Asteroid (457662) 2009 DZ passes the Earth.

Asteroid (457662) 2009 DZ passed by the Earth at a distance of 12 510 000 km (32.5 times the average distance between the Earth and the Moon, or 8.36% of the average distance between the Earth and the Sun), slightly before 2.35 am GMT on Tuesday 23 February 2016. There was no danger of the asteroid hitting us, though had it done so it would have presented a considerable threat.  (457662) 2009 DZ has an estimated equivalent diameter of 75-250 m (i.e. a spherical body with the same mass would be 75-250 m in diameter), and an object towards the upper end of this range would pass through the atmosphere and directly impact the ground with a force of about 600 megatons (about 35 000 times the explosive energy of the Hiroshima bomb), causing devastation over a wide area and creating a crater about 4 km across, and resulting in global climatic problems that could last for decades.

The calculated orbit of  (457662) 2009 DZ. JPL Small Body Database.

(457662) 2009 DZ was discovered on 18 February 2009 by the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research Laboratory in Socorro, New Mexico. The designation 2009 DZ implies that it was the 25th asteroid (asteroid Z) discovered in the second half of February 2009 (period 2009 Z). The longer designation, (457662), indicates that the asteroid was the 457 662nd asteroid ever discovered. Asteroids are not given this longer designation immediately, to avoid duplicate or false sightings.

(457662) 2009 DZ has a 639 day year orbital period and an eccentric orbit tilted at an angle of 14.1° to the plane of the Solar System that takes it from 1.01 AU from the Sun (i.e. 101 % of the average distance at which the Earth orbits the Sun) to 1.89 AU from the Sun (i.e. 189% of the average distance at which the Earth orbits the Sun, considerably outside the orbit of the planet Mars). It is therefore classed as an Amor Group Asteroid (an asteroid which comes close to the Earth, but which is always outside the Earth's orbit). This means that close encounters between the asteroid and Earth are fairly common, with the most recent having occurred in February 2009 next predicted in February 2023 . As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, (457662) 2009 DZ is also classified as a Potentially Hazardous Asteroid (it comes no closer to the Sun than 101% of the average distance at which the Earth orbit's the Sun, but the Earth's orbit is not completely circular).

See also...

Asteroid 2016 DB passes the Earth.       Asteroid 2016 DB passed by the Earth at a distance of 123 900 km (0.32 times the average distance between the Earth and the Moon, or 0.08% of the average distance between the Earth and the Sun; 103 900 km above the orbit at which the satellites supporting...

Fireball seen over southern France and northern Italy.                                                   A bright fireball was seen over much of southeast France and northern Italy at about 6.20 pm local time on Wednesday 17...

Asteroid 2016 CG18 passes the Earth.   Asteroid 2016 CG18 passed by the Earth at a distance of 151 400 km (0.39 times the average distance between the Earth and the Moon, or 0.10% of the average distance between the Earth and the Sun; 131 400 km above the orbit at which the satellites...

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Prolyda dimidia and Prolyda elegantula: Two new species of Xyelyid Sawflies from the Middle Jurassic of Inner Mongolia.

Sawflies, Symphyta, are thought to be the oldest group of Hymenopterans, with a fossil record dating back to the Triassic, and the oldest group of Sawflies are considered to be the Xyeloids. The Xyeloids are considered to be paraphyletic (i.e. not everything descended from the last common ancestor of all Xyeloids is classifies as a Xyeloid), and can be split into two groups, the Xyelids, from which all other Sawflies are thought to be derived, and the Xyphidrids, which are thought to have been ancestral to the Wood Wasps, and thence all other Wasps, Ants and Bees, though the relationships between early members of these groups is unclear, and it is likely that this classification system will be replaced with something quite different in the future.

