CryovolcanoA cryovolcano (sometimes informally called an ice volcano) is a type of volcano that erupts volatiles such as water, ammonia or methane into an extremely cold environment that is at or below their freezing point. The process of formation is known as cryovolcanism. Collectively referred to as cryomagma, cryolava or ice-volcanic melt, these substances are usually liquids and can form plumes, but can also be in vapour form. After the eruption, cryomagma is expected to condense to a solid form when exposed to the very low surrounding temperature.
Rubble pileIn astronomy, a rubble pile is a celestial body that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity. Rubble piles have low density because there are large cavities between the various chunks that make them up. The asteroids Bennu and Ryugu have a measured bulk density which suggests a rubble pile internal structure. Many comets and most smaller minor planets (
4 VestaVesta (minor-planet designation: 4 Vesta) is one of the largest objects in the asteroid belt, with a mean diameter of . It was discovered by the German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807 and is named after Vesta, the virgin goddess of home and hearth from Roman mythology. Vesta is thought to be the second-largest asteroid, both by mass and by volume, after the dwarf planet Ceres, though in volume it overlaps with the uncertainty in the measurements of 2 Pallas.
Asteroid beltThe asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids or minor planets. The identified objects are of many sizes, but much smaller than planets, and, on average, are about one million kilometers (or six hundred thousand miles) apart. This asteroid belt is also called the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System.
Dawn (spacecraft)Dawn is a retired space probe that was launched by NASA in September 2007 with the mission of studying two of the three known protoplanets of the asteroid belt: Vesta and Ceres. In the fulfillment of that mission—the ninth in NASA's Discovery Program—Dawn entered orbit around Vesta on July 16, 2011, and completed a 14-month survey mission before leaving for Ceres in late 2012. It entered orbit around Ceres on March 6, 2015. In 2017, NASA announced that the planned nine-year mission would be extended until the probe's hydrazine fuel supply was depleted.
Dwarf planetA dwarf planet is a small planetary-mass object that is in direct orbit of the Sun, smaller than any of the eight classical planets but still a world in its own right. The prototypical dwarf planet is Pluto. The interest of dwarf planets to planetary geologists is that they may be geologically active bodies, an expectation that was borne out in 2015 by the Dawn mission to and the New Horizons mission to Pluto. Astronomers are in general agreement that at least the nine largest candidates are dwarf planets: , , , , , , , , and .
Rotation period (astronomy)In astronomy, the rotation period or spin period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) has two definitions. The first one corresponds to the sidereal rotation period, i.e., the time that the object takes to complete a full rotation around its axis relative to the background stars (inertial space). The other type of commonly used "rotation period" is the object's synodic rotation period (or solar day), which may differ, by a fraction of a rotation or more than one rotation, to accommodate the portion of the object's orbital period around a star or another body during one day.
Giuseppe PiazziGiuseppe Piazzi (USˈpjɑːtsi , dʒuˈzɛppe ˈpjattsi; 16 July 1746 – 22 July 1826) was an Italian Catholic priest of the Theatine order, mathematician, and astronomer. He established an observatory at Palermo, now the Osservatorio Astronomico di Palermo – Giuseppe S. Vaiana. He is perhaps most famous for his discovery of the first dwarf planet, Ceres. No documented account of Piazzi's scientific education is available in any of the biographies of the astronomer, even in the oldest ones.
Astronomical objectAn astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists within the observable universe. In astronomy, the terms object and body are often used interchangeably. However, an astronomical body or celestial body is a single, tightly bound, contiguous entity, while an astronomical or celestial object is a complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures.
NeptuneNeptune is the eighth planet from the Sun and the farthest IAU-recognized planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, and slightly more massive than its near-twin Uranus. Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. Being composed primarily of gases and liquids, it has no well-defined solid surface.
