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WonderScience

Saturn's largest moon, Titan, has rain, rivers, lakes and seas, but they are made of liquid methane and ethane, not water.

Titan is the only moon in the solar system with a thick atmosphere. It is mostly nitrogen, wrapped in an orange haze, and presses on the surface about one and a half times as hard as Earth's air. At around minus 179°C, methane and ethane behave as water does on Earth: they evaporate, form clouds, fall as rain and gather in rivers, lakes and seas, mostly near the poles. The Cassini spacecraft, a joint NASA and European mission, mapped these seas with radar from 2004; the largest is Kraken Mare. In January 2005 its Huygens probe landed on Titan, the first landing in the outer solar system, and photographed a dark plain scattered with rounded pebbles of ice. NASA's Dragonfly, a flying drone, is due to launch in 2028 to explore the moon's chemistry.

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WonderScience

Jupiter's moon Europa probably has a salty ocean beneath its ice, which may hold about twice as much water as all of Earth's oceans combined.

Europa is a little smaller than our Moon. NASA scientists estimate that its ice shell is 15 to 25 kilometres thick and the ocean beneath it 60 to 150 kilometres deep. The heat that keeps the water liquid comes not from the Sun but from tides: as Europa circles Jupiter, the giant planet's gravity squeezes and stretches it, warming its interior. The strongest evidence came from NASA's Galileo spacecraft around 2000, which found that Europa disturbs Jupiter's magnetic field in the way a buried layer of salty water would. Because the ocean probably touches a rocky seafloor, it could hold the chemistry that life needs. NASA's Europa Clipper, launched in October 2024, is due to reach Jupiter in 2030.

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WonderHistory

The Nebra Sky Disc, a bronze disc inlaid with a gold sun or full moon, a crescent moon and stars, was buried in Germany about 3,600 years ago and is one of the oldest known pictures of the sky.

Two treasure hunters with a metal detector dug the disc up illegally in 1999 on a hill near Nebra, in eastern Germany. It passed through the black market until police seized it in a sting operation in Basel, Switzerland, in 2002. Swords and axes buried with it, and birch bark from the sword hilts, date the burial to about 1600 BC, in the Early Bronze Age. A cluster of seven gold dots is usually read as the Pleiades, a star group that early farmers watched to time the seasons. Gold arcs added later along the edges span the angle between sunrise at midsummer and midwinter, and a curved shape at the bottom is often read as a sun boat. The disc is kept at the State Museum of Prehistory in Halle and is on UNESCO's Memory of the World register.

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WonderSpace

A comet from another star system, named 3I/ATLAS, was discovered in July 2025: only the third object from interstellar space ever seen passing through our Solar System.

The NASA-funded ATLAS survey telescope at Río Hurtado in Chile spotted it on 1 July 2025; the name marks it as the third interstellar object, found by ATLAS. The first two were 'Oumuamua in 2017 and Borisov in 2019. Its path is hyperbolic, an open curve rather than a closed orbit, so the Sun's gravity cannot hold it: it arrived at about 58 km a second and will leave for good. It passed closest to the Sun on 29 October 2025, about 203 million km away, between the orbits of Earth and Mars. Judging by its route through the galaxy, it may be older than the Solar System; one estimate puts it at 7 billion years or more.

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WonderSpace

The Vera C. Rubin Observatory, a new telescope in Chile, released its first images in June 2025. In about ten hours of test observations it found 2,104 asteroids no one had seen before, and its first wide views captured some 10 million galaxies.

Rubin stands on Cerro Pachón in the Chilean Andes. It pairs an 8.4-metre mirror with the largest digital camera ever built, a 3,200-megapixel instrument about the size of a small car. It is named after the American astronomer Vera Rubin, whose studies of how galaxies spin gave key evidence for dark matter. In 2026 it began its ten-year Legacy Survey of Space and Time, photographing the whole southern sky every few nights to catch anything that moves, brightens or fades. For scale, all other observatories together discover about 20,000 new asteroids a year; Rubin found 2,104 in its first ten hours, seven of them near-Earth asteroids.

