Instruct: Given a question, retrieve relevant documents that can help answer the question.
Query: What is the largest asteroid?
The largest asteroids with an accurately measured mass, due to the fact that they have been (and are being) studied by the probe Dawn, are 1 Ceres with a mass of 939.3 ± 0.5×1018 kg, and 4 Vesta at 259.076 ± 0.001×1018 kg. The third-largest asteroid with an accurately measured mass, due to the fact that it has moons, is 87 Sylvia at 14.78 ± 0.06×1018 kg.
Hygiea is the largest carbonaceous asteroid[67] and, unlike the other largest asteroids, lies relatively close to the plane of the ecliptic.[68] It is the largest member and presumed parent body of the Hygiean family of asteroids.
The Hygiea or Hygiean family of asteroids is a grouping of dark, carbonaceous C-type and B-type asteroids in outer asteroid belt, the largest member of which is 10 Hygiea. About 1% of all known asteroids in the asteroid belt belong to this family.
The physical composition of asteroids is varied and in most cases poorly understood. Ceres appears to be composed of a rocky core covered by an icy mantle, where Vesta is thought to have a nickel-iron core, olivine mantle, and basaltic crust.[74] 10 Hygiea, however, which appears to have a uniformly primitive composition of carbonaceous chondrite, is thought to be the largest undifferentiated asteroid. Most of the smaller asteroids are thought to be piles of rubble held together loosely by gravity, though the largest are probably solid. Some asteroids have moons or are co-orbiting binaries: Rubble piles, moons, binaries, and scattered asteroid families are thought to be the results of collisions that disrupted a parent asteroid, or, possibly, a planet.[75]
The Eunomia or Eunomian family () is a large asteroid family of S-type asteroids named after the asteroid 15 Eunomia. It is the most prominent family in the intermediate asteroid belt and the 6th-largest family with nearly six thousand known members, or approximately 1.4% of all asteroids in the asteroid belt.
After Ceres, Asteroid 433 Eros is perhaps the most-commonly mentioned asteroid, probably because it is one of the largest near-Earth asteroids.
The other Eunomian asteroids are quite regularly distributed in orbital space around Eunomia. The next largest member identified by the analysis was 258 Tyche of 65 km diameter. However, its orbit lies at the very margin of what can be considered the family region, and it may well be an interloper. The largest clear family members are about 30 km diameter, with several asteroids in this size range. 
"Demoulina" is a member of the Flora family (), a giant asteroid family and the largest family of stony asteroids in the asteroid belt. However, it is a non-family asteroid of the main belt's background population when applying the Hierarchical Clustering Method to its proper orbital elements.
Until the age of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes and their shapes and terrain remained a mystery. The best modern ground-based telescopes and the Earth-orbiting Hubble Space Telescope can resolve a small amount of detail on the surfaces of the largest asteroids, but even these mostly remain little more than fuzzy blobs. Limited information about the shapes and compositions of asteroids can be inferred from their light curves (their variation in brightness as they rotate) and their spectral properties, and asteroid sizes can be estimated by timing the lengths of star occulations (when an asteroid passes directly in front of a star). Radar imaging can yield good information about asteroid shapes and orbital and rotational parameters, especially for near-Earth asteroids. In terms of delta-v and propellant requirements, NEOs are more easily accessible than the Moon.[111]
"Shkodrov" is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. Based on osculating Keplerian orbital elements, the asteroid has also been classified as a member of the Flora family (), a giant asteroid family and the largest family of stony asteroids in the asteroid belt.
The asteroid belt is the circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt is also termed the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such as near-Earth asteroids and trojan asteroids. About half the mass of the belt is contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea. The total mass of the asteroid belt is approximately 4% that of the Moon, or 22% that of Pluto, and roughly twice that of Pluto's moon Charon (whose diameter is 1200 km).
Eunomia (minor planet designation 15 Eunomia) is a very large asteroid in the inner asteroid belt. It is the largest of the stony (S-type) asteroids, and somewhere between the 8th- and 12th-largest main-belt asteroid overall (uncertainty in diameters causes uncertainty in its ranking). It is the largest Eunomian asteroid, and is estimated to contain 1% of the mass of the asteroid belt.
Bamberga (minor planet designation: 324 Bamberga) is one of the largest asteroids in the asteroid belt. It was discovered by Johann Palisa on 25 February 1892 in Vienna. It is the 14th-largest asteroid in the asteroid belt. Apart from the near-Earth asteroid Eros, it was the last asteroid which is "ever" easily visible with binoculars to be discovered.
The dwarf planet Ceres is by far the largest asteroid, with a diameter of 975km (606mi). The next largest are 4 Vesta and 2 Pallas, both with diameters of just over 500km (300mi). Vesta is the only main-belt asteroid that can, on occasion, be visible to the naked eye. On some rare occasions, a near-Earth asteroid may briefly become visible without technical aid; see 99942 Apophis.
