Wednesday, 1 December 2021

Total Solar Eclipse to be visible from parts of Antarctica.

A total eclipse of the Sun will be visible from parts of Antarctica on Saturday 4 December 2021, with a partial eclipse visible from other parts of Antarctica, as well as Tierra del Fuego, parts of South Africa, Namibia, Botswana, and Lesotho, as well as Tasmania, and parts of Victoria in Australia. The event will occur between 5.29 pm and 9.37 am GMT, although local start and end times will vary within this window.

 
The path of the 4 December 2021 Solar Eclipse. The total eclipse will be visible along the central dark grey path. A partial eclipse will be visible from the shaded areas; in the lighters area the full eclipse will not be visible as it will have started before dawn (west) or will continue after sunset (east). The solid red lines are the Equator, the Greenwich Meridian and the International Date Line, the dashed red line is the Tropic of Capricorn. HM Nautical Almanac Office.

Eclipses are a product of the way the Earth, Moon and Sun move about one-another. The Moon orbits the Earth every 28 days, while the Earth orbits the Sun every 365 days, and because the two Sun and Moon appear roughly the same size when seen from Earth, it is quite possible for the Moon to block out the light of the Sun. At first sight this would seem likely to happen every month at the New Moon, when the Moon is on the same side of the Earth as the Sun, and therefore invisible (the Moon produced no light of its own, when we see the Moon, we are seeing reflected sunlight, but this can only happen when we can see parts of the Moon illuminated by the Sun).

 
The relative positions of the Sun, Moon and Earth during a Solar eclipse. Starry Night.

However, the Moon does not orbit in quite the same plane as the Earth orbits the Sun, so the Eclipses only occur when the two orbital planes cross one-another; this typically happens two or three times a year, and always at the New Moon. During Total Eclipses the Moon entirely blocks the light of the Sun, however most Eclipses are Partial, the Moon only partially blocks the light of the Sun.

 
How the differing inclinations of the Earth and Moon's orbits prevent us having an eclipse every 28 days. Starry Skies.

Although the light of the Sun is reduced during an Eclipse, it is still extremely dangerous to look directly at the Sun, and viewing eclipses should not be undertaken without appropriate equipment.

 
Animation showing the shadow of the Moon at five minute intervals on Monday 14 December 2020. Andrew Sinclair/HM Nautical Almanac.

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Tuesday, 30 November 2021

Cremastra saprophytica: A new species of semi-mycoheterotrophic Orchid from Gifu Prefecture, Japan.

Whilst Plants are primarily photosynthetic organisms, a lifestyle retained by the vast majority of species, a few, particularly those living in dark places, have lost this ability, and instead have become parasitic, obtaining nutrients from other organisms. The overwhelming majority of Parasitic Plants are mycoheterotrophs, Plants which parasitise the Mycorrhizal Fungi of other Plants, obtaining nutrients from the Fungi (including those nutrients the Fungi have themselves obtained from other Plants), but not providing the Fungi with anything in return. The evolution of such mycoheterotrophial systems is of great interest to botanists, making Plant groups in which this trait appears to be evolving a focus of study. One such group is the Orchid genus Cremastra, found in the dark understories of temperate forests in the Himalayas and East Asia. The genus Cremastra currently contains five species of Orchid, four of which are leafy, photosynthetic Plants, while the fifth, Cremastra aphylla, from Hokkaido Island, Japan, is a mycoheterotroph which lacks leaves and produces no chlorophyll.

In a paper published in the journal Phytotaxa on 30 November 2021, Kenji Suetsugu of the Department of Biology at Kobe University, describes a new species of Cremastra from Gifu Prefecture in central Honshu, Japan.

The new species is named Cremastra saprophytica, as it is associated with the saprotrophic Fungus Coprinellus disseminates, which obtains nutrients from decaying wood rather than mycorrhizal associations with Plants, apparently making the new species an indirect saprotroph via parasitism of this Fungus.

 
Cremastra saprophytica from the type locality. (A)–(C) Flowering plant. (D) Flower, dorsal view. (E) Flower, lateral view. (F) Flower, front view. Central arrow points to a small smooth callus of lip positioned at the base of midlobe, whereas the other arrows point to the inconspicuous lateral lobes. (G) Fruiting plants. (H) Fruiting body of Coprinellus disseminates, one of the associated fungi of Cremastra saprophytica. Suetsugu (2021).

