Which is the smallest planet?
MOA-2007-BLG-192L
The discovery of a planet, MOA-2007-BLG-192Lb, orbiting this object was announced on June 2, 2008. This planet, with a mass of approximately 3.3 times that of Earth, is one of the smallest known extrasolar planets. It was found when it caused a gravitational microlensing event on the night of May 24, 2007, which was detected as part of the MOA-II gravitational microlensing survey at the Mount John University Observatory in New Zealand.
Exoplanet
The least massive planet known is Draugr (also known as PSR B1257+12 A or PSR B1257+12 b), which is about twice the mass of the Moon. The most massive planet listed on the NASA Exoplanet Archive is HR 2562 b, about 30 times the mass of Jupiter, although according to some definitions of a planet, it is too massive to be a planet and may be a brown dwarf instead. There are planets that are so near to their star that they take only a few hours to orbit and there are others so far away that they take thousands of years to orbit. Some are so far out that it is difficult to tell whether they are gravitationally bound to the star. Almost all of the planets detected so far are within the Milky Way. Nonetheless, evidence suggests that extragalactic planets, exoplanets farther away in galaxies beyond the local Milky Way galaxy, may exist. The nearest exoplanet is Proxima Centauri b, located 4.2 light-years (1.3 parsecs) from Earth and orbiting Proxima Centauri, the closest star to the Sun.
List of bats of the Caribbean by island
Aruba is the smallest of the ABC islands and the closest to the mainland.
Ariel (moon)
After Miranda, Ariel is the second-smallest of Uranus' five major rounded satellites and the second-closest to its planet. Among the smallest of the Solar System's 19 known spherical moons (it ranks 14th among them in diameter), it is believed to be composed of roughly equal parts ice and rocky material. Its mass is approximately equal in magnitude to Earth's hydrosphere.
Minor planet
Objects are called dwarf planets if their own gravity is sufficient to achieve hydrostatic equilibrium and form an ellipsoidal shape. All other minor planets and comets are called "small Solar System bodies". The IAU stated that the term "minor planet" may still be used, but the term "small Solar System body" will be preferred. However, for purposes of numbering and naming, the traditional distinction between minor planet and comet is still used.
Draco (constellation)
The constellation contains the star recently named Kepler-10, which has been confirmed to be orbited by Kepler-10b, the smallest rocky Earth-sized planet yet detected outside of the Solar System.
Kepler-37
Kepler-37b is the closest planet to the Kepler-37. At the time of its discovery in February 2013, it was the smallest known exoplanet. At in diameter, it is slightly larger than the Moon. It orbits Kepler-37 once every 13 days at a distance of about 0.1 astronomical units (AU). Kepler-37b has a rocky surface and is believed to be too small and too close to its star to support water or maintain an atmosphere. Surface temperature is estimated at .
K2-138b
K2-138b is the smallest planet of K2-138 with a radius of 1.57 , meaning it could be rocky. It orbits its host star every 2.35 days at a distance of 0.0338 AU. At this proximity, the planet is likely very hot and receives 486 times the stellar flux as Earth.
Gliese 581 planetary system
Gliese 581e is the innermost planet and, with a minimum mass of 1.7 Earth masses, is the least massive of the three. Discovered in 2009, it is also the most recent confirmed planet to have been discovered in this system. It takes 3.15 days to complete an orbit. Initial analyses suggested that the planet's orbit is quite elliptical but after correcting the radial velocity measurements for stellar activity, the data now indicate a circular orbit.
Gliese 777 c
Gliese 777 c, often catalogued as Gliese 777 Ac or simply HD 190360 c, is an extrasolar planet approximately 52 light-years away in the constellation of Cygnus. The planet was discovered orbiting the primary star of the Gliese 777 system in 2005 using the radial velocity method and confirmed in 2009. The planet was once called the "smallest extrasolar planet discovered", but this is currently no longer the case. With a minimum mass just 18 times that of the Earth, the planet is likely a "hot Neptune" planet, a small Jovian planet, or possibly a large terrestrial planet (a super-Earth).
51 Eridani
51 Eridani b is a young Jupiter-like planet and was photographed, in near-infrared light, on December 21, 2014. The study, led by Bruce Macintosh, a professor of physics at Stanford University and confirmed by Christian Marois found that methane and water were abundant in the atmosphere of the planet and its mass was only slightly larger than Jupiter’s. It is the smallest exoplanet directly imaged to date.
List of airports in Tuvalu
Tuvalu, formerly known as the Ellice Islands, is a Polynesian island nation located in the Pacific Ocean, midway between Hawaii and Australia. Its nearest neighbours are Kiribati, Nauru, Samoa and Fiji. It comprises four reef islands and five true atolls. Its population of 12,373 makes it the second-least-populated sovereign state in the world, with only Vatican City having fewer inhabitants. In terms of physical land size, at just Tuvalu is the fourth smallest country in the world, larger only than the Vatican City at , Monaco at and Nauru at .
IAU definition of planet
In 1978, Pluto's moon Charon was discovered. By measuring Charon's orbital period, astronomers could accurately calculate Pluto's mass for the first time, which they found to be much smaller than expected. Pluto's mass was roughly one twenty-fifth of Mercury's, making it by far the smallest planet, smaller even than the Earth's Moon, although it was still over ten times as massive as the largest asteroid, Ceres.
Kepler-186
The five planets discovered around Kepler-186 are all expected to have a solid surface. The smallest one, Kepler-186b, is only 8% larger than Earth, while the largest one, Kepler-186d, is almost 40% larger.
Comoros
At , it is one of the smallest countries in the world. The Comoros also has claim to of territorial seas. The interiors of the islands vary from steep mountains to low hills.