The Hungaria group is a dynamical group of asteroids in the asteroid belt. The Hungaria asteroids orbit the Sun with a semi-major axis (longest radius of an ellipse) between 1.78 and 2.00 astronomical units (AU). They are the innermost dense concentration of asteroids in the Solar System—the near-Earth asteroids are much more sparse—and derive their name from their largest member 434 Hungaria. The Hungaria group includes the Hungaria family (), a collisional asteroid family which dominates its population.
The largest known Apollo asteroid is 1866 Sisyphus, with a diameter of about 8.5 km. Examples of known Apollo asteroids include:
The largest unequivocally C-type asteroid is 10 Hygiea, although the SMASS classification places the largest asteroid, 1 Ceres, here as well, because that scheme lacks a G-type.
Ceres is the largest object in the asteroid belt.
It is sometimes assumed that Ceres has been "re"classified as a dwarf planet, and that it is therefore no longer considered an asteroid. For example, a news update at Space.com spoke of "Pallas, the largest asteroid, and Ceres, the dwarf planet formerly classified as an asteroid", whereas an IAU question-and-answer posting states, "Ceres is (or now we can say it was) the largest asteroid", though it then speaks of "other asteroids" crossing Ceres' path and otherwise implies that Ceres is still considered an asteroid. The Minor Planet Center notes that such bodies may have dual designations. The 2006 IAU decision that classified Ceres as a dwarf planet never addressed whether it is or is not an asteroid. Indeed, the IAU has never defined the word 'asteroid' at all, having preferred the term 'minor planet' until 2006, and preferring the terms 'small Solar System body' and 'dwarf planet' after 2006. Lang (2011) comments "the [IAU has] added a new designation to Ceres, classifying it as a dwarf planet. ... By [its] definition, Eris, Haumea, Makemake and Pluto, as well as the largest asteroid, 1 Ceres, are all dwarf planets", and describes it elsewhere as "the dwarf planet–asteroid 1 Ceres". NASA continues to refer to Ceres as an asteroid, as do various academic textbooks.
"Maupertuis" is a member of the Vesta family (), a giant asteroid family of typically bright V-type asteroids. Vestian asteroids have a composition akin to cumulate eucrites (HED meteorites) and are thought to have originated deep within 4 Vesta's crust, possibly from the Rheasilvia crater, a large impact crater on its southern hemisphere near the South pole, formed as a result of a subcatastrophic collision. Vesta is the main belt's second-largest and second-most-massive body after . Based on osculating Keplerian orbital elements, the asteroid has also been classified as a member of the Flora family (), a giant asteroid family and the largest family of stony asteroids in the main-belt.
Hygiea (minor planet designation: 10 Hygiea) is the fourth-largest asteroid in the Solar System by volume and mass, and it is located in the asteroid belt. With somewhat oblong diameters of and a mass estimated to be 2.9% of the total mass of the belt, it is the largest of the class of dark C-type asteroids with a carbonaceous surface.
Juno (minor-planet designation: 3 Juno) is an asteroid in the asteroid belt. Juno was the third asteroid discovered, in 1804, by German astronomer Karl Harding. It is the 11th-largest asteroid, and one of the two largest stony (S-type) asteroids, along with 15 Eunomia. It is estimated to contain 1% of the total mass of the asteroid belt.
B-type asteroids are a relatively uncommon type of carbonaceous asteroid, falling into the wider C-group. In the asteroid population, B-class objects can be found in the outer asteroid belt, and also dominate the high-inclination Pallas family which includes the second-largest asteroid 2 Pallas. They are thought to be primitive, volatile-rich remnants from the early Solar System. There are 65 known B-type asteroids in the SMASS classification, and 9 in the Tholen classification as of March 2015.
With an absolute magnitude of 26.8, the asteroid is about in diameter depending on the albedo. Observations by the NASA Infrared Telescope Facility conclude the asteroid is a fairly bright Sq-class asteroid which have an average albedo of around 0.24, and would give the asteroid a spherical equivalent diameter of . Measurements by multiple telescopes indicate that the asteroid rotates in 15.8 seconds making it the fastest rotating asteroid so far discovered. Using the 15.8 second rotation period, more accurate radar observations by Goldstone shows the asteroid has a largest axis of at least . Due to the asteroid's fast rotation, it is a monolith and not a rubble pile.
Asteroid 3 Juno is one of the largest belt asteroids, the second-most-massive stony S-type.
Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery.
Several asteroids have now been visited by probes, the first of which was "Galileo", which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to "Galileo"'s planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the "NEAR Shoemaker" probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA's "Dawn" spacecraft, launched in 2007.