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WonderSpace

Dust that NASA brought back from the asteroid Bennu contains amino acids and all five nucleobases, the chemical 'letters' of DNA and RNA: key ingredients for the chemistry of life, though not signs of life itself.

NASA's OSIRIS-REx spacecraft launched in 2016, reached Bennu, a carbon-rich asteroid about 500 metres wide, in 2018, and in 2020 touched its surface for a few seconds to collect loose rock and dust. The capsule landed in Utah in September 2023 with 121.6 grams of material. Studies published in 2025 found 14 of the 20 amino acids that life on Earth uses to build proteins, all five nucleobases, and salt minerals left behind as ancient brine evaporated. Life on Earth uses almost only 'left-handed' amino acids; Bennu's came in a roughly equal mix of left- and right-handed forms. None of this is evidence of life; it shows these ingredients were widespread in the early Solar System.

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WonderSpace

In 2025 astronomers reported that the atmosphere of K2-18b, a planet 124 light-years away, may contain gases that on Earth are made mostly by living things. Other scientists quickly cautioned that the signal is weak and is not proof of life.

The planet is about 8.6 times Earth's mass and orbits a small red star in the zone where liquid water could exist. A Cambridge team led by Nikku Madhusudhan argues it may be a 'hycean' world, an ocean under a hydrogen-rich atmosphere. Using the James Webb Space Telescope, the team reported signs of dimethyl sulfide, a gas made on Earth mainly by marine plankton, but at a statistical strength below what scientists normally require for a discovery. Other groups reanalysed the same data and found the signal weak or absent, and noted that the gas can also form without life. The debate shows how such claims are tested: by checking the data again and again.

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WonderSpace

The most massive black-hole merger yet detected was announced in 2025: two black holes, roughly 100 and 140 times the Sun's mass, collided and formed one of more than 225, sending out gravitational waves that reached Earth in November 2023.

Gravitational waves are ripples in space itself, sent out when very heavy objects such as black holes spiral together. The signal, called GW231123 after its date, was caught on 23 November 2023 by the two LIGO detectors in the United States and announced in 2025 by the LIGO–Virgo–KAGRA collaboration, which also runs detectors in Italy and Japan. At least one of the pair falls in a 'mass gap' of roughly 60 to 130 solar masses: stars heavy enough to leave such black holes are expected to blow themselves apart completely instead. The likeliest answer is that each was born from an earlier merger, which also fits their unusually fast spin.

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WonderSpace

In 2025 astronomers confirmed a giant black hole in a galaxy seen as it was only about 500 million years after the Big Bang, one of the earliest such black holes known.

The galaxy, CAPERS-LRD-z9, was studied by a team led from the University of Texas at Austin as part of the CAPERS survey with the James Webb Space Telescope. It is one of the 'little red dots', small, compact and very red galaxies that Webb has found in large numbers in the early universe. Webb split the galaxy's light into a spectrum and revealed fast-moving gas swirling around a growing black hole, the clearest sign of one. Estimates of its mass vary, but it may weigh as much as half of all the galaxy's stars together, at a time when the universe was under 4% of its present age. Such early giants suggest black holes either grew very fast or started out unusually heavy.

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WonderSpace

Saturn gained 128 new moons in a single announcement in March 2025, raising its total to 274. At the time, that was more than all the other planets' moons put together.

The moons were found by a team led by Edward Ashton of Academia Sinica in Taiwan, using the Canada-France-Hawaii Telescope. An earlier search in 2019 to 2021 had already turned up dozens of moons, so the team watched the same patches of sky for three months in 2023, stacking many exposures so that faint, moving specks stood out. The Minor Planet Center, the International Astronomical Union's clearing house for Solar System discoveries, confirmed 128 of them in March 2025. All are irregular moons: small bodies a few kilometres across on distant, tilted orbits. They are probably fragments of larger moons that Saturn captured long ago and that later broke apart in collisions.

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WonderSpace

In 1954 Ann Hodges was asleep on her sofa in Alabama when a 4-kilogram rock from space came through the ceiling, bounced off her radio and struck her hip. She remains one of the few people confirmed to have been directly injured by a meteorite.

