367943 Duende (

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been cal ...

) is a micro- asteroid and a

near-Earth object A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). ...

of the

Aten Aten also Aton, Atonu, or Itn ( egy, jtn, ''reconstructed'' ) was the focus of Atenism, the religious system established in ancient Egypt by the Eighteenth Dynasty pharaoh Akhenaten. The Aten was the disc of the sun and originally an aspect o ...

and Atira group, approximately in diameter. It was discovered by astronomers of the Astronomical Observatory of Mallorca at its robotic La Sagra Observatory in 2012, and named for the

duende A duende is a humanoid figure of folklore, with variations from Iberian, Ibero American, and Filipino cultures, comparable to dwarves, gnomes, or leprechauns. In Spanish ''duende'' originated as a contraction of the phrase or , effectively ...

, a goblin-like creature from Iberian and Filipino mythology and folklore. ''Duende'' is likely an uncommon

L-type asteroid L-type asteroids are relatively uncommon asteroids with a strongly reddish spectrum shortwards of 0.75 μm, and a featureless flat spectrum longwards of this. In comparison with the K-type, they exhibit a more reddish spectrum at visible wavele ...

and significantly elongated. For an asteroid of its size, it has a relatively long rotation period of 9.485 hours. On 15 February 2013, ''Duende'' passed at a record distance of or 4.3

Earth radii Earth radius (denoted as ''R''🜨 or R_E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid, the radius ranges from a maximum of nearly (equatorial radius, deno ...

from Earth's surface. Due to its close passage, its orbit was perturbed significantly enough that it changed from an

Apollo asteroid The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Earth ...

to an

Aten asteroid The Aten asteroids are a dynamical group of asteroids whose orbits bring them into proximity with Earth. By definition, Atens are Earth-crossing asteroids . The group is named after 2062 Aten, the first of its kind, discovered on 7 January ...

. ''Duende'' passage also coincided with the completely unrelated Chelyabinsk meteor, which entered Earth's atmosphere above Russia just 16 hours earlier.

Discovery and past risk assessments

''Duende'' was discovered on 23 February 2012, seven days after passing from Earth, by the La Sagra Observatory in

Granada Province Granada is a province of southern Spain, in the eastern part of the autonomous community of Andalusia. It is bordered by the provinces of Albacete, Murcia, Almería, Jaén, Córdoba, Málaga, and the Mediterranean Sea (along the Costa Tropical). ...

, Spain, using a 0.45-m reflector which was remotely operated by

amateur astronomers Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomer ...

at the Astronomical Observatory of Mallorca. The still relatively imprecise orbit deduced from the short arc of the 2012 observations already made clear that Duende would pass no closer to Earth's surface than 3.2

during its 2013 passage. There was at the time, however, a cumulative risk of 0.033% (1 in 3,030) that ''Duende'' would impact Earth during one of its 2026 to 2069 approaches.

2013 passage

On 9 January 2013, Duende was observed again by

Las Campanas Observatory Las Campanas Observatory (LCO) is an astronomical observatory owned and operated by the Carnegie Institution for Science (CIS). It is in the southern Atacama Desert of Chile in the Atacama Region approximately northeast of the city of La Serena. ...

and the observation arc immediately increased from 79 days to 321 days. On 15 February 2013 at 19:25 UT, Duende passed from the center of Earth, with an uncertainty region of about . It passed above Earth's surface, closer than satellites in geosynchronous orbit. It briefly peaked at an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

of roughly 7.2, a factor of a few fainter than would have been visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to normal ...

. The best observation location for the closest approach was Indonesia. Eastern Europe, Asia, and Australia also were well situated to observe Duende during its closest approach. ''Duende'' was not expected to pass any closer than 1950 km to any satellites.

Goldstone Observatory The Goldstone Deep Space Communications Complex (GDSCC), commonly called the Goldstone Observatory, is a satellite ground station located in Fort Irwin in the U.S. state of California. Operated by NASA's Jet Propulsion Laboratory (JPL), its m ...

observed Duende with

radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, we ...

from February 16 to February 20. Radar observations showed that it is an elongated asteroid with dimensions of . This gives Duende a geometric mean (spherical) diameter equivalent to . During the close approach, an observational campaign involving 5 different telescopes in 4 different observatories was carried on in order to get information on the physical properties of this NEO. Visible and near-Infrared photometry and visible spectroscopy were obtained at

Gran Telescopio Canarias The Gran Telescopio Canarias (GranTeCan or GTC) is a reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain. It is the world's largest single-aperture optical telescope. Constr ...

Telescopio Nazionale Galileo The Galileo National Telescope, ( it, Telescopio Nazionale Galileo; TNG; code: Z19) is a 3.58-meter Italian telescope, located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain. The TNG is operated ...

and Calar Alto Observatory and put together. The classification using the M4AST online tool says this is an L-type asteroid. Those peculiar asteroids are characterized by a strongly reddish spectrum shortward of 0.8 μm, and a featureless flat spectrum longward of this, with little or no concave-up curvature related to a 1 μm silicon absorption band. Time-series photometry was also obtained in the Observatorio de La Hita () and Observatorio de Sierra Nevada during two consecutive nights (15–16 February 2013). All of this data were co-phased to build a

lightcurve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular freq ...

of the object. This lightcurve is double-peak and presents large variations in magnitude, implying a very elongated object, which is compatible with radar observations. The amplitude of the lightcurve yields an axial ratio that, together with the long axis of 40 m inferred from the radar images by Goldstone, results in an equivalent diameter of 18 m, much smaller than the estimations before the close-approach. The

rotational period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the b ...

