Wednesday, 23 October 2019

The Leonis Minorid Meteor Shower.

The Leonis Minorid Meteor Shower is visible between 14 and 27 October each year, with peak activity due on the night of Thursday 24 October 2019, when 1-2 meteors per hour may be visible in the Northern Hemisphere. The shower takes its name from the constellation of Leo Minor (to the north of Leo), from which the meteors appear to radiate. The Leonis Minorid Meteor Shower is generally easier to spot in the Northern Hemisphere than the Southern, though it is possible to see the meteors from anywhere on Earth. Although the number of meteors is low, the individual meteors tend to be quite bright, which, combined with the fact that the shower will peak after the Last Quater Moon on 21 October, should make for a reasonable chance of seeing a meteor for anyone with the patience, with optimum viewing accruing just before dawn.

The Radiant Point of the Leonis Minorid Meteors. Modified from Dominic Ford/Map of the Constelations/In The Sky.

Meteor streams are thought to come from dust shed by comets as they come close to the Sun and their icy surfaces begin to evaporate away. Although the dust is separated from the comet, it continues to orbit the Sun on roughly the same orbital path, creating a visible meteor shower when the Earth crosses that path, and flecks of dust burn in the upper atmosphere, due to friction with the atmosphere.The Leonis Minorid Meteor Shower is caused by the Earth passing through the trail of the Comet C/1739 K1, and encountering dust from the trail of this comet. The dust particles strike the atmosphere at speeds of about 223 200 km per hour, burning up in the upper atmosphere and producing a light show in the process.  

The orbital trajectory and current position of C/1739 K1. JPL Small Body Database.

Comet C/1739 K1 was discovered on 28 May 1739 by Italian astronomer Eustachio Zanotti. Its name implies that it was the first comet discovered in the second half of May 1739 (period 1739 K). Unlike most comets it does not have the name of its discoverer appended to the end of the name, as this convention had not been invented in 1739.

C/1739 K1  is a Parabolic Comet, which is to say a comet that was disrupted from an orbit in the Oort Cloud, and passed through the Inner Solar System on a parabolic orbit that will probably not bring it back again. This parabolic trajectory tilted at an angle of 124° to the plain of the Solar System, that brought it in to 0.67 AU from the Sun at perihelion (i.e. 0.67 times as far from the Sun as the planet Earth, slightly inside the orbit of the planet Venus) in 1739. It is now 240 AU from the Sun, eight times as far as the planet Neptune, considerably beyond the Kuiper Belt (which extends to about 50 AU from the Sun), but still not as far as the Oort Cloud (which starts at about 2000 AU from the Sun).

See also...

http://sciencythoughts.blogspot.com/2019/10/the-orionid-meteor-shower.htmlhttp://sciencythoughts.blogspot.com/2019/10/the-epsilon-geminid-meteor-shower.html
https://sciencythoughts.blogspot.com/2019/10/bright-fireball-meteor-over-northeast.htmlhttps://sciencythoughts.blogspot.com/2019/10/the-delta-aurigid-meteors.html
https://sciencythoughts.blogspot.com/2019/10/the-southern-taurid-meteor-shower.htmlhttps://sciencythoughts.blogspot.com/2019/10/costa-rican-mud-meterorite-acquired-by.html
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Tourist badly injured in Shark attack in French Polynesia.

A tourist has been severely injured in a Shark attack off the island of Moorea in French Polynesia. The 35-year-old woman, described as a French Citizen, was attacked by the Shark while taking part in a diving trip to see Dolphins in the ocean outside the island's lagoon, when she was attacked by the Shark, believed to have been an Oceanic Whitetip, Carcharhinus longimanus,  at about 10 am local time on Monday 21 October 2019. The woman is reported to have lost both hands at the wrist and a breast in the attack. She was given first aid by a nurse and firefighters at a hotel on Moorea, before being airlifted to a hospital on Tahiti.

