices and the fall and spring equinoxes.

He contended that thunder and lightning were cause by blasts of wind, not by Zeus’s thunderbolts. Anaximander appears to have stated that the world is governed by the opposites like hot and cold, wet and dry. It is by the working of the opposites that the world goes on.
Philosophy of science by Anaximander of Miletus

Ancient astronomy at Stonehenge

Stonehenge, one of the most famous archeological sites in the world, has long been associated with astronomy.

It is located in the county of Wiltshire in south central England. The construction of this monument begins around 3100 BC and continues above 10,000 years.

The positions of each stone have been carefully surveyed and mapped and the age of the monument had estimated by radiocarbon dating of associated organic remains.

An American astronomer, Gerald Hawkins, in the 1960s was one of the first to propose a theory that explained a reason for building Stonehenge. Hawkins became interested in the structure when he learned one-long established fact: that the northeast axis of the monument aligns with Sun during the summer solstice, suggesting that the site may have been used for astronomical observation.

When a smaller stone, the ‘heel stone’ is viewed through the gap in one of the trilithons, the summer solstice sun rises directly the heel stone.

He used an IBM mainframe computer to plot the positions of 175 key points: stones, stone holes, earthworks and other fixed points. Hawkins called Stonehenge a ‘Neolithic computer’ used for predicting lunar eclipses.
Ancient astronomy at Stonehenge

Discovery of Crab Nebula

The AD 1054 supernova remnant, the Crab Nebula, one of the brightest in history, recorded by Chinese and Arab astronomers and also by the monks of St. Gallen monastery. Crab Nebula was discovered by English physician and amateur astronomer John Bevis in 1731. One of the most active observers of the heavens in Georgian England, Bevis maintained a private observatory outside the city and about the year 1745, compiled a set of ornate star chars, the Uranographia Brittanica.

Crab Nebula

The same year that Bevis died, Crab Nebula was rediscovered by Charles Messier in 1758.  William Herschel, who observed it not long after Messier, thought he could see individual stars in the cloud.

In 1884, Lord Rosse published a first sketch of M1, and gave the name ‘Crab Nebula’ because it look a bit like a scorpion or a crab.

John Duncan found in 1921 that the nebula is expanding. In 1949, the radio astronomers Boltoin, Stanley and Slee identified the Crab Nebula as a radio source, making it the first non-solar system radio to be identified with a known optical object.

The detection of the Crab Pulsar at the centre of the Crab Nebula gave final confirmation to the theory that the core of a gravitational collapsing star settles down to the equilibrium state of a neutron star, if it is mass is inferior to the relevant Chandrasekhar limit.
Discovery of Crab Nebula

Cleostratus of Tenedos astronomical calendar

Greek astronomer, Cleostratus of Tenedos (520-432 BC) who lived rather outside the Ionian zone, made two important contributions to astronomy.

One was an improvement in the calendar, involving a better measure of the solar year. Together with Eudoxus, Cleostratus is credited with trying an 8-year cycle to commensurate the lunar and solar calendars.

Cleostratus proposed in the course of the eight years, to insert three intercalary months, of 30 days each, at the end of the third, fifth and eighth years respectively. He thus got a period of 2922 days, comprising 99 lunar revolutions.

The other was the knowledge of the signs of the zodiac and constellations in it which he introduced from Mesopotamia.

Zodiacal signs are frequently encountered upon Mesopotamia boundary stones and indicate the time of year at which the stones were erected.
Cleostratus of Tenedos astronomical calendar

Theory of planetary motion

For 2,000 years, astronomers placed the earth at the center of the universe and assumed that all heavenly bodies moved in perfect circles around it. Copernicus discovered that the sun lay at the center of the solar system, but still assumed that all planets traveled in perfect circles.

Copernicus put forth the idea of the heliocentric universe in his book De Revolutionibus Orbium Coelestium. Howevr, he was not the forts person to arote about it. The idea can be traced back almost two thousand years earlier to the Greek mathematician and philosopher Aristarchus of Samos (310-230 BC).

Johannes Kepler was born in Southern Germany in 1571, 28 years after the release of Copernicus’s discovery.

