Ring of fire. Light swirls around the edge of a supermassive black hole at the centre of galaxy M87, 17 million parsecs (55 million light years) from Earth. This image, the first ever of a black hole, was released by the Event Horizon Telescope collaboration on 10 April. Putting it together was a massive undertaking, and involved combining petabytes’ worth of data (1 petabyte is 1015 bytes), captured by eight radio observatories around the world.

Credit: Schmidt Ocean Institute

Underwater towers. A research team at the Schmidt Ocean Institute in Palo Alto, California, came across these mineral towers while exploring hydrothermal vents in the Gulf of California. The towers, up to 23 metres tall, had outcroppings known as flanges, pictured here, that have super-heated liquids flowing across their undersides. Despite the high levels of metals and sulfides present, the sites are teeming with life.

Credit: Martin Sanchez @zekedrone/SkyPixel

Glorious mud. This aerial shot of a hippopotamus party — appropriately titled ‘Hungry hippos’ — won first prize in the Nature category of the 2018 SkyPixel Aerial Photo & Video Contest. It was shot by Martin Sanchez.

Credit: Thomas Peter/Reuters

Life on Mars. A lone astronaut peers through sandstorms towards a Mars base — or, at least, a mock-up of one. This is the C-Space Project Mars simulation base, an education facility situated in the Gobi Desert near Jinchang, China. The base is split into nine capsules, including living quarters, medical facilities and an entertainment and fitness room, and is open for visits from school students, to show what living on Mars could be like.

Credit: Team Ciel Austral

Thousand-hour photo. It took 1,060 hours of exposure time to capture this spectacular image of the Large Magellanic Cloud, a satellite galaxy that orbits the Milky Way. And although it might look like the work of NASA, the image was produced by a group called ﻿Ciel Austral, five amateur astronomers from France. Between July 2017 and January 2019, the team observed the galaxy from the El Sauce Observatory in Chile, then stitched the images together to form this single high-resolution photo.

Credit: Jeremy Gilchrist

Pollen storm. It’s the time of year when allergies start to kick in — so spare a thought for those in Durham, North Carolina, at the beginning of April. A storm that hit the region stirred up a massive cloud of pollen, seen here as a yellow-green haze over the city. The pollen was thick enough to be mistaken for a real cloud by a local weather sensor.

Credit: Michael Theusner

Eerie lights. These strange, ethereal lights appeared in the sky above Norway in early April, captured by a surprised bystander. Butit wasn’t aliens — instead, the lights came from colourful gas tracers 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 work out how electrically charged particles move through the atmosphere during an aurora.

Credit: CNES/Airbus; DigitalGlobe

Healthy haloes. Satellite imagery shows ‘haloes’ of bare sand surrounding coral reefs in the Red Sea. These haloes are formed as a result of coral-dwelling fishes eating plants and invertebrates from the sea floor, and are more numerous in marine reserves, which ban fishing, than elsewhere, according to a pair of studies published on 24 April1,2. The research suggests that haloes could provide a useful indicator of the health of the reef ecosystem.

Credit: Leon Neal/Getty

Sticky situation. Police try to release an environmental campaigner’s hands, which had been glued to the window of a train at Canary Wharf Underground Station in London. Members of the Extinction Rebellion group spent 11 days last month protesting in the streets of the city, occupying areas including Oxford Circus and Waterloo Bridge. The group uses non-violent protest in an attempt to persuade governments to take stronger action against climate change.