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The Torino scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets. It is intended as a communication tool for astronomers and the public to assess the seriousness of collision predictions, by combining probability statistics and known kinetic damage potentials into a single threat value. The Palermo Technical Impact Hazard Scale is a similar, but more complex scale. Near-Earth objects with a Torino scale of 1 pop up every couple of months or so and may last a few weeks until they have a longer observation arc.
Sentry is a highly automated impact prediction system operated by the JPL Center for NEO Studies (CNEOS) since 2002. It continually monitors the most up-to-date asteroid catalog for possibilities of future impact with Earth over the next 100+ years. Whenever a potential impact is detected it will be analyzed and the results immediately published by the Center for Near-Earth Object Studies. However, several weeks of optical data are not enough to conclusively identify an impact years in the future. By contrast, eliminating an entry on the risk page is a negative prediction; a prediction of where it will not be.
2007 VK184 is a sub-kilometer asteroid, classified as a near-Earth object of the Apollo group, and estimated to be approximately 130 meters (430 ft) in diameter. It was listed on the Sentry Risk Table with a Torino Scale rating of 1. A Torino scale rating of 1 is a routine discovery in which a pass near the Earth is predicted that poses no unusual level of danger.
(367789) 2011 AG5, provisional designation 2011 AG5, is a sub-kilometer asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group. It has a diameter of about 140 meters (460 ft). It was removed from the Sentry Risk Table on 21 December 2012 and as such it now has a rating of 0 on the Torino Scale.
(471240) 2011 BT15, provisional designation 2011 BT15, is a stony, sub-kilometer sized asteroid and fast rotator, classified as a near-Earth object and potentially hazardous asteroid of the Apollo group. It had been one of the objects with the highest impact threat on the Palermo Technical Impact Hazard Scale.
(454101) 2013 BP73, provisional designation 2013 BP73, is a sub-kilometer asteroid, classified as a near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 310 meters (1,020 ft) in diameter.
2008 CK70 (also written 2008 CK70) is an Apollo near-Earth asteroid. In 2013 it had the 7th highest impact threat on the Palermo Technical Impact Hazard Scale. It was discovered on 9 February 2008 by Lincoln Near-Earth Asteroid Research (LINEAR) at an apparent magnitude of 19 using a 1.0-meter (39 in) reflecting telescope. It has an estimated diameter of 31 meters (102 ft) and is not large enough to qualify as a potentially hazardous object. Ten precovery images from January 2008 have been located. It was removed from the Sentry Risk Table on 21 December 2013. It may be possible to recover the asteroid in late September 2017, but it will have an apparent magnitude of about 22.
2008 AO112 (also written 2008 AO112) is an Apollo near-Earth asteroid and potentially hazardous object. It was discovered on 12 January 2008 by the Mount Lemmon Survey at an apparent magnitude of 21 using a 1.5-meter (59 in) reflecting telescope. The asteroid was quickly lost and had an estimated diameter of 310 meters (1,020 ft). On 25 June 2009, with an observation arc of only 1 day in January 2008, the asteroid had a 1 in 4 million chance of impacting Earth on that very day. The virtual impactor had not been eliminated from the Sentry Risk Table by the day of the potential impact.
In observational astronomy, the observation arc of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly used in the discovery and tracking of asteroids and comets. Arc length has the greatest influence on the accuracy of an orbit. The number and spacing of intermediate observations has a lesser effect.
2012 FN is an Apollo asteroid and a near-Earth object that has a 1 in 4 billion chance of impacting Earth on 7 March 2113. It is estimated to be 5 meters in diameter, which means that it poses no threat if it impacts Earth. An impact would have the kinetic energy of about 3 kt of TNT, and would probably result in an air burst in the upper atmosphere. It is the least threatening asteroid listed on the Sentry Risk Table. The very short observation arc of only 3 hours results in a very poorly constrained orbit, and it could just as easily be 2 AU from Earth on 7 March 2113.
2014 UR116, also known as 2008 XB, is an eccentric sub-kilometer asteroid, categorized as a near-Earth object and potentially hazardous asteroid of the Apollo group with a diameter of approximately 400 meters (1,300 ft). It was first observed on 1 December 2008, by the Mount Lemmon Survey at Mount Lemmon Observatory in Arizona, United States.