In a paper published in the journal ZooKeys on 26 February 2016, Chen Wang and Chungkun Shih of the College of Life Sciences at Capital Normal University, Alexandr Rasnitsyn of the PaleontologicalInstitute of the Russian Academy of Sciences and the Invertebrate Palaeontology Department at the Natural History Museum, and Mei Wang, also of the College of Life Sciences at Capital Normal University, describe two new species of Xyelyid Sawfly from the Middle Jurassic Jiulongshan Formation of Inner Mongolia. Both new species are placed in the genus Prolyda, which was erected by Alexandr Rasnitsyn in 1968 to describe Sawflies from the Jurassic of Kazakhstan.

The first new species is named Prolyda dimidia, meaning 'half', in reference to the pterostigma cell on the forewing, which has a darker posterior half. The species is described from a single specimen preserved in ventral viewon a slab from which the counterpart is not known. The specimen is about 11.4 mm in length, with a large, circular head.

Prolyda dimidia, photograph of only known specimen. Wang et al. (2016).

The second new species is named Prolyda elegantula, meaning 'graceful'. This species is also described from a single known specimen, again preserved on a slab with the counterpart missing. This specimen is 12 mm in length, with a massive and wide head.

Prolyda elegantula, photograph of only known specimen. Wang et al. (2016).

See also...

Xyelydid Sawflies from the Middle Jurassic of Inner Mongolia.                                            The Xyelydidae are an extinct group of Sawflies, Pamphilioidea, known from the Middle Jurassic to Early Cretaceous of Eurasia. They are possibly ancestral to other members of the group, though their relationships are poorly understood, though since Sawflies...

An early Woodwasp from the Early Cretaceous of Brazil.                                   The Hymenoptera are one of the largest groups of insects, comprising Sawflies, Wasps, Ants and Bees. The earliest members of the group were Sawflies, which appeared around the beginning of the Late Triassic. Sawflies have caterpillar-like larvae...

 

 

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Rafflesia consueloae: A dwarf Corpse Flower form Luzon Island, The Philippines.

The genus Rafflesia contains 32 described species of parasitic plants from Indonesia, Malaysia, Thailand and the Philippines. The maximum diversity in the group is found in the Philippines, where 12 species have been previously described, including five from Luzon Island. All members of the genus are parasitic on vines of the genus Tetrastigma, with almost the entire body of the parasite reduced to a haustorium that grows within the tissue of the host. The only part of the parasite that extends outside the host is the flower (and later the fruiting bodies derived from this), thought these flowers are exceptionally large and distinctive. All Rafflesia flowers are massive, with the largest, Rafflesia arnoldii, reaching over 100 cm in diameter and weighing as  much as 10 kg, making it officially the world's largest flower. Rafflesia flowers are a mottled reddish brown in colour, and extrude a strong aroma of rotting meat, used to attract the flies which act as pollenators. This gives the plants their common name, 'Corpse Flowers', although this can be slightly confusing, as this temr is also applied to the Titam Arum, Amorphophallus titanum, a Sumatran Plant which also has a reputation for producing the world's largest flowers (which produces the world's largest unbranched inflorescence, though it is not as massive as the flower of Rafflesia arnoldii), and which also uses a rotting meat smell to attract Flies to act as pollenators. The Genus was formerly clasified along with a number of other parasitic plants in the Order Rafflesiales, but this has been shown by genetic studies to be an invalid taxon, made up of unrelated plants which superficially resemble one-another due to convergent evolution, with the genus Rafflesia now placed in the Euphorbiaceae.

In a paper published in the journal Phytotaxa on 25 February 2015, John Galindon amd Pery Ong of the Institute of Biology at the University of the Philippines, Diliman and the Diliman Science Research Foundation and Edwino Fernando of the Diliman Science Research Foundation and the College of Forestry and Natural Resources at the University of the Philippines, Los Baños, describe a new species of  Rafflesia from Nueva Ecija Province on Luzon Island.