Kepler-20
On December 20, 2011, the Kepler Space Telescope team reported the discovery of a five-planet system containing three small gas giants and the first two Earth-sized extrasolar planets, Kepler-20e (the first known extrasolar planet smaller than Earth orbiting a main-sequence star) and Kepler-20f, orbiting a Sun-like star. Although the planets are Earth-sized, they are not Earth-like in the respect that they are much closer to their star than Earth, and are hence not near the habitable zone, with expected surface temperatures of and , respectively. The three other Neptune-sized planets in the system, Kepler-20b, Kepler-20c, and Kepler-20d, all orbit similarly close to the star. Kepler-20g is a non-transiting exoplanet orbiting Kepler-20.
Monte Iberia eleuth
The Monte Iberia eleuth (Eleutherodactylus iberia) is a small eleutherodactylid frog endemic to eastern Cuba. It is the smallest living frog in the Northern Hemisphere, about in snout–vent length. It is the third-smallest frog (and tetrapod) in the world, following "Paedophryne amauensis" and the Brazilian gold frog. It was first discovered in 1993 on Mount Iberia (Holguín Province), from which it gets its name, and exists in only two small regions of Cuba. Much remains unknown about this small creature.
HD 40307 b
HD 40307 b is an extrasolar planet orbiting the star HD 40307, located 42 light-years away in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, using the European Southern Obervatory's HARPS apparatus, in June 2008. It is the second smallest of the planets orbiting the star, after HD 40307 e. The planet is of interest as this star has relatively low metallicity, supporting a hypothesis that different metallicities in protostars determine what kind of planets they will form.
Mini-Neptune
A mini-Neptune or sub-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet of up to 10 Earth masses (), less massive than Uranus and Neptune, which have about 14.5 and 17 , respectively. Mini-Neptunes have thick hydrogen–helium atmospheres, probably with deep layers of ice, rock or liquid oceans (made of water, ammonia, a mixture of both, or heavier volatiles).
Kepler-124b
It is the smallest discovered planet in the Kepler-124 system, and has the closest orbit of the three known planets. Kepler-124b orbits 96% closer to its star than Earth (approximately 3 Earth days), which in the Kepler-124 system is inside the inner limit of the star's habitable zone.
Discheramocephalus minutissimus
Discheramocephalus minutissimus is a species of feather-winged beetle, the smallest beetles on earth, first found in Indonesia. This species' adults have a body length of approximately 400 to 426µm. According to Grebennikov, the main factor limiting miniaturisation of female insects is an egg size significant enough in size to produce viable larvae. This size threshold is sometimes overcome, reaching limits of 180 and 130 µm in females and males, respectively, according to the author. Brain size is possibly the second most important factor limiting miniaturisation in this class.
Monoceros
Monoceros contains two super-Earth exoplanets in one planetary system: COROT-7b was detected by the COROT satellite and COROT-7c was detected by HARPS from ground-based telescopes. Until the announcement of Kepler-10b in January 2011, COROT-7b was the smallest exoplanet to have its diameter measured, at 1.58 times that of the Earth (which would give it a volume 3.95 times Earth's). Both planets in this system were discovered in 2009.
Super-Earth
In general, super-Earths are defined by their masses, and the term does not imply temperatures, compositions, orbital properties, habitability, or environments. While sources generally agree on an upper bound of 10 Earth masses (~69% of the mass of Uranus, which is the Solar System's giant planet with the least mass), the lower bound varies from 1 or 1.9 to 5, with various other definitions appearing in the popular media. The term "super-Earth" is also used by astronomers to refer to planets bigger than Earth-like planets (from 0.8 to 1.25 Earth-radii), but smaller than mini-Neptunes (from 2 to 4 Earth-radii). 
This definition was made by the Kepler Mission. 
Some authors further suggest that the term Super-Earth might be limited to rocky planets without a significant atmosphere, or planets that have not just atmospheres but also solid surfaces or oceans with a sharp boundary between liquid and atmosphere, which the four giant planets in the Solar System do not have. 
Planets above 10 Earth masses are termed massive solid planets/mega-Earths or gas giant planets depending on whether they are mostly rock and ice or mostly gas.
Eris (dwarf planet)
Eris (minor-planet designation 136199 Eris) is the most massive and second-largest (by volume) dwarf planet (and plutoid) in the known Solar System. Eris was discovered in January 2005 by a Palomar Observatory-based team led by Mike Brown, and its discovery was verified later that year. In September 2006 it was named after Eris, the Greek goddess of strife and discord. Eris is the ninth most massive object directly orbiting the Sun, and the 16th most massive overall, because seven moons are more massive than all known dwarf planets. It is also the largest which has not yet been visited by a spacecraft. Eris was measured to be in diameter. Eris's mass is about 0.27% of the Earth mass, about 27% more than dwarf planet Pluto, although Pluto is slightly larger by volume.
Kepler-22b
Kepler-22b, dubbed by scientists as a 'waterworld', might be an 'ocean-like' planet. It might also be comparable to the water-rich planet GJ 1214 b although Kepler-22b, unlike GJ 1214 b, is in the habitable zone. An Earth-like composition is ruled out to at least 1-sigma uncertainty by radial velocity measurements of the system. It is thus likely to have a more volatile-rich composition with a liquid or gaseous outer shell; this would make it similar to Kepler-11f, the smallest known gas planet. Natalie Batalha, one of the scientists on the Kepler Space Telescope project, has speculated, "If it is mostly ocean with a small rocky core, it's not beyond the realm of possibility that life could exist in such an ocean". This possibility has spurred SETI to perform research on top candidates for extraterrestrial life.
Brown dwarf
The brown dwarf Cha 110913-773444, located 500 light years away in the constellation Chamaeleon, may be in the process of forming a miniature planetary system. Astronomers from Pennsylvania State University have detected what they believe to be a disk of gas and dust similar to the one hypothesized to have formed the Solar System. Cha 110913-773444 is the smallest brown dwarf found to date (), and if it formed a planetary system, it would be the smallest known object to have one. Their findings were published in the December 10, 2005 issue of Astrophysical Journal Letters.
