99942 Apophis
Encyclopedia
99942 Apophis is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a small probability (up to 2.7%) that it would strike the Earth
in 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth
or the Moon
in 2029. However, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole
, a precise region in space no more than about a half-mile wide, that would set up a future impact on April 13, 2036. This possibility kept the asteroid at Level 1 on the Torino impact hazard scale
until August 2006, when the probability that Apophis will pass through the keyhole was determined to be very small. Apophis broke the record for the highest level on the Torino Scale, being, for only a short time, a level 4, before it was lowered. Its diameter is approximately 270 meters (885 ft). , the probability of an April 13, 2036 impact is considered to be 1 in 250,000. Of objects not recently observed, there are 7 asteroids with a more notable Palermo Technical Impact Hazard Scale
than Apophis.
's Infrared Telescope Facility
in Hawaii by Binzel, Rivkin, Bus, and Tokunaga (2005) is 350 metres (1,148.3 ft).
During the 2029 approach, Apophis’ brightness will peak at magnitude
3.4, with a maximum angular speed of 42° per hour. The maximum apparent angular diameter
will be ~2 arcseconds, so that it will be barely resolved
by telescopes not equipped with adaptive optics
.
, David J. Tholen
and Fabrizio Bernardi
and the Kitt Peak National Observatory
. Precovery
observations from March 15, 2004, were identified on December 27, and an improved orbit was computed. Radar
astrometry further refined the orbit.
When first discovered, the object received the provisional designation (sometimes written 2004 MN4), and news and scientific articles about it referred to it by that name. When its orbit was sufficiently well calculated, it received the permanent number 99942 (on June 24, 2005). Receiving a permanent number made it eligible for naming, and it received the name "Apophis" on July 19, 2005. Apophis
is the Greek
name of the Ancient Egyptian enemy of Ra
: Apep
, the Uncreator, an evil serpent that dwells in the eternal darkness of the Duat
(earth's middle) and tries to swallow Ra during His nightly passage. Apep is held at bay by Set
, the Ancient Egyptian god of storms and the desert.
Tholen and Tucker — two of the co-discoverers of the asteroid — are reportedly fans of the TV series Stargate SG-1
. One of the show's persistent villains is an alien named Apophis who, on the show, gave rise to the myth of the Egyptian god.
After the Minor Planet Center
confirmed the June discovery of Apophis, an April 13, 2029 close approach was flagged by NASA's automatic Sentry
system and NEODyS
, a similar automatic program run by the University of Pisa
and the University of Valladolid
. On that date, it will become as bright as magnitude 3.4 (visible to the naked eye
from rural as well as darker suburban areas, visible with binoculars
from most locations). This close approach will be visible from Europe
, Africa
, and western Asia
. As a result of its close passage, it will move from the Aten
to the Apollo
class.
After Sentry and NEODyS announced the possible impact, additional observations decreased the uncertainty in Apophis' trajectory. As they did, the probability of an impact event temporarily climbed, peaking at 2.7% (1 in 37). Combined with its size, this caused Apophis to be assessed at level 4 on the Torino Scale
and 1.10 on the Palermo Technical Impact Hazard Scale
, scales scientists use to represent the danger of an asteroid hitting Earth. These are the highest values for which any object has been rated on either scale. It has since been downgraded to level 0 on the Torino Scale for both the 2029 and 2036 passes. With a cumulative Palermo Scale rating of -2.9, the risk of impact from Apophis is less than the background hazard level.
On Friday, April 13, 2029, Apophis will pass Earth within the orbits of geosynchronous communication satellites. It will return for another close Earth approach in 2036.
The 2029 pass will actually be much closer than the first predictions, but the uncertainty is such that an impact is ruled out. Similarly, the pass on April 13, 2036, carries little risk of an impact.
In July 2005, former Apollo astronaut Rusty Schweickart
, as chairman of the B612 Foundation
, formally asked NASA to investigate the possibility that the asteroid's post-2029 orbit could be in orbital resonance
with Earth, which would increase the probability of future impacts. Schweickart asked for an investigation of the necessity of placing a transponder
on the asteroid for more accurate tracking of how its orbit is affected by the Yarkovsky effect
.
. A later, more refined NASA estimate was 880 megatons, then revised to 510 megatons. The impacts which created the Barringer Crater or the Tunguska event
are estimated to be in the 3–10 megaton range. The 1883 eruption of Krakatoa
was the equivalent of roughly 200 megatons and the biggest hydrogen bomb ever exploded, the Tsar Bomba
, was around 50 megatons. In comparison, the Chicxulub impact
, believed by many to be a significant factor in the extinction of the dinosaurs, has been estimated to have released about as much energy as 100,000,000 megatons (100 Teratons).
The exact effects of any impact would vary based on the asteroid's composition, and the location and angle of impact. Any impact would be extremely detrimental to an area of thousands of square kilometres, but would be unlikely to have long-lasting global effects, such as the initiation of an impact winter
.