The new species is named Rafflesia consueloae, in honour of Consuelo Lopez, the partner of industrialist Oscar M. Lopez, for her love of plants and inspiration for Mr Lopez’s pursuit of biodiversity conservation in the Philippines. This species is exceptionally small for a Rafflesia, with the largest flowers recorded reaching only 12.7 cm in diameter. The flowers arre reddish brown in colour and covered with powdery white warts; as they age the flowers darken.

Rafflesia consueloae, open flower. Galindon et al. (2016).

The flowers were found growing at two separate sites, growing on the roots of Tetrastigma vines in stands of Bamboo in  the remnants of lowland tropical evergreen rainforest, between altitudes of 300 m and 500 m on mounts Balukbok and Pantaburon. The sites were about 2 km apart within the Pantabangan-Carranglan Watershed. Due to this limited range Galindon et al. recomend that be considered to be Criticall Endangered under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species.They further note that the land occupied by the plants falls under the jurestriction of the National Irrigation Administration and the Pantabangan-Carranglan Watershed Protected Area Management Board, while the First Gen Hydro Power Corporation operates facilities in the area and provides support in biodiversity monitoring in the surrounding forests. They suggest that the plants could be at threat from forest fires in the dry season as well as local hunters operating in the area; the way in which the seeds of Rafflesia plants are distributed and find Tetrastigma vines is unknown and it is thought that a mammalian vector may be involved.

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Gastrodia madagascariensis: A (not so) new species of parasitic Orchid from Madagascar. The German botanist Rudolf Schlechter published Orchidaceae Perrierianae, a description of all then known species of Orchids from Madagascar, including 332 new species based upon material supplied by...

Balanophora coralliformis: A new species of parasitic plant from Luzon Island in the Philippines.                                                          Balanophoras, Balanophoraceae, are parasitic plants related to Sandlewoods and Mistletoes found in...

A new species of parasitic Orchid from Takeshima Island, Japan.

Orchids of the genus Gastrodia are found across temperate and tropical Asia, Oceania and Madagascar. They are mycoheterotrophs; parasitic plants which obtain nutrients and sugars from Mycorrhizal Fungi (Fungi which normally form symbiotic...

 

 

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Cleanup underway after sewage spill in Bellingham, Washington.

A cleanup operation is underway after about 1 140 000 liters of sewage was spilt into Padden Creek in the south of Bellingham in Whatcom County, Washington, on Tuesday 23-Thursday 25 February 2016. The spill occured during work to replace sewer pipes in the area, and was shut off as soon as it was discovered. Acces to an are of the creek between Seventeenth Street and Padden Lagoon has been shut off.

A sign warning of the dangers of spilt sewage on Padden Creek on Friday 26 February 2016. Philip Dwyer/The Bellingham Herald.

As well as the obvious dangers to health presented by sewage, which is likely to contain a variety of Bacteria and other micro-organisms harmful to Human health, sewage provides a source of nutrients which can lead to eutrophication and the rapid growth of blooms of Algae, Bacteria or other micro-organisms, which absorb oxygen from the water leading Fish and other aquatic organisms to asphyxiate.

Paddne Creek was culvertized (covered and channeled through a concrete culvert) in the late nineteenth century) but has recently undergone restoration work intended to return it to a natural state, both to improve the local habitat and to provide a run for Salmon and Trout, which historically used the creek to access Padden Lake and the waterways which supply it. Officials involved in the project have describes the spill as 'disheartening'.

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Widespread lead poisonng prompts city of Flint, Michigan, to declare a state of emergnecy.                                                   The City of Flint, in Genesee County, Michigan, has declared a stare of emergency, following an outbreak of lead poisoning in the city. Mayor Karen Weaver...

Dairy wastewater spill kills hundreds of Fish in Alabama creek.                                            A spill of dairy wastewater has killed several hundred Fish in the Shades Creek at Homewood, Alabama, close to West Homewood Park, on Monday 19 October 2015. The comprised about 380 liters of wastewater from the Mayfield Creamery, which turned the creek a...