2013 TX68 is an Apollo asteroid and near-Earth object discovered on 6 October 2013 by the Catalina Sky Survey, during which it was near a close approach of 5.4 Lunar distances (LD) from the Earth. The asteroid only has a 10-day observation arc which makes long-term predictions of its position less certain. It was observed for three days as it approached Earth in the night sky starting with the sixth of October, 2013. Then it became unobservable by being between the Earth and the Sun, then not recovered due to its small size and dimness. Precovery images by Pan-STARRS from 29 September 2013 were announced on 11 February 2016 that extended the observation arc to 10 days. It was removed from the Sentry Risk Table on 11 February 2016, so there is no risk of impact from this object for the next hundred years or more. The asteroid was last observed on 9 October 2013.
(415029) 2011 UL21, provisional designation 2011 UL21, is an Apollo class potentially hazardous asteroid discovered on October 17, 2011 by the Catalina Sky Survey project. The asteroid is estimated to have a diameter of 2.5 kilometres (1.6 mi). It was rated at Torino Scale 1 on October 27, 2011 with an observation arc of 9.6 days.
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.
2017 XO2, also written 2017 XO2, is a sub-kilometer asteroid and near-Earth object of the Apollo group approximately 110 meters (360 feet) in diameter. The asteroid was discovered by Pan-STARRS in December 2017, after it already had approached Earth at 0.051 AU (7,600,000 km) or 20 lunar distances (LD) on 6 November 2017. On 26 April 2057, it will pass Earth at a similar distance of 21 LD again.
2014 MV67 (also written 2014 MV67) was a lost asteroid with an observation arc less than 1 day. It had an assumed orbital eccentricity and a very poorly constrained orbit. Depending on the orbit, it could have been a potentially hazardous asteroid, roughly 540 meters (1,770 feet) in diameter, or it could turn out to be a Mars-crosser or even a main-belt asteroid as were the cases with 2004 BX159 and 2010 GZ60. It was recovered by Pan-STARRS in September 2021 and is now known to be a Mars-crossing asteroid.
2019 TF7 is an asteroid from the inner regions of the asteroid belt, approximately 800 meters (0.50 miles) in diameter. It was discovered on 7 October 2019 and with the orbital uncertainty still high after 4 days of observation, it had the rare chance of impacting Earth in less than 2 years on 26 June 2021. The line of variation (LOV) was 730 million km long and overlapped Earth's position. It was listed at the top of the European Space Agency risk list due to its large size and near-term threat. Precovery images from 18 September 2019 were located, extending the observation arc to 23 days, and the object was removed from the Sentry Risk Table. On 26 June 2021 the asteroid will be 4.9 AU (730 million km) from Earth.
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.
2017 QC36 is a near-Earth object and a potentially hazardous asteroid of the Aten group, It measures approximately 200 meters (660 feet) in diameter and was briefly observed by the Wide-field Infrared Survey Explorer on 18 August 2017 before it became a lost asteroid on the following day. It was later recovered in 2021 from archival Pan-STARRS and Cerro Tololo observations.
2020 XR is an Apollo near-Earth object and potentially hazardous asteroid roughly 390 meters in diameter. With a 5-day observation arc it was briefly listed as having a 1 in 11,000 chance of impacting Earth on 1 December 2028 placing it at the top of the Sentry Risk Table with a Palermo scale rating of -0.70.
References
- 1 2 3 4 5 6 7 8 "JPL Small-Body Database Browser: (2004 BX159)" (2017-07-02 last obs.). Jet Propulsion Laboratory . Retrieved 3 August 2017.
- 1 2 3 "2004 BX159". Minor Planet Center. Retrieved 3 August 2017.
- ↑ "Asteroid 2004 BX159 Impact Risk". Wayback Machine: NASA/JPL Near-Earth Object Program Office. 1 April 2014 [computed on 2011-09-14]. Archived from the original on 1 April 2014.
- ↑ "Asteroid Size Estimator". CNEOS/JPL. Retrieved 2 August 2017.
- 1 2 "WayBack Machine archive from 18 Feb 2007". Wayback Machine. 18 February 2007. Archived from the original on 18 February 2007.
- ↑ Removed Objects "Near Earth Object Program". Archived from the original on 3 April 2014. Retrieved 2 March 2018.
- ↑ JPL solution 3 (solution date 2011-Sep-14) "(2004 BX159)". Archived from the original on 13 December 2012. Retrieved 8 March 2019.