The B612 Foundation
made estimates of Apophis' path if a 2036 Earth impact were to occur, as part of an effort to develop viable deflection strategies
. The result is a narrow corridor a few kilometres wide, called the "path of risk", extending across southern Russia
, across the north Pacific (relatively close to the coastlines of California
and Mexico
), then right between Nicaragua
and Costa Rica
, crossing northern Colombia
and Venezuela
, ending in the Atlantic, just before reaching Africa
. Using the computer simulation tool NEOSim, it was estimated that the hypothetical impact of Apophis in countries such as Colombia and Venezuela, which are in the path of risk, could have more than 10 million casualties. An impact in the Atlantic or Pacific oceans would produce a devastating tsunami
.
, a California
-based space advocacy group, organized a $50,000 competition to design an unmanned space probe that would 'shadow' Apophis for almost a year, taking measurements that would "determine whether it will impact Earth, thus helping governments decide whether to mount a deflection mission to alter its orbit." The society received 37 entries from 20 countries on 6 continents.
The commercial competition was won by a design called 'Foresight' created by SpaceWorks Enterprises, Inc. SpaceWorks proposed a simple orbiter with only two instruments and a radio beacon at a cost of ~140 million USD, launched aboard a Minotaur IV between 2012 and 2014, to arrive at Apophis five to ten months later. It would then rendezvous with, observe, and track the asteroid. Foresight would orbit the asteroid to gather data with a multi-spectral image
r for one month. It would then leave orbit and fly in formation with Apophis around the Sun at a range of two kilometers (1.2 miles). The spacecraft would use laser ranging to the asteroid and radio tracking from Earth for ten months to accurately determine the asteroid's orbit and how it might change.
Pharos, the winning student entry, would be an orbiter with four science instruments (a multi-spectral imager, near-infrared spectrometer, laser rangefinder, and magnetometer
) that would rendezvous with and track Apophis. Earth-based tracking of the spacecraft would then allow precise tracking of the asteroid. The Pharos spacecraft would also carry four instrumented probes that it would launch individually over the course of two weeks. Accelerometer
s and temperature sensors on the probes would measure the seismic effects of successive probe impacts, a creative way to explore the interior structure and dynamics of the asteroid.
Second place, for $10,000, went to a European team led by Deimos Space S.L. of Madrid
, Spain
, in cooperation with EADS Astrium
, Friedrichshafen, Germany; University of Stuttgart
, Germany; and Università di Pisa, Italy. Juan L. Cano was Principal Investigator
.
Another European team took home $5,000 for third place. Their team lead was EADS Astrium Ltd, United Kingdom, in conjunction with EADS Astrium SAS, France; IASF-Roma, INAF, Rome, Italy; Open University
, UK; Rheinisches Institut für Umweltforschung, Germany; Royal Observatory of Belgium; and Telespazio
, Italy. The Principal Investigator was Paolo D'Arrigo.
Two teams tied for second place in the Student Category: Monash University
, Clayton Campus, Australia, with Dilani Kahawala as Principal Investigator; and University of Michigan
, with Jeremy Hollander as Principal Investigator. Each second place team won $2,000. A team from Hong Kong Polytechnic University
and Hong Kong University of Science and Technology
, under the leadership of Peter Weiss, received an honorable mention and $1,000 for the most innovative student proposal.
as the target of its Don Quijote mission
to study the effects of impacting an asteroid.
, and nuclear bomb methods.
On December 30, 2009, Anatoly Perminov
, the director of the Russian Federal Space Agency
, said in an interview that Roscosmos will also study designs for a possible deflection mission to Apophis.
On August 16, 2011, researchers at China's Tsinghua University
proposed a launching a mission to knock Apophis onto a safer course using an impactor spacecraft in a retrograde orbit, steered and powered by a solar sail. Instead of moving the asteroid on its potential resonant return to Earth, Shengping Gong and his team believe the secret is shifting the asteroid away from entering the gravitational keyhole in the first place.
Risk assessment
NASA
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
in 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth
Impact event
An impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Throughout recorded history, hundreds of minor impact events have been reported, with some occurrences causing deaths, injuries, property damage or other significant...
or the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
in 2029. However, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole
Gravitational keyhole
A gravitational keyhole, or resonance keyhole, is a small region of space that could alter the course of a passing asteroid due to a planet's gravity in a way that could cause such an asteroid to collide with that planet on its next orbital pass...
