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An asteroid is a minor planet—an object that is neither a true planet nor an identified comet— that orbits within the inner Solar System. They are rocky, metallic, or icy bodies with no atmosphere, classified as C-type (carbonaceous), M-type (metallic), or S-type (silicaceous). The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across and larger than meteoroids, to Ceres, a dwarf planet almost 1000 km in diameter. A body is classified as a comet, not an asteroid, if it shows a coma (tail) when warmed by solar radiation, although recent observations suggest a continuum between these types of bodies.
A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun (perihelion) is less than 1.3 times the Earth–Sun distance. This definition applies to the object's orbit around the Sun, rather than its current position, thus an object with such an orbit is considered an NEO even at times when it is far from making a close approach of Earth. If an NEO's orbit crosses the Earth's orbit, and the object is larger than 140 meters (460 ft) across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but about 0.35% are comets.
The Solar System is the gravitationally bound system of the Sun and the objects that orbit it. It formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc. The Sun is a typical star that maintains a balanced equilibrium by the fusion of hydrogen into helium at its core, releasing this energy from its outer photosphere. Astronomers classify it as a G-type main-sequence star.
3753 Cruithne is a Q-type, Aten asteroid in orbit around the Sun in 1:1 orbital resonance with Earth, making it a co-orbital object. It is an asteroid that, relative to Earth, orbits the Sun in a bean-shaped orbit that effectively describes a horseshoe, and that can change into a quasi-satellite orbit. Cruithne does not orbit Earth and at times it is on the other side of the Sun, placing Cruithne well outside of Earth's Hill sphere. Its orbit takes it near the orbit of Mercury and outside the orbit of Mars. Cruithne orbits the Sun in about one Earth year, but it takes 770 years for the series to complete a horseshoe-shaped movement around Earth.
A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body. Natural satellites are colloquially referred to as moons, a derivation from the Moon of Earth.
A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. As of January 2022, there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons are important because the determination of their orbits provides estimates on the mass and density of the primary, allowing insights into their physical properties that are generally not otherwise accessible.
Giordano Bruno is a 22-kilometre (14 mi) lunar impact crater on the far side of the Moon, just beyond the northeastern limb. It lies in an area that can be viewed during a favorable libration, although the area is viewed from the side and not much detail can be seen. It lies between the craters Harkhebi to the northwest and Szilard to the southeast.
A geocentric orbit, Earth-centered orbit, or Earth orbit involves any object orbiting Earth, such as the Moon or artificial satellites. In 1997, NASA estimated there were approximately 2,465 artificial satellite payloads orbiting Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. More than 16,291 objects previously launched have undergone orbital decay and entered Earth's atmosphere.
2002 AA29 (also written 2002 AA29) is a small near-Earth asteroid that was discovered on January 9, 2002 by the LINEAR (Lincoln Near Earth Asteroid Research) automatic sky survey. The diameter of the asteroid is only about 20–100 metres (70–300 ft). It revolves about the Sun on an almost circular orbit very similar to that of the Earth. This lies for the most part inside the Earth's orbit, which it crosses near the asteroid's furthest point from the Sun, the aphelion. Because of this orbit, the asteroid is classified as Aten type, named after the asteroid 2062 Aten.
A quasi-satellite is an object in a specific type of co-orbital configuration with a planet where the object stays close to that planet over many orbital periods.
In celestial mechanics, a horseshoe orbit is a type of co-orbital motion of a small orbiting body relative to a larger orbiting body. The osculating (instantaneous) orbital period of the smaller body remains very near that of the larger body, and if its orbit is a little more eccentric than that of the larger body, during every period it appears to trace an ellipse around a point on the larger object's orbit. However, the loop is not closed but drifts forward or backward so that the point it circles will appear to move smoothly along the larger body's orbit over a long period of time. When the object approaches the larger body closely at either end of its trajectory, its apparent direction changes. Over an entire cycle the center traces the outline of a horseshoe, with the larger body between the 'horns'.
