Curated category
Solar System
- Solar SystemAbout 4.6 billion years ago, a dense region within a large molecular cloud collapsed under its own gravity. This event birthed the Sun and a surrounding…
- Mercury (planet)The MUL.APIN tablets from the 14th century BC contain the earliest known records of Mercury. An Assyrian astronomer wrote about this planet using cuneiform…
- VENUSVenus is the second planet from the Sun, yet it shares a striking physical resemblance to Earth. It has a diameter of 12,104 kilometers, which is only about…
- SednoidAstronomers classify a specific group of distant solar system bodies as sednoids based on strict orbital criteria. These objects possess large semi-major…
- Detached objectIn the year 2003, astronomers discovered an object named Sedna that did not fit any known category of trans-Neptunian objects.
- JupiterJupiter formed just one million years after the Sun, roughly 50 million years before Earth came into existence. Current models suggest this massive planet…
- Moons of PlutoJames Christy spotted Charon on the 22nd of June 1978 while examining photographic plates at the United States Naval Observatory.
- Terrestrial planetA terrestrial planet is a class of planet that is composed primarily of silicate, rocks, or metals. Scientists sometimes call these tellurian planets or…
- SaturnSaturn is the sixth planet from the Sun and the second largest in the Solar System. It has an average radius about 9 times that of Earth, yet it possesses…
- HaumeaOn the 28th of December 2004, a team led by Mike Brown at Caltech spotted the object that would become Haumea. They captured images on the 6th of May 2004…
- MarsMars formed approximately 4.5 billion years ago alongside the other planets in our solar system. Scientists theorize that this creation resulted from a…
- Dysnomia (moon)On the 10th of September 2005, astronomers at the W. M. Keck Observatory in Hawaii spotted a faint point of light orbiting the distant dwarf planet Eris.
- Io (moon)On the 8th of January 1610, Galileo Galilei observed a single point of light that was actually two moons, Io and Europa, moving together in his telescope.
- Galilean moonsOn the 7th of January 1610, Galileo Galilei wrote a letter containing the first mention of Jupiter's moons. He saw only three of them at that time and…
- Europa (moon)On the 8th of January 1610, Galileo Galilei observed a faint point of light near Jupiter that would become known as Europa.
- NeptuneOn the 23rd of September 1846, Johann Gottfried Galle pointed a telescope toward the constellation Aquarius and found a planet that had never been seen by…
- Scattered discThe scattered disc is a distant circumstellar disc in the Solar System that is sparsely populated by icy small Solar System bodies.
- PlutoOn the 18th of February 1930, Clyde Tombaugh spotted a faint moving point of light on photographic plates taken at Lowell Observatory in Flagstaff, Arizona.
- Exploration of MarsOn the 14th of July 1965, the Mariner 4 spacecraft flew past Mars at a distance of about 9,800 kilometers. It returned the first close-up photographs of…
- 4 VestaHeinrich Wilhelm Matthias Olbers discovered 4 Vesta on the 29th of March 1807 in the constellation Virgo. This event marked the fourth object found in what…
- Moons of NeptuneWilliam Lassell spotted Neptune's largest moon on the 10th of October 1846. This event occurred just seventeen days after astronomers first identified the…
- Human spaceflightOn the 12th of April 1961, Soviet cosmonaut Yuri Gagarin became the first human to orbit Earth aboard Vostok 1. This single flight ignited a geopolitical…
- Callisto (moon)In 1610, Galileo Galilei pointed his telescope toward Jupiter and saw four points of light that did not move like stars.
- MakemakeOn the 31st of March 2005, astronomers Michael E. Brown, Chad Trujillo, and David Rabinowitz captured images of a faint point of light using the 1.22-meter…
- Moons of MarsAsaph Hall III stood at the US Naval Observatory in Washington, D.C. on the 12th of August 1877. He spotted Deimos at about 07:48 UTC through a 26-inch…
- CometThe solid core of a comet is known as the nucleus. It measures from a few hundred meters to tens of kilometers across. These nuclei are loose collections of…
- PlanetIn August 2006, the International Astronomical Union voted to reclassify Pluto as a dwarf planet. This decision changed the count of planets in our Solar…
- Natural satelliteJohannes Kepler published a pamphlet in 1610 titled Narratio de Observatis a se quatuor Iouis satellitibus erronous. He derived the word satellite from the…
- Kuiper beltFrederick C. Leonard pondered the existence of a trans-Neptunian population shortly after Clyde Tombaugh discovered Pluto in 1930.
- Discovery and exploration of the Solar SystemIn 560 BCE, a map of the universe drawn by Anaximander placed Earth at the center of a flat disk. Ancient civilizations from Egypt to China viewed the sky as…
- Space colonizationIn 1969, a human placed the first national flag on the lunar surface during the Apollo 11 mission. This image of a flag planted in dust became an iconic…
- Eris (dwarf planet)On the 5th of January 2005, a team led by Mike Brown at Palomar Observatory announced the discovery of Eris. The object had actually been captured in images…
- SunThe Sun formed about 4.6 billion years ago from the collapse of part of a giant molecular cloud that consisted mostly of hydrogen and helium.
- AsteroidOn the 1st of January 1801, Giuseppe Piazzi spotted a faint point of light in the constellation Taurus. He was searching for the 87th star listed in the…
- Moons of SaturnIn 1655, Christiaan Huygens peered through a telescope of his own design and saw the first moon orbiting Saturn. He named it Titan.
- Phobos (moon)On the 18th of August 1877, American astronomer Asaph Hall spotted a faint point of light through the 26-inch Great Equatorial telescope at the United States…
- Formation and evolution of the Solar SystemEmanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace developed the nebular hypothesis in the 18th century. This model proposed that the Solar System…
- Deimos (moon)Asaph Hall III stood at the United States Naval Observatory in Washington, D.C. on the 12th of August 1877. He spotted Deimos at about 07:48 UTC that morning.
- Moons of UranusSir William Herschel spotted the first two moons of Uranus on the 11th of January 1787. This event occurred six years after he had discovered the planet…
- Trojan (celestial body)In 1772, the Italian-French mathematician and astronomer Joseph-Louis Lagrange obtained two constant-pattern solutions of the general three-body problem.
- AstronomyThe Nebra sky disc, found near a possibly astronomical complex in Germany, serves as an ancient calendar defining a year as twelve lunar months of 354 days.
- SpaceflightScottish astronomer William Leitch published an essay titled A Journey Through Space in 1861. This document contained the first theoretical proposal for…
- Space explorationThe first human-made object to reach outer space was a German V-2 rocket test launch designated MW 18014. It took place on the 20th of June 1944 at the…
- Space stationEdward Everett Hale published a story called The Brick Moon in 1868. This tale featured the first mention of anything resembling a space station.
- Moons of JupiterIn March 1610, Galileo Galilei published a book describing four new points of light near Jupiter. He had observed them with his telescope starting in January…
- Asteroid beltIn 1596, Johannes Kepler wrote in his book Mysterium Cosmographicum that he placed a planet between the orbits of Mars and Jupiter.
- Oort cloudIn 1950, the Dutch astronomer Jan Oort presented a radical idea to explain the origin of long-period comets. He proposed that these icy bodies resided in a…
- Saturn's hexagonDavid Godfrey pieced together the first view of Saturn's hexagon in 1987. He analyzed fly-by data from the Voyager mission that had flown past the planet six…
- EarthThe Modern English word Earth developed from an Old English noun most often spelled ertha. This term has cognates in every Germanic language, tracing back to…