Timeline of Solar System astronomy

The following is a timeline of Solar System astronomy and science. It includes the advances in the knowledge of the Earth at planetary scale, as part of it.

Direct observation

Humans (''Homo sapiens'') have inhabited the Earth in the last 300,000 years at least, and they had witnessed directly observable astronomical and geological phenomena. For millennia, these have arose admiration and curiosity, being admitted as of superhuman nature and scale. Multiple imaginative interpretations were being fixed in oral traditions of difficult dating, and incorporated into a variety of belief systems, as animism, shamanism, mythology, religion and/or philosophy.

Although such phenomena are not " discoveries" ''per se'', as they are part of the common human experience, their observation shape the knowledge and comprehension of the world around us, and about its position in the observable universe, in which the Sun plays a role of outmost importance for us. What today is known to be the Solar System was regarded for generations as the contents of the "whole universe".

The most relevant phenomena of these kind are:

* Basic gravity. Following the trajectory of free falling objects, the Earth is "below" us and the sky is "above" us.
* Characterization of the terrestrial surface, in four main types of terrain: lands covered with vegetation; dry deserts; bodies of liquid water, both salted ( seas and oceans) and fresh (rivers and lakes); and frozen landscapes ( glaciars, polar ice caps). Recognition of emerged lands and submerged ones. Recognition of mountain ranges and cavities ( grottos and caverns).
* Characterization of the Earth's atmosphere and its associated meteorological phenomena: clouds, rain, hail and snow; wind, storms and thunderstorms, tornadoes and hurricanes/cyclones/typhoons; fluvial floods, deluges and landslides; rainbows and halos; mirages; glacial ages.
* Diurnal apparent movement of the Sun: sunrise, noon and sunset. Recognition of the four cardinal points: north, south, east, and west.
* Nightly apparent movement of the celestial sphere with its main features regarded as " fixed": stars, the brightest of them forming casual groupings known as constellations, under different names and shapes in many cultures. Different constellations are viewed in different seasons and latitudes. Along with the faint strip of the Milky Way, they altogether conform the idea of the firmament, which as viewed from Earth it seems to be a consistent, solid unit rotating smooth and uniformly. This leads to the intuitive idea of a geocentric universe.
* Presence of the Moon, with its phases. Tides. Recognition of meteorological phenomena as sub-lunar.
* Yearly apparent transit of the Sun through the constellations of the zodiac. Recognition of the lunar cycle as a (lunar) month, and the solar cycle as the (solar) year, the basis for calendars.
* Observation of non-fixed or "wandering" objects in the night sky: the five classical planets; shooting stars and meteor showers; bolides; comets; auroras; zodiacal light.
* Solar and lunar eclipses. Planetary conjunctions.
* Identification of the frigid, temperate and torrid zones of the Earth by latitude. Equator and Tropics. Four seasons in temperate zones: spring, summer, autumn and winter. Equinoxes and solstices. Monsoons. Midnight sun.
* Telluric phenomena: seismic (earthquakes and seaquakes; tsunamis). Geysers. Volcanoes.

Along with an indeterminate number of unregistered sightings of rare events: meteor impacts; novae and supernovae.

