The Aten asteroids are a dynamical group of asteroids whose orbits bring them into proximity with Earth. By definition, Atens are Earth-crossing asteroids (a < 1.0 AU and Q > 0.983 AU). The group is named after 2062 Aten, the first of its kind, discovered on 7 January 1976 by American astronomer Eleanor Helin at Palomar Observatory. As of November 2023, 2,646 Atens have been discovered, of which 256 are numbered, 14 are named, and 102 are classified as potentially hazardous asteroids.
163693 Atira, provisional designation 2003 CP20, is a stony asteroid, dwelling in the interior of Earth's orbit. It is classified as a near-Earth object. Atira is a binary asteroid, a system of two asteroids orbiting their common barycenter. The primary component with a diameter of approximately 4.8 kilometers (3 miles) is orbited by a minor-planet moon that measures about 1 km (0.6 mi). Atira was discovered on 11 February 2003, by astronomers with the Lincoln Near-Earth Asteroid Research at Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, in the United States.
(386454) 2008 XM is a highly eccentric, sub-kilometer-sized asteroid, with one of the smallest known perihelions among all minor planets. It is classified as near-Earth object of the Apollo group and was discovered on 2 December 2008, by the LINEAR program at Lincoln Laboratory's Experimental Test Site in Socorro, New Mexico, United States.
(394130) 2006 HY51 is a near-Earth object of the Apollo asteroid group with a high orbital eccentricity, approximately 1.2 kilometers in diameter. It was discovered on 26 April 2006, by LINEAR at Lincoln Lab's ETS in Socorro, New Mexico, United States.
2014 XL7 is a near-Earth object and Apollo asteroid, approximately 230 meters (750 feet) in diameter. It was the most dangerous potentially hazardous asteroid on Sentry Risk Table upon its discovery by the Mount Lemmon Survey in December 2014. At the time, the asteroid had a cumulative 1 in 83000 chance of impacting Earth on 4–5 June between the years 2048 and 2084. After the object's observation arc had been extended to 35 days, it was removed from the Sentry Risk Table on 15 January 2015. Since then the asteroid's orbit has been secured. Although it has an Earth minimum orbit intersection distance of less than one lunar distance, there are no projected close encounters with Earth in the foreseeable future, with its closest passage to occur in May 2046, still millions of kilometers away.
2012 TV is a near-Earth Apollo asteroid with an estimated diameter of 30 metres (98 ft). Its closest approach to the Earth was on October 7, 2012 with a distance of 0.0017 astronomical units. It also approached the Moon an hour earlier with a distance of 0.0028 astronomical units. With a short observation arc of 1.8 days, the asteroid is listed on the Sentry Risk Table and has a 1:500,000 chance of impacting Earth on April 2, 2081.
(585310) 2017 YZ1, provisional designation: 2017 YZ1, is a sub-kilometer asteroid on an eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 250 meters (800 feet) in diameter. It was first observed on 20 December 2017, by astronomers with the Mount Lemmon Survey at Mount Lemmon Observatory near Tucson, Arizona, in the United States. On 29 January 2018, it passed Earth at 125 lunar distances.
2010 GZ60 was originally estimated by JPL to be a near-Earth asteroid approximately 2 kilometers (1.2 miles) in diameter. But is now known to be an asteroid from the inner region of the asteroid belt that does not get closer than 1.5 AU (220 million km) to Earth.
2018 AH is a sub-kilometer asteroid, classified as near-Earth object of the Apollo group, approximately 100 m (300 ft) in diameter. It was first observed on 4 January 2018, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on Mauna Loa and quickly followed-up by many other surveys, with precovery observations found from Pan-STARRS and PTF from the day previous.
2017 YE5 is a binary pair of asteroids of approximately equal size and mass, each about 0.9 km (0.56 mi) in diameter. Classified as a near-Earth asteroid and potentially hazardous object of the Apollo group, 2017 YE5 was discovered by amateur astronomer Claudine Rinner at the Oukaïmeden Observatory on 21 December 2017. On 21 June 2018, the pair of asteroids passed within 15.5 lunar distances or approximately 6 million km (3.7 million mi) from Earth. During the close encounter, 2017 YE5 was resolved in high detail by concurrent radar observations by the Arecibo and Green Bank observatories, along with individual observations by the Goldstone Solar System Radar. 2017 YE5 is likely an extinct or dormant comet due to its distant elliptical orbit and dark red surface.