List of directly imaged exoplanets
The data given for each planet is taken from the latest published paper on the planet to have that data. In many cases it is not possible to have an exact value, and an estimated range is instead provided. The least massive planet is Fomalhaut b, which has a mass of 2 M or less. The coldest and oldest is 59 Virginis b with a mean temperature of 240 °C and age of 100–500 million years.
This list includes the four members of the multi-planet system that orbit HR 8799.
UESAC
The Minor Planet Center credits UESAC with the discovery of 1123 numbered minor planets. The discoveries range from the lowest numbered discovery, 6102 Visby, to the currently highest numbered body, . The given total also including and , which were separately credited to "Comets UESAC", while all other discoveries were credited to "UESAC". More minor planets may yet to be numbered and added to this list as their orbits are confirmed.
Little bronze cuckoo
The little bronze cuckoo ("Chrysococcyx minutillus") is a species of cuckoo in the family Cuculidae. It is found in Southeast Asia, New Guinea and northern and eastern Australia. Its natural habitat is subtropical or tropical moist lowland forests. This is the world's smallest cuckoo, at 17 grams and . The subspecies "rufomerus" and "crassirostris" are sometimes given specific status.
List of slow rotators (minor planets)
This list contains the slowest-rotating minor planets with periods of at least 1000 hours, or 41 days. See "" for minor planets with an insufficiently accurate period—that is, a LCDB quality code of less than 2.
List of exceptional asteroids
Minor planets with orbital inclinations greater than 90° (the greatest possible is 180°) orbit in a retrograde direction. , of the more than 700,000 minor planets known, there are only 95 known retrograde minor planets. In comparison, there are over 1,920 comets with retrograde orbits. This makes retrograde minor planets the rarest group of all. High-inclination asteroids are either Mars-crossers (possibly in the process of being ejected from the Solar System) or damocloids. Some of these are temporarily captured in retrograde resonance with the gas giants.The above table lists only numbered asteroids that are also comets. Note there are several cases where a non-numbered minor planets turned out to be a comet, e.g. C/2001 OG108 (LONEOS), which was provisionally designated .
HD 102117 b
HD 102117 b is a planet that orbits the star HD 102117. The planet is a small gas giant a fifth the size of Jupiter. It orbits very close to its star, but not in a "torch orbit" like the famous 51 Pegasi b. It is one of the smallest extrasolar planets discovered so far.
List of possible dwarf planets
After Brown and Tancredi made their calculations, it was discovered that Iapetus (1,470 km in diameter) and the smaller moons of Saturn down to Mimas with well-determined shapes are not in hydrostatic equilibrium as had been thought. They have a hydrostatic shape that froze in some time ago and that does not match the shape an equilibrium body would have at their current rotation rates. Ceres, at 950 km, is the smallest body for which detailed measurements are consistent with hydrostatic equilibrium. It is not clear whether trans-Neptunian objects would behave more like Ceres or Iapetus; thus, some or all trans-Neptunian dwarf planets smaller than Pluto and Eris might not actually be in equilibrium. The IAU has not addressed the issue since these findings.
73 Klytia
Klytia ( ; minor planet designation: 73 Klytia) is a main-belt asteroid. It was the second and last asteroid discovery by the prolific comet discoverer Horace Tuttle, on April 7, 1862. It is named after Clytia, who loved Apollo in Greek mythology. Of the first one hundred numbered asteroids, Klytia is the smallest.
Neptune
Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune. Neptune orbits the Sun once every 164.8 years at an average distance of . It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune's trident.
Smallest organisms
The vulnerable Kitti's hog-nosed bat ("Craseonycteris thonglongyai"), also known as the bumblebee bat, from Thailand and Myanmar is the smallest mammal, at in length and in weight.
OGLE-2005-BLG-390L
OGLE-2005-BLG-390L has one known planet, which was discovered using the technique of gravitational microlensing. Indications are that the planet is about five times Earth mass, orbiting at about 2.6 astronomical units from the parent star. The discovery was announced on January 25, 2006. OGLE-2005-BLG-390Lb is considered one of the smallest known extrasolar planets around a main sequence star, possibly rocky, with a mass around 5.5 times that of the Earth. The orbital
radius (assuming a circular orbit) of the planet is 2.6 AU, however the orbital elements are unknown. Based on its low mass and estimated temperature of around 50 K, the planet is thought to consist mainly of ices, like Pluto or Uranus, rather than being a Jupiter-like gas giant.
Gliese 876
Gliese 876d, discovered in 2005, is the innermost known planet. With an estimated minimum mass only 5.88 times that of the Earth, it is possible that it is a dense terrestrial planet.Gliese 876 c, discovered in 2001, is a giant planet at 0.62 Jupiter-mass planet. It is in a 1:2 orbital resonance with the outermost known planet, taking 30.340 days to orbit the star. The planet orbits within the habitable zone. Its mass makes it more likely to be a Class II planet in the Sudarsky extrasolar planet classification. The presence of surface liquid water is possible on sufficiently massive satellites should they exist.Gliese 876 b, discovered in 1998 is around twice the mass of Jupiter and revolves around its star in an orbit taking approximately 61 days to complete, at a distance of only 0.208 AU, less than the distance from the Sun to Mercury. Its mass makes it more likely to be a Class II or Class III planet in the Sudarsky model. The presence of surface liquid water is possible on sufficiently massive satellites should they exist.Gliese 876 e, discovered in 2010, has a mass similar to that of the planet Uranus and its orbit takes 124 days to complete.
Thumbelina (horse)
Thumbelina (born May 1, 2001) is a dwarf miniature horse and the world's smallest horse. She stands tall and weighs , and received the title of world's smallest from Guinness World Records. Thumbelina was born in St. Louis, Missouri. Her owners, Paul and Kay Goessling, and her handler, Michael Goessling, care for her along with other miniature horses on their farm in Ladue.
Island
Greenland is the world's largest island, with an area of over 2.1 million km, while Australia, the world's smallest continent, has an area of 7.6 million km, but there is no standard of size that distinguishes islands from continents, or from islets.
