paragraph_text: Planetary geologists have measured different abundances of oxygen isotopes in samples from the Earth, the Moon, Mars, and meteorites, but were long unable to obtain reference values for the isotope ratios in the Sun, believed to be the same as those of the primordial solar nebula. Analysis of a silicon wafer exposed to the solar wind in space and returned by the crashed Genesis spacecraft has shown that the Sun has a higher proportion of oxygen-16 than does the Earth. The measurement implies that an unknown process depleted oxygen-16 from the Sun's disk of protoplanetary material prior to the coalescence of dust grains that formed the Earth.

paragraph_text: What we now call gravity was not identified as a universal force until the work of Isaac Newton. Before Newton, the tendency for objects to fall towards the Earth was not understood to be related to the motions of celestial objects. Galileo was instrumental in describing the characteristics of falling objects by determining that the acceleration of every object in free-fall was constant and independent of the mass of the object. Today, this acceleration due to gravity towards the surface of the Earth is usually designated as  and has a magnitude of about 9.81 meters per second squared (this measurement is taken from sea level and may vary depending on location), and points toward the center of the Earth. This observation means that the force of gravity on an object at the Earth's surface is directly proportional to the object's mass. Thus an object that has a mass of  will experience a force:

paragraph_text: Heliocentrism is the astronomical model in which the Earth and planets revolve around the Sun at the center of the Solar System. Historically, Heliocentrism was opposed to geocentrism, which placed the Earth at the center. The notion that the Earth revolves around the Sun had been proposed as early as the 3rd century BC by Aristarchus of Samos, but at least in the medieval world, Aristarchus's Heliocentrism attracted little attention -- possibly because of the loss of scientific works of the Hellenistic Era.

paragraph_text: Olympus Mons (/ əˌlɪmpəs ˈmɒnz, oʊ -, - ˈmɒns /; Latin for Mount Olympus) is a very large shield volcano on the planet Mars. By one measure, it has a height of nearly 22 km (13.6 mi or 72,000 ft). Olympus Mons stands about two and a half times as tall as Mount Everest's height above sea level. It is the tallest mountain of all planets and other rounded bodies in the Solar System, and is the second tallest mountain in the Solar System overall, after Rheasilvia on the Asteroid Vesta. It is the youngest of the large volcanoes on Mars, having formed during Mars's Hesperian Period. It is currently the largest volcano discovered in the Solar System and had been known to astronomers since the late 19th century as the albedo feature Nix Olympica (Latin for ``Olympic Snow ''). Its mountainous nature was suspected well before space probes confirmed its identity as a mountain.

paragraph_text: In 2008, the extrasolar planet WASP-12b was discovered orbiting WASP-12 by the transit method. Its high carbon-to-oxygen ratio indicates that rocky planets that might have formed in the star system; it may be a carbon planet.

paragraph_text: There are 69 known moons of Jupiter. This gives Jupiter the largest number of moons with reasonably stable orbits of any planet in the Solar System. The most massive of the moons are the four Galilean moons, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither Earth nor the Sun. From the end of the 19th century, dozens of much smaller Jovian moons have been discovered and have received the names of lovers or daughters of the Roman god Jupiter or his Greek equivalent Zeus. The Galilean moons are by far the largest and most massive objects to orbit Jupiter, with the remaining 65 known moons and the rings together comprising just 0.003% of the total orbiting mass.

paragraph_text: In terms of an object on the celestial sphere, Kappa Fornacis is a fifth magnitude star that lies close to the border between the northerly border of Fornax with Cetus. At magnitude 5.2, it is approximately the seventh-brightest star in the constellation.

paragraph_text: Time has long been a major subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems. Some simple definitions of time include "time is what clocks measure", which is a problematically vague and self-referential definition that utilizes the device used to measure the subject as the definition of the subject, and "time is what keeps everything from happening at once", which is without substantive meaning in the absence of the definition of simultaneity in the context of the limitations of human sensation, observation of events, and the perception of such events.

paragraph_text: Astronomers like Hipparchus (c. 190 – c. 120 BC) built upon the measurements of the Babylonian astronomers before him, to measure the precession of the Earth. Pliny reports that Hipparchus produced the first systematic star catalog after he observed a new star (it is uncertain whether this was a nova or a comet) and wished to preserve astronomical record of the stars, so that other new stars could be discovered. It has recently been claimed that a celestial globe based on Hipparchus's star catalog sits atop the broad shoulders of a large 2nd-century Roman statue known as the Farnese Atlas. Another astronomer, Aristarchos of Samos developed a heliocentric system.

paragraph_text: Oxygen was discovered independently by Carl Wilhelm Scheele, in Uppsala, in 1773 or earlier, and Joseph Priestley in Wiltshire, in 1774, but Priestley is often given priority because his work was published first. The name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. Its name derives from the Greek roots ὀξύς oxys, "acid", literally "sharp", referring to the sour taste of acids and -γενής -genes, "producer", literally "begetter", because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition. Common uses of oxygen includes the production cycle of steel, plastics and textiles, brazing, welding and cutting of steels and other metals, rocket propellant, in oxygen therapy and life support systems in aircraft, submarines, spaceflight and diving.