Cryptosporidium discovery at water treatment plant leaves around 300 000 without drinkable water in Lancashire, England.                                                   Around 300 000 homes were left without drinkable...

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Eruption on Mount Sinabung.

Residents of villages close to Mount Sinabung on North Sumatra have been forced to evacuate their homes following two eruptions on the volcano on Thursday 25 February 2016. The first eruption occured at about 6.45 pm the second slightly after 11.20 pm. Both produced ash columns reaching about 2 km above the summit of the mountain, and threw hot ash and lava up to 500 m from the crater.

An ash column over Mount Sinabung on 25 February 2016. Dedi Sahputra/SAPO.

Mount Sinabung, a 2460 m stratovolcano (cone shaped volcano made up of layers of ash and lava) in the Karo Regency; it is potentially a very dangerous volcano, as a large number of people live in its immediate vicinity. The last major eruption prior to the twenty-first century happened in about 1600, with small eruptions occurring in 1889 and 1912. However the volcano returned to life in late August 2010, erupting throughout September and causing about 12 000 people to flee their homes.

 

 The location of Mount Sinabung. Google Maps.

 

The Indo-Australian Plate, which underlies the Indian Ocean to the west of Sumatra, is being subducted beneath the Sunda Plate, a breakaway part of the Eurasian Plate which underlies Sumatra and neighboring Java, along the Sunda Trench, passing under Sumatra, where friction between the two plates can cause Earthquakes. As the Indo-Australian Plate sinks further into the Earth it is partially melted and some of the melted material rises through the overlying Sunda Plate as magma, fueling the volcanoes of Sumatra.

 

 The Subduction zone beneath Sumatra. NASA/Earth Observatory.

 

This does not happen at a 90° angle, as occurs in the subduction zones along the western margins of North and South America, but at a steeply oblique angle. This means that as well as the subduction of the Indo-Australian plate beneath the Sunda, the two plates are also moving past one-another. This causes rifting within the plates, as parts of each plate become stuck to the other, and are dragged along in the opposing plate's direction. The most obvious example of this is the Sumatran Fault, which runs the length of Sumatra, with the two halves of the island moving independently of one-another. This fault is the cause of most of the quakes on the island, and most of the island's volcanoes lie on it.

 The movement of the tectonic plates around Sumatra. NASA/Earth Observatory.

 

See also...

 

Thousands of new evacuations from villages around Mount Sinabung, Sumatra.      Authorities on the Indonesian island of Sumatra have begun to evacuate people from four villages to the   south and southeast of Mount Sinabung, an active...

Further evacuations on North Sumatra as Mount Sinabung continues to erupt.             The number of people evacuated from villages around Mount Sinabung, an active volcano on North Sumatra, has risen to around 20 000 following a series of about 50 eruptions over the first... 

Thousands evacuated following series of eruptions on Mount Sinabung, Sumatra.

Over 6300 people have been evacuated following a series of nine eruptions on Mount Sinabung, northern Sumatra, Indonesia on Saturday 23-Sunday 24...

 

 

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Deciphering the rings of 10199 Chariklo.

10199 Chariklo is a Centuar (asteroid or comet-like body found between the orbits of Jupiter and Neptune), which was first discovered in 1997 and subsequently found to be the largest such body, with an estimated diameter of about 300 km. Like other Centaurs it is thought to have originally been a Kuiper Belt Object, i.e. a body orbiting outside Neptune, that was pushed further into the Solar System by an encounter with the planet. In 2014 10199 was discovered to have a system of rings, the first non-planetary mass object to have such a system, though a similar ring system has since been found around another Centaur, Chiron.

In a paper published on the online arXiv database at Cornell University Library on 4 February 2016, Margaret Pan and Yanqin Wu of the Department of Astronomy & Astrophysics at the University of Toronto examine the rings of 10199 Chariklo, in order to determine their properties and try tounderstand their origins.

Artist's impression of 10199 Chariklo. Institute of Astrophysics of Andalusia.