Super-Earth
On 30 July 2015, Astronomy & Astrophysics said they found a planetary system with three super-Earths orbiting a bright, dwarf star. The four-planet system, dubbed HD 219134, had been found 21 light years from Earth in the M-shaped northern hemisphere of constellation Cassiopeia, but it is not in the habitable zone of its star. The planet with the shortest orbit is HD 219134 b, and is Earth's closest known rocky, and transiting, exoplanet.
List of minor planets
The vast majority of minor planets are evenly distributed between the inner-, central and outer parts of the asteroid belt, which are separated by the two Kirkwood gaps at 2.5 and 2.82 AU. Nearly 97.5% of all minor planets are main-belt asteroids (MBA), while Jupiter trojans, Mars-crossing and near-Earth asteroids each account for less than 1% of the overall population. Only a small number of distant minor planets, that is the centaurs and trans-Neptunian objects, have been numbered so far. In the partial lists, table column "category" further refines this principal grouping:
Planets in astrology
Ceres () is the smallest identified dwarf planet in the Solar System, but is significantly the largest object in the asteroid belt. It was discovered on 1 January 1801 by Giuseppe Piazzi, and is named after Ceres, the Roman goddess of growing plants, the harvest, and of motherly love. It was the first asteroid discovered, taking up about one-third of the entire mass of its asteroid belt. The classification of Ceres has changed more than once and has been the subject of some disagreement. Johann Elert Bode believed Ceres to be the "missing planet" he had proposed to exist between Mars and Jupiter, at a distance of 419 million km (2.8 AU) from the Sun. Ceres was assigned a planetary symbol, and remained listed as a planet in astronomy books and tables for about half a century. The 2006 debate surrounding Pluto and what constitutes a planet led to Ceres being considered for reclassification as a planet, but in the end Ceres and Pluto were classified as the first members of the new dwarf planet category.
Kepler-47
The binary system is known to host three planets, all larger than Earth with no solid surface. The innermost planet, Kepler-47b, is a gas giant and resides close to its parent stars and therefore is inhospitable to life. It is thought to be smaller than Kepler-47c and is roughly three times the radius of Earth. The second planet, Kepler-47c, is also a gas giant and the outermost planet. It is situated within the habitable zone and its radius is 4 times the Earth's. Although it is assumed Kepler-47c is not capable of harboring life, it is marginally larger than Neptune and could possibly have a dense atmosphere of water vapor. The latest exoplanet to be discovered in the system was Kepler-47d, announced as being discovered in November 2013. This planet is about the size of planet "c", but orbits farther in then c does. It completes an orbit every 187.3 days.
Smallest organisms
The smallest land snail is "Acmella nana". Discovered in Borneo, Malaysia, and described in November 2015, it measures only 0.7 mm. The previous record was that of "Angustopila dominikae" from China, which was reported in September 2015. This snail measures 0.86 mm.
Planet
There are exoplanets that are much closer to their parent star than any planet in the Solar System is to the Sun, and there are also exoplanets that are much farther from their star. Mercury, the closest planet to the Sun at 0.4 AU, takes 88 days for an orbit, but the shortest known orbits for exoplanets take only a few hours, e.g. Kepler-70b. The Kepler-11 system has five of its planets in shorter orbits than Mercury's, all of them much more massive than Mercury. Neptune is 30 AU from the Sun and takes 165 years to orbit, but there are exoplanets that are hundreds of AU from their star and take more than a thousand years to orbit, e.g. 1RXS1609 b.
PSR B1257+12
The pulsar has a planetary system with three known extrasolar planets, named "Draugr" (PSR B1257+12 b or PSR B1257+12 A), "Poltergeist" (PSR B1257+12 c, or PSR B1257+12 B) and "Phobetor" (PSR B1257+12 d, or PSR B1257+12 C), respectively. They were both the first extrasolar planets and the first pulsar planets to be discovered; B and C in 1992 and A in 1994. A is the lowest-mass planet yet discovered by any observational technique, with somewhat less than twice the mass of Earth's moon.
Kepler-124b
Kepler-124b is an extrasolar planet discovered in 2014. It is located from Earth, orbiting the unclassified star Kepler-124 in the constellation Cygnus. Within The Kepler-124 system (KOI-241) there are three known planets, Kepler-124b being both the smallest and closest to its parent star.
Terrestrial planet
In 2005, the first planets around main-sequence stars that may be terrestrial were found: Gliese 876 d, has a mass 7 to 9 times that of Earth and an orbital period of just two Earth days. It orbits the red dwarf Gliese 876, 15 light years from Earth. OGLE-2005-BLG-390Lb, about 5.5 times the mass of Earth, orbits a star about 21,000 light years away in the constellation Scorpius.
From 2007 to 2010, three (possibly four) potential terrestrial planets were found orbiting within the Gliese 581 planetary system. The smallest, Gliese 581e, is only about 1.9 Earth mass, but orbits very close to the star. An ideal terrestrial planet would be 2 Earth masses with a 25-day orbital period around a red dwarf. Two others, Gliese 581c and Gliese 581d, as well as a disputed planet, Gliese 581g, are more-massive super-Earths orbiting in or close to the habitable zone of the star, so they could potentially be habitable, with Earth-like temperatures.
Kepler-11
Kepler-11 is a Sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,150 light years from Earth. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission uses to detect planets that may be transiting their stars. Announced on February 2, 2011, the star system is among the most compact and flattest systems yet discovered. It is the first discovered case of a star system with six transiting planets. All discovered planets are larger than Earth, with the larger ones being about Neptune's size.
Mercury (planet)
Mercury's axis has the smallest tilt of any of the Solar System's planets (about degree). Its orbital eccentricity is the largest of all known planets in the Solar System; at perihelion, Mercury's distance from the Sun is only about two-thirds (or 66%) of its distance at aphelion. Mercury's surface appears heavily cratered and is similar in appearance to the Moon's, indicating that it has been geologically inactive for billions of years. Having almost no atmosphere to retain heat, it has surface temperatures that vary diurnally more than on any other planet in the Solar System, ranging from at night to during the day across the equatorial regions. The polar regions are constantly below . The planet has no known natural satellites.
