01 janeiro 2018

Unexpected X Rays from Perseus Galaxy Cluster


Why does the Perseus galaxy cluster shine so strangely in one specific color of X-rays? No one is sure, but a much-debated hypothesis holds that these X-rays are a clue to the long-sought identity of dark matter. At the center of this mystery is a 3.5 Kilo-electronvolt (KeV) X-ray color that appears to glow excessively only when regions well outside the cluster center are observed, whereas the area directly surrounding a likely central supermassive black hole is actually deficient in 3.5 KeV X-rays. One proposed resolution -- quite controversial -- is that something never seen before might be present: florescent dark matter (FDM). This form of particle dark matter might be able to absorb 3.5 KeV X-radiation. If operating, FDM, after absorption, might later emit these X-rays from all over the cluster, creating an emission line. However, when seen superposed in front of the central region surrounding the black hole, FDM's absorption would be more prominent, creating an absorption line. Pictured, a composite image of the Perseus galaxy cluster shows visible and radio light in red, and X-ray light from the Earth-orbiting Chandra Observatory in blue.

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La Llorona

In English, her name means “the Weeping Woman.” She is a legendary figure in Mexico, who wanders for eternity, seeking her lost children. To hear her cries brings misfortune. According to legend, La Llorona was once a living woman, whose husband on day left her for a younger woman. In her grief and anger, La Llorona drowned her children, to hurt their unfaithful father. When she realized what she had done, she drowned herself too.

According to some versions, La Llorona will kidnap wandering children who even vaguely resemble her dead children. Crying and apologizing, she will then drown the children, so they can take the place of her own. La Llorona is understandably a popular threat to keep Mexican children from wandering.

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An Old, Old City

Gwangju, a major city in the south of South Korea, was founded in 57 BCE. Which is pretty amazing to think about – it is that old, and yet, we have a precisely dated record for when it was founded. Many ancient cities, including Pyongchang in Korea, Beijing in China, London in England, and Rome in Italy, are just ancient. Their actual age isn’t known, they just have legends and myths. That makes Gwangju a pretty special city. It recently, or recently in comparison, celebrated its two thousandth birthday in 1957.

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