The meteorite, a stone about 4.5 billion years old, broke in two as it fell over the town of Sylacauga; a local farmer found the second piece a few kilometres away. Hodges was left with a large bruise on her hip. Her landlady, Birdie Guy, claimed the rock as the owner of the house, and Hodges eventually paid her $500 to keep it. The flood of reporters and visitors wore her down, and in 1956 she gave the meteorite to the Alabama Museum of Natural History, where it is still on display. The case is often described as the first well-documented instance of a meteorite injuring a person.

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WonderSpace

The Wow! signal was a strong radio signal picked up in August 1977 by an Ohio telescope searching for messages from other civilisations. It came from the direction of Sagittarius, and the astronomer checking the printout circled it and wrote 'Wow!' beside it. It has never been detected again.

The telescope was Ohio State University's Big Ear, and the astronomer was Jerry Ehman, a volunteer on its search. The signal lasted 72 seconds, the time a fixed point in the sky took to drift across the telescope's view, and it sat near 1,420 megahertz, the radio frequency naturally given off by hydrogen, the commonest element in the universe. Scientists had suggested that frequency as one other civilisations might choose to call on. The printout recorded strength as letters and numbers, and the sequence '6EQUJ5' shows it rising to about 30 times the background noise. Big Ear and other telescopes have searched the same patch of sky many times without success. A 2017 idea that a passing comet caused it was rejected by other astronomers; a 2024 study suggested a hydrogen cloud briefly brightened by a burst of radiation, which is also unconfirmed.

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WonderSpace

In 1967, as a graduate student at Cambridge, Jocelyn Bell Burnell spotted the regular radio pulses that led to the discovery of pulsars: collapsed, fast-spinning stars that sweep out radio waves like a lighthouse beam. She was left out of the 1974 Nobel Prize, which went to her supervisor Antony Hewish and to Martin Ryle.

Bell Burnell had spent two years helping to build the radio telescope near Cambridge, and she checked up to 29 metres of chart paper from it a night. Among the traces she noticed a faint, regular 'bit of scruff'. She and Hewish half-jokingly labelled it LGM-1, for 'Little Green Men', before it was identified as a neutron star, the tiny, dense core left when a massive star explodes, spinning and sending out a pulse every 1.33 seconds. When the 1974 Nobel Prize in Physics went to Hewish and Ryle, the astronomer Fred Hoyle publicly objected. Bell Burnell herself said it would demean the prizes to give them to research students except in very exceptional cases. In 2018 she won the $3 million Special Breakthrough Prize in Fundamental Physics and gave all of it to fund physics scholarships for students from under-represented groups.

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WonderSpace

On 30 June 1908 a space rock, probably a stony asteroid 50 to 60 metres wide, exploded in the air above the Tunguska region of Siberia and flattened about 2,000 square kilometres of forest. No impact crater has ever been found.

The asteroid is thought to have burst 5 to 10 kilometres above the ground, so the blast knocked trees down instead of digging a hole. They fell in a vast butterfly-shaped area about 70 kilometres across, all pointing away from the centre, while some trees right below the blast stayed upright, stripped of their branches. Estimates of the energy range from 3 to 50 megatons of TNT, hundreds of times the Hiroshima bomb. The region was so remote, and Russia so shaken by war and revolution, that Leonid Kulik's expedition reached the site only in 1927. Witnesses at a trading post 65 kilometres away felt the heat. It is still the largest impact event in recorded history.

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WonderTechnology

In April 1970 an oxygen tank exploded on Apollo 13, more than 300,000 km from Earth, forcing the three astronauts into a lunar module built for two. Engineers on the ground then had to make the command module's square air filters fit the lunar module's round sockets, using only what was aboard.

