Tuesday, 24 October 2017

Asteroid 2017 TE5 passes the Earth.

Asteroid 2017 TE5 passed by the Earth at a distance of about 513 850 km (1.34 times the average distance between the Earth and the Moon, or 0.34% of the distance between the Earth and the Sun), slightly before 11.10 am GMT on Tuesday 17 October 2017. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2017 TE5 has an estimated equivalent diameter of 12-38 m (i.e. it is estimated that a spherical object with the same volume would be 12-38 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 between 30 and 12 km above the ground, with only fragmentary material reaching the Earth's surface.

 Image of 2017 TE50 taken on 17 October 2017 from Ceccano in Italy with the Elena Telescope. The asteroid is the point in the centre of the picture. The longer lines are stars, their elongation being caused by the telescope tracking the asteroid over the length of the exposure, in this case three 90 second exposures, giving each star a triple line. Gianluca Masi/Virtual Telescope.

2017 TE5 was discovered on 14 October 2017 (three days before 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 2017 TE5 implies that it was the 130th asteroid (asteroid E5) discovered in the first half of October 2017 (period 2017 T).
The calculated orbit of 2017 TE5. Minor Planet Center.

2017 TE5 has an 899 day orbital period and an eccentric orbit tilted at an angle of 10.3° to the plane of the Solar System, which takes it from 0.92 AU from the Sun (i.e. 92% of he average distance at which the Earth orbits the Sun) to 2.73 AU from the Sun (i.e. 273% of the average distance at which the Earth orbits the Sun, considerably more than the distance at which the planet Mars orbits the Sun). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). This means that the asteroid has occasional close encounters with the Earth, with the last thought to have happened in January 2013.

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Monday, 23 October 2017

Seven dead in Thailand flooding.

Seven people have died in flooding in northern Thailand since 10 October 2017, as the country has suffered its heaviest rains for thirty years, with 214 mm of rain falling on Bangkok in a single night this weekend (more than two thirds of the rain that would usually be expected to fall on the city in the entire of October). In order to protect the city, authorities have restricted the outflow of water from the Chao Phraya Barrage, leading to flooding in communities behind the dam; this comes after a decision to increase the outflow from the dam earlier this month that resulted in flooding in communities downstream of the dam, an operation which cannot be repeated without effecting the city, as high rain levels have prevented the floods from subsiding.

An earth barrage in the Khok Samrong district of Lop Buri Province that gave way on Tuesday 17 October 2017, causing flooding in villages downstream. Thia Visa.

Thailand has a tropical climate, with a monsoon season that usually lasts from June to October. Typically September produces the highest rainfall, with the rains trailing off in October. However, as with other countries in Southeast Asia this year, the rains have been exceptionally heavy this year, so that reservoirs and barrages have filled to capacity by the beginning of October, and the rains have persisted longer, pushing water storage systems beyond their capacity.

Flooding in the Sapphaya District of Chai Nat Province, caused by a discharge of water from the Chao Phraya Barrage earlier this month. Chudet Sihawong/The Straits Times.
Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate. This situation is particularly intense in South Asia, due to the presence of the Himalayas. High mountain ranges tend to force winds hitting them upwards, which amplifies the South Asian Summer Monsoon, with higher winds leading to more upward air movement, thus drawing in further air from the sea. 

Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.

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Bombus trophonius: A new species of Bumble Bee from the Czech Republic.

Bumble Bees, Bombini, are one of the most familiar groups of Bees, Apidae, in temperate regions, being large, robust, solitary, social or parasitic Bees (the parasitic Bumble Bees are brood parasites, that lay their eggs in the nests of other Bee species, like Cuckoos) covered with dense fur, found on every continent except Africa and Australia. They are thought to have derived from their nearest ancestors in the Late Cretaceous, although all 263 described living species appear to have derived from a more recent common ancestor and are all placed in a single genus, Bombus, leaving a long stem lineage (i.e. Bees more closely related to modern Bumble Bees than they are to any other group of Bees, but less closely related to them than any living Bumble Bee is to any other living Bumble Bee). However the fossil record of Bumble Bees is somewhat sparse compared to other Bee groups, with two Late Eocene species known, from Teller County in Colorado and the Isle of Wight in England, and one Late Miocene specimen known from Catalonia, Spain, this last specimen being the oldest species assigned to the living genus Bombus.