An Oceanic Whitetip Shark, Carcharhinus longimanus, off the Elphinstone Reef on the Red Sea coast of Egypt accompanied by Pilot Fish, Naucrates ductor. Thomas Ehrensperger/Wikimedia Commons.

Oceanic Whitetip Sharks are notoriously vicious, and are the species most commonly associated with attacks on shipwreck victims. They are generally slow moving, but are capable of busts of speed, and will tend to hover near potential prey in packs, waiting for an opportunity for a sudden lunge attack. However as an oceanic Shark they are seldom encountered close to shore, so attacks by them are uncommon in the twenty first century, when most Shark attacks involve sea-bathing tourists in inshore waters rather than ship-wrecked sailors on the high seas. 

Once one of the most abundant large Sharks, Oceanic Whitetips are now considered to be Vulnerable
under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species, due to overfishing, with the population in the northwest and west-central Atlantic considered to be Critically Endangered. The species is protected in the United States and New Zealand, and listed on Appendix II of the Convention on the International Trade in Endangered Species (CITES), which forbids the trade in the species or its bodyparts without a permit issued by an appropriate government department.

See also...

https://sciencythoughts.blogspot.com/2019/08/sharks-and-rays-from-eocene-of.htmlhttps://sciencythoughts.blogspot.com/2019/06/mollisquama-mississippiensis-new.html
https://sciencythoughts.blogspot.com/2019/06/american-tourist-killed-in-shark-attack.htmlhttps://sciencythoughts.blogspot.com/2019/06/icelandic-fishermen-fired-for-cruelty.html
https://sciencythoughts.blogspot.com/2019/06/teenager-injured-by-shark-in-north.htmlhttps://1.bp.blogspot.com/-e4PiM56eG4E/XRktRJIbgZI/AAAAAAABMJ0/k4dcJSzJBX0EyIzCLXE3R-cfubeqzUNkwCLcBGAs/s200/Sphyrna%2Bmokarran%2BPregnant%2BGreat%2BHammerhead%2Bfound%2Bdead%2Bon%2BCaptiva%2BIsland%252C%2BFlorida..png
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Tuesday, 22 October 2019

Palaeopathology in a Permian Varanopid.

Bone remodelling is an essential physiological process in growth and healing, and deviations from normal bone physiology in the form of pathologies aid in the understanding of normal bone metabolism. The study of such pathologies in the fossil record therefore offers insight into the biology of extinct groups, and the evolutionary history of groups alive today.

In a paper published in the journal PLoS One on 7 August 2019, Yara Haridy and Florian Witzmann of the Museum für Naturkunde at the Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Patrick Asbach of the Institut für Radiologie at the  Charité-Universitätsmedizin Berlin, and Robert  Reisz of the Dinosaur Evolution Research Centre at Jilin University, and the Department of Biology at the University of Toronto Mississauga, discuss an example of a pathological condition in a Varanopid from the Early Permian Richards Spur deposits.

The Early Permian Richards Spur locality at the Dolese Brothers Quarry in Oklahoma preserve one of the most diverse assemblages of terrestrial vertebrates known from any Permian site. The remains are preserved in fissure deposits within the Ordovician Arbuckle Limestone, in a unique depositional environment that has been interpreted as cave systems that underwent periods of flooding not unlike present-day conditions that are commonly associated with monsoonal episodes, preserving an upland biota that is seldom recorded in the fossil record. The fissure fill sediments are early Permian (about 289 million years old) and consist of soft clays and mudstone. They contain articulated specimens or isolated bones of mostly small to medium sized terrestrial Tetrapods.

Varanopids are generally considered to be early Synapsids related to Pelycosaurs (although an alternative suggestion, that they are early Diapsids, has recently been made by Ford and Benson). Varanopids range from the latest Carboniferous to the latest Middle Permian with a broad geographic distribution in Pangea. They were small to medium-sized (1.5 - 2m total body length) predators, superficially resembling extant Varanids (Monitor Lizards) in their habits.