Unlike Cremastra aphylla, Cremastra saprophytica does produce chlorophyll, although it lacks leaves, and the majority of its nutrition appears to be obtained mycoheterotrophicly. The Plants reach between 28 and 48 cm tall, and produce dark purple, tubular flowers in May and June, followed by green fruiting bodies between June and October. The flowers appear to be entirely self-pollenating, which is a common adaptation in forest understory plants, whose habitat contains few potential pollinators.

 
Cremastra aphylla from Hokkaido. (A) Flowering plant. (B) Flowers; central arrow points to a large verruculose callus of lip positioned at the base of midlobe, whereas the other arrows point to the conspicuous lateral lobes. (C) Close-up of the upper part of the lip and column, lateral view. (D) Close-up of the upper part of the lip, dorsal view. (E) Close-up of the upper part of column and anther cap (lateral and ventral views); arrow points to a large, folded viscidium attached to pollinia. Suetsugu (2021).

Cremastra saprophytica is currently known only from a single location, near the town of Ibigawa in Ibi County.  It can be difficult to determine the distribution or range of Parasitic Plants, as they tend o be small and inconspicuous, and are typically found in dark forest understories or other dimly lit places, producing flowers and fruiting bodies at certain times of year. However, the relatively large size and conspicuous flowers of Cremastra saprophytica make it unlikely that it could be very widespread and have remained overlooked.

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Monday, 29 November 2021

Magnitude 7.5 Earthquake beneath Departamento de Loreto, northern Peru.

The United States Geological Survey recorded a Magnitude 7.5 Earthquake at a depth of 112.5 km, beneath Departamento de Loreto, Peru, slightly after 5.50 pm local time (slightly before 10.50 pm GMT) on Sunday 28 November 2021. There are no reports of any casualties associated with this event, although it is reported to have destroyed 75 homes, and was felt across northern Peru, as well as parts of southern Colombia and western Brazil. This is common with large deep Earthquakes, with the event being felt over a wide area, but relatively little damage, as the energy of the quake is dissipated over a wide area before it reaches the surface.

 
Damage caused by an Earthquake in northern Peru on 28 November 2021. Peru Presidency/Reuters.

Peru is on the west coast of South America and the western margin of the South American Plate, close to where the Nazca Plate, which underlies part of the east Pacific, is being subducted along the Peru-Chile Trench. The Nazca Plate passes under the South American Plate as it sinks into the Earth, this is not a smooth process and the plates repeatedly stick together then break apart as the pressure builds up, causing Earthquakes. As the Nazca Plate sinks further it is partially melted by the friction and the heat of the Earth's interior. Some of this melted material then rises through the overlying South American Plate, fuelling the volcanoes of Peru and neighbouring countries.

 
The approximate location of the 28 November  2021 Departamento de Loreto Earthquake. USGS.

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Fireball meteor over southern California.

The American Meteor Society has received reports of a bright fireball meteor being seen over southern California slightly after 8.10 pm on Wednesday 24 November 2021 Pacific Time (slightly after 4.10 am on Thursday 25 November GMT). Most of the reports came from the California, but sightings were also reported from Arizona. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

 
The 24 November 2021 southern California fireball seen from the city of Corona in Riverside County, California. Tom Harkins/American Meteor Society.
 
Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as an luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).
 
Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society.
 
These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.
 
Witness reports can help astronomers to understand these events. If you witness a fireball-type meteor over the US you can report it to the American Meteor Society here.
 
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Sunday, 28 November 2021

Two tourists killed by landslide on Bali.

Two tourists have died following a landslide near the village of Kedewatan on southern Bali, Indonesia, on Thursday 25 November 2021. The pair, identified as Nuryanti, 36, and Julius Hans Wijaya, 10, both Indonesian nationals, were part of a group of Indonesian and Swedish tourists who had just taken part in a white-water rafting event, when the landslide hit. Both the victims were trapped beneath debris in soft mud; a third victim, 8-year-old Marvel Sanjaya, initially reported missing and feared to have also died, was later found safe. 

 
Rescue workers searching for victims following a landslide on Bali on 25 November 2021. Basarnas Bali/Coconuts.

The event is reported to have happened following a sudden heavy downpour. 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. November marks the onset of the rainy season on Bali, which lasts until April each year, driven by water laden winds from the South China Sea, associated with the Northeast Monsoon in Indonesia and Southeast Asia.

 
The winds that drive the Northeast and Southwest Monsoons in Southeast Asia. Mynewshub.

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