Kepler used Copernicus’s model as the foundation for his laws of planetary motion.  Kepler accepted Copernicus’s heliocentric idea, but he also found parts of De Revolutionibus troubling. Kepler believed that earth and other know planets revolved around the sun, called the heliocentric model.

Elliptical orbits became Kepler’s first law, Kepler then added his Second Law each planet’s speed altered as a function of its distance from the sun. As a planet flew closer, it flew faster.

Kepler published his discoveries in 1609 and then spent the next 18 years calculating detailed tables of planetary motion and position for all six known planets.
Theory of planetary motion

Discovery of supernova

In the year 1054, Chinese astronomers saw a ‘guest star’ appear in the constellation known as Taurus the Bull.

The star quickly became so bright it was visible in the daytime for a month and then took nearly two years to fade from sight.

At the site of that ancient supernova, modern telescope revel a many-legged nebula known as the Crab Nebula. In fact, the legs of the Crab Nebula are filaments of gas that are moving away from the site of the explosion at about 1400 km/s.

The Chinese were not the only ones who might have recorded the guest star of 1054. In 1054, native American records consisting of a rock carving in what is now Chaco Canyon, New Mexico, welcomed a bright star in Taurus with a waning crescent Moon right next to it.

Only a few supernova have been visible to the naked eye, Arab astronomers saw one in the year 1006, and the Chinese saw one in 1054, Tycho’s supernova appeared in 1572 and Kepler’s supernova in 1604.

The new star which appeared in the autumn of 1604 was discovered in Europe on 9 October 1604, and first noticed only a day later in China and by Korean astronomers on 13 October.

The supernova, which remained visible for a whole year, was extensively observed by European astronomers, including Johannes Kepler and this supernova is often referred to as Kepler’s SN.

Since the invention of the telescope in 1609, no one had seen a bright supernova until 1987 when astronomers in Chile spotted a naked eye supernova brightening in the southern sky. It was in the early morning hours of February 21, 1987, astronomers around the world were startled by the discovery of a naked eye supernova still growing brighter in the southern sky.

The supernova, known officially as SN1987A, is 53,000 pc away in the Large Magellanic Cloud, a small satellite galaxy to Milky Way Galaxy.
Discovery of supernova

Anaximander of Miletus

Anaximander (611-547 BC), Miletan pupils of Thales took much interest in geography. Anaximander is generally regarded as the second philosopher in the western philosophical tradition after Thales.

Anaximander also can be called the West’s first astronomer and geographer. He was the first among the Greeks to represent the details of the surface of the earth by maps. The idea of map-making was known in Egypt where plans of particular districts or objects as mines, houses and temples were being drawn up as early as 1400 BC. Anaximander, however, sought to convey a concrete picture of the surface of the earth as a whole.

From Babylon also he introduced the sun-dial. It consisted in essence of a gnomon, a fixed upright rod, the direction and length of the shadow of which can be measured hour by hour.

Anaximander was the first to speculate on the size and distance of the heavenly bodies. Departing from the Homeric view that the earth was a flat plate or disk, Anaximander characterized earth as a drum shaped cylinder suspended in midair. This idea looks remarkably like a guess at the celestial law of gravity.

This placement strongly suggested that the heavenly bodies passed through the sky and then under the Earth to reappear again the next day, thereby superseding earlier cosmological tendencies that limited the movement of heavenly bodies only to the sky above.

Anaximander seems to have guessed at the biological process of evolution. He is recorded as having believed that humankind originally emerged from fishes to step forth onto land.
Anaximander of Miletus 

Supernova

A supernova occurs when a star explodes. From the earth, people can see a new start appear in the sky and then fade over months back to invisibility.

Such explosion can be exploded can be caused by a massive star near the end of its life collapsing into a black hole or neutron star or a dead star; a white dwarf, collapsing into a neutron star.

At the turn of the 19th century, the binary star system Eta Carinae was faint and undistinguished.

In the first decades of the century, it became brighter and brighter, until, by April 1843 when it was exploded. The blast spat matter out at nearly 2.5 million kilometers an hour, and was so bright that it was thought to be a supernova explosion.