Haridy et al. describe two pathologically fused caudal (tail) vertebrae of an undescribed Varanopid based on outer morphology and the internal microstructure as revealed by X-ray microtomography. The collective anteroposterior length (front to back length) of the fused vertebrae is 23 mm. Taking the midpoint of the ventral fusion zone between the centra (disks) as the boundary between the two elements, the anterior vertebra has a length of 11 mm and the posterior one of 12 mm. The vertebrae can be assigned to Varanopidae based on the proportionally elongate, slender vertebral bodies with a small perforating foramen in the mid-portion of the centrum and the double keelation on the ventral surface. In addition, the neural arches are slender and slightly concave, and the neural spines are delicate, and posterodorsally slanted.

The two vertebral centra are completely fused to one another without any superficial trace of an intervertebral suture, the proximal part of a haemapophyses (part of the bony arch on the ventral side of a tail vertebra) is fused to the posteroventral margin (back) of the anterior centrum and to the anteroventral margin (front) of the posterior centrum. The proximal part of another haemapophysis is fused to the anteroventral margin of the anterior vertebra. The neural arches are completely fused to the centra such that there is no evidence of a neurocentral suture. The fusion zone between the centra protrudes outwardly and forms a large swelling of bone on the right side. In ventral view, the proximal part of the haemapophyses is visible and shows a left/right-asymmetry in the bases of their paired ventral processes; the base of the right process is larger than the left one and extends further anteriorly. In both haemapophyses, the ventral processes are broken off.

On the right dorsolateral surface of the neural arch, a small osseous (bony) growth is present at about the mid-length of the anterior vertebra. The abnormal growth is penetrated by several small foramina (openings) on its dorsal side and has a distinct concavity (indentation) on its posterior part. The pre- and postzygapophysis (articular processes of the neural arch of a vertebra) are fused, but the boundary between them is still discernible. The right postzygapophysis of the anterior vertebra is enlarged as compared to the left one, corresponding to the swelling of the centra in the fusion zone and the larger base of the haemapophyses on the right side. Accordingly, the right prezygapophysis is also larger than the left one in the posterior vertebra. Apart from the zygapophyses, the dorsal side of the neural arch of the posterior vertebra seems to be pathologically unaltered, whereas the dorsal side of the neural arch of the anterior vertebra bears many irregular depressions and crests.

The bone surface is irregular on the left side of the centra, there are irregular grooves, depressions and crests on the right side, sometimes resembling the imprints of large vessels. The bone surface, however, is always smooth with some nutrient foramina penetrating the bone. The right intervertebral foramen for the spinal nerve root between the anterior and posterior vertebra is largely filled with bone; only two smaller openings of unequal size are present in the depression that represents the original foramen. From the larger of these openings, a shallow groove extends in a dorsal direction. In contrast, the intervertebral foramen on the right side is open but slightly constricted by bone growth on the anteroventral margin. A smaller opening is located ventrally on the lateral side of the swollen fusion zone of the centra, also showing a shallow groove running dorsally from the opening. The posterior edge of the posterior vertebra shows that at least the anterior margin of the intervertebral foramen between this and the posteriorly following vertebra was unaltered. The exposed (not fused) anterior and posterior articulation surfaces of the vertebral centra are concave and have a roughened, unfinished surface indicative of a cartilage cover in life. They are round in outline in anterior and posterior view, respectively, and have a centrally located, large notochordal canal. These joint surfaces were not pathologically altered. The opening of the neural canal is well preserved on the anterior face of the anterior vertebra. It is broad ovate in outline, measuring 2.5 mm in width and 1.5 mm in height, and is not constricted by pathological bone growth.