Pan and Wu calculate that 10199 Chariklo has an oblateness of 0.213 (i.e. its equatorial radius is 21.3% larger than its polar radius) and that its equatorial radius is 144.9 km. The body has two known rings, an inner ring with a radius of 390.6 km and a width that varies between 5.5 and 7.1 km, while the outer ring has a radius of 404.8 km and has a width of 3.6 km. Using these measurements combined with the optical depth of the rings (i.e. their transparency, the amount of light they absorb as it passes through them), Pan and Wu calculate that the rings have a total mass of about 10 billion tonnes.

Next Pan and Wu considered possible scenarios for the formation of the rings of 10199 Chariklo. In order to do this it was assumed that the average residency in a Centaur-type orbit is about five million years; Centaurs orbit in an area of the Solar System where they are perturbed by the gravitational influences of the giant planets, and ate therefore thought likely to be disrupted from these orbits in a relatively short time (astronomically speaking). Prior to becoming a Centaur 10199 Chariklo is assumed to have been a Kuiper Belt Object, orbiting outside the orbit of Neptune for about five billion years (i.e. the age of the Solar System). Furthermore Pan and Wu calculate that given the week gravitational pull of 10199 Chariklo, the rings should disperse to the point of no longer being visible within about 500 000 years of their formation, unless they are being constantly replenished from some source. This lifetime could be lengthened if the rings are accompanied by several shepherding satellites (i.e. larger bodies orbiting 10199 Chariklo that excerpt gravitational influences on the rings), however this would require several kilometre sized objects, which are unlikely to have remained undetected.

Firstly Pan and Wu examined the possibility that the rings might have originated while 10199 Chariklo was still within the Kuiper Belt. The most likely cause of ring-formation around a body in the Kuiper Belt would be a collision with a smaller body. Impact events are thought to be extremely rare in the Kuiper Belt (where matter is extremely thinly spread), but over the course of five billion years an object the size of 10199 Chariklo might be expected to undergo several such collisions. However the likelihood of such an event having happened within the last 500 000 years is extremely low, and the likelihood of our having observed two bodies (Chariklo and Chiron) with ring systems caused by collisions in the Kuiper Belt within the last 500 000 years is negligible.

An alternative scenario is that matter could have been removed from the surface of 10199 Chariklo by rotational disruption, however the body currently only rotates on its access roughly once every seven hours, not fast enough to cause such disruption, and there is no reason to believe that it would have rotated significantly faster within the last 500 000 years.

A third possible scenario is that the rings began as a small satellite orbiting 10199 Chariklo while it was in the Kuiper Belt, which was broken up by tidal forces during the encounter with Neptune that pushed it into a Centaur-type orbit. Such small moons are thought likely to be quite common around Kuiper Belt Objects, so this scenario has some plausibility, however in order for rings generated by such an encounter to survive, the object would have to be shifted from a Kuiper Belt orbit to a Centaur orbit in a single encounter with Neptune. Models of such processes suggest that most Kuiper Belt Objects take several close encounters with Neptune to disrupt them into the Solar System, with only a very small percentage being shifted in a single encounter. Again this is just about plausible for a single body, but the presence of two ringed Centaurs suggests that some other factor is at play.

As an alternative Pan and Wu suggest that the rings could be the result of dust being carried from the surface of the body during outgassing events. For the purpose of the study they model outgassing of carbon monoxide, but note that essentially the same processes could apply to outgassing of carbon dioxide, nitrogen, cyanide or other volatile compounds,

Carbon monoxide has a very low sublimation point (point at which it turns directly from a solid to a gas), so that it can be removed from a body even by the gentle warming the Sun provides in the Kuiper Belt. This means that a Kuiper Belt Object orbiting at about 20 AU (20 times as far from the Sun as the Earth) would have lost all of its carbon monoxide over the five billion year history if the Solar System. However a body at 40 AU would only have lost carbon monoxide down from its surface down to a depth of about 1 km,  with more deeply buried carbon monoxide protected from the Sun's heat.