524522 Zoozve (provisional designation 2002 VE68) is a sub-kilometer sized asteroid and temporary quasi-satellite of Venus. Discovered in 2002, it was the first such object to be discovered around a major planet in the Solar System. It has nearly the same orbital period around the Sun that Venus does. In a frame of reference rotating with Venus, it appears to travel around it during one Venerean year, but it orbits the Sun, not Venus.
Claims of the existence of other moons of Earth—that is, of one or more natural satellites with relatively stable orbits of Earth, other than the Moon—have existed for some time. Several candidates have been proposed, but none have been confirmed. Since the 19th century, scientists have made genuine searches for more moons, but the possibility has also been the subject of a number of dubious non-scientific speculations as well as a number of likely hoaxes.
In astronomy, a co-orbital configuration is a configuration of two or more astronomical objects orbiting at the same, or very similar, distance from their primary; i.e., they are in a 1:1 mean-motion resonance..
An Earth trojan is an asteroid that orbits the Sun in the vicinity of the Earth–Sun Lagrange points L4 (leading 60°) or L5 (trailing 60°), thus having an orbit similar to Earth's. Only two Earth trojans have so far been discovered. The name "trojan" was first used in 1906 for the Jupiter trojans, the asteroids that were observed near the Lagrangian points of Jupiter's orbit.
(164207) 2004 GU9 is a sub-kilometer asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group. It will be a quasi-satellite of Earth until around 2600.
2014 OL339 (also written 2014 OL339) is an Aten asteroid that is a temporary quasi-satellite of Earth, the fourth known Earth quasi-satellite.
469219 Kamoʻoalewa, provisionally designated 2016 HO3, is a very small asteroid, fast rotator and near-Earth object of the Apollo group, approximately 40–100 meters (130–330 feet) in diameter. At present it is a quasi-satellite of Earth, and currently the second-smallest, closest, and most stable known such quasi-satellite (after 2023 FW13). The asteroid was discovered by Pan-STARRS at Haleakala Observatory on 27 April 2016. It was named Kamoʻoalewa, a Hawaiian word that refers to an oscillating celestial object. The object's Earth-like orbit and its composition of lunar-like silicates may be a result of it being lunar ejecta.
A temporary satellite is an object which has been captured by the gravitational field of a planet and thus has become the planet's natural satellite, but, unlike irregular moons of the larger outer planets of the Solar System, will eventually either leave its orbit around the planet or collide with the planet. The only observed examples are 2006 RH120, a temporary satellite of Earth for twelve months from July 2006 to July 2007, 2020 CD3 and 2022 NX1. Some defunct space probes or rockets have also been observed on temporary satellite orbits.
2020 CD3 (also CD3 for short) is a tiny near-Earth asteroid (or minimoon) that ordinarily orbits the Sun but makes close approaches to the Earth–Moon system, in which it can temporarily enter Earth orbit through temporary satellite capture (TSC). It was discovered at the Mount Lemmon Observatory by astronomers Theodore Pruyne and Kacper Wierzchoś on 15 February 2020, as part of the Mount Lemmon Survey or Catalina Sky Survey. The asteroid's discovery was announced by the Minor Planet Center on 25 February 2020, after subsequent observations confirmed that it was orbiting Earth.
References
- 1 2 3 "2023 FW13". Minor Planet Center. Archived from the original on 10 April 2023. Retrieved 21 May 2023.
- 1 2 3 "JPL Small-Body Database Browser: (2023 FW13)" (2023-04-01 last obs.). Jet Propulsion Laboratory. Archived from the original on 18 November 2022. Retrieved 21 May 2023.
- 1 2 Kuthunur, Sharmila (12 April 2023). "Newfound asteroid is a long-term 'quasi-moon' of Earth". Space.com . Archived from the original on 20 May 2023. Retrieved 20 May 2023.
- 1 2 3 Chandler, David. "DOES EARTH HAVE A NEW QUASI-MOON?". Archived from the original on 14 May 2023. Retrieved 20 May 2023.
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