The larger of the two stars in the Eta Carinae system is a huge and unstable star that is nearing the end of its life.

The event observed in the 19th century was a stellar near-death experience. Scientists call these outbursts supernova impostor events, because they appear similar to supernovae, but stop just short of destroying their star. In 2004, an explosion thought to be similar to the 1843 Eta Carinae event was seen in a galaxy over seventy million light years from the Milky Way. Just two years later, the star exploded as a supernova.

Today nearly 300 supernova remnants are known, the majority having estimated ages from several thousand to several hundred thousand years.

Six supernova explosions have been witnessed with naked eye in historical times, many being recorded by Chinese astronomers, like the Crab nebula in AD 1054.

The first was recorder in AD 185 and the last appeared in 1987 in the Large Magellanic Cloud.  A neutrino burst from a supernova in the Large Magellanic Cloud was observed in the proton decay detectors Kamiokande and IMB on February 23, 1987. This supernova originated 160,000 light years from earth.

Two more are known to have ex0loded in the Milky Way during historic times) around 1671 and 1870), but were not seen because of the high interstellar dust obscuration.
Supernova

Thales of Miletus (c.624 – 565 BC)

It was in general, a time travel, a movement of the breakdown of old and of the rise of new civilizations.  Such was the stage such the atmosphere of change in which science became first clearly distinguished.

Science emerging can be seen into the light of historic day in the person of the Ionian Greek Thales.

Diogenes Laertius says that Ionian philosophy began with Anaximander but that Thales instructed Anaximander.  Aristotle considered Thales to be ‘the first founder of this kind of philosophy, for example, the thought of those subject who sought to find what he called the ‘material cause ‘ of things.

Though he was the son of a Phoenician mother, Thales of Miletus was a citizen of the Ionian city of Miletus.

He was a founder of the Ionian school and was numbered among the Seven Sages of Ancient Greece in the pre-Socratic Era. Thales was an astronomer, mathematician and philosopher.

Thales established a heritage of searching for knowledge for knowledge’s sake, development of the scientific method, establishment of practical methods and application of a conjectural approach to question of natural phenomena.

As a young man, he traveled to Egypt and the Near East to study geometry, a branch of mathematics concerned with points, lines and surfaces in two dimensions.

In Mesopotamian he learned of the ‘Saronic cycle’ that is to say the interval of eighteen years and eleven days, a multiple of which the observation of ages by temple star-gazers had shown to be usual between eclipses of the sun. Knowledge of this enabled the shrewd travel to make a lucky forecast of the eclipse visible at Miletus in 585 BC.

It was Thales of Miletus, who was credited with the discovery of the electrostatic attraction. Thales noted that after amber was rubbed, straw was attracted to the piece of amber.

The Neo-Platonist philosopher Proclus, writing in the fifth century AD, says that Thales learned geometry from the Egyptian and brought the knowledge back to Greece. Thales was also supposed to be the first to prove various geometrical theorems and it was said that he used geometry to measure the heights of the pyramids in Egypt and the distance of ships at sea.
Thales of Miletus

Discovery of Galilean Moons by Galileo Galilei

As a result of improvements Galileo Galilei made to the telescope, he was able to see celestial bodies more distinctly that was ever possible before. On January 7, 1610 he turned his newly developed telescope to Jupiter.

He discovered four objects orbiting the giant planet. It took him another night’s observations to clearly distinguish between two of them.

He called them ‘The Medicean Planets’ after the Medici family and gave them numbers.

Having previously been encouraged in his other scientific studies by the Church in Rome Galileo made his findings known to the Pope. Much of his disappointments, the Church soon took exception to his assertions that Earth was not the center of the universe and forbade his to continue his research or to even discuss it openly.

It was nearly 250 years later before they were given names: Io, Europa, Ganymede and Callisto. Galileo initially named his discovery the Cosmica Sidera but names that eventually were chooses by Simon Marius.