Were such a body moved into a Centaur-type orbit by an encounter with Neptune, then such buried carbon monoxide would be heated to above its sublimation point and degas into space, in the same way as comets (thought to be Kuiper Belt Objects knocked into the Inner Solar System) emit gas and dust to form a coma and tail as they approach the Sun. 10199 Chariklo currently orbits at an average distance of 15.8 AU, at which distance Pan and Wu calculate the body would be warmed through sufficiently for all carbon monoxide to be lost from its interior within 500 000 years. However the body has a highly eccentric orbit, varying from 13.1 to 18.5 AU over an orbital period of 22 915 days, sufficient to provoke distinct seasonality on the surface. This means that even though the interior of the body had warmed sufficiently for carbon monoxide to sublimate, temperature variations at the surface could lead to the gas resolidifying close to the surface during the 'winter' season when it is furthest from the Sun.

 The calculated orbit of 10199 Chariklo. JPL Small Body Database Browser.

This seasonality could lead to a spring on 10199 Chariklo (possibly quite close to perihelion, when the body is at its nearest to the Sun), when the surface could reach a critical temperature and large quantities of accumulated subsurface carbon monoxide could degas over a very short period of time, carrying considerable volumes of dust from the surface. Even if the majority of this dust fell back to the surface a sufficient amount could reach an altitude high enough to remain in orbit to create at least a temporary orbit, creating at least a temporary ring system. Crucially such a series of events would slow down the rate at which carbon monoxide is lost from 10199 Chariklo, so that instead of a slow degasing over 500 000 years, a series of interrupted degasing events could go on for several million years.

See also...

Molecular oxygen in the coma of Comet 67P/Churymov-Gerasimenko.                             In recent years studies of the comas of numerous active comets (the coma of an active comet is the gas and dust envelope which surrounds it; this is not a true atmosphere as it is continuously replenished by...

Sinkholes on Comet 67P/Churyumov-Gerasimenko.

Many comets have been observed to have pitted surfaces. Initially these pits were thought to be the result of collisions with smaller bodies, as with craters on planets and moons, but they have been shown to be far to numerous for this to be the case, as...

Emissions from Comet C/2002 VQ94 (LINEAR).                                                C/2002 VQ94 (LINEAR) was discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) team at the...

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Boreonykus certekorum: A new species of Velociraptorine Dromaeosaur from the Late Cretaceous of west-cemtral Alberta.

Dromaeosaurs are thought to have been the group of Theropod Dinosaurs most closely related to birds, making them of great interest to palaeontologists. They were smal-to-medium sized predatory Dinosaurs, which all appear to have had extensive featheres plumage, and some forms are believed to have evolved flight independently of the Birds. However most species appear to have been fast running ground predators likely to have brought down prey with the enlarged claws on their second toes,claws which give the group their popular name 'Raptors' ('Raptor' means claw in Latin, and also serves to highlight their similarity to Birds, as Birds of Prey are also known as 'Raptors', while 'Dromaeosaur' derives from Greek and means 'Running Lizard'). Dromaeosaurs appear to have been present on every continent rom the Middle Jurassic to the end of the Cretaceous, and as mostly small animals are thought likely to have had high rates of species turnover, howver their small size and fragile skeletons mean that specimens are rare, and generally cosist of either fragmentary bones or isolated teeth or claws, making studies of the groups true diversity and range difficult.

In a paper published in the Journal of Vertebrate Paleontology on  18 December 2015, Phil Bell of the School of Environmental and Rural Science at the University of New England and Philip Currie of the Department of Biological Sciences at the University of Alberta describe a new species of Dromaeosuaur from the Late Cretaceous Pipestone Creek Bonebed (part of the Wapati Formation) near Grand Prairie in west-central Alberta.