In a paper published in the journal ZooKeys on 19 October 2017, Jakub Prokop of the Department of Zoology at Charles University, Manuel Dehon and Denis Michez of the Laboratory of Zoology at the University of Mons, and Michael Engel of the Division of Entomology at the Natural History Museum, and Department of Ecology & Evolutionary Biology of the University of Kansas and Division of Invertebrate Zoology at the American Museum of Natural History, describe a new species of Bumble Bee from the Early Eocene Most Formation of Teplice District in the Czech Republic.

The fossils of the Most Formation has been studies since the nineteenth century, and are noted for their high quality Plant and Insect fossils, with Ants being the most abundant group. The fossils occur in a lucastrine (lake derived) clay, laid down a subtropical to temperate climate.

The new species is placed within the genus Bombus, making it both the oldest known Bumble Bee and the oldest member of the crown group, and given the specific name trophonius, in reference to the Greek hero Trophonius, who died in a cave while hiding with stolen treasure, was lost and forgotten, and was rediscovered and worshipped as a demigod after a boy followed a trail of Bees to his final resting place. The species is described from a single female specimen, preserved as a black film, with a forewing length of 14.6 mm.

Photograph of Bombus trophonius, from the Early Miocene of Bílina Mine in northern Bohemia, Czech Republic. Prokop et al. (2017).

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Magnitude 5.4 Earthquake in Batangas Province, the Philippines.

The United States Geological Survey recorded a Magnitude 5.4 Earthquake at a depth of 198 km beneath Batangas Province on southwestern Luzon Island, the Philippines, slightly after 10.20 pm local time (slightly after 2.20 pm GMT) on Sunday 22 October 2017. There are no reports of any damage or injuries associated with this event, though it was felt across much of the southwestern part of Luzon. This is typical for such large deep earthquakes; releases of energy that would be deadly close to the surface have spread over a wide area before reaching ground level, so that they are felt over a wide area but not particularly dangerous.

The approximate location of the 22 October 2017 Luzon Earthquake. USGS.

The geology of the Philippines is complex, with the majority of the islands located on the east of the Sunda Plate. To the east of this lies the Philippine Sea plate, which is being subducted beneath the Sunda Plate (a breakaway part of the Eurasian Plate); further east, in the Mariana Islands, the Pacific Plate is being subducted beneath the Philippine Sea Plate. This is not a smooth process, and the rocks of the tectonic plates frequently stick together before eventually being broken apart by the rising pressure, leading to Earthquakes in the process.

Subduction beneath the Philippines. Yves Descatoire/Singapore Earth Observatory.

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.

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Seven workers killed at unlicensed coal mine in Şırnak Province, Turkey.

Seven men have died and another has been seriously injured following a collapse at an unlicensed open pit coal mine in Şırnak Province in southeastern Turkey on Tuesday 17 October 2017. All of the deceased men ate understood to have been pulled from the rubble alive and died later in hospital. The cause of the incident is unclear, but the company that employed the men has claimed they were involved in preparatory work to re-open the mine, which was closed by the General Directorate of Mining Works in 2013 following breaches of health and safety regulations, rather than actual mining.

Rescue operations at a mine in Sirnk Province, Turkey, on 17 October 2017. Associated Press.

The precise cause of the accident is still yet to be determined, though unlicensed mines tend to have poor safety standards. It is possible that the gas in the mine was caused by the miners encountering a pocket of pressurised mine gas within the coal seam, the release of which may also have caused the rockface to partially collapse.

