11 Space Facts So Unsettling, You Might Never Look At The Night Sky The Same Way, As Shared By This Page

On February 7, 1984, NASA astronaut Bruce McCandless II became the first astronaut to move around in space untethered, with nothing connecting him to his spacecraft. Spacewalkers before him had always stayed attached by a line, including Ed White, the first American to walk in space, in 1965. During Space Shuttle Challenger’s STS-41-B mission, McCandless strapped into the Manned Maneuvering Unit, a backpack powered by small nitrogen-gas thrusters that he steered with hand controls, then drifted about 320 feet (98 m) away from the shuttle. Roughly 190 miles above Earth and circling the planet at about 17,500 mph, he became, in effect, a one-man spacecraft.

His crewmates captured the moment from inside Challenger; the famous shot is usually credited to pilot Robert “Hoot” Gibson. The image shows McCandless near his maximum distance from the shuttle, a lone figure suspended in the endless darkness above Earth, and it became one of the most iconic photos in NASA history. McCandless, however, seemed to be enjoying himself. Echoing Neil Armstrong, he joked, “It may have been one small step for Neil, but it’s a heck of a big leap for me.” The jetpack flew on only three missions in 1984 before being retired for safety reasons, and today it’s on display at the Smithsonian’s Udvar-Hazy Center in Virginia.

The Milky Way and its neighboring galaxies are racing through space at roughly 1.3 million mph (about 600 km per second). They’re being pulled toward a mysterious region called the Great Attractor, 150 to 250 million light-years away. For decades it was frustratingly hard to study because it sits in the “Zone of Avoidance,” a patch of sky hidden behind the dust and stars of our own galaxy. Radio and X-ray telescopes have since peered through that veil. In 2016 alone, Australia’s Parkes radio telescope uncovered 883 hidden galaxies in the region, but scientists still can’t fully explain what’s causing such a strong pull.

This sounds impossible until you remember that space itself has been expanding the entire time light has been traveling toward us. The light from the most distant objects we can see set off about 13.8 billion years ago, but in the meantime those objects have been carried much farther away. Today they’re roughly 46 billion light-years from us in every direction.

Stars, planets, gas, dust and people are all made of ordinary matter, and it accounts for only about 5% of the universe’s total mass and energy. Roughly 27% is dark matter, an invisible substance we detect only through its gravity. The remaining 68% is dark energy, a mysterious force that’s making the universe expand faster and faster. Scientists still don’t know what either of them actually is.

On August 15, 1977, Ohio State University’s Big Ear radio telescope picked up an unusually strong burst from space that lasted the full 72 seconds the telescope could observe it. When astronomer Jerry Ehman spotted it on a printout, he circled it and wrote “Wow!” in the margin, and the name stuck. Despite decades of searching, the signal has never been detected again. A 2024 study proposed a natural explanation: a powerful flare from a magnetar may have briefly lit up a cloud of hydrogen gas. That’s still just a hypothesis, though, and the “Wow!” signal remains one of astronomy’s most famous unsolved mysteries.

Near a black hole, gravity pulls much harder on your feet than on your head, a difference called tidal force. At the edge of a black hole the mass of the Sun, that difference would be about 2 billion times Earth’s gravity, enough to stretch a person into a thin strand. Scientists call it “spaghettification.” Strangely, a supermassive black hole is gentler: its edge is so far from the center that you could cross it without feeling stretched. You just could never come back out.

It may look like a rock formation in the Utah desert, but this towering spire sits on Io, one of Jupiter’s moons. The image is a NASA animation rather than a photograph. It was built from data the Juno spacecraft collected during two daring flybys in December 2023 and February 2024, when it swooped about 930 miles (1,500 km) above Io’s surface. Scientists estimated the peak’s height from the long shadow it cast, at roughly 3 to 4 miles (5 to 7 km). That falls a little short of Everest, but Io has giants that easily beat it: Boösaule Montes soars about 57,000 feet (17.5 km), nearly twice the height of Earth’s tallest mountain. Add hundreds of active volcanoes, and Io earns its title as the most volcanically restless world in the solar system.

If you ever tuned an old analog TV to an empty channel, you saw a screen of fuzzy black-and-white “snow.” Most of it came from ordinary sources, like electronics inside the TV, radio signals and even the Sun. About 1% of it, though, came from something far older: the cosmic microwave background, the faint afterglow of the Big Bang. This light was released about 380,000 years after the universe began, when it had cooled enough for the first atoms to form and light could finally travel freely. Over the following 13.8 billion years, the expansion of space stretched that light into microwaves, and some of it ended up on living room TV screens. Today it’s incredibly cold, about −455°F (−270°C), just 2.7 degrees above absolute zero.

Scientists discovered it almost by accident. In 1964, Arno Penzias and Robert Wilson of Bell Labs were using a large horn-shaped antenna in Holmdel, New Jersey, and kept picking up a strange hiss coming from every direction. Suspecting the pigeons nesting inside, they cleaned out what they politely called a “white dielectric substance” and relocated the birds, which soon flew back. The noise remained. It turned out they had stumbled onto the leftover glow of the universe’s birth, a discovery that earned them the 1978 Nobel Prize in Physics.

The supermassive black hole at the center of the Perseus galaxy cluster, about 240 million light-years away, sends pressure waves through the hot gas around it. In 2003, astronomers worked out that these waves correspond to a B-flat about 57 octaves below middle C, far too low for human ears. In 2022, NASA scaled the sound up to an audible range, and the result is so eerie that one newspaper described the listeners’ reactions as “cosmic horror.”

When a massive star collapses, it can leave behind a neutron star, one of the densest objects in the universe. Neutron stars pack more mass than the Sun into a ball only about 12 miles (20 km) across, roughly the size of a city. According to NASA, a sugar-cube-sized piece of one would weigh about a billion tons on Earth, as much as a mountain.

The fastest-spinning star ever found is a neutron star called PSR J1748-2446ad. It completes about 43,000 rotations a minute. It was discovered in 2004 in a star cluster called Terzan 5, about 18,000 light-years away. At its equator, its surface moves at roughly 24% of the speed of light.