External anatomy of a pathological Varanopid vertebrae. (a) schematic of Varanopid tail with a normal vertebrae used for comparison represented in blue, and the pathological fused vertebrae presented in orange.; (b)-(f) right lateral, left lateral, dorsal, ventral, and anterior views respectively. Abbreviations: as, articular surface; fz, fusion zone; gn, growth nodule; hp, haemapophyses; irg, irregular groove; ivf, intervertebral foramen; na, neural arch; nc, neural canal; ntc, notochordal canal; poz, postzygapophysis fused; vph, ventral processes of haemapophyses. Scale bar is 5mm. Haridy et al. (2019).

The X-ray microtomography scans of the pathological fused vertebrae show that the smooth exterior of the vertebrae did not indicate the extreme pathology that lay beneath the surface. The notochordal canal and the neural canal remain open and unobstructed in longitudinal and cross sections. However, the notochordal canal maintains a consistent diameter throughout both vertebrae, which is unlike the unaffected vertebrae in which the notochordal canal has a wider diameter towards the anterior and posterior ends. The cross-sectional outline of the neural canal is broad-ovate to reniform in the anterior and posterior regions of each vertebra. In the middle of the vertebra, it becomes nearly circular in cross section, as in the normal vertebra. In sagittal section, the neural canal expands at the boundary of the two vertebrae. The intervertebral space is almost absent and restricted to a very thin gap.

The X-ray microtomography scansreveal in great detail the structure of the external cortical compact bone and of the inner trabecular bone of centra and neural arches. The original outer cortex of the vertebrae has been extensively altered through resorption and by addition of bone, and secondary formation of trabecular bone and cortical bone outside the original vertebral cortex has taken place. The cortical bone that surrounds the vertebrae is thickened, and there is a distinguishable difference between the old cortical bone that made up the original surface and the new cortical bone that covers the old cortex. The new cortical bone is denser and thus brighter in the images.

X-ray microtomography internal anatomy of pathological Varanopid vertebrae. (a) Serial cross sections showing the extent of the pathology throughout from most anterior to the posterior the two vertebrae (1)–(12). (b). Closeup of cross section through neural arch showing the old cortical bone overlain by new less dense cortical bone; the wavy line shows the unevenness in the Howship’s lacunae. (c) Closeup of the outward-growth in the fusion zone showing lysis to the old cortical bone and thick erratic trabeculae overlain by a layer of cortical bone. (d) Closeup of the growth node on the second vertebrae’s neural arch, the growth overlays the old cortical bone and has thick trabeculae and large lytic spaces covered by cortical bone. (e) Closeup of the ventral portion of the second vertebrae showing the extent of resorption of old bone and deposition of new pathological bone. Abbreviations: cb, cortical bone; ocb, old cortical bone; nc, neural canal; ntc, notochordal canal. Scale bar is 2mm. Haridy et al. (2019).

The old cortical bone of the centrum and neural arch is covered in Howship’s lacunae, i.e. resorption bays, which are indicative of extensive osteoclastic activity. In some regions of the centrum, the old cortical bone has been so extensively resorbed that it is either a thin remnant covered in resorption bays or has been completely replaced by thickened trabeculae. The trabecular bone consists of thickened trabeculae in both the centra and the neural arch. Most trabeculae are present in about the anterior and posterior thirds of each vertebra, whereas the middle part is nearly devoid of trabeculae and consists of a large hollow space, as seen in the normal vertebra scans. The osseous bump mentioned above on the right side of the neural arch of the anterior vertebra consists of course trabecular bone with a thin external cortex, the trabecular bone is so pervasive that it continues into the neural arch where the cortical bone has been resorbed and replaced with thickened trabecular bone.

X-ray microtomography internal anatomy of pathological Varanopid vertebrae. (a) Off-centre sagittal section showing the internally altered pathological bone. (b) Closeup of the anterior portion of vertebrae 1 showing thickened trabeculae, lytic lesions and cortical bone thickening. (c) Centered sagittal section showing the notochord is still continuous through the pathological vertebrae, also showing the degree of alteration to the neural arch via lytic lesions; (d) Closeup of the ventral region of the fusion zone, showing old cortical bone, large lytic lesions and cortical thickening. Abbreviations: ct, cortical thickening; ocb, old cortical bone; ll, lytic lesion; nc, neural canal; ntc, notochordal canal; tt, thickened trabeculae. Scale bar is 2mm. Haridy et al. (2019).