Antiquity

* 2nd millennium BCE – Earliest possible date for the composition of the Babylonian Venus tablet of Ammisaduqa, a 7th-century BC copy of a list of observations of the motions of the planet Venus, and the oldest planetary table currently known.
* 2nd millennium BCE – Babylonian astronomers identify the inner planets Mercury and Venus and the outer planets Mars, Jupiter and Saturn, which would remain the only known planets until the invention of the telescope in early modern times.
* Late 2nd millennium BCE – Chinese astronomers record a solar eclipse during the reign of Zhong Kang, described as part of the document ''Punitive Expedition of Yin'' in the '' Book of Documents''.
* Late 2nd millennium BCE – Chinese established their timing cycle of 12 Earthly Branches based on the approximate number of years (11.86) it takes Jupiter to complete a single revolution in the sky.
* 1200 BCE – Earliest Babylonian star catalogues.
* 1100 BCE – Chinese first determine the spring equinox.
* 750 BCE – During the reign of Nabonassar (747–733 BC), the systematic records of ominous phenomena in Babylonian astronomical diaries that began at this time allowed for the discovery of a repeating 18-year cycle of lunar eclipses.
* 776 BCE – Chinese make the earliest reliable record of a solar eclipse.
* 687 BCE – Chinese make earliest known record of meteor shower.
* 7th century BCE – Egyptian astronomers alleged to have predicted a solar eclipse.
* 613 BCE – A comet, possibly Comet Halley, is recorded in ''Spring and Autumn Annals'' by the Chinese.
* 586 BCE – Thales of Miletus alleged to have predicted a solar eclipse.
* 560 BCE – Anaximander is arguably the first to conceive a mechanical model of the world, although highly inaccurate: a cylindrical Earth floats freely in space surrounded by three concentric wheels turning at different distances: the closest for the stars and planets, the second for the Moon and the farthest for the Sun, all conceived not as bodies but as "fire seen thru holes" in every wheel. But he starts to feed the idea of celestial mechanics as different of the notion of planets being heavenly deities, leaving mythology aside.
* 475 BCE – Parmenides is credited to be the first Greek who declared that the Earth is spherical and is situated in the centre of the universe, believed to have been the first to detect the identity of Hesperus, the evening-star, and Phosphorus, the morning-star (Venus), and by some, the first to claim that moonlight is a reflection of sunlight.
* 450 BCE – Anaxagoras shows that the Moon shines by reflected sunlight: the phases of the Moon are caused by the illumination of its sphere by the Sun in different angles along the lunar month. He was also the first to give a correct explanation of eclipses, by asserting that the Moon is rocky, thus opaque, and closer to the Earth than the Sun.
* 400 BCE – Philolaus and other Pythagoreans propose a model in which the Earth and the Sun revolve around an invisible "Central Fire" (not the Sun), and the Moon and the planets orbit the Earth. Due to philosophical concerns about the number 10, they also added a tenth "hidden body" or Counter-Earth (''Antichthon''), always in the opposite side of the invisible Central Fire and therefore also invisible from Earth.
* 360 BCE – Plato claims in his ''Timaeus'' that circles and spheres are the preferred shape of the universe and that the Earth is at the centre. These circles are the orbits of the heavenly bodies, varying in size for every of them. He arranged these celestial orbs, in increasing order from the Earth: Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, and the fixed stars located on the celestial sphere forming the outermost shell.
* 360 BCE – Eudoxus of Cnidus proposes for first time a purely geometric-mathematical, geocentric model of the planetary movements, including that of the Sun and the Moon.
* 350 BCE – Aristotle argues for a spherical Earth using lunar eclipses and other observations. Also, he asserts his conception of the heavenly spheres, and of an outer space fulfilled with aether.
* 330 BCE – Heraclides Ponticus is said to be the first Greek who proposes that the Earth rotates on its axis, from west to east, once every 24 hours, contradicting Aristotle's teachings. Simplicius says that Heraclides proposed that the irregular movements of the planets can be explained if the Earth moves while the Sun stays still, but these statements are disputed.
* 280 BCE – Aristarchus of Samos offers the first definite discussion of the possibility of a heliocentric cosmos, and uses the size of the Earth's shadow on the Moon to estimate the Moon's orbital radius at 60 Earth radii, and its physical radius as one-third that of the Earth. He also makes an inaccurate attempt to measure the distance to the Sun.
* 250 BCE – Following the heliocentric ideas of Aristarcus, Archimedes in his work ''The Sand Reckoner'' computes the diameter of the universe centered around the Sun to be about 10¹⁴ stadia (in modern units, about 2 light years, , ).Archimedes, The Sand Reckoner 511 R U, by Ilan Vardi
accessed 28-II-2007.
* 210 BCE – Apollonius of Perga shows the equivalence of two descriptions of the apparent retrograde planet motions (assuming the geocentric model), one using eccentrics and another deferent and epicycles.
* 200 BCE – Eratosthenes determines that the radius of the Earth is roughly .
* 150 BCE – According to Strabo (1.1.9), Seleucus of Seleucia is the first to state that the tides are due to the attraction of the Moon, and that the height of the tides depends on the Moon's position relative to the Sun.
* 150 BCE – Hipparchus uses parallax to determine that the distance to the Moon is roughly .
* 134 BCE – Hipparchus discovers the precession of the equinoxes.
* 87 BCE – The Antikythera mechanism, the earliest known computer, is built. It is an extremely complex astronomical computer designed to predict solar and lunar eclipses accurately and track the movements of the planets and the Sun. It could also calculate the differences in the apsidial and axial precession of heavenly bodies with extreme degree of accuracy.
* 28 BCE – Chinese history book ''Book of Han'' makes earliest known dated record of sunspot.
* 150 CE – Claudius Ptolemy completes his work '' Almagest'', that codifies the astronomical knowledge of his time and cements the geocentric model in the West, and it remained the most authoritative text on astronomy for more than 1,500 years. The ''Almagest'' put forward extremely complex and accurate methods to determine the position and structure of planets, stars (including some objects as nebulae, supernovas and galaxies then regarded as stars also) and heavenly bodies. It includes a catalogue of 1,022 stars (largely based on a previous one by Hipparchus of about 850 entries) and a large amount of constellations, comets and other astronomical phenomena. Following a long astrological tradition, he arranged the heavenly spheres ordering them (from Earth outward): Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn and fixed stars.

