An asteroid is a minor planet—an object that is neither a true planet nor a comet—that orbits within the inner Solar System. They are rocky, metallic or icy bodies with no atmosphere. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter.
In celestial mechanics, the Lagrange points are points of equilibrium for small-mass objects under the gravitational influence of two massive orbiting bodies. Mathematically, this involves the solution of the restricted three-body problem.
The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum. It is usually considered in relation to meteoroids or small asteroids, as its influence is most significant for these bodies.
Geophysics is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. Geophysicists, who usually study geophysics, physics, or one of the earth sciences at the graduate level, complete investigations across a wide range of scientific disciplines. The term geophysics classically refers to solid earth applications: Earth's shape; its gravitational, magnetic fields, and electromagnetic fields ; its internal structure and composition; its dynamics and their surface expression in plate tectonics, the generation of magmas, volcanism and rock formation. However, modern geophysics organizations and pure scientists use a broader definition that includes the water cycle including snow and ice; fluid dynamics of the oceans and the atmosphere; electricity and magnetism in the ionosphere and magnetosphere and solar-terrestrial physics; and analogous problems associated with the Moon and other planets.
Asteroid impact avoidance comprises the methods by which near-Earth objects (NEO) on a potential collision course with Earth could be diverted away, preventing destructive impact events. An impact by a sufficiently large asteroid or other NEOs would cause, depending on its impact location, massive tsunamis or multiple firestorms, and an impact winter caused by the sunlight-blocking effect of large quantities of pulverized rock dust and other debris placed into the stratosphere. A collision 66 million years ago between the Earth and an object approximately 10 kilometres wide is thought to have produced the Chicxulub crater and triggered the Cretaceous–Paleogene extinction event that is understood by the scientific community to have caused the extinction of all non-avian dinosaurs.
The B612 Foundation is a private nonprofit foundation headquartered in Mill Valley, California, United States, dedicated to planetary science and planetary defense against asteroids and other near-Earth object (NEO) impacts. It is led mainly by scientists, former astronauts and engineers from the Institute for Advanced Study, Southwest Research Institute, Stanford University, NASA and the space industry.
The vulcanoids are a hypothetical population of asteroids that orbit the Sun in a dynamically stable zone inside the orbit of the planet Mercury. They are named after the hypothetical planet Vulcan, which was proposed on the basis of irregularities in Mercury's orbit that were later found to be explained by general relativity. So far, no vulcanoids have been discovered, and it is not yet clear whether any exist.
Orbital decay is a gradual decrease of the distance between two orbiting bodies at their closest approach over many orbital periods. These orbiting bodies can be a planet and its satellite, a star and any object orbiting it, or components of any binary system. If left unchecked, the decay eventually results in termination of the orbit when the smaller object strikes the surface of the primary; or for objects where the primary has an atmosphere, the smaller object burns, explodes, or otherwise breaks up in the larger object's atmosphere; or for objects where the primary is a star, ends with incineration by the star's radiation. Collisions of stellar-mass objects are usually accompanied by effects such as gamma-ray bursts and detectable gravitational waves.
The Yarkovsky–O'Keefe–Radzievskii–Paddack effect, or YORP effect for short, changes the rotation state of a small astronomical body – that is, the body's spin rate and the obliquity of its pole(s) – due to the scattering of solar radiation off its surface and the emission of its own thermal radiation.
99942 Apophis is a near-Earth asteroid and potentially hazardous asteroid with a diameter of 370 metres that caused a brief period of concern in December 2004 when initial observations indicated a probability up to 2.7% that it would hit Earth on April 13, 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth in 2029. Until 2006, a small probability nevertheless remained that, during its 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole of no more than about 800 metres in diameter, which would have set up a future impact exactly seven years later on April 13, 2036. This possibility kept it at Level 1 on the Torino impact hazard scale until August 2006, when the probability that Apophis would pass through the keyhole was determined to be very small and Apophis' rating on the Torino scale was lowered to zero. By 2008, the keyhole had been determined to be less than 1 km wide. During the short time when it had been of greatest concern, Apophis set the record for highest rating ever on the Torino scale, reaching level 4 on December 27, 2004.
The formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed.
