Tuesday, 19 February, 2019

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

Watch - Lassa Fever in Nigeria Thursday, 7 February, 2019
Nigerian health officials have declared an outbreak of Lassa fever in Nigeria. Travelers to Nigeria should avoid contact with rats, especially rat urine and feces, and keep their accommodations or campsites clean.
Watch - Andes Virus (Hantavirus) in Argentina Monday, 28 January, 2019
There is an outbreak of Andes virus in Argentina, specifically in Chubut Province of Patagonia. Travelers to Argentina should avoid contact with rodents and their droppings (urine and feces), and avoid close contact with anyone who may be sick.

ASTRONOMY PICTURE OF THE DAY: NGC 7822. Credit & Copyright: Neil Fleming. At the edge of a giant molecular cloud toward the northern constellation Cepheus, the glowing star forming region lies about 3,000 light-years away. The image maps emission from atomic oxygen, hydrogen, and sulfur into blue, green, and red hues. The atomic emission is powered by the energetic radiation from the hot stars, whose powerful winds and radiation also sculpt and erode the denser pillar shapes. Stars could still be forming inside the pillars by gravitational collapse, but as the pillars are eroded away, any forming stars will ultimately be cut-off from their reservoir of star stuff. This field spans around 60 light-years.

Florida Students to Speak with NASA Astronaut Aboard International Space Station Friday, 15 February, 2019
University and high school students from Florida will have an opportunity to talk with a NASA astronaut on the International Space Station next week.
NASA Selects New Mission to Explore Origins of Universe Wednesday, 13 February, 2019
NASA has selected a new space mission that will help astronomers understand both how our universe evolved and how common are the ingredients for life in our galaxy’s planetary systems.

IMAGO DEI: The Ndebele tribe or amaNdebele, one of the smaller ones of the Nguni speaking tribes that migrated to South Africa, were the first Nguni speaking people to move into the interior of the country instead of the coastal areas. The Nguni tribes represent nearly two thirds of South Africa’s Black population and can be divided into four distinct groups; the Central Nguni (the Zulu-speaking peoples), the Southern Nguni (the Xhosa-speaking peoples), the Swazi people from Swaziland and adjacent areas and the Ndebele people of the Northern Province and Mpumalanga.

Yemen - Level 4: Do Not Travel Thursday, 14 February, 2019
Do not travel to Yemen due to terrorism, civil unrest, health risks, and armed conflict. Terrorist groups continue to plot and conduct attacks in Yemen. Terrorists may attack with little or no warning, targeting public sites, transportation hubs, markets/shopping malls, and local government facilities. Additionally, there is a continuing threat of kidnapping/detention by terrorists, criminal elements, […]
Burkina Faso - Level 3: Reconsider Travel Thursday, 14 February, 2019
Reconsider travel to Burkina Faso due to terrorism. Some areas have increased risk. Read the entire Travel Advisory. Do not travel to: The Sahel Region due to crime and terrorism. The East Region due to crime and terrorism. The Provinces of Koulpelogo, Loroum, Yatenga, Sourou, Kossi, Banwa, Kenedougou, or within 50km of the Mali border […]

Jordan Sunday, 17 February, 2019
Summary - Due to an ongoing incident in in the Anjara and Ajlun areas we urge caution in visiting this part of Jordan. Anyone already in this area should follow the advice of the local authorities
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Nigeria Saturday, 16 February, 2019
Summary - Presidential and National Assembly elections, due to take place in Nigeria on 16 February 2019, have been delayed a week until 23 February. The Gubernatorial and State House of Assembly elections, due on 2 March, have also been delayed by a week until 9 March. You should continue to avoid rallies, public gatherings […]
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WORK OF ART: Studies of the Foetus in the Womb are two-coloured annotated sketches by Leonardo da Vinci made in around 1511. Da Vinci studied human embryology with the help of anatomist Marcantonio della Torre and saw the foetus within a cadaver. The studies were initially bequeathed to Francesco Melzi. In c. 1582–90 they were bought from his heirs by Pompeo Leoni, and by 1630 they belonged to Thomas Howard, 2nd Earl of Arundel. Since 1690 the studies have been housed in the Royal Collection, United Kingdom.