2018 PD20 is a small asteroid, classified as a near-Earth object of the Apollo group, approximately 9–20 meters (30–66 feet) in diameter. On 11 August 2018, it was first observed by ATLAS at the Mauna Loa Observatory on Hawaii (T08), when it passed 33,500 kilometers (20,800 miles) from the Earth. This is notable because it came within a tenth of the lunar distance, or 0.10 LD which is closer to Earth than satellites in a geostationary orbit. These have an altitude of 0.11 LD, about 36,000 km (22,000 mi), approximately 3 times the width of the Earth.
2019 AQ3 is an inclined near-Earth object of the small Atira group from the innermost region of the Solar System, estimated to measure 1.4 kilometers (0.9 miles) in diameter. Among the hundreds of thousands known asteroids, 2019 AQ3's orbit was thought to have likely the smallest semi-major axis (0.589 AU) and aphelion (0.77 AU), that is, the orbit's average distance and farthest point from the Sun, respectively. The object was first observed on 4 January 2019, by astronomers at Palomar's Zwicky Transient Facility in California, with recovered images dating back to 2015.
2020 BX12 is a sub-kilometer binary asteroid, classified as a near-Earth asteroid and potentially hazardous object of the Apollo group. It was discovered on 27 January 2020 by the Asteroid Terrestrial-impact Last Alert System survey at the Mauna Loa Observatory during its approach to Earth of 0.02915 AU (4.361 million km; 11.34 LD). Radar observations of the asteroid were carried out by the Arecibo Observatory on 4 February 2020, revealing a natural satellite orbiting 360 m (1,180 ft) from the primary body.
2020 AP1 is an Apollo near-Earth object roughly 5 meters (20 feet) in diameter. On 2 January 2020 it passed 0.00218 AU (326 thousand km; 0.85 LD) from Earth. With a short 1-day observation arc it was roughly expected to pass about 0.01 AU (1.5 million km; 3.9 LD) from Earth on 7 January 2022, but with an uncertainty of ±8 days for the close approach date it could have passed significantly closer or further.
2020 SL1 is a near-Earth asteroid of the Apollo group, discovered by the Pan-STARRS 1 survey at Haleakala Observatory, Hawaii on 18 September 2020. With an estimated diameter of 0.9–2.0 km (0.56–1.24 mi), it is the largest potentially hazardous asteroid discovered in 2020.
2020 SW is a tiny near-Earth asteroid discovered by the Mount Lemmon Survey on 18 September 2020, six days before it made its closest approach to Earth. The asteroid passed within 21,600 kilometres (13,400 mi) from Earth's surface on 24 September 2020 11:13 UT, within the geostationary altitude of 36,000 kilometres (22,000 mi). The encounter with Earth perturbed the asteroid's heliocentric trajectory from an Apollo-type orbit to an Aten-type orbit with a semi-major axis within one astronomical unit from the Sun. As a result, the asteroid will not make any close approaches to Earth within 0.01 astronomical units (4 LD) in the next 200 years.
2021 PH27 is a near-Earth asteroid of the Atira group. It was discovered by Scott Sheppard using the Dark Energy Survey's DECam imager at NOIRLab's Cerro Tololo Inter-American Observatory on 13 August 2021. 2021 PH27 has the smallest semi-major axis and shortest orbital period among all known asteroids as of 2021, with a velocity at perihelion of 106 km/s (240,000 mph). It also has the largest value of the relativistic perihelion shift, 1.6 times that of Mercury. With an absolute magnitude of 17.7, the asteroid is estimated to be larger than 1 kilometer (0.6 miles) in diameter.
(620094) 2016 AJ193 (provisional designation 2016 AJ193; also known as 2010 KV134) is a near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 1.4 kilometres (0.87 mi) in diameter. It was discovered on 17 May 2010 by the Wide-field Infrared Survey Explorer (WISE) satellite, but was lost until it was reobserved on 16 January 2016. With an observation arc over 11 years, 2016 AJ193 has a well-determined orbit and trajectory through the year 2086. The asteroid's orbit is only potentially hazardous on a time scale of thousands of years.
2021 RR205 is an extreme trans-Neptunian object and sednoid discovered by astronomers Scott Sheppard, David Tholen, and Chad Trujillo with the Subaru Telescope at Mauna Kea Observatory on 5 September 2021. It resides beyond the outer extent of the Kuiper belt on a distant and highly eccentric orbit detached from Neptune's gravitational influence, with a large perihelion distance of 55.5 astronomical units (AU). Its large orbital semi-major axis (~1,000 AU) suggests it is potentially from the inner Oort cloud. Like 2013 SY99, 2021 RR205 lies in the 50–75 AU perihelion gap that separates the detached objects from the more distant sednoids; dynamical studies indicate that such objects in the inner edge this gap weakly experience "diffusion", or inward orbital migration due to minuscule perturbations by Neptune.
