(
provisional designation ) is a risk-listed
asteroid
An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
, classified as a
near-Earth object
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 (astronomical unit, AU). This definition applies to the object's orbit a ...
and
potentially hazardous asteroid of the
Apollo group, approximately in diameter.
It once had the highest known
probability
Probability is a branch of mathematics and statistics concerning events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1; the larger the probability, the more likely an e ...
of
impacting Earth.
In 2002, it had the highest
Palermo scale rating with a value of 0.17 and a probability of 1 in 306 (0.33%) for a possible collision in 2880.
Since that time, the estimated risk has been updated several times. In December 2015, the odds of an Earth impact were revised to 1 in 8,300 (0.012%) with a Palermo scale rating of −1.42.
, it is listed on the
Sentry Risk Table with the highest cumulative Palermo scale rating of −0.92.
is not assigned a
Torino scale rating, because the 2880 date is over 100 years in the future. As of 29 April 2025, the odds of an Earth impact are 1 in 2,600 (0.039%).
Discovery and nomenclature
was first discovered on 23 February 1950 by
Carl A. Wirtanen at
Lick Observatory
The Lick Observatory is an astronomical observatory owned and operated by the University of California. It is on the summit of Mount Hamilton (California), Mount Hamilton, in the Diablo Range just east of San Jose, California, United States. The ...
.
[ It was observed for seventeen days] and then lost because this short observation arc resulted in large uncertainties in Wirtanen's orbital solution. On 31 December 2000, it was recovered at Lowell Observatory and was announced as on 4 January 2001. Just two hours later it was recognized as .
Observations
On 5 March 2001, made a close approach to Earth at a distance of .[ It was studied by radar at the Goldstone and ]Arecibo
Arecibo (; ) is a Arecibo barrio-pueblo, city and Municipalities of Puerto Rico, municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado, Puerto Rico, Utuado and Ciales, Puerto Rico, Ciale ...
observatories from March 3 to 7, 2001.
The studies showed that the asteroid has a mean diameter of 1.1 km, assuming that is a retrograde rotator. Optical lightcurve
In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...
analysis by Lenka Šarounová
Lenka Eden Kripac (born 19 March 1978) is an Australian singer-songwriter and actress best known for her song "The Show (Lenka song), The Show", from her debut album, Lenka (album), ''Lenka''. "The Show" has been used in numerous advertisements ...
and Petr Pravec shows that its rotation period is hours. Due to its short rotation period and high radar albedo
Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...
, is thought to be fairly dense (more than 3.5 g/cm3, assuming that it has no internal strength) and likely composed of nickel
Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...
–iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
. In August 2014, scientists from the University of Tennessee
The University of Tennessee, Knoxville (or The University of Tennessee; UT; UT Knoxville; or colloquially UTK or Tennessee) is a Public university, public Land-grant university, land-grant research university in Knoxville, Tennessee, United St ...
determined that ' is a rubble pile rotating faster than the breakup limit for its density, implying the asteroid is held together by van der Waals force
In molecular physics and chemistry, the van der Waals force (sometimes van der Waals' force) is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical elec ...
s rather than gravity.
made distant approaches to Earth on 20 May 2012, 5 February 2021 and 5 February 2023.[ However, at these times it was a quarter to half an AU away from Earth, preventing more useful astrometrics and timing that occurs when an object is closer to Earth. The next close approach that presents a good opportunity to observe the asteroid will be on 2 March 2032, when it will be from Earth. The following table lists the approaches closer than 0.1 AU until the year 2500.] By 2136 the close approach solutions are becoming notably more divergent.
Possible Earth impact
has one of the best-determined asteroid orbital solutions. This is due to a combination of:
* an orbit moderately inclined (12 degrees)[ to the ecliptic plane (reducing in-plane perturbations);
* high-precision radar astrometry, which provides its distance and is complementary to the measurements of angular positions;
* a 74-year ]observation arc
In observational astronomy, the observation arc (or arc length) 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 use ...
;[
* an uncertainty region controlled by ]resonance
Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...
.
Main-belt asteroid 78 Diana
78 Diana is a large and dark main-belt asteroid. It was discovered by German astronomer Robert Luther on March 15, 1863, and named after Diana, Roman goddess of the hunt. The asteroid is orbiting the Sun at a distance of with a period of ...
(~125 km in diameter) will pass about from on 5 August 2150. At that distance and size, Diana will perturb enough so that the change in trajectory is notable by 2880 (730 years later). In addition, over the intervening time, 's rotation will cause its orbit to slightly change as a result of the Yarkovsky effect. If continues on its present orbit, it may approach Earth on 16 March 2880, though the mean trajectory passes many millions of kilometres from Earth, so does not have a significant chance of impacting Earth. , according to the latest solution dated 2 February 2025, the probability of an impact in 2880 is 1 in 2,600 (0.039%).[
The energy released by a collision with an object the size of would cause major effects on the ]climate
Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteoro ...
and biosphere
The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...
, which would be devastating to human
Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...
civilization
A civilization (also spelled civilisation in British English) is any complex society characterized by the development of state (polity), the state, social stratification, urban area, urbanization, and symbolic systems of communication beyon ...
. The discovery of the potential impact heightened interest in asteroid deflection strategies.
See also
*
* Asteroid impact prediction
*Earth-grazing fireball
An Earth-grazing fireball (or Earth grazer) is a fireball (meteor), fireball, a very bright meteor that enters Earth’s atmosphere and leaves again. Some fragments may impact Earth as meteorites, if the meteor starts to break up or explodes in m ...
* List of asteroid close approaches to Earth
Notes
References
External links
MPEC 2001-A26 : 1950 DA = 2000 YK66
(K00Y66K). '' MPC'' 4 January 2001
3D model
Rotating model of the asteroid (preferred rotation model is ''retrograde''
NeoDys
Asteroid Lightcurve Database (LCDB)
query form
)
Observatoire de Genève, Raoul Behrend
Minor Planet Center
*
*
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Discoveries by Carl A. Wirtanen
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