Wednesday 29 April 2020

Trans-Neptunian Object A/2019 K6 (PANSTARRS) makes its closest approach to the Earth.

Trans-Neptunian Object A/2019 K6 (PANSTARRS) will make its closest approach to the Earth on Friday 1 May 2020, reaching a distance of 2.93 AU from the Earth (293% of the distance between the Earth and the Sun, or 438 322 000 km). At this distance the comet will be not naked eye visible, having a magnitude of 13.6, (roughly the same as Uranus' moon Titania), in the Constellation of Libra, which is better observed from the Southern Hemisphere at this time of year.

A/2019 K6 (PANSTARRS) imaged from the Brixiis Observatory in Kruibeke, Belgium on 27 June 2019. Composite image made up of 30 two minute exposures. The A/2019 K6 is the point at the centre of the image indicated by the two lines, the more elongate objects are stars that have moved over the course of the exposure. Erik Bryssinck/Seiichi Yoshida's Comet Page.

A/2019 K6 (PANSTARRS) was discovered on 31 May 2019 by the University of Hawaii's PANSTARRS telescope. The name C/2016 M1 (PANSTARRS) implies that it is an asteroid (A/) (the body is on a comet-like orbit, but has shown no sign of cometary activity), that it was the sixth comet'like body (comet 6) discovered in the second half of May 2019 (period 2019 K) and that it was discovered by the PANSTARRS telescope.

The orbit and current position of A/2019 K6 (PANSTARRS). In The Sky.

A/2019 K6 (PANSTARRS) has an estimated orbital period of 61 602 years and a highly eccentric orbit tilted at an angle of 132° to the plain of the Solar System, that brings it to 3.93 AU from the Sun at perihelion (393% of the distance between the Earth and the Sun; between the orbits of the planets Mars and Jupiter); to 3116 AU from the Sun at aphelion (3116 times as far from the Sun as the Earth or 103 times as far from the Sun as the planet Neptune), between the outer Kuiper Belt and the inner Oort Cloud. As an object which spends most of its time outside of the orbit of the planet Neptune, and shows no sign of cometary activity when at perihelion, A/2019 K6 (PANSTARRS) is classified as a Trans-Neptunian Object.

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Avalanche kills skier on Mount Emmons, Colorado.

A skier has died after being caught in an avalanche at an altitude of about 3110 m above sealevel on the northeast slope of Mount Emmons, a 3780 m ridge mountain to the east of Crested Butte in the Elk Mountain Range (part of the Rocky Mountains) in Gunnison County, Colorado, on Tuesday 28 April 2020. The skier, a 40-year-old man whose identity has not been released, but who has been described as being local and highly experienced, was part of a group of four skiers on the slope, but was the only one caught by the avalanche. He was not buried by the event, and his companions attempted to provide first aid, but he died at the scene.

The approximate location of the 28 April 2020 Mount Emmons avalanche. Colorado Avalanche Information Center.

Avalanches are caused by the mechanical failure of snowpacks; essentially when the weight of the snow above a certain point exceeds the carrying capacity of the snow at that point to support its weight. This can happen for two reasons, because more snow falls upslope, causing the weight to rise, or because snow begins to melt downslope, causing the carrying capacity to fall. Avalanches may also be triggered by other events, such as Earthquakes or rockfalls. Contrary to what is often seen in films and on television, avalanches are not usually triggered by loud noises. Because snow forms layers, with each layer typically occurring due to a different snowfall, and having different physical properties, multiple avalanches can occur at the same spot, with the failure of a weaker layer losing to the loss of the snow above it, but other layers below left in place - to potentially fail later.

 Diagrammatic representation of an avalanche, showing how layering of snow contributes to these events. Expedition Earth.

This is the latest in a series of lethal skiing accidents in Colorado this month, despite pleas from local authorities for people to avoid travelling to the area during the Covid-19 epidemic, in order to free up local emergency services to deal with that crisis.

The location of Mount Emmons, Colorado. Google Maps.

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Canadian city flooded by ice jam.

Around 15 000 residents of the city of Fort McMurray in northeast Alberta, Canada, have been forced to evacuate after the lower part of the town began to flood on Sunday 26 April 2020. The flooding has been caused by ice jams that have formed on the Athabasca and Clearwater rivers, creating a blockage almost 25 km long, resulting in water piling up behind the obstruction to form a dam lake, which has begun to invade the town.

Flooding in Fort McMurry, Alberta, caused by ice jams on the Athabasca and Clearwater rivers. McMurray Aviation.

Ice jams can be a problem in areas where there is a strong seasonal freeze and thaw cycle. They are generally associated with a rapid spring thaw, which can cause many large chunks of ice to be deposited into a river at the same time. When these ice blocks reach an obstruction on the river, such as a narrow or shallow stretch they can become jammed together, forming a blockage. These blockages cause flooding in two ways; firstly by creating a dam lake behind them, and secondly (and more dangerously) by suddenly giving way, allowing all the water piled up behind them to escape at once, and causing a flash flood downstream. Although generally associated with the spring thaw, ice jams can also occur at the onset of the winter freeze, if an unseasonal warm spell causes a sudden thawing.

An ice jam on the Athabasca River in Alberta, Canada, on 26 April 2020. Vincent McDermott/Fort McMurray Today/Postmedia Network.

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Landlide kills three workers at a quarry in Odisha State, India.

Three workers, including two women, have died following a landslide at a quarry near the village of Bhatakamarada in the Ganjam District of Odisha State, India, on Tuesday 28 April 2020. The immediate cause of the landslip is unclear, though the incident is being investigated by the local police, who reportedly believe that the event may have been triggered by severe rain in the area. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.

The approximate location of the Bhatakamarada Quarry. Google Maps.

The areas around Bhatakamarada is home to a number of small quarries extracting rock and sand for the construction industry. These typically operate by blasting the rock with explosives before removing it with hand tools or light machinery. Such mining operations tend to be small scale, locally owned and poorly regulated, with the industry known to have low safety standards and prone to illegal activities such as unlicensed extraction (which usually also implies no outside safety inspections).

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Asteroid 2020 HM6 passes the Earth.

Asteroid 2020 HM6 passed by the Earth at a distance of about 162 900 km (0.42 times the average  distance between the Earth and the Moon, 0.11% of the distance between the Earth and the Sun, or 399 times the distance at which the International Space Station orbots the Earth, and 4.55 times the distance of satellites in geostationary orbits), slightly after 5.50 am GMT on Wednesday 22 April April 2020. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2020 HM6 has an estimated equivalent diameter of 9-29 m (i.e. it is estimated that a spherical object with the same volume would be 9-29 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 32 and 17  km above the ground, with only fragmentary material reaching the Earth's  surface.

The calculated orbit of 2020 HM6. JPL Small Body Database.

2020 HM6 was discovered on 24 April 2020 (two days after 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 2020 HM6 implies that the asteroid was the 156th object (asteroid M6 - 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, so that M6 = (24 x 6) + 12 = 156) discovered in the second half of April 2020 (period 2020 H).

2020 HM6 has a 1119 day (3.06 year) orbital period and an eccentric orbit tilted at an angle of 2.29° to the plane of the Solar System, which takes it from 0.76 AU from the Sun (i.e. 76% of he average distance at which the Earth orbits the Sun) to 3.46 AU from the Sun (i.e. 346% of the average distance at which the Earth orbits the Sun, and more that twice 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 2020 HM6 has occassional close encounters with the Earth, with the next predicted in May 2023.

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