Haridy et al. consider a number of possible causes of the pathology seen, including infectious arthritis, spondylitis tuberculosa, ankylosing spondylitis, Scheuermann’s disease, spondylitis ankylosans, vertebral tumor, fracture callus causing the growth and subsequent fusion, osteochondrosis intervertebralis, and chronic osteomyelitis, but only two conditions were found to fit the observed symptoms, fibrous dysplasia and Paget’s disease. Of these, Paget’s disease seems the more likely cause as cases of fibrous dysplasia affecting more than one bone are rare.

The cause of Paget’s disease is unclear, though correlations have been suggested between cases of the disease and wood-fired heating, tobacco smoking, consumption of brains, rural life, and especially contact with farm or wildlife animals. This has led to the suggestion that the disease is linked to a zoonotic Virus (Virus typically found in animals but which can infect Humans under some circumstances), with a combination of infection by the Virus and exposure to certain environmental triggers needed to activate the condition. If this theory is correct, and if it also holds true for the infection seen in the Varanopid, then this would represent the oldest known example of a Viral infection in the fossil record.

See also...

https://sciencythoughts.blogspot.com/2018/03/caudal-autotomy-in-early-permian.htmlhttps://sciencythoughts.blogspot.com/2017/07/australopithecus-africanus-deciphering.html
https://sciencythoughts.blogspot.com/2017/02/odontoma-found-in-late-permian.htmlhttps://sciencythoughts.blogspot.com/2016/09/an-osteogenic-tumour-in-198-million.html
https://sciencythoughts.blogspot.com/2016/08/malignant-osteosarcoma-in-17-million.htmlhttps://sciencythoughts.blogspot.com/2014/01/bone-pathology-in-triassic-phytosaur.html
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Notorious Tiger-poacher arrested in Madhya Pradesh, India.

The Madhya Pradesh Special Taskforce, a police unit set up in 2002 to fight organised crime a terrorism, has captured a notorious Tiger poacher during a raid on a cottage by the Gujarat-Vadodara Highway this week. The Yarlen, 30, also known as Luzalen and Jazrat, went missing in 2014 while facing charges of poaching, after being caught with a Tiger skin. He has reportedly confessed to a number of wildlife crimes, including the death of T13, a female Tiger who went missing in the Pench Tiger Reserve in Madhya Pradesh, while raising two cubs. T13 was last recorded in the reserve by a camera trap on 28 February 2012, her skin was confiscated from a smuggler in Nepal on 12 January 2013. Yarlen is also believed to have confessed to the killing of several other Tigers, and as well as a number of Sloth Bears, Melursus ursinus, which have been found dead in the state with their penises removed. Some news reports have suggested that Yerlan was eating the penises to boost his own sexual prowess, but wildlife authorities suspect him of selling them to smugglers, who will in sell them on for their supposed aphrodisiac purposes.

The poacher Yerlan, 30, arrested in Madhya Pradesh this week after a six year hunt. Opindia.

Tigers are considered to be Endangered under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species, with the Indian subspecies, Panthera tigris tigris, threatened by poaching, loss and fragmentation of habitat, with the result that the total adult Tiger population in India is currently thought to be about 3890 (up from about 1400 in 2006). As such Tigers are heavily protected in India, and those found in possession of Tiger body parts can face severe penalties.

Sloth Bears are considered to be Vulnerable under the terms of the Red List, with a population of no more than 20 000, though the exact population size is unclear, due to the difficulties of surveying a wide-ranging species with large territories. The species is still found in India, Nepal and Sri Lanka, but considered to be extinct in Bangladesh, which once formed part of its range. It may still be present in Bhutan. Sloth Bears are considered to be at risk due to habitat loss and conflict with Humans over resources, as well as active hunting.