Euryplatea nanaknihali
Euryplatea nanaknihali is the world's smallest fly, measuring in size.
John Johnson (astronomer)
In 2012, Johnson's team discovered three small rocky exoplanets in a red dwarf star system observed with the Kepler space telescope. The system was renamed Kepler-42 and the outermost planet was found to be nearly as small as Mars, making it the smallest known exoplanet at the time. A subsequent study used the host star's similarity to Barnard's Star and observations from the Keck Observatory to more precisely measure the properties of the system, including the sizes of the three planets.
(3708) 1974 FV1
As of 2018, it has not received a name. This makes "" the lowest-numbered unnamed minor planet (there are more than half a million numbered minor planets with more than 20,000 of them being named). This contrasts with the neighboring asteroid, 3707 Schröter and 3709 Polypoites, that were already named in September 1993 and April 1988, respectively (). The asteroid is the next low-numbered, unnamed minor planet.
Super-Earth
The discovery of Gliese 581e with a minimum mass of 1.9 Earth masses was announced on 21 April 2009. It was at the time the smallest extrasolar planet discovered around a normal star and the closest in mass to Earth. Being at an orbital distance of just 0.03 AU and orbiting its star in just 3.15 days, it is not in the habitable zone, and may have 100 times more tidal heating than Jupiter's volcanic satellite Io.
Least pygmy squirrel
The least pygmy squirrel ("Exilisciurus exilis"), also known as the plain pygmy squirrel, is a species of rodent in the family Sciuridae. This plain olive-brown squirrel is endemic to forest in Borneo and the Banggi Island. It is among the smallest squirrels in the world.
Outline of Nauru
Nauru – sovereign island nation located in the Micronesian South Pacific. Its nearest neighbour is Banaba Island in the Republic of Kiribati, due east. Nauru is the world's smallest island nation, covering just , the smallest independent republic, and the only republican state in the world without an official capital. It is the least populous member of the United Nations.
Asteroid
In 2006, the term "small Solar System body" was also introduced to cover both most minor planets and comets. Other languages prefer "planetoid" (Greek for "planet-like"), and this term is occasionally used in English especially for larger minor planets such as the dwarf planets as well as an alternative for asteroids since they are not star-like. The word "planetesimal" has a similar meaning, but refers specifically to the small building blocks of the planets that existed when the Solar System was forming. The term "planetule" was coined by the geologist William Daniel Conybeare to describe minor planets, but is not in common use. The three largest objects in the asteroid belt, Ceres, Pallas, and Vesta, grew to the stage of protoplanets. Ceres is a dwarf planet, the only one in the inner Solar System.
2012 VP113
is the minor planet with the farthest known perihelion (closest approach to the Sun) in the Solar System, greater than that of 's. Though its perihelion is farther, has an aphelion only about half that of Sedna's. It is the second discovered sednoid, with semi-major axis beyond and perihelion greater than . The similarity of the orbit of to other known extreme trans-Neptunian objects led Scott Sheppard and Chad Trujillo to suggest that an undiscovered object, Planet Nine, in the outer Solar System is shepherding these distant objects into similar type orbits.
10199 Chariklo
10199 Chariklo ( or ; ; provisional designation ) is the largest confirmed centaur (minor planet of the outer Solar System). It orbits the Sun between Saturn and Uranus, grazing the orbit of Uranus. On 26 March 2014, astronomers announced the discovery of two rings (nicknamed Oiapoque and Chuí) around Chariklo by observing a stellar occultation, making it the first minor planet known to have rings.
List of minor planets
The list of minor planets consists of more than 500 partial lists, each containing 1000 minor planets grouped into 10 tables. The data is sourced from the Minor Planet Center (MPC) and expanded with data from the JPL SBDB (mean-diameter), Johnston's archive (sub-classification) and others "(see detailed field descriptions below)". For an overview of all existing partial lists, "see ".
Planet
There are eight planets in the Solar System, which are in increasing distance from the Sun:Jupiter is the largest, at 318 Earth masses, whereas Mercury is the smallest, at 0.055 Earth masses.
2019 AQ3
orbit has the smallest aphelion of any known asteroid in the Solar System, never distancing itself more than 0.774 AU from the Sun (77% of Earth's average orbital distance). Before its discovery, the record was held by at an aphelion of 0.804 AU, which is notably larger. orbit also has a semi-major axis below that of Venus (0.723 AU) and an orbital period of 165 days, which is the second shortest among all asteroids. (The record 161-day orbit of is poorly defined and still may change considerably).
Super-Earth
The smallest super-Earth found as of 2008 was MOA-2007-BLG-192Lb. The planet was announced by astrophysicist David P. Bennett for the international MOA collaboration on June 2, 2008. This planet has approximately 3.3 Earth masses and orbits a brown dwarf. It was detected by gravitational microlensing.
Kepler-11f
Kepler-11f is, at 2.3 times the mass of Earth, the least massive of the six planets discovered in the orbit of Kepler-11, although the planet's mass may range from 1.1 to 4.5, or from approximately that of Earth's mass to that of Kepler-10b, a rather large confidence interval. Its radius is the second smallest of the six planets discovered in the system at 2.61 times the radius of Earth. Kepler-11f has a density of about 0.7 g/cm, comparable to that of the Solar System's least dense planet, Saturn. Kepler-11f is the fifth planet from Kepler-11, orbiting its host star every 46.68876 days at a distance of 0.25 AU. Its orbital eccentricity is unknown. In comparison, Mercury orbits the Sun every 87.97 days at a distance of 0.387 AU. Kepler-11f has an orbital inclination of 89.4°; it can be seen almost edge-on with respect to Earth. Its surface equilibrium temperature is 544 K, over twice the surface equilibrium temperature of Earth and about two-thirds the surface temperature of Venus.
