Terrifying unexplained mysteries of deep space

Space is big and dark, and since there is no air, no one can hear you scream as you float away forever and ever and ever. But those are only the human-sized terrors that space has to offer our nightmares. Because, as you will see, if you step back a few thousand light years from your simple humanoid perspective, you will discover that the universe contains some much stranger, much larger, and much more terrifying mysteries than you ever thought to be afraid of.

'Wow' signal

In 1977, the Big Ear radio telescope at Ohio State University was busy listening. Big Ear was built in 1963 for the purpose of listening to wideband radio emissions from the stars, but in 1973 it was converted for the use of SETI (the Search for ExtraTerrestrial Intelligence), and began searching the skies for more specific narrowband signals that might indicate intelligent life. Being the 1970s, however, the analysis of the incoming radio signals wasn't particularly complex—mostly recording frequency, signal strength, and bandwidth—but in 1977 it was good enough for the operators to know it had picked up something interesting.

In August 1977, astronomer Jerry Ehman was looking at computer printouts of the signals received by Big Ear over the previous few days, when he came across a sequence of numbers and letters that have since become famous. 6EQUJ5 might seem innocuous, but along with other data, it represents a continuous narrow band signal of around 1420 megahertz, from a fixed point in space in the constellation Sagittarius, that gradually grows in strength and then fades as the radio telescope orientation passes across its source (an explanation of the sequence can be found here, provided by Mr. Ehman himself). When Ehman saw this sequence on the paper, he was so surprised he circled it and immediately wrote "Wow!" in the margin, hence the name.

Over the years, Ehman and others have repeatedly searched for the signal again, and tried to come up with more mundane explanations for its existence. But after ruling out aircraft, asteroids, reflected terrestrial signals, space farts, and the Bat Phone as alternate sources, the only explanation they haven't been able to rule out is … extraterrestrial intelligence.

1991 VG

In 1991, American astronomer James Scotti spotted something strange in the sky. From his first observations, he made predictions about where the object would show up again, but when he pointed his telescope in that direction, he failed to spot the object. Because it was so weird, the standard assumptions he had made about its likely speed and direction were wrong, and it was only by accident that he caught another glimpse of it in a later observation.

When he put two and two together, he realized that this strange object was circling the Sun in a very similar orbit to the Earth. This is quite rare for a natural object, because the proximity of Earth and its gravitational field will usually disrupt its orbit, sending it off on a new path. The only realistic explanation was that the object was some remnant of the various big-budget Cold War space launches, like a Saturn 5 second stage, or some Russian hardware. But when the course of the object was plotted backwards to its last close Earth approach around 1973, it failed to match up with any of the known launches of that era, leaving the whole thing a mystery … or a possible alien space probe.

The traveling black hole

Black holes are bad news, but here's one way to make them worse: send them flying across space. That's apparently what happened to one particularly large black hole, and scientists can't quite figure out why.

In 2012, NASA discovered what, in all likelihood, was a humongous black hole being kicked out of its galaxy. It was observed hurtling away at speeds of "several million miles per hour." That a black hole got chucked like an unruly bar patron is bizarre enough, but consider just how massive a black hole is. As astronomer Francesca Civano — who led the study that discovered the black hole — explained, this black hole is millions of times more massive than the Sun, and this galaxy just sent it packing like nothing. That's like lifting an elephant with your pinkie and flinging it into the next state.

There are a few theories about how this happened, though none are proven. Civano and her team theorize that two galaxies (and the black holes in each) merged; the resulting gravitational waves gave the now-single hole a humongous kick-start, causing it to escape. Meanwhile, another theory involves three supermassive black holes clashing, with the lightest one getting kicked out of the party. Yet another theory says there are two supermassive holes, but the one that looks like it's leaving is actually arriving, attracted by the second hole. Current data supports the gravitational wave theory, but nothing's proven, aside from how a massive, invisible matter-sucker speeding through space is the stuff of nightmares.

ASASSN-15lh

Supernovas are some of the largest explosions humans are ever likely to witness, and like most loud bangs, it doesn't take too many before we start getting used to them. That is, until an even larger bang happens — then you sit up and take notice. That is the case with ASASSN-15lh, a superluminous supernova first observed in June 2015, that originated 2.8 billion light years away (and thus, 2.8 billion years ago!).

What makes ASASSN-15lh special is that scientists can't explain it. Unlike a regular supernova, ASASSN-15lh was ten times brighter, and considerably more powerful. Also, when astronomers analysed the light it was emitting, they couldn't find evidence of the hydrogen that should have been present. The best explanation involves something called a magnetar—a kind of magnetic neutron star—that by rapidly spinning with a powerful magnetic field, could provide extra energy to the expanding ball of superheated gas. However, it didn't take long for ASASSN-15lh to emit more energy than a magnetar should have been able to provide, and it just kept on going. Months after it first bloomed, it was still giving off more energy than the entire Milky Way galaxy we reside in.