See also...

https://sciencythoughts.blogspot.com/2019/09/suspected-poacher-killed-in-shootout.htmlhttps://sciencythoughts.blogspot.com/2019/09/investigation-under-way-after-two-bear.html
https://sciencythoughts.blogspot.com/2019/09/assessing-how-wildlife-attacks-upon.htmlhttps://sciencythoughts.blogspot.com/2019/08/pensioner-killed-by-bear-in-russian-far.html
https://sciencythoughts.blogspot.com/2019/07/villagers-kill-tiger-in-uttar-pradesh.htmlhttps://sciencythoughts.blogspot.com/2019/05/himachal-pradesh-man-arrested-with-two.html
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People warned to keep away from a sinkhole on the Beara Peninsula in County Cork, Ireland,

Cork County Council has issued a warning to people to keep away from a sinkhole that appeared on the  L-8912-0 road to the south of the village of Allihies on the Beara Peninsula in the west of the county over the weekend. The sinkhole is about six metres in diameter, and it is unclear if it is likely to grow further, which has prompted the council to close the road, which is described by locals as 'quite busy'.

Sinkhole on the Beara Peninsula in County Cork that opened up this weekend. Teddy Kelly/Irish Independent.

Sinkholes are generally caused by water eroding soft limestone or unconsolidated deposits from beneath, causing a hole that works its way upwards and eventually opening spectacularly at the surface. Where there are unconsolidated deposits at the surface they can infill from the sides, apparently swallowing objects at the surface, including people, without trace.

The approximate location of the October 2019 Beara Peninsula sinkhole. Google Maps.

On this occasion the sinkhole is thought likely to have been caused by the collapse of a shaft at a former copper mine in the area. The Allihies Copper Mine operated from the early nineteenth century until the late 1950s,  at its peak employing around 1600 people. It is possible that part of the mine has collapsed due to recent wet weather in the area, and Cork County Council has asked the Exploration and Mining Division of the Department of Communications, Climate Action and Environment to carry out a survey of the site. The council is also trying to ascertain who now owns the former mine.

Remaining surface structures at the Allihies Copper Mine. Allihies Copper Mine Museum.

See also...

https://sciencythoughts.blogspot.com/2019/09/warning-issued-to-bathers-after-large.htmlhttps://sciencythoughts.blogspot.com/2018/09/gaelic-football-club-forced-to-close.html
https://sciencythoughts.blogspot.com/2018/09/atlantic-storm-ali-kills-two-in-ireland.htmlhttps://sciencythoughts.blogspot.com/2017/10/measles-outbreak-in-dublin-and-county.html
https://sciencythoughts.blogspot.com/2016/10/selenium-arsenic-and-molybdenum-in.htmlhttps://sciencythoughts.blogspot.com/2016/07/jellyfish-damage-to-farmed-salmon-on.html
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Magnitude 5,4 Earthauke in Hormozgān Province, Iran.

The United States Geological Survey recorded a Magnitude 5.4 Earthquake at a depth of 10.0 km roughly 73 km to the north of the city of Bandar-e Lengeh in Hormozgān Province, Iran, slightly before 2.00 pm local time (slightly before 11.00 am GMT) on Friday 21 October 2019. There are no reports of any damage or casualties associated with this event, but it was felt across much of southern Iran, as well as in Bahrain and the United Arab Emirates.

The location of the 21 October 2019 Hormozgān Province Earthquake. Contour lines show rates of movement during the quake, the red line is a boundary between two tectonic plates, in this case the Arabian and Eurasian plates. USGS.