was precisely determined from the lightcurve obtaining a value of . This value is confirmed with an analysis of all the photometry of this objects reported to the Minor Planet Center. Using data pre and post close approach the authors find that the object suffered a spin-up during the event that decreased the rotational period from down to hours, which is compatible with the more accurate value estimated from the light-curve. Earth and 2012 DA14 - 2013

Orbital shift

The close approach to Earth reduced the orbital period of Duende from 368 days to 317 days, Its aphelion was reduced from 1.110 to 0.9917 AU, leaving it almost entirely inside Earth's orbit and perturbing it from the

Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label= Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label ...

class to the

class of near-Earth asteroids. Its next close approach to Earth will be on 15 February 2046, when it will pass about from Earth. Based on 7 radar observations, the next close approach to Earth similar to the 2013 passage will be on 16 February 2123, when Duende will pass no closer than from the center of Earth. For the 2123 passage, the

nominal Nominal may refer to: Linguistics and grammar * Nominal (linguistics), one of the parts of speech * Nominal, the adjectival form of "noun", as in "nominal agreement" (= "noun agreement") * Nominal sentence, a sentence without a finite verb * Nou ...

pass will be from the center of the Moon and then from the center of Earth.

Risks

Risk assessments calculated before the 2013 passage were based on a diameter of 45 meters and a mass of 130,000

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...

s. It was estimated that, if it were ever to impact Earth, it would enter the atmosphere at a speed of 12.7 km/s, would have a

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acc ...

equivalent to 2.4 megatons of TNT, and would produce an air burst with the equivalent of 2.1 megatons of TNT at an altitude of roughly . The

Tunguska event The Tunguska event (occasionally also called the Tunguska incident) was an approximately 12- megaton explosion that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of June 3 ...

has been estimated at 3–20 megatons. Asteroids of approximately 50 meters in diameter are expected to impact Earth once every 1200 years or so. Asteroids larger than 35 meters across can pose a threat to a town or city, and the Chelyabinsk meteor which serendipitously occurred on the day of the 2013 passage was due to a 17-meter asteroid. As a result of radar observations it is now known that Duende is only about 30 meters in diameter. * The uncertainty region of Duende during planetary encounters is now well determined through 2123. * Duende was therefore removed from the

Sentry Risk Table 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+ y ...

on 16 February 2013. * It is estimated that there are more than a million near-Earth asteroids smaller than 100 meters. The table above uses

Sentry Sentry or The Sentry may refer to: Comics *Sentry (Kree) *Sentry (Curtis Elkins) * Sentry (Robert Reynolds) *Senator Ward (comics) or Sentry Vehicles *Sentry (AUV), an autonomous underwater vehicle used to measure deep-ocean data *E-3 Sentry AWAC ...

's stony asteroid density of 2600 kg/m³, Sentry's atmospheric entry velocity (V_impact) of 12.7 km/s, and an angle of 45 degrees. For kinetic energy at atmospheric entry, 3.3 Mt is equivalent to DF-4, 9 Mt is equivalent to

Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab ...

and 15.6 Mt is equivalent to

Castle Bravo Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of '' Operation Castle''. Detonated on March 1, 1954, the device was the most powerful ...

. For air burst energy, 530 kt is equivalent to

W88 The W88 is an American thermonuclear warhead, with an estimated yield of , and is small enough to fit on MIRVed missiles. The W88 was designed at the Los Alamos National Laboratory in the 1970s. In 1999, the director of Los Alamos who had pres ...

and 2.9 Mt is equivalent to R-12 Dvina.

Naming

This

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''mino ...

was named after the

, fairy- or

goblin A goblin is a small, grotesque, monstrous creature that appears in the folklore of multiple European cultures. First attested in stories from the Middle Ages, they are ascribed conflicting abilities, temperaments, and appearances depending on ...

-like mythological creatures from Iberian, Latin American and

Filipino Filipino may refer to: * Something from or related to the Philippines ** Filipino language, standardized variety of 'Tagalog', the national language and one of the official languages of the Philippines. ** Filipinos, people who are citizens of th ...

folklore. The approved naming citation was published by the Minor Planet Center 17 November 2013 .

Notes

References

External links

around the time of its minimum distance from the Earth
(Virtual Telescope Project, 15 February 2013)
Video: Fly by
15 February 2013
Asteroid to Safely Pass Earth
(JPLnews video, 4 February 2013)

(Bruce Betts, 4 February 2013, includes video)
Physical characteristics of
nasa.gov

nasa.gov
Real-time video of asteroid passing Earth
(Clay Center Observatory, beginning 6 p.m. EST on 15 February 2013)
No, asteroid will not hit us next year
Bad Astronomy blog (

Phil Plait Philip Cary Plait (born September 30, 1964), also known as The Bad Astronomer, is an American astronomer, skeptic, and popular science blogger. Plait has worked as part of the Hubble Space Telescope team, images and spectra of astronomical objec ...

, 4 March 2012)
Cool animation showing asteroid DA 14′s near miss next year
Bad Astronomy blog (Phil Plait, 8 March 2012)
sparks asteroid fever
(Astro Bob, 6 March 2012)

(ESA 15 March 2012)

( Jaime Nomen for OAM team La Sagra Sky Survey), includes animated discovery images
orbit calculation with a 3 day observation arc
(mpml : 26 February 2012)
Meteoroid hazard to satellites comes overwhelmingly from the marbles, not the mountains
(mpml : 26 March 2012)

(Sormano Astronomical Observatory)

(Sormano Astronomical Observatory) * * * {{DEFAULTSORT:Duende 367943 367943 367943 Named minor planets Near-Earth objects removed from the Sentry Risk Table 367943 367943 20130215 20120223