The new species is named Boreonykus certekorum, where 'Boreonykus' means 'Boreal Claw' in reference to the Boreal Forests that cover the area where it was found ('onykus' is Greek for 'claw') and 'certekorum' honours Certek Heating Solutions and the Barendregt family for their support of palaeontology in the Peace region of western Canada.

The species is described from fragmentary material found in a bonebed comprising largely bones of the Ceratopsid Pachyrhinosaurus lakustai, but with material from other species present. The material, which is nt thought to come from a single individual, comprises a right frontal bone (i.e. the bone that would form the right half of the forehead in a Human), two claws, one from the right hand and one from the left foot, a caudal (tail) vertebra and a number of fragmentary teeth.

Boreonykus certekorum, left pedal ungual II-3. (A) Lateral and (B) medial views. Bell & Currie (2015).

Boreonykus certekorum is considered to be a member of the Velociraptorinae, a group of Dromaeosuars largely know from Asia, expanding our knowledge of North American members of this group. The identification of this material as represnting a new and distinct species also adds to the emerging picture of a distictive fauna being present in west-central Alberta in the Late Cretaceous, distinct from the faunas of southern Alberta and Montana to the south or Alaska to the west, but forming a conection between them.

See also...

Partial Dromaeosaur remains from the Early Cretaceous of Inner Mongolia.          Dromaeosaurs are thought to have been the Dinosaur group most closely related to the earliest Birds, making them of great interest to palaeontologists...

Dakotaraptor steini: A giant, feathered Dromaeosaurid from the End Cretaceous Hell Creek Formation of South Dakota. Dromaeosaurids were first described in the 1920s, but received relatively little attention from palaeontologists until the late 1960s. However in recent years it has been realized that the group were...

Zhenyuanlong suni: A large feathered Dromaeosaur from the Jehol Biota. Dromaeosaurid Dinosaurs are among the closest non-Avian relatives of the Birds and show many similarities to the earliest members of that group, making understanding Dromaeosaurs important for understanding the origin of Birds. In particular...

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Asteroid 2016 DB passes the Earth.

Asteroid 2016 DB passed by the Earth at a distance of 123 900 km (0.32 times the average distance between the Earth and the Moon, or 0.08% of the average distance between the Earth and the Sun; 103 900 km above the orbit at which the satellites supporting GPS systems operate), at about 4.50 am GMT on Monday 15 February 2016. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2016 DB has an estimated equivalent diameter of 3-12 m (i.e. it is estimated that a spherical object with the same volume would be 3-12  m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere more than 60 km above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of  2016 DB. JPL Small Body Database.
 

2016 DB was discovered on 16 February 2016 (the day after its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2016 DB implies that it was the second asteroid (asteroid B) discovered in the second half of February 2016 (period 2016 D).

2016 DB has a 313 day orbital period, with an elliptical orbit tilted at an angle of 1.53° to the plain of the Solar System which takes in to 0.61 AU from the Sun (61% of the distance at which the Earth orbits the Sun and considerably inside the orbit of the planet Venus) and out to 1.20 AU (20% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in May 2011 and the next predicted in September this year. 2016 DB also has frequent close encounters with the planet Venus, with the last thought to have occurred in September 2010 and the next predicted for Sepember 2017. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2016 DB spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. 

See also...

Fireball seen over southern France and northern Italy.                                                   A bright fireball was seen over much of southeast France and northern Italy at about 6.20 pm local time on Wednesday 17...

Asteroid 2016 CG18 passes the Earth.   Asteroid 2016 CG18 passed by the Earth at a distance of 151 400 km (0.39 times the average distance between the Earth and the Moon, or 0.10% of the average distance between the Earth and the Sun; 131 400 km above the orbit at which the satellites...

Meteorite unlikely to have killed man in Tamil Nadu.                                                          Indian newspaper The Hindu carried a report on Sunday 7 February 2016 in which the death of a man and injury of three other people as well as causing damage to several nearby buildings at the campus of a college in Vellore, Tamil Nadu, were described as...

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