Middle Ages

* 420 – Martianus Capella describes a modified geocentric model, in which the Earth is at rest in the center of the universe and circled by the Moon, the Sun, three planets and the stars, while Mercury and Venus circle the Sun.
* 500 – Indian mathematician-astronomer Aryabhata accurately computes the solar and lunar eclipses, and the length of Earth's revolution around the Sun.
* 500 – Aryabhata discovers the oblique motion of the apsidial precession of the Sun and notes that it is changing with respect to the motion of stars and Earth. He also puts forward a theory of cosmic pluralism and multiverse theory in which there are thousands of universes apart from own and each one has its own unique laws of physics.
* 500 – Aryabhata discovers the rotation of the Earth by conducting experiments and giving empirical examples for his theories. He also explains the cause of day and night through the diurnal rotation of the Earth. He also developed highly accurate models for the orbital motion of the Moon, Mercury and Mars. He also developed an early version of the geoheliocentric model of the universe.
* 620 – Indian mathematician-astronomer Brahmagupta hypothesizes that the heavenly bodies and celestial spheres are subject to the same laws of physics as Earth, and proposes that there is a force of attraction (the gravity) between heavenly bodies.
* 628 – Brahmagupta gives methods for calculations of the motions and places of various planets, their rising and setting, conjunctions, and calculations of the solar and lunar eclipses.
* 820 – Persian astronomer, Muhammad ibn Musa al-Khwarizmi, composes his Zij astronomical tables, utilising Arabic numerals and the Hindu–Arabic numeral system in his calculations. He also translates Aryabhata's astronomical and mathematical treatises into Arabic.
* 850 – Al-Farghani (Alfraganus) translated and wrote commentary on Ptolemy's ''Almagest'' and gave values for the motion of the ecliptic, and the precessional movement of the heavenly bodies based on the values given by Ptolemy and Hipparchus.
* 1019 – Al-Biruni observes and describes the lunar eclipse on September 17 in detail and gives the exact latitudes of the stars during it.
* 1030 – In his major astronomical work, the ''Mas'ud Canon'', Al-Biruni observed that, contrary to Ptolemy, the Sun's apogee (highest point in the heavens) was mobile, not fixed.
* 1031 – Chinese astronomer and scientist Shen Kuo calculates the distance between the Earth and the Sun in his mathematical treatises.
* 1054 – Chinese astronomers record the sighting of the Crab Nebula as a "guest star", and they record several other supernovae during the 10th and 11th centuries.
* 1060 – Andalusi astronomer Al-Zarqali corrects geographical data from Ptolemy and Al-Khwarizmi, specifically by correcting Ptolemy's estimate of the longitude of the Mediterranean Sea from 62 degrees to the correct value of 42 degrees. He was the first to demonstrate the motion of the solar apogee relative to the fixed background of the stars, measuring its rate of motion as 12.9 seconds per year, which is remarkably close to the modern calculation of 11.77 seconds. Al-Zarqālī also contributed to the famous ''Tables of Toledo''.
* 1175 – Gerard of Cremona translates Ptolemy's '' Almagest'' from Arabic into Latin.
* 1180s (decade) – Robert Grosseteste described the birth of the Universe in an explosion and the crystallisation of matter. He also put forward several new ideas such as rotation of the Earth around its axis and the cause of day and night. His treatise ''De Luce'' is the first attempt to describe the heavens and Earth using a single set of physical laws.
* 1200 – Fakhr al-Din al-Razi, in dealing with his conception of physics and the physical world, rejected the Aristotelian and Avicennian view of a single world, but instead proposed that there are "a thousand thousand worlds (''alfa alfi 'awalim'') beyond this world such that each one of those worlds be bigger and more massive than this world as well as having the like of what this world has."