, a precise region in space no more than about a half-mile wide, that would set up a future impact on April 13, 2036. This possibility kept the asteroid at Level 1 on the Torino impact hazard scale
Torino Scale
The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects 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...
until August 2006, when the probability that Apophis will pass through the keyhole was determined to be very small. Apophis broke the record for the highest level on the Torino Scale, being, for only a short time, a level 4, before it was lowered. Its diameter is approximately 270 meters (885 ft). , the probability of an April 13, 2036 impact is considered to be 1 in 250,000. Of objects not recently observed, there are 7 asteroids with a more notable Palermo Technical Impact Hazard Scale
Palermo Technical Impact Hazard Scale
The Palermo Technical Impact Hazard Scale is a logarithmic scale used by astronomers to rate the potential hazard of impact of a near-earth object . It combines two types of data—probability of impact, and estimated kinetic yield—into a single "hazard" value...
than Apophis.
Physical characteristics
Based upon the observed brightness, Apophis' diameter was initially estimated at 450 metres (1,476.4 ft); a more refined estimate based on spectroscopic observations at NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Infrared Telescope Facility
Infrared Telescope Facility
The NASA Infrared Telescope Facility is a telescope optimized for use in infrared astronomy and located at the Mauna Kea Observatory in Hawai'i. It was first built to support the Voyager missions and is now the USA national facility for infrared astronomy, providing continued support to...
in Hawaii by Binzel, Rivkin, Bus, and Tokunaga (2005) is 350 metres (1,148.3 ft).
During the 2029 approach, Apophis’ brightness will peak at magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
3.4, with a maximum angular speed of 42° per hour. The maximum apparent angular diameter
Angular diameter
The angular diameter or apparent size of an object as seen from a given position is the “visual diameter” of the object measured as an angle. In the vision sciences it is called the visual angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its...
will be ~2 arcseconds, so that it will be barely resolved
Optical resolution
Optical resolution describes the ability of an imaging system to resolve detail in the object that is being imaged.An imaging system may have many individual components including a lens and recording and display components...
by telescopes not equipped with adaptive optics
Adaptive optics
Adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, and in retinal imaging systems to reduce the...
.
Discovery and naming
Apophis was discovered on June 19, 2004, by Roy A. TuckerRoy A. Tucker
Roy A. Tucker is an American astronomer. He is a prolific discoverer of asteroids, identifying at least 404 and co-discovering one, between 1996 and 2009.Tucker was raised in Memphis, Tennessee...
, David J. Tholen
David J. Tholen
David James Tholen is an American astronomer at the Institute for Astronomy of the University of Hawaii, who specializes in planetary and solar system astronomy.-Professional life:...
and Fabrizio Bernardi
Fabrizio Bernardi
Fabrizio Bernardi is an astronomer.-Contributions:In October of 2001 he discovered an asteroid, proceeded by near earth objects : 2002 RQ25 3 , 2002 WP11 and the NEO 2003 FB5 Fabrizio Bernardi is an astronomer.-Contributions:In October of 2001 he discovered an asteroid, proceeded by near earth...
and the Kitt Peak National Observatory
Kitt Peak National Observatory
The Kitt Peak National Observatory is a United States astronomical observatory located on 2,096 m Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O'odham Nation, southwest of Tucson...
. Precovery
Precovery
Precovery is a term used in astronomy that describes the process of finding the image of an object in old archived images or photographic plates, for the purpose of calculating a more accurate orbit...
observations from March 15, 2004, were identified on December 27, and an improved orbit was computed. Radar
Radar astronomy
Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the echoes. This research has been conducted for six decades. Radar astronomy differs from radio astronomy in that the latter is a passive observation and the former an...
astrometry further refined the orbit.
When first discovered, the object received the provisional designation (sometimes written 2004 MN4), and news and scientific articles about it referred to it by that name. When its orbit was sufficiently well calculated, it received the permanent number 99942 (on June 24, 2005). Receiving a permanent number made it eligible for naming, and it received the name "Apophis" on July 19, 2005. Apophis
Apep
In Egyptian mythology, Apep was an evil god, the deification of darkness and chaos , and thus opponent of light and Ma'at , whose existence was believed from the 8th Dynasty onwards...
is the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
name of the Ancient Egyptian enemy of Ra
Ra
Ra is the ancient Egyptian sun god. By the Fifth Dynasty he had become a major deity in ancient Egyptian religion, identified primarily with the mid-day sun...
: Apep
Apep
In Egyptian mythology, Apep was an evil god, the deification of darkness and chaos , and thus opponent of light and Ma'at , whose existence was believed from the 8th Dynasty onwards...
, the Uncreator, an evil serpent that dwells in the eternal darkness of the Duat
Duat
In Egyptian mythology, Duat is the underworld. The Duat is a vast area under the Earth, connected with Nun, the waters of the primordial abyss. The Duat is the realm of the god Osiris and the residence of other gods and supernatural beings...
(earth's middle) and tries to swallow Ra during His nightly passage. Apep is held at bay by Set
Set (mythology)
Set was in Ancient Egyptian religion, a god of the desert, storms, and foreigners. In later myths he was also the god of darkness, and chaos...