Maria T. Zuber is an American geophysicist who is the vice president for research at the Massachusetts Institute of Technology, where she also holds the position of the E. A. Griswold Professor of Geophysics in the Department of Earth, Atmospheric and Planetary Sciences. Zuber has been involved in more than half a dozen NASA planetary missions aimed at mapping the Moon, Mars, Mercury, and several asteroids. She was the principal investigator for the Gravity Recovery and Interior Laboratory (GRAIL) Mission, which was managed by NASA's Jet Propulsion Laboratory.
James F. Bell III is a professor of Astronomy at Arizona State University, specializing in the study of planetary geology, geochemistry and mineralogy using data obtained from telescopes and from various spacecraft missions. Bell's active research has involved the NASA Mars Pathfinder, Near Earth Asteroid Rendezvous (NEAR), Comet Nucleus Tour (CONTOUR), 2001 Mars Odyssey, Mars Reconnaissance Orbiter, Lunar Reconnaissance Orbiter, and the Mars Science Laboratory missions. His book Postcards from Mars includes many images taken by the Mars rovers. Bell is currently an editor of the space science journal Icarus and president of The Planetary Society. He has served as the lead scientist in charge of the Panoramic camera (Pancam) color imaging system on Mars rovers Spirit and Opportunity.
9921 Rubincam, provisional designation 1981 EO18, is a stony asteroid from the inner regions of the asteroid belt, approximately 4 kilometers in diameter. It was discovered on 2 March 1981, by American astronomer Schelte Bus at the Siding Spring Observatory in Australia, and later named after American geophysicist David Rubincam.
Bruce Martin Jakosky is a professor of Geological Sciences and associate director of the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Boulder. He has been involved with the Viking, Solar Mesosphere Explorer, Clementine, Mars Observer, Mars Global Surveyor, Mars Odyssey, Mars Science Laboratory and MAVEN spacecraft missions, and is involved in planning future spacecraft missions.
101955 Bennu (provisional designation 1999 RQ36) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table and has the highest cumulative rating on the Palermo Technical Impact Hazard Scale. It has a cumulative 1-in-1,800 chance of impacting Earth between 2178 and 2290 with the greatest risk being on 24 September 2182. It is named after the Bennu, the ancient Egyptian mythological bird associated with the Sun, creation, and rebirth.
(4953) 1990 MU is a large Earth-crossing asteroid (ECA) belonging to the Apollo group of near-Earth objects which also cross the orbits of Mars and Venus. At approximately 3 km in diameter, it is one of the largest known ECAs. It has been assigned a permanent number from the Minor Planet Center (4953) indicating that its orbit has been very well determined. With an observation arc of 45 years, the asteroid's trajectory and uncertainty regions are well known through to the year 2186.
Paolo Farinella was an Italian scientist very active in the field of planetary science and in particular in the study of asteroids and small bodies of the Solar System.
Planetary science is the scientific study of planets, celestial bodies and planetary systems and the processes of their formation. It studies objects ranging in size from micrometeoroids to gas giants, aiming to determine their composition, dynamics, formation, interrelations and history. It is a strongly interdisciplinary field, which originally grew from astronomy and Earth science, and now incorporates many disciplines, including planetary geology, cosmochemistry, atmospheric science, physics, oceanography, hydrology, theoretical planetary science, glaciology, and exoplanetology. Allied disciplines include space physics, when concerned with the effects of the Sun on the bodies of the Solar System, and astrobiology.
A satellite system is a set of gravitationally bound objects in orbit around a planetary mass object or minor planet, or its barycenter. Generally speaking, it is a set of natural satellites (moons), although such systems may also consist of bodies such as circumplanetary disks, ring systems, moonlets, minor-planet moons and artificial satellites any of which may themselves have satellite systems of their own. Some bodies also possess quasi-satellites that have orbits gravitationally influenced by their primary, but are generally not considered to be part of a satellite system. Satellite systems can have complex interactions including magnetic, tidal, atmospheric and orbital interactions such as orbital resonances and libration. Individually major satellite objects are designated in Roman numerals. Satellite systems are referred to either by the possessive adjectives of their primary, or less commonly by the name of their primary. Where only one satellite is known, or it is a binary with a common centre of gravity, it may be referred to using the hyphenated names of the primary and major satellite.
