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.
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 term Spaceguard loosely refers to a number of efforts to discover, catalogue, and study near-Earth objects (NEO), especially those that may impact Earth.
Near-Earth Asteroid Tracking (NEAT) was a program run by NASA and the Jet Propulsion Laboratory, surveying the sky for near-Earth objects. NEAT was conducted from December 1995 until April 2007, at GEODSS on Hawaii, as well as at Palomar Observatory in California. With the discovery of more than 40 thousand minor planets, NEAT has been one of the most successful programs in this field, comparable to the Catalina Sky Survey, LONEOS and Mount Lemmon Survey.
The Spacewatch Project is an astronomical survey that specializes in the study of minor planets, including various types of asteroids and comets at University of Arizona telescopes on Kitt Peak near Tucson, Arizona, in the United States. The Spacewatch Project has been active longer than any other similar currently active programs.
Mount Lemmon Survey (MLS) is a part of the Catalina Sky Survey with observatory code G96. MLS uses a 1.52 m (60 in) cassegrain reflector telescope operated by the Steward Observatory at Mount Lemmon Observatory, which is located at 2,791 meters (9,157 ft) in the Santa Catalina Mountains northeast of Tucson, Arizona.
James Whitney Young is an American astronomer who worked in the field of asteroid research. After nearly 47 years with the Jet Propulsion Laboratory at their Table Mountain Facility, Young retired July 16, 2009.
2006 RH120 is a tiny near-Earth asteroid and fast rotator with a diameter of approximately 2–3 meters that ordinarily orbits the Sun but makes close approaches to the Earth–Moon system around every twenty years, when it can temporarily enter Earth orbit through temporary satellite capture (TSC). Most recently, it was in Earth orbit from July 2006 to July 2007, during which time it was never more than 0.0116 AU (1.74 million km) from Earth. As a consequence of its temporary orbit around the Earth, it is currently the second smallest asteroid in the Solar System with a well-known orbit, after 2021 GM1. Until given a minor planet designation on 18 February 2008, the object was known as 6R10DB9, an internal identification number assigned by the Catalina Sky Survey.
2007 WD5 is an Apollo asteroid some 50 m (160 ft) in diameter and a Mars-crosser asteroid first observed on 20 November 2007, by Andrea Boattini of the Catalina Sky Survey. Early observations of 2007 WD5 caused excitement amongst the scientific community when it was estimated as having as high as a 1 in 25 chance of colliding with Mars on 30 January 2008. However, by 9 January 2008, additional observations allowed NASA's Near Earth Object Program (NEOP) to reduce the uncertainty region resulting in only a 1-in-10,000 chance of impact. 2007 WD5 most likely passed Mars at a distance of 6.5 Mars radii. Due to this relatively small distance and the uncertainty level of the prior observations, the gravitational effects of Mars on its trajectory are unknown and, according to Steven Chesley of NASA's Jet Propulsion Laboratory Near-Earth Object program, 2007 WD5 is currently considered 'lost' (see lost asteroids).
A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of impact. They are conventionally defined as having a minimum orbit intersection distance with Earth of less than 0.05 astronomical units and an absolute magnitude of 22 or brighter, the latter of which roughly corresponds to a size larger than 140 meters. More than 99% of the known potentially hazardous objects are no impact threat over the next 100 years. As of September 2022, just 17 of the known potentially hazardous objects listed on the Sentry Risk Table could not be excluded as potential threats over the next hundred years. Over hundreds if not thousands of years though, the orbits of some "potentially hazardous" asteroids can evolve to live up to their namesake.
Richard A. Kowalski is an American astronomer who has discovered numerous asteroids and comets, among them, many near-Earth objects.
2010 KQ is a small asteroid-like object that has been discovered in an orbit about the Sun that is so similar to the Earth's orbit that scientists strongly suspect it to be a rocket stage that escaped years ago from the Earth–Moon system. The object was discovered on May 16, 2010 by Richard Kowalski at the Catalina Sky Survey, and has subsequently been observed by many observers, including Bill Ryan and Peter Birtwhistle (England). It was given the asteroid designation 2010 KQ by the Minor Planet Center in Cambridge, Massachusetts, who identified its orbit as being very similar to that of the Earth.
2011 CQ1 is a meteoroid discovered on 4 February 2011 by Richard A. Kowalski, at the Catalina Sky Survey. On the same day the meteoroid passed within 0.85 Earth radii (5,480 kilometers (3,410 mi)) of Earth's surface, and was perturbed from the Apollo class to the Aten class of near-Earth objects. With a relative velocity of only 9.7 km/s, had the asteroid passed less than 0.5 Earth radii from Earth's surface, it would have fallen as a brilliant fireball. The meteoroid is between 80 centimeters (31 in) and 2.6 meters (100 in) wide. The meteoroid was removed from the Sentry Risk Table on 5 February 2011.
La Sagra Observatory is an astronomical observatory located in the province of Granada, Spain. It uses four robotic telescopes both designed and built by the scientists of the Observatorio Astronómico de Mallorca (OAM) who operate them remotely by telecontrol daily, discharging data from Mallorca using the Internet, to process them by means of algorithms designed "in house" which helped to detect asteroid 367943 Duende. among the other 1706 asteroids, with a 12th place in the ranking of asteroid discoveries. Its activities include, as part of its La Sagra Sky Survey, tracking small Solar System bodies, particularly near-Earth objects, and space debris.
(523662) 2012 MU2, provisional designation 2012 MU2, is a sub-kilometer asteroid on an eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group. It was discovered on 18 June 2012 by astronomers of the Catalina Sky Survey at an apparent magnitude of 19.9 using a 0.68-meter (27 in) Schmidt–Cassegrain telescope. It has an estimated diameter of 240 meters (790 ft). The asteroid was listed on Sentry Risk Table with a Torino Scale rating of 1 on 23 June 2012.
2014 AA was a small Apollo near-Earth asteroid roughly 2–4 meters in diameter that struck Earth on 2 January 2014. It was discovered on 1 January 2014 by Richard Kowalski at the Mount Lemmon Survey at an apparent magnitude of 19 using a 1.52-meter (60 in) reflecting telescope at Mount Lemmon Observatory. 2014 AA was only observed over a short observation arc of about 70 minutes, and entered Earth's atmosphere about 21 hours after discovery. Nonetheless, it remains one of only a few asteroids observed before impact.
(505657) 2014 SR339, provisional designation 2014 SR339, is a dark and elongated asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 970 meters (3,200 feet) in diameter. It was discovered on 30 September 2014, by NASA's Wide-field Infrared Survey Explorer telescope (WISE) in Earth's orbit. Closely observed at Goldstone and Arecibo in February 2018, it has a rotation period of 8.7 hours.
Asteroid impact prediction is the prediction of the dates and times of asteroids impacting Earth, along with the locations and severities of the impacts.
(481394) 2006 SF6 is a sub-kilometer near-Earth object and potentially hazardous asteroid of the Aten group, approximately 300 meters (1,000 feet) in diameter. It was discovered on 17 September 2006, by the Catalina Sky Survey at Catalina Station in Arizona. On 21 November 2019, it passed Earth at a distance of 11 lunar distances (0.0288 AU), which is the object's closest flyby for centuries. The stony A/S-type asteroid is highly elongated in shape and has a rotation period of 11.5 hours.