, the Ancient Egyptian god of storms and the desert.
Tholen and Tucker — two of the co-discoverers of the asteroid — are reportedly fans of the TV series Stargate SG-1
Stargate SG-1
Stargate SG-1 is a Canadian-American adventure and military science fiction television series and part of Metro-Goldwyn-Mayer's Stargate franchise. The show, created by Brad Wright and Jonathan Glassner, is based on the 1994 feature film Stargate by Dean Devlin and Roland Emmerich...
. One of the show's persistent villains is an alien named Apophis who, on the show, gave rise to the myth of the Egyptian god.
Close approaches
Minor Planet Center
The Minor Planet Center operates at the Smithsonian Astrophysical Observatory , which is part of the Center for Astrophysics along with the Harvard College Observatory ....
confirmed the June discovery of Apophis, an April 13, 2029 close approach was flagged by NASA's automatic Sentry
Sentry (monitoring system)
Sentry is a highly automated collision monitoring system that continually scans the most current asteroid catalog for possibilities of future impact with Earth over the next 100 years...
system and NEODyS
NEODyS
NEODyS is an Italian and Spanish service that provides information on Near Earth Objects with a convenient Web-based interface. It is based on a continually and automatically maintained database of near earth asteroid orbits. This site provides a number of services to the NEO community...
, a similar automatic program run by the University of Pisa
University of Pisa
The University of Pisa , located in Pisa, Tuscany, is one of the oldest universities in Italy. It was formally founded on September 3, 1343 by an edict of Pope Clement VI, although there had been lectures on law in Pisa since the 11th century...
and the University of Valladolid
University of Valladolid
The University of Valladolid is a public university in the city of Valladolid, province of Valladolid, in the autonomous region of Castile-Leon, Spain...
. On that date, it will become as bright as magnitude 3.4 (visible to the naked eye
Naked eye
The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...
from rural as well as darker suburban areas, visible with binoculars
Binoculars
Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...
from most locations). This close approach will be visible from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, and western Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
. As a result of its close passage, it will move from the Aten
Aten asteroid
The Aten asteroids are a group of near-Earth asteroids, named after the first of the group to be discovered . They are defined by having semi-major axes of less than one astronomical unit...
to the Apollo
Apollo asteroid
The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, the first asteroid of this group to be discovered by Karl Wilhelm Reinmuth...
class.
After Sentry and NEODyS announced the possible impact, additional observations decreased the uncertainty in Apophis' trajectory. As they did, the probability of an impact event temporarily climbed, peaking at 2.7% (1 in 37). Combined with its size, this caused Apophis to be assessed at level 4 on the Torino Scale
Torino Scale
The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects 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...
and 1.10 on the Palermo Technical Impact Hazard Scale
Palermo Technical Impact Hazard Scale
The Palermo Technical Impact Hazard Scale is a logarithmic scale used by astronomers to rate the potential hazard of impact of a near-earth object . It combines two types of data—probability of impact, and estimated kinetic yield—into a single "hazard" value...
, scales scientists use to represent the danger of an asteroid hitting Earth. These are the highest values for which any object has been rated on either scale. It has since been downgraded to level 0 on the Torino Scale for both the 2029 and 2036 passes. With a cumulative Palermo Scale rating of -2.9, the risk of impact from Apophis is less than the background hazard level.
On Friday, April 13, 2029, Apophis will pass Earth within the orbits of geosynchronous communication satellites. It will return for another close Earth approach in 2036.
The 2029 pass will actually be much closer than the first predictions, but the uncertainty is such that an impact is ruled out. Similarly, the pass on April 13, 2036, carries little risk of an impact.
2013 refinement
The close approach in 2029 will substantially alter the object's orbit, making predictions uncertain without more data. "If we get radar ranging in 2013 [the next good opportunity], we should be able to predict the location of out to at least 2070." said Jon Giorgini of JPL. Apophis will pass within 0.0966 AU of the Earth in 2013, allowing astronomers to refine the trajectory for future close passes. Just after the close approach on 9 January 2013, the asteroid should peak at about apparent magnitude 15.7, On January 31, 2011, astronomers took the first new images of Apophis in more than 3 years.In July 2005, former Apollo astronaut Rusty Schweickart
Rusty Schweickart
Russell Louis "Rusty" Schweickart aka Schweikart is an American former astronaut, research scientist, US Air Force fighter pilot, business and government executive...
, as chairman of the B612 Foundation
B612 Foundation
The B612 Foundation is a private foundation dedicated to protecting the Earth from asteroid strikes. Their immediate goal is to "significantly alter the orbit of an asteroid in a controlled manner by 2015"....
, formally asked NASA to investigate the possibility that the asteroid's post-2029 orbit could be in orbital resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
with Earth, which would increase the probability of future impacts. Schweickart asked for an investigation of the necessity of placing a transponder
Transponder
In telecommunication, the term transponder has the following meanings:...
on the asteroid for more accurate tracking of how its orbit is affected by the Yarkovsky effect
Yarkovsky effect
The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum...