Iran is situated on the southern margin of the Eurasian Plate. Immediately to the south lies the Arabian Plate, which is being pushed northward by the impact of Africa from the south. This has created a zone of faulting and fold mountains along the southwest coast of the country, known as the Zagros Thrust Belt, while to the northeast of this the geology is dominated by three large tectonic blocks, the Central Iran, Lut and Helmand, which move separately in response to pressure from the south, stretching and compressing the rock layers close to the surface and creating frequent Earthquakes, some of which can be very large.

 The movement of the Arabian Plate and extent of the Zagros Thrust Belt. Rasoul Sorkhabi/Geo ExPro.

To the northeast of this the geology is dominated by three large tectonic blocks, the Central Iran, Lut and Helmand, which move separately in response to pressure from the south, stretching and compressing the rock layers close to the surface and again creating frequent Earthquakes.

The population of Iran is particularly at risk from Earthquakes as, unlike most other Earthquake-prone nations, very few buildings in the country are quake-resistant. The majority of residential buildings in Iran are made of mud-brick, a building material particularly vulnerable to Earthquakes as the bricks often liquefy, trapping people inside and quickly asphyxiating them with dust. This is particularly dangerous at night when the majority of people are inside sleeping.

Section through the Zagros Fold Belt. Sarkarinejad & Azizi (2007).

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.
 
See also...
 
https://sciencythoughts.blogspot.com/2019/10/mirabad-e-emam-qoli-sassanid-era-fire.htmlhttps://sciencythoughts.blogspot.com/2019/05/magnitude-41-earthquake-in-hormozgan.html
https://sciencythoughts.blogspot.com/2019/05/tamarix-humboldtiana-new-species-of.htmlhttps://sciencythoughts.blogspot.com/2019/03/former-footballer-killed-by-landslide.html
https://sciencythoughts.blogspot.com/2018/12/zercon-triangularis-new-species-of.htmlhttps://sciencythoughts.blogspot.com/2018/11/heavy-rains-bring-flooding-to-iran-iraq.html
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Asteroid 2019 UL passes the Earth.

Asteroid 2019 UL passed by the Earth at a distance of about 477 800 km (1.24 times the average  distance between the Earth and the Moon, or 0.31% of the distance between the Earth and the Sun), slightly after 4.15 pm GMT on Wednesday 16 October 2019. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2019 UL has an estimated equivalent diameter of 3-10 m (i.e. it is estimated that a spherical object with the same volume would be 3-10 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 32 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2019 UL. JPL Small Body Database.

2019 UL was discovered on 19 October 2019 (three days before its closest encounter with the Earth) by the University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount Lemmon in the Catalina Mountains north of Tucson. The designation 2019 UL implies that the asteroid was the eleventh object (asteroid L - in numbering asteroids the letters A-Y, excluding I, are assigned numbers from 1 to 24, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 25, A2 = 49, etc., which means that L = 11) discovered in the second half of October 2019 (period 2010 U).

2019 UL has a 282 day orbital period, with an elliptical orbit tilted at an angle of 1.92° to the plain of the Solar System which takes in to 0.67 AU from the Sun (67% of the distance at which the Earth orbits the Sun, and slightly less than the distance at which Venus orbits the Sun) and out to 1.01 AU (1% 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 November 2016 and the next predicted in October 2022. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2019 UL spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. This also means that the asteroid has occasional close encounters with the planet Venus, with the last calculated to have occurred in December 2017, and the next predicted for December next year.

See also...

https://sciencythoughts.blogspot.com/2019/10/the-orionid-meteor-shower.htmlhttps://sciencythoughts.blogspot.com/2019/10/asteroid-2019-tt1-passes-earth.html
http://sciencythoughts.blogspot.com/2019/10/comet-c2018-n2-asassn-makes-its-closest.htmlhttp://sciencythoughts.blogspot.com/2019/10/the-epsilon-geminid-meteor-shower.html
http://sciencythoughts.blogspot.com/2019/10/asteroid-2018-eb-passes-earth.htmlhttps://sciencythoughts.blogspot.com/2019/10/asteroid-2019-tw1-passes-earth.html
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