Pluto
Pluto is the largest and second-most-massive (after Eris) known dwarf planet in the Solar System, and the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—about one-sixth the mass of the Moon and one-third its volume. It has a moderately eccentric and inclined orbit during which it ranges from 30 to 49 astronomical units or AU (4.4–7.4 billion km) from the Sun. This means that Pluto periodically comes closer to the Sun than Neptune, but a stable orbital resonance with Neptune prevents them from colliding. Light from the Sun takes about 5.5 hours to reach Pluto at its average distance (39.5 AU).
Outline of Mercury (planet)
Mercury – smallest and innermost planet in the Solar System. Its orbital period (about 88 Earth days) is less than any other planet in the Solar System. Seen from Earth, it appears to move around its orbit in about 116 days. It has no known natural satellites. It is named after the Roman deity Mercury, the messenger to the gods.
History of Mercury –
List of slow rotators (minor planets)
The periods given in this list are sourced from the "Light Curve Data Base" (LCDB), which contains lightcurve data for more than 15,000 bodies. Most minor planets have rotation periods between 2 and 20 hours. , a group of approximately 650 bodies, typically measuring 1–20 kilometers in diameter, have periods of more than 100 hours or 4 days. Among the , there are currently 14 bodies with a period longer than 1000 hours. According to the Minor Planet Center, the sharp lower limit of approximately 2.2 hours is due to the fact that most smaller bodies are thought to be rubble piles – conglomerations of smaller pieces, loosely coalesced under the influence of gravity – that fly apart if the period is shorter than this limit. The few minor planets rotating faster than 2.2 hours, therefor, can not be merely held together by self-gravity, but must be formed of a contiguous solid.
List of transiting exoplanets
The most massive transiting exoplanet is KELT-1b which masses 27.23 M (making it a brown dwarf) while the least massive is Kepler-42d which masses less than 0.003 M or 0.9 M. The largest exoplanet known is HAT-P-32b which is 2.037 R. The smallest exoplanet known is also Kepler-42d which is 0.051 R or 0.57 R. The densest transiting exoplanet known is COROT-3b, which has density of 26.4 g/cm; the diffusest transiting planet known is Kepler-12b, which has density of only 0.111 g/cm. The longest period of any transiting planets is Kepler-1647b, which takes 1107 days to orbit its (double) stars. The shortest period is Kepler-42c, which takes just 0.45 days to orbit its star
Neptune
Because of the distance of Neptune from Earth, its angular diameter only ranges from 2.2 to 2.4 arcseconds, the smallest of the Solar System planets. Its small apparent size makes it challenging to study visually. Most telescopic data was fairly limited until the advent of the "Hubble Space Telescope" and large ground-based telescopes with adaptive optics (AO).
The first scientifically useful observation of Neptune from ground-based telescopes using adaptive optics, was commenced in 1997 from Hawaii. Neptune is currently entering its spring and summer season and has been shown to be heating up, with increased atmospheric activity and brightness as a consequence. Combined with technological advancements, ground-based telescopes with adaptive optics are recording increasingly more detailed images of it. Both "Hubble" and the adaptive-optics telescopes on Earth have made many new discoveries within the Solar System since the mid-1990s, with a large increase in the number of known satellites and moons around the outer planet, among others. In 2004 and 2005, five new small satellites of Neptune with diameters between 38 and 61 kilometres were discovered.
Smallest organisms
Frogs include the smallest vertebrates known. The smallest known frog species is "Paedophryne amauensis", with a snout-vent length reported as 7.7 mm, which occurs among leaf-litter in the tropical montane forests of New Guinea. Other very small frogs include "Brachycephalus didactylus" from Brazil (reported as 9.6-9.8 mm), several species of "Eleutherodactylus" such as "Eleutherodactylus iberia" (around 10mm) and "Eleutherodactylus limbatus" (8.5–12 mm) and "Eleutherodactylus orientalis" (12.5 mm) from Cuba, Gardiner's Frog "Sechellophryne gardineri" from the Seychelles (up to 11 mm), several species of "Stumpffia" such as "Stumpffia tridactyla"(8.6–12  mm) and "Stumpffia pygmaea"(10–12.5 mm；females:11 mm) and "Wakea madinika"(males:11–13 mm；females:mm 15–16 mm) from Madagascar. "Paedophryne swiftorum"(Body length 8.5 mm) is not included in the smallest vertebrates known with other nine species of frogs. The two species "Microhyla borneensis"(males:10.6–13 mm；females:16–19 mm) and "Arthroleptella rugosa"(males:11.9–14.1 mm；females:15.5mm) were once the smallest known frogs from the Old World. In general these extremely small frogs occur in tropical forest and montane environments. There is relatively little data on size variation among individuals, growth from metamorphosis to adulthood or size variation among populations in these species. Additional studies and the discovery of further minute frog species are likely to change the rank order of this list.
Ceres (dwarf planet)
Ceres (; minor-planet designation: 1 Ceres) is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter, slightly closer to Mars's orbit. With a diameter of , Ceres is the largest of the minor planets and the only dwarf planet inside Neptune's orbit. It is the 33rd-largest known body in the Solar System.
Outline of Mars
Mars – fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is often referred to as the "Red Planet" because the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth.
Lyra
Lyra is one of three constellations (along with neighboring Cygnus and Draco) to be in the Kepler Mission's field of view, and as such it contains many more known exoplanets than most constellations. One of the first discovered by the mission is Kepler-7b, an extremely low-density exoplanet with less than half the mass of Jupiter, yet nearly 1.5 times the radius. Almost as sparse is Kepler-8b, only slightly more massive and of a similar radius. The Kepler-20 system contains five known planets; three of them are only slightly smaller than Neptune, and two while the other two are some of the first Earth-sized exoplanets to be discovered. Kepler-37 is another star with an exoplanet discovered by Kepler; the planet is the smallest known extrasolar planet known as of February 2013.