.
History of impact estimates
- The original NASA report on December 23, 2004, mentioned impact chances of "around 1 in 300" in 2029, which was widely reported in the media. The actual NASA estimates at the time were 1 in 233; they resulted in the Torino scale rating of 2, the first time any asteroid had received a rating above 1.
- Later that day, based on a total of 64 observations, the estimates were changed to 1 in 62 (1.6%), resulting in an update to the initial report and an upgrade to a Torino scale rating of 4.
- On December 25, 2004, the chances were first reported as 1 in 42 (2.4%) and later that day (based on 101 observations) as 1 in 45 (2.2%). At the same time, the asteroid's estimated diameter was lowered from 440 m to 390 m and its mass from 1.2×1011 kg to 8.3×1010 kg.
- On December 26, 2004 (based on a total of 169 observations), the impact probability was still estimated as 1 in 45 (2.2%), the estimates for diameter and mass were lowered to 380 m and 7.5×1010 kg, respectively.
- On December 27, 2004 (based on a total of 176 observations), the impact probability was raised to 1 in 37 (2.7%); diameter was increased to 390 m, and mass to 7.9×1010 kg.
- On December 27, 2004, in the afternoon, a precoveryPrecoveryPrecovery is a term used in astronomy that describes the process of finding the image of an object in old archived images or photographic plates, for the purpose of calculating a more accurate orbit...
increased the span of observations to 287 days and allowed more accurate calculations to re-rate the asteroid's 2029 approach as level zero on the Torino scale (no threat). The cumulative impact probability was estimated to be around 0.004%, a lower risk than asteroid , which once again became the greatest risk object. A 2053 approach to Earth still poses a minor risk of impact, and Apophis was still rated at level one on the Torino scale for this orbit, and thus remains that way. - On December 28, 2004 at 12:23 GMT and (based on a total of 139 observations), produced a value of one on the Torino scale for 2044-04-13.29 and 2053-04-13.51.
- By 01:10 GMT on December 29, 2004 the only pass rated 1 on the Torino scale was for 2053-04-13.51 based on 139 observations spanning 287.71 days (2004-Mar-15.1104 to 2004-Dec-27.8243). (As of 2010, the 2053 is now a 2056-04-13 risk of 1 in 10 million.)
- By 19:18 GMT on December 29, 2004 this was still the case based upon 147 observations spanning 288.92 days (2004-Mar-15.1104 to 2004-Dec-29.02821), though the close encounters have changed and been reduced to 4 in total.
- By 13:46 GMT on December 30, 2004 no passes were rated above 0, based upon 157 observations spanning 289.33 days (2004-Mar-15.1104 to 2004-Dec-29.44434). The most dangerous pass was rated at 1 in 7,143,000.
- By 22:34 GMT on December 30, 2004, 157 observations spanning 289.33 days (2004-Mar-15.1104 to 2004-Dec-29.44434). One pass at 1 (Torino scale) 3 other passes.
- By 03:57 GMT on January 2, 2005, 182 observations spanning 290.97 days (2004-Mar-15.1104 to 2004-Dec-31.07992) One pass at 1 (Torino scale) 19 other passes.
- By 14:49 GMT on January 3, 2005, observations spanning 292.72 days (2004-Mar-15.1104 to 2005-Jan-01.82787) One pass at 1 (Torino scale) 15 other passes.
- Extremely precise radarRadarRadar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
observations at Arecibo ObservatoryArecibo ObservatoryThe Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
on January 27, 28, and 30 refine the orbit further and show that the April, 2029 close approach will occur at only 5.6 Earth radii, approximately one-half the distance previously estimated. - A radar observation on August 7, 2005, refines the orbit further and eliminates the possibility of an impact in 2035. Only the pass in 2036 remains at Torino Scale 1.
- In October 2005 it is predicted that the asteroid will pass just below the altitude of geosynchronous satelliteGeosynchronous satelliteA geosynchronous Satellite is a satellite whose orbit on the Earth repeats regularly over points on the Earth over time. If such a satellite's orbit lies over the equator, the orbit is circular and its angular velocity is the same as the earth's, then it is called a geostationary satellite...
s, which are at 35786 kilometres (22,236.4 mi). Such a close approach by an asteroid of this size is expected to occur every 800 years or so. - A new radar observation at Arecibo Observatory on May 6, 2006, slightly lowered the Palermo scale rating, but the pass in 2036 remained at Torino Scale 1 despite the impact probability dropping by a factor of four.
- Additional observations through 2006 resulted in Apophis being lowered to Torino Scale 0 on August 6, 2006. Around this time, the impact probability was lowered to 1 in 45,000.