With three people breathing in a craft designed for two, carbon dioxide was climbing towards dangerous levels, and the lunar module's own lithium hydroxide canisters, which absorb the gas, could not keep up. Engineers led by Ed Smylie designed an adapter from items known to be aboard: plastic bags, cardboard from a flight-plan cover, duct tape, a spacesuit hose and a sock. Mission Control read the instructions to the crew step by step over the radio, and it worked. The lunar module, never meant as a lifeboat, kept Jim Lovell, Jack Swigert and Fred Haise alive for about four days, and all three splashed down safely on 17 April 1970. NASA later called the mission a 'successful failure'.

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WonderSpace

The overview effect is what many astronauts report on seeing Earth from space: a sudden, powerful sense that the planet is small, fragile and has no visible borders. The writer Frank White named it in 1987.

White, an American writer on space, interviewed astronauts for his book The Overview Effect and heard the same themes again and again: a strong sense of connection with everyone on the planet, impatience with conflict and a wish to protect Earth. The Apollo 14 astronaut Edgar Mitchell, for instance, described a sudden sense of oneness with humanity on his way home from the Moon in 1971. A 2016 paper by the psychologist David Yaden and colleagues described the effect as a form of awe, the feeling of facing something vast that changes how we see ourselves. The evidence still rests mostly on astronauts' own accounts rather than on measurements.

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WonderSpace

In 1962 John Glenn asked for NASA mathematician Katherine Johnson to check the electronic computer's orbit calculations by hand before his flight. If she said the numbers were good, he said, he was ready to go. He became the first American to orbit Earth.

Johnson worked from 1953 at the Langley research centre in Virginia, first for NASA's predecessor, NACA, and then for NASA. She began among the 'human computers', mostly women who did calculations by hand, in the segregated West Area Computing unit for Black mathematicians. She calculated the trajectory for Alan Shepard's 1961 flight, checked Glenn's orbit and later worked on Apollo 11's path to the Moon. When Apollo 13 was crippled in 1970, her work on backup procedures and charts helped the crew return safely. She retired in 1986, received the Presidential Medal of Freedom in 2015 and became widely known through the 2016 book and film Hidden Figures. She died in 2020, aged 101.

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WonderSpace

A solar sail is a huge, ultra-thin mirror that lets a spacecraft travel on the faint push of sunlight. It needs no fuel, and the tiny push keeps adding speed for as long as light falls on it.

Light has no mass, but it carries momentum, so when it bounces off a mirror it gives it a tiny push. The idea goes back to Johannes Kepler, who noticed in the early 1600s that comet tails point away from the Sun and imagined ships sailing on a heavenly breeze. In 2010 Japan's IKAROS became the first spacecraft to use a solar sail in interplanetary space, on its way past Venus. In 2019 the Planetary Society's LightSail 2, partly funded by public donations, showed that a small satellite could raise its orbit using sunlight alone; it burned up in the atmosphere in 2022. The push is tiny, but it never runs out, so over months it adds up.

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DriveSpace

On 26 September 2022, NASA's DART spacecraft deliberately crashed into Dimorphos, a small asteroid orbiting a larger one, and cut the time it takes to circle its partner by about 33 minutes. It was the first proof that an impact can change an asteroid's path.

DART, short for Double Asteroid Redirection Test, launched in November 2021 and hit Dimorphos, about 150 metres across, at roughly 6.1 kilometres per second. Neither Dimorphos nor its partner Didymos was ever a threat to Earth; the pair was chosen because a change in the small asteroid's orbit is easy to measure with telescopes. Before the impact, Dimorphos circled Didymos every 11 hours and 55 minutes. The team would have counted a change of 73 seconds as success; the actual change was about 33 minutes, partly because the impact threw off a huge plume of rock and dust that pushed the asteroid further. A small Italian satellite, LICIACube, photographed the plume, and the European Space Agency's Hera probe, launched in 2024, is due to arrive in late 2026 to study the crater.

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WonderSpace

NASA's Parker Solar Probe, launched in 2018, flies through the Sun's outer atmosphere, the corona. In December 2024 it passed just 6.1 million kilometres from the solar surface, closer than any spacecraft before it.