List of exoplanets detected by microlensing
The most massive planet detected by microlensing is MOA-bin-1b, which masses ; the least massive is MOA-2007-BLG-192Lb, which masses or . The widest separation between a planet and a star is MOA-bin-1b, which is 8.3 AU; the shortest separation is MOA-2007-BLG-192Lb, which is 0.66 AU.
Atira asteroid
In great part because of the search methods used to look for asteroids, there are currently no known asteroids with orbits contained within Venus (Q = 0.728 AU) or Mercury's (Q = 0.467 AU, e.g. vulcanoids). As of January 2019, the asteroid with the smallest known aphelion is , with an aphelion of 0.773 AU.
Atira asteroid
Atira asteroids or Apohele asteroids, also known as Interior-Earth Objects (IEOs), are asteroids, whose orbits are entirely confined within Earth's orbit, that is, their orbit has an aphelion (farthest point from the Sun) smaller than Earth's perihelion (nearest point to the Sun), which is 0.983 astronomical units (AU). Atira asteroids are by far the smallest group of near-Earth objects, compared to the Aten, Apollo and Amor asteroids.
List of nearest exoplanets
Most known nearby exoplanets orbit close to their star and have highly eccentric orbits. A majority are significantly larger than Earth, but a few have similar masses, including two planets (around YZ Ceti, 12 ly) which may be less massive than Earth. Several confirmed exoplanets are hypothesized to be potentially habitable, with Proxima Centauri b and three around Gliese 667 C (23.6 ly) considered the most likely candidates. The International Astronomical Union took a public survey in 2015 about renaming some known extrasolar bodies, including the planets around Epsilon Eridani (10.5 ly) and Fomalhaut.
PSR B1257+12 A
PSR B1257+12 b, alternatively designated PSR B1257+12 A, also named Draugr, is an extrasolar planet approximately 2,300 light-years away in the constellation of Virgo. The planet is the innermost object orbiting the pulsar PSR B1257+12, i.e. a pulsar planet in the dead stellar system. It is about twice as massive as the Moon, and is listed as the least massive planet (with the mass accurately determined) known, including among the planets in the Solar System.
HR 8799 e
HR 8799 e is the innermost known planet as it orbits closer to its star than the other three known planets in this planetary system. This planet orbits at an estimated distance of 14.5 AU based on the relationship between angular separation measured by direct imaging observations and the star's distance from Earth. The estimated period of this planet if the orbit is face-on is about 50 years.
Smallest organisms
The Etruscan shrew ("Suncus etruscus"), is the smallest mammal by mass, weighing only about on average. The bumblebee bat has a smaller skull size. The smallest mammal that ever lived, the shrew-like "Batodonoides vanhouteni", weighed only .
Gliese 1132
As of June 12, 2018, there are two confirmed planets and one candidate planet orbiting GJ 1132. Gliese 1132 b is the innermost planet of the Gliese 1132 system, as well as the smallest. It is very similar in size and mass to Earth, with a radius of 1.13 and a mass of 1.66 . It is slightly denser than Earth with 30% more surface gravity, meaning it has a rocky composition. Despite its physical similarities to Earth, it is considered too hot to be habitable, getting 19 times more sunlight due to its 1.6 day orbital period. In April 2017, it was revealed that the planet has an atmosphere, potentially rich in water vapor and methane.
Minor planet
A minor planet is an astronomical object in direct orbit around the Sun (or more broadly, any star with a planetary system) that is neither a planet nor exclusively classified as a comet. Before 2006 the International Astronomical Union (IAU) officially used the term "minor planet", but during that year's meeting it reclassified minor planets and comets into dwarf planets and small Solar System bodies (SSSBs).
HD 49674
At the time of discovery of the planet HD 49674 b in 2002, it was the least massive planet known, very close to the boundary between sub-Jupiter mass and Neptune-mass at 0.1 M. This planet orbits very close to the star.
Kepler-11c
Kepler-11c is an exoplanet discovered in the orbit of the Sun-like star Kepler-11 by the Kepler spacecraft, a NASA telescope aiming to discover Earth-like planets. It is the second planet from its star, and is most likely a water planet with a thin hydrogen–helium atmosphere. Kepler-11c orbits Kepler-11 every 10 days, and has an estimated density twice that of pure water. It is estimated to have a mass thirteen times that of Earth and a radius three times that of Earth. Kepler-11c and its five sister planets form the first discovered system with more than three transiting planets. The Kepler-11 system also holds the record of being the most compact and the flattest system discovered. Kepler-11c and the other Kepler-11 planets were announced to the public on February 2, 2011, and was published in "Nature" a day later.
Planetary habitability
"Low mass" is partly a relative label: the Earth is low mass when compared to the Solar System's gas giants, but it is the largest, by diameter and mass, and the densest of all terrestrial bodies. It is large enough to retain an atmosphere through gravity alone and large enough that its molten core remains a heat engine, driving the diverse geology of the surface (the decay of radioactive elements within a planet's core is the other significant component of planetary heating). Mars, by contrast, is nearly (or perhaps totally) geologically dead and has lost much of its atmosphere. Thus it would be fair to infer that the lower mass limit for habitability lies somewhere between that of Mars and that of Earth or Venus: 0.3 Earth masses has been offered as a rough dividing line for habitable planets. However, a 2008 study by the Harvard-Smithsonian Center for Astrophysics suggests that the dividing line may be higher. Earth may in fact lie on the lower boundary of habitability: if it were any smaller, plate tectonics would be impossible. Venus, which has 85% of Earth's mass, shows no signs of tectonic activity. Conversely, "super-Earths", terrestrial planets with higher masses than Earth, would have higher levels of plate tectonics and thus be firmly placed in the habitable range.