Galileo’s discovery proved the importance of the telescope as a tool for astronomers by showing that there were objects in space to be discovered that until then had remained unseen by the naked eye.
Discovery of Galilean Moons by Galileo Galilei 

Discovery of Cone Nebula by William Herschel

The word nebula means ‘cloud’ in Latin. The Cone Nebula is an H II region in the constellation of Monoceros. It was discovered by a British astronomer William Herschel (1738-1822) on December 26, 1785. At which time he designed it H V.27.

Herschel’s telescope was not very strong. It did not enlarge images the way powerful modern telescopes do. All Herschel could see was that the nebulas looked round, like planets.

The nebula is located about 800 parsecs or 2,600 light years away from earth. The Cone Nebula forms part of the nebulosity surrounding the Christmas Tree Cluster. The nebula is typical of its dark, silhouetted class in that it is virtually impossible to detect visually.
Discovery of Cone Nebula by William Herschel

Geocentric model of the solar system by Ptolemy

Humans have long wondered how the solar system is organized and how it formed. The Greek astronomer, Claudius Ptolemy was the first to devise a widely accepted system or model to explain the motion of the earth and other heavenly bodies.

Claudius Ptolemy was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer and poet,

His book, The Almagest, described the solar system as ‘geocentric’ meaning earth-centered. He believed that the sun, moon and planets all revolved around the earth in perfect circles, which readily explained the apparent motion of the sun and moon, but not the planets. The Greeks considered the circle to b ea pure and perfect shape; thus all orbits around the earth were deemed to be perfectly circular.

This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece.

Ptolemy’s geocentric model was not seriously challenged until the sixteenth century. Then Polish mathematician named Nicolaus Copernicus described a heliocentric model that place the sun at the center of solar system.
Geocentric model of the solar system by Ptolemy 

The Birth of the Galaxy

Because globular clusters contain the oldest stars associated with the Galaxy the halo marks the fossil remains of its birth.

Within it, globulars orbit the Galaxy on extremely elongated elliptical paths. Most of the time, the globulars move slowly through the halo at the outer extremes of their orbits; only briefly do they whip in and around the nucleus.

These stars exhibit the motions of the cloud from which they were formed. So the Galaxy must have been born form a gas cloud that was initially huge- at least 300,000 ly in radius.

Imagine a tremendous, ragged cloud of gas roughly twice as big as the Galaxy’s halo today. Its density is low. This proto Galaxy cloud probably is turbulent, swirling around with random churning currents.

Slowly at first, the cloud’s self-gravity pulls it together, with it central regions getting denser faster than its outer parts.

Throughout the cloud, turbulent eddies of different sizes form, break up, and die away. Eventually, the eddies become dense enough to contain sufficient mass to hold themselves together. These might be hundreds of light years in size – incipient globular clusters.

Each blob then splits up to form individual stars – all born at about the same time.

Meanwhile, the gas contracts more and fall slowly into a disk. Why a disk? Because the original cloud had a little spin, and the conservation of angular momentum requires that it spin faster around its rotational axis as it contracts.

The kinetic energy energy of the cloud slowly decreases, as gas clouds collide and heat is radiated away.

The disk rapidly flattens. As the disk forms, its density increases and more stars form. Each burst of starbirth leaves behind representative stars at different distances from the present disk.

Finally, the remaining gas and dust settle into the narrow layer as we see today. Somehow density waves appear and drive the formation of spiral arms.

During this time, massive stars were manufacturing heavy elements and flinging them back into the cloud by supernova explosions.

So as stars were born in succession, each later type had more heavy elements. That enrichment continues today in the disk of the Galaxy.
The Birth of the Galaxy

The Antikythera Mechanism

The earliest known purely mechanical clock appears to have been discovered on a ship wreck.

Shortly before Easter of 1900 a party of Greek sponge fishers returned from their normal fishing grounds near Tunisia, they were driven off course by a gale and found shelter close to Kythera, near the barren island of Antikythera.

They discovered the device known as the Antikythera mechanism, when they explored the shallow rock shelves below them which they had dropped their anchored.