paragraph_text: PSR J1719-1438 was discovered in 2011 by the High Time Resolution Survey, a radio astronomy search for astronomical objects that rapidly vary in radio brightness, such as pulsars. Timing measurements using the Parkes Telescope and Lovell Telescope showed that it has a low-mass companion: PSR J1719-1438 b. The companion has a mass similar to that of Jupiter, but 40% of the diameter. It orbits the pulsar with a period of 2 hours 10 minutes and 37 seconds, at a distance of around 600,000 km (0.89 solar radii). The companion is likely the remnant of a star whose outer layers were siphoned off by the more massive pulsar. Calculations show the companion has a minimum density of 23 grams per cubic centimeter and is probably an ultra-low-mass carbon–oxygen white dwarf.

paragraph_text: In this equation, a dimensional constant  is used to describe the relative strength of gravity. This constant has come to be known as Newton's Universal Gravitation Constant, though its value was unknown in Newton's lifetime. Not until 1798 was Henry Cavendish able to make the first measurement of  using a torsion balance; this was widely reported in the press as a measurement of the mass of the Earth since knowing  could allow one to solve for the Earth's mass given the above equation. Newton, however, realized that since all celestial bodies followed the same laws of motion, his law of gravity had to be universal. Succinctly stated, Newton's Law of Gravitation states that the force on a spherical object of mass  due to the gravitational pull of mass  is

paragraph_text: Charles Thomas Kowal (November 8, 1940 – November 28, 2011) was an American astronomer known for his observations and discoveries in the Solar System. As a staff astronomer at Caltech's Mount Wilson and Palomar Mountain observatories between 1961 and 1984, he found the first of a new class of Solar System objects, the centaurs, discovered two moons of the planet Jupiter, and discovered or co-discovered a number of asteroids, comets and supernovae. He was awarded the James Craig Watson Medal for his contributions to astronomy in 1979.

paragraph_text: NGC 210 is a barred spiral galaxy located roughly 67 million light-years from the Solar System in the constellation Cetus. It was discovered on October 3, 1785 by William Herschel and later added to the New General Catalogue.

paragraph_text: NGC 47 (also known as NGC 58, MCG -1-1-55, IRAS00119-0726 and PGC 967) is a barred spiral galaxy in the constellation Cetus, discovered in 1886 by Ernst Wilhelm Leberecht Tempel. Its alternate name NGC 58 is due to the observation by Lewis Swift, who was unaware that Tempel had already discovered the celestial object earlier. It appears as a small, faint spiral nebula with a bright core and is slightly oval.

paragraph_text: The galactic year, also known as a cosmic year, is the duration of time required for the Sun to orbit once around the center of the Milky Way Galaxy. Estimates of the length of one orbit range from 225 to 250 million terrestrial years. The Solar System is traveling at an average speed of 828,000 km / h (230 km / s) or 514,000 mph (143 mi / s) within its trajectory around the galactic center, a speed at which an object could circumnavigate the Earth's equator in 2 minutes and 54 seconds; that speed corresponds to approximately one 1300th of the speed of light.

paragraph_text: The galactic year, also known as a cosmic year, is the duration of time required for the Sun to orbit once around the center of the Milky Way Galaxy. Estimates of the length of one orbit range from 225 to 250 million terrestrial years. The Solar System is traveling at an average speed of 828,000 km / h (230 km / s) or 514,000 mph (143 mi / s) within its trajectory around the galactic center, a speed at which an object could circumnavigate the Earth's equator in 2 minutes and 54 seconds; that speed corresponds to approximately 1 / 1300 of the speed of light.

paragraph_text: GD 40 is a white dwarf in the constellation Cetus. The star's spectrum has been found to show traces of external of metal contamination due to disruption of an extrasolar dwarf planet or an asteroid. The disrupted object should have had roughly the same mass of the Solar System asteroid 3 Juno.

paragraph_text: Olympus Mons (; Latin for Mount Olympus) is a very large shield volcano on the planet Mars. The volcano has a height of nearly 22 km (13.6 mi or 72,000 ft) as measured by the Mars Orbiter Laser Altimeter (MOLA). Olympus Mons is about two and a half times Mount Everest's height above sea level. It is the largest volcano, the tallest planetary mountain, and the second tallest mountain currently discovered in the Solar System, comparable to Rheasilvia on Vesta. In terms of surface area, Olympus Mons is the second-largest volcano in the solar system, second only to Earth's Tamu Massif. Olympus Mons is the youngest of the large volcanoes on Mars, having formed during Mars's Hesperian Period. It had been known to astronomers since the late 19th century as the albedo feature Nix Olympica (Latin for "Olympic Snow"). Its mountainous nature was suspected well before space probes confirmed its identity as a mountain.

paragraph_text: Solar noon is when the Sun transits the local celestial meridian; this is when the sun is at its highest altitude in the sky, at 12 noon apparent solar time. The local or clock time of solar noon depends on the longitude and date.

Question: When was the celestial object that eluded efforts to measure oxygen discovered to be the center of the solar system?
Answer: as early as the 3rd century BC