* 1252 – Alfonso X of Castile sponsored the creation and compilation of the '' Alfonsine Tables'' by scholars he assemble in the Toledo School of Translators in Toledo, Spain. These astronomical tables were used and updated during the following three centuries, as the main source of astronomical data, mainly to calculate ephemerides (which were in turn used by astrologers to cast horoscopes).
* 1300 – Jewish astronomer Levi ben Gershon (Gersonides) recognized that the stars are much larger than the planets. Gersonides appears to be among the few astronomers before modern times, along Aristarcus, to have surmized that the fixed stars are much further away than the planets. While all other astronomers put the fixed stars on a rotating sphere just beyond the outer planets, Gersonides estimated the distance to the fixed stars to be no less than 159,651,513,380,944 Earth radii, or about 100,000 light-years in modern units.
* 1350 – Ibn al-Shatir anticipates Copernicus by abandoning the equant of Ptolemy in his calculations of planetary motion, and he provides a proto empirical model of lunar motion which accurately matches observations.
* 1350 – Nicole Oresme put forward several revolutionary theories like mean speed theorem, which he used in calculating the position and shape of the planetary orbits, measuring the apsidial and axial precession of the lunar and solar orbits, measuring the angles and distance between ecliptics and calculating stellar and planetary distances. In his ''Livre du Ciel et du Monde'', Oresme discussed a range of evidence for the daily rotation of the Earth on its axis.
* 1440 – Nicholas of Cusa proposes that the Earth rotates on its axis in his book, ''On Learned Ignorance''. Like Oresme, he also wrote about the possibility of the plurality of worlds.