The probe is named after the astrophysicist Eugene Parker, who in 1958 predicted the solar wind, the stream of charged particles flowing out from the Sun; it was the first NASA spacecraft named after a living person. A carbon-composite heat shield about 11 centimetres thick faces the Sun and heats to around 1,000 °C, while the instruments behind it stay near room temperature. Seven flybys of Venus shrank its orbit step by step. At its closest passes it travels at about 690,000 kilometres per hour, the fastest any human-made object has gone. In 2021 it became the first spacecraft to fly through the corona. Its measurements help explain how the solar wind is launched and how solar storms can disrupt satellites and power grids.

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WonderBiography

In her 1925 doctoral thesis, the British-American astronomer Cecilia Payne showed that stars are made mostly of hydrogen and helium, unlike the Earth. She read this from starlight split into its colours, using new physics that explained how heat strips electrons from atoms.

At the time, astronomers assumed stars had roughly the same make-up as the Earth. Working at Harvard College Observatory, Payne showed that the differences between star spectra, starlight spread out into its colours, came mainly from temperature rather than composition, and that hydrogen was vastly more abundant than anyone expected. Henry Norris Russell, the leading American astronomer, found this implausible, and in the published thesis she called her own hydrogen figure 'almost certainly not real'. Four years later Russell reached the same result by other means and acknowledged her work. The astronomers Otto Struve and Velta Zebergs later called hers the most brilliant PhD thesis ever written in astronomy. In 1956 she became the first woman promoted to full professor in Harvard's Faculty of Arts and Sciences.

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WonderBiography

In 1912 Henrietta Swan Leavitt found that certain pulsing stars, called Cepheids, take longer to brighten and dim the brighter they really are. That rule turned them into cosmic measuring sticks: by timing a Cepheid, astronomers can work out how far away it is.

Leavitt joined Harvard College Observatory in 1893, at first as a volunteer, as one of the women known as 'computers' who measured stars on photographic plates for low pay. Studying the Magellanic Clouds, two small galaxies whose stars all lie at roughly the same distance from us, she catalogued 1,777 variable stars. Because they were all about equally far away, a Cepheid that looked brighter really was brighter, which revealed the link between brightness and period. Once others had measured the distances to a few nearby Cepheids, the rule could be used anywhere. In the 1920s Edwin Hubble used it to show that the Andromeda nebula lies far outside the Milky Way. Leavitt died in 1921, before the importance of her work was widely recognised.

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WonderBiography

At 19, Subrahmanyan Chandrasekhar calculated that a white dwarf, the dense core left when a star like the Sun dies, cannot be more than about 1.4 times the Sun's mass. Above this limit, now named after him, it can no longer hold itself up against its own gravity.

Chandrasekhar did the calculation in 1930 on the ship taking him from India to England to study at Cambridge, combining quantum mechanics with Einstein's special relativity. A white dwarf is held up by electron degeneracy pressure: when electrons are squeezed very tightly together, they resist being packed any closer, a purely quantum effect. He showed that this resistance has a ceiling. When he presented the result in 1935, the influential astronomer Arthur Eddington mocked it in public, and many colleagues sided with Eddington for years, although the mathematics was right. The limit is now central to understanding supernovae and neutron stars. Chandrasekhar shared the 1983 Nobel Prize in Physics for his work on the structure and evolution of stars.

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DriveSpace

Nancy Grace Roman, NASA's first Chief of Astronomy, built the agency's space astronomy programme in the 1960s and spent years winning support for the telescope later named Hubble.

Roman, an astronomer who had studied the motions of stars, joined NASA in 1959 and became the first woman in an executive post at the agency. She ran its early orbiting observatories and, once they worked, began arguing for a large telescope above the atmosphere, which blurs and blocks much of the light from space. In 1971 she set up a steering group of astronomers and engineers to define what the telescope had to do, then spent the 1970s building support and writing testimony for Congress. She also backed investment in electronic light detectors, and Hubble became the first major observatory to use CCDs, the kind of sensor later found in digital cameras. She retired in 1979; Hubble was launched in 1990, and she is often called the 'Mother of Hubble'. In 2020 NASA named a new space telescope after her.

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