Shell Galaxies in Pisces

This intergalactic skyscape features a peculiar system of galaxies cataloged as Arp 227 some 100 million light-years distant. Swimming within the boundaries of the constellation Pisces, Arp 227 consists of the two galaxies prominent right of center, the curious shell galaxy NGC 474 and its blue, spiral-armed neighbor NGC 470. The faint, wide arcs or shells of NGC 474 could have been formed by a gravitational encounter with neighbor NGC 470. Alternately the shells could be caused by a merger with a smaller galaxy producing an effect analogous to ripples across the surface of a pond. The large galaxy on the top lefthand side of the deep image, NGC 467, appears to be surrounded by faint shells too, evidence of another interacting galaxy system. Intriguing background galaxies are scattered around the field that also includes spiky foreground stars. Of course, those stars lie well within our own Milky Way Galaxy. The field of view spans 25 arc minutes or about 1/2 degree on the sky. via wordpress

Wikipedia article of the day for August 27, 2020

Wikipedia article of the day is Operation PBFortune. Check it out: Summary: Operation PBFortune was a covert United States operation to overthrow the democratically elected Guatemalan president Jacobo Árbenz (pictured) in 1952. The operation was planned by the Central Intelligence Agency and authorized by President Harry Truman. It was motivated by US fears that Árbenz was being influenced by communists, and lobbied for by the United Fruit Company. The operation was planned with the support of Anastasio Somoza García, Rafael Leonidas Trujillo and Marcos Pérez Jiménez, the dictators of Nicaragua, the Dominican Republic and Venezuela, respectively. The plan involved providing weapons to the exiled Guatemalan military officer Carlos Castillo Armas, who was to lead an invasion from Nicaragua. US secretary of state Dean Acheson became concerned that the coup attempt would damage the image of the US and terminated the operation. Two years later, another covert CIA action, Operation PBSuccess, toppled the Árbenz government and ended the Guatemalan Revolution.

Visualization: A Black Hole Accretion Disk

What would it look like to circle a black hole? If the black hole was surrounded by a swirling disk of glowing and accreting gas, then the great gravity of the black hole would deflect light emitted by the disk to make it look very unusual. The featured animated video gives a visualization. The video starts with you, the observer, looking toward the black hole from just above the plane of the accretion disk. Surrounding the central black hole is a thin circular image of the orbiting disk that marks the position of the photon sphere — inside of which lies the black hole’s event horizon. Toward the left, parts of the large main image of the disk appear brighter as they move toward you. As the video continues, you loop over the black hole, soon looking down from the top, then passing through the disk plane on the far side, then returning to your original vantage point. The accretion disk does some interesting image inversions — but never appears flat. Visualizations such as this are particularly relevant today as black holes are being imaged in unprecedented detail by the Event Horizon Telescope. via wordpress