16th century

* 1501 – Indian astronomer Nilakantha Somayaji proposes a universe in which the planets orbit the Sun, but the Sun orbits the Earth.George G. Joseph (2000). ''The Crest of the Peacock: Non-European Roots of Mathematics'', p. 421. Princeton University Press.
* 1514 – Nicolaus Copernicus states his heliocentric theory in ''Commentariolus''.
* 1522 – First circumnavigation of the world by Magellan- Elcano expedition shows that the Earth is, in effect, a sphere.
* 1543 – Copernicus publishes his heliocentric theory in ''De revolutionibus orbium coelestium''.
* 1576 – Tycho Brahe founds the first modern astronomical observatory in modern Europe, Uraniborg.
* 1577 – Tycho Brahe records the position of the Great Comet of that year as viewed from Uraniborg (in the island Hven, near Copenhagen) and compares it with that observed by Thadaeus Hagecius from Prague at the same time, giving deliberate consideration to the movement of the Moon. It was discovered that, while the comet was in approximately the same place for both of them, the Moon was not, and this meant that the comet was much further out, contrary to what was previously conceived as an atmospheric phenomenon.
* 1582 – Pope Gregory XIII introduces the Gregorian calendar, an enhanced solar calendar more accurate than the previous Roman Julian calendar. The principal change was to space leap years differently so as to make the average calendar year 365.2425 days long, more closely approximating the 365.2422-day 'tropical' or 'solar' year that is determined by the Earth's revolution around the Sun. The reform advanced the date by 10 days: Thursday 4 October 1582 was followed by Friday 15 October 1582. The Gregoran calendar is still in use today.
* 1584 – Giordano Bruno published two important philosophical dialogues (''La Cena de le Ceneri'' and ''De l'infinito universo et mondi'') in which he argued against the planetary spheres and affirmed the Copernican principle. Bruno's infinite universe was filled with a substance—a "pure air", aether, or ''spiritus''—that offered no resistance to the heavenly bodies which, in Bruno's view, rather than being fixed, moved under their own impetus (momentum). Most dramatically, he completely abandoned the idea of a hierarchical universe. Bruno's cosmology distinguishes between "suns" which produce their own light and heat, and have other bodies moving around them; and "earths" which move around suns and receive light and heat from them. Bruno suggested that some, if not all, of the objects classically known as fixed stars are in fact suns, so he was arguably the first person to grasp that "stars are other suns with their own planets." Bruno wrote that other worlds "have no less virtue nor a nature different from that of our Earth" and, like Earth, "contain animals and inhabitants".
* 1588 – Tycho Brahe publishes his own Tychonic system, a blend between Ptolemy's classical geocentric model and Copernicus' heliocentric model, in which the Sun and the Moon revolve around the Earth, in the center of universe, and all other planets revolve around the Sun.

17th century

* 1600 – William Gilbert with his model called the terrella, shows the Earth behaves like a huge but low intensity magnet with its own magnetic field, which explains the behaviour of the compass pointing to the magnetic poles.
* 1604 – Galileo Galilei correctly hypothesized that the distance of a falling object is proportional to the square of the time elapsed.
* 1609 – Johannes Kepler states his first two empirical laws of planetary motion, stating that the orbits of the planets around the Sun are elliptical rather than circular, and thus resolving many ancient problems with planetary models, without the need of any epicycle.
* 1609 – Galileo Galilei starts to make telescopes with about 3x up to 30x magnification, based only on descriptions of the first practical telescope which Hans Lippershey tried to patent in the Netherlands in 1608. With a Galilean telescope, the observer could see magnified, upright images on the Earth—what is commonly known as a ''spyglass''—but also it can be used to observe the sky, a key tool for further astronomical discoveries.
* 1609 – Galileo Galilei aimed his telescope at the Moon. While not being the first person to observe the Moon through a telescope (English mathematician Thomas Harriot had done it four months before but only saw a "strange spottednesse"), Galileo was the first to deduce the cause of the uneven waning as light occlusion from lunar mountains and craters. He also estimated the heights of that mountains. The Moon was not what was long thought to have been a translucent and perfect sphere, as Aristotle claimed, and hardly the first "planet".
* 1610 – Galileo Galilei observes the four main moons of Jupiter: Callisto, Europa, Ganymede, and Io; sees Saturn's planetary rings (but does not recognize that they are rings), and observes the phases of Venus, disproving the Ptolemaic system though not the geocentric model.
* 1619 – Johannes Kepler states his third empirical law of planetary motion, which relates the distance and period of the planetary orbits.
* 1631 – Pierre Gassendi is the first to observe the transit of Mercury. He was surprised by the small size of the planet compared to the Sun.
* 1632 – Galileo Galilei is sometimes credited with the discovery of the lunar libration in latitude, although Thomas Harriot or William Gilbert might have done so before.
* 1639 – Jeremiah Horrocks and his friend and correspondent William Crabtree are the first astronomers known to observe and record a transit of Venus.
* 1643 – Evangelista Torricelli, disciple of Galileo, builds an elementary barometer, which shows that the air weigths, and incidentally creating the first artificial vacuum in a laboratory.
* 1648 – Johannes Hevelius discovers the lunar libration in longitude. It can reach 7°54′ in amplitude.
* 1648 – Blaise Pascal, aided by his brother-in-law Florin Périer at mount Puy de Dôme, shows that air pressure on a high mountain is less than at a lower altitude, proving his idea that, as air has a finite weight, Earth's atmosphere must have a maximum height.
* 1655 – Giovanni Domenico Cassini and Robert Hooke separately discover Jupiter's Great Red Spot.
* 1656 – Christiaan Huygens identifies Saturn's rings as rings and discovers its moon Titan.
* 1659 – Huygens estimated a value of about 24,000 Earth radii for the distance Earth-Sun, remarkably close to modern values but he was based on many unproven (and incorrect) assumptions; the accuracy of his value seems to be based more on luck than good measurement, with his various errors cancelling each other out.
* 1665 – Cassini determines the rotational speeds of Jupiter, Mars, and Venus.
* 1668 – Isaac Newton builds his own reflecting telescope, the first fully functional of this kind, and a landmark for future developings as it reduces spherical aberration with no chromatic aberration.
* 1672 – Cassini discovers Saturn's moons Iapetus and Rhea.
* 1672 – Jean Richer and Cassini measure the Earth-Sun distance, the astronomical unit, to be about 138,370,000 km.
* 1675 – Ole Rømer uses the orbital mechanics of Jupiter's moons to estimate that the speed of light is about 227,000 km/s.
* 1675 – Cassini discovers the main division in the rings of Saturn, named after him, the Cassini Division.
* 1686 – Cassini discovers Saturn's moons Tethys and Dione.
* 1687 – Isaac Newton publishes his law of universal gravitation in his work '' Philosophiæ Naturalis Principia Mathematica''.
* 1690 – Cassini observes differential rotation within Jupiter's atmosphere.