- As of October 7, 2009, refinements to the precoveryPrecoveryPrecovery is a term used in astronomy that describes the process of finding the image of an object in old archived images or photographic plates, for the purpose of calculating a more accurate orbit...
images of Apophis by the University of Hawaii's Institute for AstronomyInstitute for AstronomyThe Institute for Astronomy is a research unit within the University of Hawaii system, led by Günther Hasinger as Director. IfA main headquarters are located at 2680 Woodlawn Drive in Honolulu, Hawaii, , on the University of Hawaii at Mānoa campus. Additional facilities are located at Pukalani,...
, the 90-inch Bok TelescopeBok TelescopeThe Bok Telescope is the largest telescope operated solely by Steward Observatory. It finds much use from astronomers from University of Arizona, Arizona State University, and Northern Arizona University, with instruments capable of both imaging and spectroscopy...
, and the Arecibo ObservatoryArecibo ObservatoryThe Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
have generated a refined path that reduces the odds of an April 13, 2036 impact to about 1 in 250,000. - 2009-Apr-29: An animation is released that shows how unmeasured physical parameters of Apophis bias the entire statistical uncertainty region. If Apophis is a RETROGRADE rotatorRetrograde motionRetrograde motion is motion in the direction opposite to the movement of something else, and is the contrary of direct or prograde motion. This motion can be the orbit of one body about another body or about some other point, or the rotation of a single body about its axis, or other phenomena such...
on the small, less-massive end of what is possible, the measurement uncertainty region will get pushed back such that the center of the distribution encounters the Earth's orbit. This would result in an impact probability much higher than computed with the Standard Dynamical Model. Conversely, if Apophis is a small, less-massive PROGRADE rotator, the uncertainty region is advanced along the orbit. Only the remote tails of the probability distribution could encounter the Earth, producing a negligible impact probability
- Criticism of all published impact probabilites rests on the fact that important physical parameters such as mass and spin that affect its precise trajectory have not yet been accurately measured and hence there are no associated probability distributions. The Standard Dynamical Model used for making predictions simplifies calculations by assuming the Earth is a point mass; this can introduce up to 2.9 Earth radii of prediction error for the 2036 approach, and the Earth's oblateness must be considered to predict an impact reliably. Additional factors that can greatly influence the predicted motion in ways that depend on unknown details, are the spin of the asteroid, its precise mass, the way it reflects and absorbs sunlight, radiates heat, and the gravitational pull of other asteroids passing nearby. Small uncertainties in the masses and positions of the planetPlanetA planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s and SunSunThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
can cause up to a 23 Earth radii of prediction error for Apophis by 2036.
Possible impact effects
NASA initially estimated the energy that Apophis would have released if it struck Earth as the equivalent of 1480 megatons of TNTTNT equivalent
TNT equivalent is a method of quantifying the energy released in explosions. The ton of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT...
. A later, more refined NASA estimate was 880 megatons, then revised to 510 megatons. The impacts which created the Barringer Crater or the Tunguska event
Tunguska event
The Tunguska event, or Tunguska blast or Tunguska explosion, was an enormously powerful explosion that occurred near the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia, at about 7:14 a.m...
are estimated to be in the 3–10 megaton range. The 1883 eruption of Krakatoa
Krakatoa
Krakatoa is a volcanic island made of a'a lava in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island , and the volcano as a whole. The island exploded in 1883, killing approximately 40,000 people, although some estimates...
was the equivalent of roughly 200 megatons and the biggest hydrogen bomb ever exploded, the Tsar Bomba
Tsar Bomba
Tsar Bomba is the nickname for the AN602 hydrogen bomb, the most powerful nuclear weapon ever detonated. It was also referred to as Kuz'kina Mat , in this usage meaning "something that has not been seen before"....
, was around 50 megatons. In comparison, the Chicxulub impact
Chicxulub Crater
The Chicxulub crater is an ancient impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is located near the town of Chicxulub, after which the crater is named...
, believed by many to be a significant factor in the extinction of the dinosaurs, has been estimated to have released about as much energy as 100,000,000 megatons (100 Teratons).
Impact winter
An impact winter is a period of prolonged cold weather caused by the impact on the Earth of a large asteroid or comet. If such an impact occurred on land or the floor of a shallow sea, it could cause large amounts of dust or ash to be thrown into the Earth's atmosphere, blocking the Sun's light...
.
The B612 Foundation
B612 Foundation
The B612 Foundation is a private foundation dedicated to protecting the Earth from asteroid strikes. Their immediate goal is to "significantly alter the orbit of an asteroid in a controlled manner by 2015"....
made estimates of Apophis' path if a 2036 Earth impact were to occur, as part of an effort to develop viable deflection strategies
Asteroid deflection strategies
Asteroid mitigation strategies are "planetary defense" methods by which near-Earth objects could be diverted, preventing potentially catastrophic impact events. A sufficiently large impact would cause massive tsunamis or an impact winter, or both...
