Monday, 25 June, 2018

Gamma-Ray Bursts

Posted on Thursday, 10 October, 2013Sunday, 20 August, 2017 by Zheluo Cai

In 1997, a host of ground-based and space telescopes confirmed that gamma-ray bursts – fleeting blasts of high energy radiation – are nature’s biggest explosions. The Italian-Dutch satellite BeppoSAX pin-pointed the February 28 burst, and Earth-based optical instruments were then able to spot its faint host galaxy several billion light-years from our planet. A typical gamma-ray burst radiates more energy in a few seconds than the Sun will in its entire 10 billion year lifetime. A gamma-ray burst (GRB) occurring in our own galaxy could decimate life on Earth, destroying the ozone layer, triggering climate change and drastically altering life’s cycle. However, the good news is that the likelihood of a natural disaster due to a GRB is much lower than previously thought.

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The Rippled Red Ribbons of SNR 0509.
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA); Acknowledgment: J. Hughes (Rutgers U). The ripples of supernova remnant SNR 0509-67.5, as well as the greater nebula, were imaged in unprecedented detail by the Hubble Space Telescope in 2006 and again late 2011. The red colour was recoded by a Hubble filter that left only the light emitted by energetic hydrogen. The precise reason for the ripples remains unknown, with two considered hypotheses relating them to relatively dense portions of either ejected or impacted gas. The reason for the broader red glowing ring is more clear, with expansion speed and light echoes relating it to a classic Type Ia supernova explosion that must have occurred about 400 years earlier. SNR 0509 currently spans about 23 light years and lies about 160,000 light years away toward the constellation of the dolphinfish (Dorado) in the Large Magellanic Cloud. The expanding ring carries with it another great mystery: why wasn't this supernova seen 400 years ago when light from the initial blast should have passed the Earth?

The Mohawk people are the most easterly tribe of the Haudenosaunee, or Iroquois Confederacy, an Iroquoian-speaking indigenous people of North America. The Mohawk were historically based in the Mohawk Valley in present-day upstate New York west of the Hudson River; their territory ranged north to the St. Lawrence River, southern Quebec and eastern Ontario; south to greater New Jersey and into Pennsylvania; eastward to the Green Mountains of Vermont; and westward to the border with the Iroquoian Oneida Nation's traditional homeland territory. Their current major settlements include areas around Lake Ontario and the St Lawrence River in Canada and New York.

The flag of Malaysia is composed of a field of 14 alternating red and white stripes along the fly and a blue canton bearing a crescent and a 14-point star known as the Bintang Persekutuan (Federal Star). The 14 stripes, of equal width, represent the equal status in the federation of the 13 member states and the federal territories, while the 14 points of the star represent the unity between these entities. The crescent represents Islam, the country's state religion; the blue canton symbolises the unity of the Malaysian people; the yellow of the star and crescent is the royal colour of the Malay rulers. It was first raised on 16 September 1963.

Germany - Level 2: Exercise Increased Caution Tuesday, 19 June, 2018
Exercise increased caution in Germany due to terrorism. Terrorist groups continue plotting possible attacks in Germany. Terrorists may attack with little or no warning, targeting tourist locations, transportation hubs, markets/shopping malls, local government facilities, hotels, clubs, restaurants, places of worship, parks, major sporting and cultural events, educational institutions, airports, and other public areas. Read the […]
Belarus - Level 1: Exercise Normal Precautions Monday, 18 June, 2018
Exercise normal precautions in Belarus. Read the Safety and Security section on the country information page. If you decide to travel to Belarus: Enroll in the Smart Traveler Enrollment Program (STEP) to receive Alerts and make it easier to locate you in an emergency. Follow the Department of State on Facebook and Twitter. Review the […]

Ethiopia Saturday, 23 June, 2018
Summary: Addis Ababa: Saturday 23 June: A large rally in support of Ethiopian Prime Minister, Dr Abiy Ahmed, was disrupted by a grenade attack, resulting in c80 injured, some seriously. Minor incidents were reported as crowds dispersed, but the streets are now mostly calm. We encourage visitors to continue to follow our advice below on […]
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South Africa Friday, 22 June, 2018
Latest update: Safety and Security section (Crime) - revised information; risk of crime increases in urban areas, particularly central business districts of major cities and townships on the outskirts of major cities; a higher state of awareness is required if travelling through these areas
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