Coal is formed when buried organic material, principally wood, in heated and pressurised, forcing off hydrogen and oxygen (i.e. water) and leaving more-or-less pure carbon. Methane is formed by the decay of organic material within the coal. There is typically little pore-space within coal, but the methane can be trapped in a liquid form under pressure. Some countries have started to extract this gas as a fuel in its own right. When this pressure is released suddenly, as by mining activity, then the methane turns back to a gas, expanding rapidly causing, an explosion. This is a bit like the pressure being released on a carbonated drink; the term 'explosion' does not necessarily imply fire in this context, although as methane is flammable this is quite likely.

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Sunday, 22 October 2017

Outbreak of Marburg Virus thought to have killed at least two in Kween District, Uganda.

Two people have died and two more are sick in an of Marburg Virus, a form of hemorrhagic fever similar to Ebola, in the Kween District of eastern Uganda. The alarm was raised after a 50-year-old woman died in a health clinic on 11 October 2017, of a fever combined with extensive bleeding and diarrhoea. Blood samples collected from the patient were sent for testing, and were confirmed to contain the Marburg Virus on 17 October. An investigation found that the woman's brother had died of a similar fever three weeks earlier, in what is thought to be an almost certain second case of the disease, as the man is known to have been a hunter who operated in an area with caves home to Fruit Bats of the genus Rousettus, the natural hosts of the Virus. 

Artificially coloured SEM image of the Marburg Virus. BSIP/UIG/Getty Images.

Marburg Virus is a form of Filovirus, the group of Bat-infecting RNA Viruses that also includes Ebola. It takes its name from the German city of Marburg, where the first outbreak was recorded in 1967, among workers that had been exposed to infected Monkey tissue, seven of whom died. Despite this European discovery, the Virus is now recognised as being endemic to tropical Africa, where it occasionally spreads from its usual Bat hosts to Human or other Primate hosts, resulting in short-lived but extremely lethal outbreaks.

Zoonotic diseases (diseases in which the pathogen usually infects an animal host, but which occasionally spreads to Humans) can be particularly dangerous, as Humans are not part of their natural life-cycle, with the effect that they are not under evolutionary pressure to keep Human hosts alive in order to perpetuate themselves. Such diseases typically have short duration and a high fatality rate, though epidemics usually burn out quickly.

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Asteroid 2011 UG20 passes the Earth.

Asteroid 2011 UG20 passed by the Earth at a distance of about 10 222 000 km (26.6 times the average distance between the Earth and the Moon, or 6.83% of the distance between the Earth and the Sun), slightly after 7.15 pm GMT on Sunday 15 October 2017. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2011 UG20 has an estimated equivalent diameter of 99-310 m (i.e. it is estimated that a spherical object with the same volume would be 99-310 m in diameter), and an object of this size would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground directly with an explosion that would be 225-88 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater 1-5 km in diameter and devastation on a global scale, as well as climatic effects that would last years or even decades.

The calculated orbit of 2011 UG20. Minor Planet Center.

2011 UG20 was discovered on 18 October 2011 by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2011 UG20 implies that it was the 507th asteroid (asteroid G20) discovered in the second half of October 2011 (period 2011 U).

2011 UG20 has a 436 day orbital period and an eccentric orbit tilted at an angle of 19.0° to the plane of the Solar System, which takes it from 0.35 AU from the Sun (i.e. 35% of he average distance at which the Earth orbits the Sun, somewhat less the distance at which the planet Mercury orbits the Sun) to 1.89 AU from the Sun (i.e. 1.89% of the average distance at which the Earth orbits the Sun, and more distant from the Sun than the planet Mars). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). This means that close encounters between the asteroid and Earth are extremely common, with the last having occurred in June 2014 and the next predicted in May 2020. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2011 UG20 is also classified as a Potentially Hazardous Asteroid.

2011 UG20 also has frequent close encounters with the planets Mercury, which it is thought to have last passed in October 2010, and is next predicted to pass in August 2034, and Venus, which it last came close to in November 2005 and is next predicted to pass in December 2024. Asteroids which make close passes to multiple planets are considered to be in unstable orbits, and are often eventually knocked out of these orbits by these encounters, either being knocked onto a new, more stable orbit, dropped into the Sun, knocked out of the Solar System or occasionally colliding with a planet.

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