Nauru
Nauru ( or ; ), officially the Republic of Nauru () and formerly known as Pleasant Island, is an island country in Micronesia, a subregion of Oceania, in the Central Pacific. Its nearest neighbour is Banaba Island in Kiribati, to the east. It further lies northwest of Tuvalu, north of the Solomon Islands, east-northeast of Papua New Guinea, southeast of the Federated States of Micronesia and south of the Marshall Islands. With residents in a area, Nauru is the smallest state in the South Pacific, smallest republic and third-smallest state by area in the world, behind only Vatican City and Monaco.
Smallest organisms
With a mass of approximately and a length of 5 centimetres (2.0 in), the bee hummingbird ("Mellisuga helenae") is the world's smallest bird species and the smallest warm-blooded vertebrate. Called the "zunzún" in its native habitat on Cuba, it is lighter than a Canadian or U.S. penny. It is said that it is "more apt to be mistaken for a bee than a bird". The bee hummingbird eats half its total body mass and drinks eight times its total body mass each day. Its nest is 3 cm across.
Kepler-37b
To date, Kepler-37b is the smallest planet discovered around a main-sequence star outside the Solar System. Detection of Kepler-37b was possible due to its short orbital period, relative brightness, and low activity of its host star, allowing brightness data to average out quickly. The discovery of Kepler-37b has led Jack Lissauer, a scientist at NASA's Ames Research Center, to conjecture that "such little planets are common".
Sub-Earth
The "Kepler" space telescope opened the realm of sub-Earths by its discovery of them. On January 10, 2012, Kepler discovered the first three sub-Earths around an ordinary star, Kepler-42. As of June 2014, Kepler has 45 confirmed planets that are smaller than Earth, with 17 of them being smaller than 0.8 R. In addition, there are over 310 planet candidates with an estimated radius of <1R, with 135 of them being smaller than 0.8 R.
Mercury (planet)
Mercury is the smallest and innermost planet in the Solar System. Its orbital period around the Sun of 87.97 days is the shortest of all the planets in the Solar System. It is named after the Roman deity Mercury, the messenger of the gods.
Kodkod
The kodkod ("Leopardus guigna") (), also called güiña, is the smallest cat in the Americas. It lives primarily in central and southern Chile and marginally in adjoining areas of Argentina. Its area of distribution is small compared to the other South American cats. Since 2002, it has been listed as Vulnerable on the IUCN Red List as the total effective population may comprise less than 10,000 mature individuals, and is threatened due to persecution and loss of habitat and prey base.
List of smallest exoplanets
Below is a list of the smallest exoplanets so far discovered, in terms of physical size, ordered by radius.
COROT-7b
COROT-7b (previously named COROT-Exo-7b) is an exoplanet orbiting around the star COROT-7, in the constellation Monoceros, at 489 light years from Earth. It was first detected photometrically by the French-led COROT mission and reported in February 2009. Until the announcement of Kepler-10b in January 2011, it was the smallest exoplanet to have its diameter measured, at 1.58 times that of the Earth (which would give it a volume 3.95 times Earth's), and the first potential extrasolar terrestrial planet to be found. The planet has a very short orbital period, revolving around its host star in about 20 hours.
Kepler-186f
The nearest-to-Earth-size planet in a habitable zone previously known was Kepler-62f with 1.4 Earth radii. Kepler-186f orbits an M-dwarf star, while Kepler-62f orbits a K-type star. A study of atmospheric evolution in Earth-size planets in habitable zones of G-Stars (a class containing the Sun, but not Kepler-186) suggested that 0.8–1.15 R is the size range for planets small enough to lose their initial accreted hydrogen envelope but large enough to retain an outgassed secondary atmosphere such as Earth's.
Pluto
Pluto (minor planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered and is the largest known plutoid (or "ice dwarf").
Super-Earth
Discovered on 5 January 2010, a planet HD 156668 b with a minimum mass of 4.15 Earth masses, is the least massive planet detected by the radial velocity method. The only confirmed radial velocity planet smaller than this planet is Gliese 581e at 1.9 Earth masses (see above). On 24 August, astronomers using ESO's HARPS instrument announced the discovery of a planetary system with up to seven planets orbiting a Sun-like star, HD 10180, one of which, although not yet confirmed, has an estimated minimum mass of 1.35 ± 0.23 times that of Earth, which would be the lowest mass of any exoplanet found to date orbiting a main-sequence star. Although unconfirmed, there is 98.6% probability that this planet does exist.
Orbit
Owing to mutual gravitational perturbations, the eccentricities of the planetary orbits vary over time. Mercury, the smallest planet in the Solar System, has the most eccentric orbit. At the present epoch, Mars has the next largest eccentricity while the smallest orbital eccentricities are seen with Venus and Neptune.
Smallest organisms
The smallest organisms found on Earth can be determined according to various aspects of organism size; including volume, mass, height, length, or genome size.
Given the incomplete nature of scientific knowledge, it is possible that the smallest organism is undiscovered. Furthermore, there is some debate over the definition of life, and what entities qualify as organisms; consequently the smallest known organism (microorganism) is debatable.
(386454) 2008 XM
(386454) 2008 XM is an outstandingly eccentric, sub-kilometer-sized asteroid, with one of the smallest known perihelions among all minor planets. It is classified as near-Earth object of the Apollo group and was discovered on 2 December 2008, by the LINEAR program at Lincoln Laboratory's Experimental Test Site in Socorro, New Mexico, United States.
ARM Cortex-M
The smallest ARM microcontrollers are of the Cortex-M0+ type (as of 2014, smallest at 1.6 mm by 2 mm is Kinetis KL03).On 21 June 2018, the "world's smallest computer'", or computer device was announced based on the ARM Cortex-M0+ (and including RAM and wireless transmitters and receivers based on photovoltaics) by University of Michigan researchers at the 2018 Symposia on VLSI Technology and Circuits with the paper "A 0.04mm3 16nW Wireless and Batteryless Sensor System with Integrated Cortex-M0+ Processor and Optical Communication for Cellular Temperature Measurement." The device is 1/10th the size of IBM's previously claimed world-record-sized computer from months back in March 2018, which is smaller than a grain of salt.