18th century

* 1704 – John Locke enters the term "Solar System" in the English language, when he used it to refer to the Sun, planets, and comets as a whole.
* 1705 – Edmond Halley publicly predicts the periodicity of the comet of 1682 and computes its expected path of return in 1757.
* 1715 – Edmond Halley calculates the shadow path of a solar eclipse.
* 1716 – Edmond Halley suggests a high-precision measurement of the Sun-Earth distance by timing the transit of Venus.
* 1718 – Edmond Halley discovers proper motion of stars, dispelling the concept of the " fixed stars".
* 1729 – James Bradley determines the cause of the aberration of starlight, providing the first direct evidence of the Earth's motion, and a more accurate method to compute the speed of light.
* 1735–1739 – The French Academy of Sciences sends two expeditions to measure the oblateness of the Earth by measuring the length of a degree of latitude at two locations: one to Lapland, close to the Arctic Circle and other to the Equator, the French Geodesic Mission. Their measurements show that the Earth is an oblate spheroid flattened at the poles.
* 1749 – Pierre Bouguer, part of French Geodesic Mission, publish that he and Charles Marie de La Condamine had been able to detect a deflection of a pendulum's plumb-bob of 8  seconds of arc in the proximity of the volcano Chimborazo. Although not enough to measure the value of the gravitational constant accurately, the experiment had at least proved that the Earth could not be a hollow shell, as some thinkers of the day had suggested.
* 1750 – The three collinear Lagrange points (L1, L2, L3) were discovered by Leonhard Euler, a decade before Joseph-Louis Lagrange discovered the remaining two.
* 1752 – Benjamin Franklin conducts his kite experiment, successfully extracting sparks from a cloud, showing that lightning bolts are huge natural electrical discharges.
* 1755 – Immanuel Kant first formulates the nebular hypothesis of Solar System formation.
* 1758 – Johann Palitzsch observes the return of the comet that Edmond Halley had anticipated in 1705. The gravitational attraction of Jupiter had slowed the return by 618 days. Parisian astronomer La Caille suggests it should be named "Halley's Comet".
* 1761 – Mikhail Lomonosov is the first to discover and appreciate the atmosphere of Venus during his observation of the transit of Venus.
* 1766 – Johann Titius finds the Titius-Bode rule for planetary distances.
* 1772 – Johann Bode publishes the Titius-Bode rule for planetary distances.
* 1772–1775 – The second voyage of James Cook definitively disproves the existence of the hypothesized Southern continent of Terra Australis.
* 1775 – Charles Hutton, based on his analysis of the Schiehallion experiment, shows the Earth has a density of at least and suggests that it has a planetary core made of metal. (In comparison with the modern accepted figure of , the density of the Earth had been computed with an error of less than 20%.)
* 1781 – William Herschel discovers a seventh planet, Uranus, during a telescopic survey of the Northern sky.
* 1781 – Charles Messier and his assistant Pierre Méchain publish the first catalogue of 110 nebulae and star clusters, the most prominent deep-sky objects that can easily be observed from Earth's Northern Hemisphere, in order not to be confused with ordinary Solar System's comets.
* 1787 – Herschel discovers Uranus's moons Titania and Oberon.
* 1789 – Herschel discovers Saturn's moons Enceladus and Mimas.
* 1796 – Pierre Laplace re-states the nebular hypothesis for the formation of the Solar System from a spinning nebula of gas and dust.
* 1798 – Henry Cavendish accurately measures the gravitational constant in the laboratory, which allows the mass of the Earth to be derived, and hence the masses of all bodies in the Solar System.