At a depth of 42 meters they found a 50 m long ship wreck containing a plainly visible pile of bronze and marble statues. The Antikythera Mechanism or mechanical computing clock device is the most complex instrument of antiquity.

Subsequent exploration of the underwater site, by explorer Jacques Cousteau, enabled scientist to date the remnants of a ship to 87 BC.

Further analysis of the Antikythera mechanism with more advanced technologies has provided several recent discoveries.

Close examination revealed the fragment of a heavily encrusted, corroded, geared device measuring around 33 cm high, 17 cm wide and 9 cm thick.

Constructed of bronze and originally contained within a wooden frame, the device was engraved with a copious text, which appears to be the device’s operating manual.

In 1950s, it was realized by the science historian Derek Price that these were parts of an astronomical computer: a kind of solar and lunar calendar. 

Scientists concluded that the device was able to predict lunar and solar eclipse based on Babylonian eclipse algorithms, as well as to display some of the planetary and lunar positions, and even had gears to simulate irregularities in the Moon’s motion.

The Antikythera Mechanism process ho sophisticated Greek technology was. It was possibly constructed the school of Posidonius on the island of Rhodes.
The Antikythera Mechanism

Ibn Ishaq Al-Tunisi (1193-1222)

In al-Andalus and the Maghreb, various astronomers continued producing zijat (planetary tables) in the tradition of Azarqueil , introducing new parameters, giving new presentation to old tables, and compiling new ones, but hardly deviating from the essential features established by their predecessors.

Among the astronomers was Ibn Ishaq Al-Tunisi.

According to Ibn Khaldun in his Muqaddima, Abul Abbas Ahmad ibn Ali ibn Ishaq al-Tamimi al-Tunisi was a Tunisian astronomer of the early thirteenth century.

He compiled an impressive astronomical handbook with tables.

It contains an important set of tables which mark the starting point of a Maghribian astronomical school. The unfinished set of tables by Ibn Ishaq survived in a unique manuscript of Hyderabad, discovered in 19878 by David. A. King.

The predominant influence in Ibn Ishaq tables was that of the Andalusia school represented by Ibn-Zarqalluh, Ibn al-Kammad and Ibn al-Haim.
Ibn Ishaq Al-Tunisi (1193-1222)

Discovery of Pluto

Astronomer expected that irregularities in Neptune’s motion would lead to the discovery of another remote, unknown planet.

In 1905, Percival Lowell, an American astronomer and a young Kansas farmer, found that the force of gravity of some unknown object seemed to be affecting the orbits of Neptune and Uranus. He made a long, laborious mathematical analysis of the small ‘left over’ deviations of Uranus not attributed to Neptune.

In 1909 William Pickering argued that both Neptune and a remote Planet O were producing gravitational tugs on Uranus.

In 1929, Clyde W. Tombaugh, an assistant at the Lowell Observatory, used predictions made by Lowell and other astronomers and photographed the sky with a more powerful, wide-angle telescope.

On February 18, 1930, Tombaugh found Pluto's image on three photographs, which were obtained a month earlier in January 23 and 29. The planet was named after the Roman god of the dead. The name also honors Percival Lowell, whose initials are the first two letters of Pluto.

The discovery was announced to the world in March 13, 1930.

In 1976, three astronomers at the University of Hawaii – Dale Cruikshank, Carl Pilcher and David Morrison – discovered hints of how just minuscule Pluto really is.

They found that Pluto’s suffice bears methane ice, which reflect much of the sunlight hitting it.

In 1978, astronomers at the U.S. Naval Observatory substation in Flagstaff detected a satellite of Pluto. They named it Charon. This satellite has a diameter of about 750 miles (1,210 kilometers). This moon has a density roughly one-third that of Earth. This reflects Charon’s rocky-icy composition.

In 1987, Jet Propulsion Laboratory, reported observations that showed Pluto has a substantial atmosphere. In 1996, the images, taken by the Hubble Space Telescope, show about 12 large bright or dark areas. 

However, in August 2006, the International Astronomical Union, for the first time, created a scientific definition for the word planet and thereby demoted the former major planet Pluto to the lesser status of dwarf planet.
Discovery of Pluto