Ring of Fire. Light whirls around the edge of a supermassive black hole in the center of galaxy M87, 17 million parsecs (55 million light-years) from Earth. This image, the first black hole of all kinds, was released on April 10 by the Event Horizon Telescope Collaboration. Merging was a daunting undertaking that combined data in the petabyte range (1 petabyte is 10 15 bytes) captured by eight radio observatories around the world.
Underwater Towers. A research team at the Schmidt Ocean Institute in Palo Alto, California discovered these mineral towers as they explored hydrothermal vents in the Gulf of California. At the towers, which are up to 23 meters high, the flanges shown here were marked with flooding, on the underside of which superheated liquids flowed. Despite the high levels of metals and sulfides, it is teeming with locations.
Gorgeous mud. This aerial photo of a hippopotamus party – appropriately titled "Hungry Hippos" – won first prize in the Nature category of the SkyPixel Aerial Photo & Video Contest 2018. It was shot by Martin Sanchez.
Life on Mars. A single astronaut looks through sandstorms at a Mars base – or at least a mock-up of one. This is the Mars simulation base of the C-Space project, an educational facility in the Gobi Desert near Jinchang, China. The base is divided into nine capsules, including living quarters, medical facilities, an entertainment and exercise room, and students can visit them to show what life on Mars might look like.
Thousand hours photo. It took 1,060 hours of exposure time to capture this spectacular image of the Large Magellanic Cloud, a satellite galaxy orbiting the Milky Way. And although it might look like NASA's work, the picture was produced by a group called Ciel Austral, five amateur astronomers from France. Between July 2017 and January 2019, the team observed the galaxy of the El Sauce Observatory in Chile and stitched the images into a single high-resolution photograph.
Pollen Storm. It's the time of the year that allergies begin – so save yourself a thought in early April in Durham, North Carolina. A storm that hit the area whirled up a huge pollen cloud, which was seen here as a yellow-green haze over the city. The pollen was thick enough to be considered a real cloud by a local weather sensor.
Eerie lights. These strange, ethereal lights appeared over the Norwegian sky in early April and were captured by a surprised onlooker. But they were not extraterrestrials – instead, the lights were made of colorful lanes of gas released by two NASA rockets as part of the Auroral Zone Upwelling Rocket Experiment (AZURE). A research team recorded the movement of the tracers to find out how electrically charged particles move through the atmosphere during an aurora.
Healthy Halos. Satellite images show "halos" of bare sand surrounding coral reefs in the Red Sea. These haloes are the result of coral fish eating plants and invertebrates from the seabed, and are more abundant in marine reserves that prohibit fishing than elsewhere, as shown by a study published on April 24 1 2 . Research suggests that halos can be a useful indicator of the health of the reef ecosystem.
Sticky situation. The police are trying to release the hands of an environmental activist who had been stuck to the pulley of Canary Wharf tube station in London. Members of the Extinction Rebellion group protested in the streets of the city last month for 11 days and occupied areas such as Oxford Circus and Waterloo Bridge. The group uses nonviolent protests to convince governments to tackle climate change more effectively.
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