Sunday, 22 April, 2018

Supernova Remnants

Posted on Friday, 30 January, 2015Sunday, 20 August, 2017 by Zheluo Cai

A supernova remnant is the structure resulting from the explosion of a star in a supernova, bounded by an expanding shock wave, and consists of ejected material expanding from the explosion and the interstellar material it sweeps up. There are two common routes to a supernova: (1) a massive star may run out of fuel, ceasing to generate fusion energy in its core, and collapsing inward under the force of its own gravity to form a neutron star or a black hole; (2) a white dwarf star may accumulate material from a companion star until it reaches a critical mass and undergoes a thermonuclear explosion. In either case, the resulting supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light, that is, about 30,000 km/s. These ejecta are highly supersonic: assuming a typical temperature of the interstellar medium of 10,000 K, the Mach number can initially be > 1000. Therefore, a strong shock wave forms ahead of the ejecta, that heats the upstream plasma up to temperatures well above millions of K. The shock continuously slows down over time as it sweeps up the ambient medium, but it can expand over hundreds of thousands of years and over tens of parsecs before its speed falls below the local sound speed.

Credit: Wikipedia

The Kadazandusun people groups are the largest indigenous grouping in Sabah. The largest of these are the Central Dusun, the Coastal Kadazan, the Labuk-Kinabatangan Kadazan, and the Bundu Dusun. Although these various people groups are scattered across more than half of the state in the western, northern and central portions, most of them live in the interior, usually along one of the many rivers rather than in coastal areas. These groups are all primarily agriculturalists, with rice growing supplemented by vegetable gardening and animal husbandry. Many have also found jobs in the timber industry that has boomed in the last two decades. Village life is usually communal, but those in urban areas tend to be less so.

The flag of Libya was originally introduced in 1951, following the creation of the Kingdom of Libya. It consisted of a white star and crescent on a triband red-black-green design, with the central black band being twice the width of the outer bands. The design was based on the banner of the Senussi dynasty from Cyrenaica, which consisted of a black field and star and crescent design, and was later used as the flag of the region. The red was selected for the blood sacrificed for the freedom of Libya, black to remember the dark days that Libyans lived under the occupation of the Italians, and green to represent its primary wealth, agriculture, (Libya once being the 'breadbasket' of the Ottoman Empire) and the future prosperity of the country.

Philippines – Level 2: Exercise increased caution Friday, 13 April, 2018
Exercise increased caution in the Philippines due to crime, terrorism, civil unrest, and a measles outbreak. Some areas have increased risk. Read the entire Travel Advisory. Do not travel to: The Sulu Archipelago, including the southern Sulu Sea, due to crime, terrorism, and civil unrest. Marawi City in Mindanao due to terrorism and civil […]
Cameroon – Level 2: Exercise increased caution Wednesday, 11 April, 2018
Exercise increased caution in Cameroon due to crime. Some areas have increased risk. Read the entire Travel Advisory. Do Not Travel to: North, Far North, Northwest and Southwest Regions, and Parts of East and Adamawa Regions due to crime, terrorism, and civil unrest. Violent crime, such as armed robbery and carjacking, is common. Local police […]

Nicaragua Saturday, 21 April, 2018
Summary: There has been ongoing street violence in many areas in Nicaragua. This has involved the use of tear gas, rubber bullets and live ammunition, resulting in serious injuries and ten reported deaths. These incidents are unpredictable and can happen at any time. Exercise extreme caution when planning travel and avoid affected areas entirely.
GOV.UK
Madagascar Saturday, 21 April, 2018
Summary: Due to political demonstrations taking place in the centre of Antananarivo from the morning of 21 April, and the possibility of robust action by the authorities to disperse them, you should avoid the area around Independence Square and the Town Hall.
GOV.UK

Eugène Galien-Laloue (1854–1941) was a French artist of French-Italian parents and was born in Paris on December 11, 1854. He was a populariser of street scenes, usually painted in autumn or winter, of the early 1900s, accurately representing the era in which he lived: a happy, bustling Paris, la Belle Époque, with horse-drawn carriages, trolley cars and its first omnibuses. Galien-Laloue's works are valued not only for their contribution to 20th-century art but for the actual history, which they document. The Paris Arc de Triomphe was painted in 1941. His work can be seen at the Musée des Beaux-Arts, Louvier; Musée des Beaux-Arts, La Rochelle; Mulhouse, France.

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