19th century

* 1801 – Giuseppe Piazzi discovers Ceres, a body that filled a gap between Mars and Jupiter following the Titius-Bode rule. At first, it was regarded as a new planet.
* 1802 – Heinrich Wilhelm Olbers discovers Pallas, at roughly the same distance to the Sun than Ceres. He proposed that the two objects were the remnants of a destroyed planet, and predicted that more of these pieces would be found.
* 1802 – Due their star-like apparience, William Herschel suggested Ceres and Pallas, and similar objects if found, be placed into a separate category, named asteroids, although they were still counted among the planets for some decades.
* 1804 – Karl Ludwig Harding discovers the asteroid Juno.
* 1807 – Olbers discovers the asteroid Vesta.
* 1821 – Alexis Bouvard detects irregularities in the orbit of Uranus.
* 1825 – Pierre Laplace completes his study of gravitation, the stability of the Solar System, tides, the precession of the equinoxes, the libration of the Moon, and Saturn's rings in his work '' Traité de mécanique céleste'' (''Treatise of celestial mechanics'').
* 1833 – Thomas Henderson successfully measures the stellar parallax of alpha Centauri, being then regarded as the Sun's closest star, but delayed the publication until 1839.
* 1838 – Friedrich Wilhelm Bessel measures the parallax of the star 61 Cygni, refuting one of the oldest arguments against heliocentrism.


* 1840 – John W. Draper takes a daguerreotype of the Moon, the first astronomical photograph.
* 1845 – John Adams predicts the existence and location of an eighth planet from irregularities in the orbit of Uranus.
* 1845 – Karl Ludwig Hencke discovers a fifth body between Mars and Jupiter, Astraea and, shortly thereafter, new objects were found there at an accelerating rate. Counting them among the planets became increasingly cumbersome. Eventually, they were dropped from the planet list (as first suggested by Alexander von Humboldt in the early 1850s) and Herschel's coinage, "asteroids", gradually came into common use. Since then, the region they occupy between Mars and Jupiter is known as the asteroid belt.
* 1846 – Urbain Le Verrier predicts the existence and location of an eighth planet from irregularities in the orbit of Uranus.
* 1846 – Johann Galle discovers the eighth planet, Neptune, following the predicted position gave to him by Le Verrier.
* 1846 – William Lassell

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