. The result is a narrow corridor a few kilometres wide, called the "path of risk", extending across southern Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, across the north Pacific (relatively close to the coastlines of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
), then right between Nicaragua
Nicaragua
Nicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...
and Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
, crossing northern Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
and Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
, ending in the Atlantic, just before reaching Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. Using the computer simulation tool NEOSim, it was estimated that the hypothetical impact of Apophis in countries such as Colombia and Venezuela, which are in the path of risk, could have more than 10 million casualties. An impact in the Atlantic or Pacific oceans would produce a devastating tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
.
Planetary Society competition
In 2008, The Planetary SocietyPlanetary Society
The Planetary Society is a large, publicly supported, non-government and non-profit organization that has many research projects related to astronomy...
, a California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
-based space advocacy group, organized a $50,000 competition to design an unmanned space probe that would 'shadow' Apophis for almost a year, taking measurements that would "determine whether it will impact Earth, thus helping governments decide whether to mount a deflection mission to alter its orbit." The society received 37 entries from 20 countries on 6 continents.
The commercial competition was won by a design called 'Foresight' created by SpaceWorks Enterprises, Inc. SpaceWorks proposed a simple orbiter with only two instruments and a radio beacon at a cost of ~140 million USD, launched aboard a Minotaur IV between 2012 and 2014, to arrive at Apophis five to ten months later. It would then rendezvous with, observe, and track the asteroid. Foresight would orbit the asteroid to gather data with a multi-spectral image
Multi-spectral image
A multispectral image is one that captures image data at specific frequencies across the electromagnetic spectrum. The wavelengths may be separated by filters or by the use of instruments that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range,...
r for one month. It would then leave orbit and fly in formation with Apophis around the Sun at a range of two kilometers (1.2 miles). The spacecraft would use laser ranging to the asteroid and radio tracking from Earth for ten months to accurately determine the asteroid's orbit and how it might change.
Pharos, the winning student entry, would be an orbiter with four science instruments (a multi-spectral imager, near-infrared spectrometer, laser rangefinder, and magnetometer
Magnetometer
A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...
) that would rendezvous with and track Apophis. Earth-based tracking of the spacecraft would then allow precise tracking of the asteroid. The Pharos spacecraft would also carry four instrumented probes that it would launch individually over the course of two weeks. Accelerometer
Accelerometer
An accelerometer is a device that measures proper acceleration, also called the four-acceleration. This is not necessarily the same as the coordinate acceleration , but is rather the type of acceleration associated with the phenomenon of weight experienced by a test mass that resides in the frame...
s and temperature sensors on the probes would measure the seismic effects of successive probe impacts, a creative way to explore the interior structure and dynamics of the asteroid.
Second place, for $10,000, went to a European team led by Deimos Space S.L. of Madrid
Madrid
Madrid is the capital and largest city of Spain. The population of the city is roughly 3.3 million and the entire population of the Madrid metropolitan area is calculated to be 6.271 million. It is the third largest city in the European Union, after London and Berlin, and its metropolitan...
, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
, in cooperation with EADS Astrium
EADS Astrium
Astrium Satellites is one of the three business units of Astrium, a subsidiary of EADS. It is a European space manufacturer involved in the manufacture of spacecraft used for science, Earth observation and telecommunication, as well as the equipment and subsystems used therein and related ground...
, Friedrichshafen, Germany; University of Stuttgart
University of Stuttgart
The University of Stuttgart is a university located in Stuttgart, Germany. It was founded in 1829 and is organized in 10 faculties....
, Germany; and Università di Pisa, Italy. Juan L. Cano was Principal Investigator
Principal investigator
A principal investigator is the lead scientist or engineer for a particular well-defined science project, such as a laboratory study or clinical trial....
.
Another European team took home $5,000 for third place. Their team lead was EADS Astrium Ltd, United Kingdom, in conjunction with EADS Astrium SAS, France; IASF-Roma, INAF, Rome, Italy; Open University
Open University
The Open University is a distance learning and research university founded by Royal Charter in the United Kingdom...
, UK; Rheinisches Institut für Umweltforschung, Germany; Royal Observatory of Belgium; and Telespazio
Telespazio
Telespazio is a space systems services company, based in Rome, Italy. Telespazio was founded in 1961; however the company as it exists today was formed on July 1 2005 with the merger of the original Telespazio with the space services division of Alcatel...
, Italy. The Principal Investigator was Paolo D'Arrigo.
Two teams tied for second place in the Student Category: Monash University
Monash University
Monash University is a public university based in Melbourne, Victoria. It was founded in 1958 and is the second oldest university in the state. Monash is a member of Australia's Group of Eight and the ASAIHL....
, Clayton Campus, Australia, with Dilani Kahawala as Principal Investigator; and University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
, with Jeremy Hollander as Principal Investigator. Each second place team won $2,000. A team from Hong Kong Polytechnic University
Hong Kong Polytechnic University
The Hong Kong Polytechnic University specialises in professional education in Hong Kong. The University’s teaching units are grouped under six faculties and two schools; the Faculty of Applied Science and Textiles, Faculty of Business, Faculty of Construction and Environment, Faculty of...
and Hong Kong University of Science and Technology
Hong Kong University of Science and Technology
The Hong Kong University of Science and Technology is a public university located in Hong Kong. Established in 1991 under Hong Kong Law Chapter 1141 , it is one of the nine universities in Hong Kong.Professor Tony F. Chan is the president of HKUST...
, under the leadership of Peter Weiss, received an honorable mention and $1,000 for the most innovative student proposal.
Don Quijote mission
Apophis is one of two asteroids under consideration by the European Space AgencyEuropean Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
as the target of its Don Quijote mission
Don Quijote (space probe)
Don Quijote is a proposed space probe under development by the European Space Agency, which would study the effects of crashing a spacecraft into an asteroid. The mission is intended to test whether a spacecraft could successfully deflect an asteroid on a collision course with Earth...
to study the effects of impacting an asteroid.
Proposed deflection strategies
Studies by NASA, ESA, and various research groups in addition to the Planetary Society contest teams, have described a number of proposals for deflecting Apophis or similar objects, including gravitational tractor, kinetic impactAsteroid deflection strategies
Asteroid mitigation strategies are "planetary defense" methods by which near-Earth objects could be diverted, preventing potentially catastrophic impact events. A sufficiently large impact would cause massive tsunamis or an impact winter, or both...
, and nuclear bomb methods.
On December 30, 2009, Anatoly Perminov
Anatoly Perminov
Dr. Prof. Anatoly Nikolayevich Perminov is a Russian rocket scientist and a mechanical engineer. He served as the General Director of Russian Federal Space Agency in 2004–2011.-Career:...
, the director of the Russian Federal Space Agency
Russian Federal Space Agency
The Russian Federal Space Agency , commonly called Roscosmos and abbreviated as FKA and RKA , is the government agency responsible for the Russian space science program and general aerospace research. It was previously the Russian Aviation and Space Agency .Headquarters of Roscosmos are located...
, said in an interview that Roscosmos will also study designs for a possible deflection mission to Apophis.
On August 16, 2011, researchers at China's Tsinghua University
Tsinghua University
Tsinghua University , colloquially known in Chinese as Qinghua, is a university in Beijing, China. The school is one of the nine universities of the C9 League. It was established in 1911 under the name "Tsinghua Xuetang" or "Tsinghua College" and was renamed the "Tsinghua School" one year later...
proposed a launching a mission to knock Apophis onto a safer course using an impactor spacecraft in a retrograde orbit, steered and powered by a solar sail. Instead of moving the asteroid on its potential resonant return to Earth, Shengping Gong and his team believe the secret is shifting the asteroid away from entering the gravitational keyhole in the first place.
Popular culture
- The asteroid Apophis is named as the cause of earth's apocalypse in id Software'sId SoftwareId Software is an American video game development company with its headquarters in Richardson, Texas. The company was founded in 1991 by four members of the computer company Softdisk: programmers John Carmack and John Romero, game designer Tom Hall, and artist Adrian Carmack...
RageRage (video game)Rage is a first-person shooter video game by id Software which was released on October 4, 2011 in North America. It uses the company's new OpenGL based id Tech 5 engine. The game was first shown as a tech demo on June 11, 2007, at Apple's WWDC, and was officially announced on August 2, 2007, at...
. - The metal band Type O NegativeType O NegativeType O Negative was a gothic metal band from Brooklyn, New York City. The band also incorporated elements of doom metal and thrash metal. Their dramatic lyrical emphasis on themes of romance, depression, and death resulted in the nickname "The Drab Four"...
names Apophis as the bringer of the Apocalypse on Friday 13th 2029, in their song "The Profit of Doom" on the album Dead AgainDead Again (Type O Negative album)Dead Again is the seventh and final studio album by Type O Negative, released through SPV/Steamhammer. This is the final Type O Negative studio album released before the death of frontman Peter Steele. The album sees the band using studio drums instead of a drum machine for the first time since...
.
External links
- Asteroid Apophis orbit from recent observations, EPSC Abstracts Vol. 6, EPSC-DPS2011-1212, 2011, EPSC-DPS Joint Meeting 2011
Risk assessment
- Apophis Orbital Prediction Page at NASA JPL
- page and impactor table from NEODySNEODySNEODyS is an Italian and Spanish service that provides information on Near Earth Objects with a convenient Web-based interface. It is based on a continually and automatically maintained database of near earth asteroid orbits. This site provides a number of services to the NEO community...
.
NASA