But the strange didn't stop there. The usual behavior for a supernova consists of a bright flash, followed by a slow fading. And while ASASSN-15lh initially followed this course, a few months after it started to fade, the ultraviolet light started to increase again. This is not entirely unknown behavior for supernovas, but the light being emitted didn't fit the usual pattern. Scientists are still at a loss to fully explain the biggest bang known to mankind since the first one, and that's pretty scary.

KIC 8462852

A popular way to look for planets these days is to measure the amount of light a star is giving off. When a planet passes in front of its host star, it will cause a small, but detectable, drop in brightness. And by measuring the frequency of these dips, plus the size, it's possible to determine much about the nature of the planet, like if it is potentially habitable and thus home to alien life. Sometimes, however, the telescopes doing the observing see things that are harder to explain.

KIC 8462852 is a star in the Cygnus constellation approximately 1400 light years away from Earth. Unlike a star with a planet in orbit, this star displayed brightness dips of up to 20 percent, and they definitely weren't regular. One explanation was a cloud of comet fragments that found their way into a tight orbit around the star, but another theory proposes something a lot more concerning.

In 1960, physicist Freeman Dyson proposed a theory that an intelligent alien civilization might grow to a point where it required more energy than could be generated on a single planet. He theorised that such an advanced civilization might be able to construct a massive orbiting structure called a Dyson Sphere, that would be able to capture a significant proportion of the solar energy of a system's star and make it available to the population. Such a "megastructure" would capture most of the visible light of the star, but would still emit some infrared radiation, and would therefore be identifiable.

A variation of this theory, known as a Dyson Swarm, has been proposed as an explanation for what's happening around KIC 8462852. In this scenario, the civilization is building a swarm of orbiting satellites to achieve a similar goal to the sphere, but without the complications of trying to actually build a ball around a star.

Any civilization that is capable of building even a Dyson Swarm would be so far ahead of us technologically, we can't even imagine what they are capable of. And while NASA has found no evidence of radio emissions coming from that part of the sky, if they are capable of constructing Dyson Swarms, they have probably found a quicker way to communicate over large distances than electromagnetic radiation … not to mention quick ways to eradicate inferior galactic neighbors.

The Great Attractor

Have you ever had a nightmare where you're trapped and being dragged towards your inescapable doom? Well, you might not want to know, but on a galactic scale, we are living that nightmare right now. That's because, at a speed of 2.2 million kilometers per hour (human-fast, space-slow), the Milky Way, its companion galaxies, and various galactic hangers-on are all moving towards an area of space we don't know much about. The speed at which we are moving implies an area of space creating a massive gravitational force, roughly equivalent to 10,000 galaxies. And since it is sucking in everything within a considerable distance, this mysterious region has been dubbed "The Great Attractor." And if that isn't terrifying enough, we also can't see it.

The Great (and terrifying) Attractor sits in a region of space referred to by astronomers as the "Zone of Avoidance," which is ironic, because we can't avoid it. It's called that because it sits exactly on the other side of the densest part of the Milky Way, thus observing it through all those stars and massive clouds of space dust is nearly impossible. Nevertheless, astronomers have turned some of their instruments in the direction of the attractor, and determined that while there are a bunch of previously undiscovered galaxies in that region, there are still not enough to explain the force being exerted.

This leaves the true source of our eventual doom as either a previously inconceivable gravitational mass that we can't identify, or perhaps the interstellar equivalent of an internet dating serial killer: obscuring its identity behind a perfectly crafted profile to entice everyone within reach and draw them inexorably into their grubby space-van with blacked-out windows, dirty carpet, matching shovel accessories, and an entire superclusters' worth of chloroform..

Dark energy

In 1998, the Hubble telescope discovered that the universe was expanding much faster than it was before. Since then, NASA and friends have been trying to figure out why, and they still don't really know. They've got theories, like what NASA dubbed "some strange kind of energy-fluid that filled space." While such "energy-fluid" hasn't been proven or disproven, they've still dubbed whatever it is "dark energy," like a couple naming their kid years before making one.

So what is "dark energy"? We don't really know. Really, all we know for sure is that there's a lot more of it than light energy. NASA estimates the universe is about 68 percent dark energy, or roughly the amount Darth Vader had when he started questioning his loyalty to the Emperor. Dark energy's cousin, the almost-as-mysterious "dark matter," makes up an additional 27 percent of the universe. The remaining 5 percent is "light" energy, or stuff we can actually see. Yes: 95 percent of the universe is invisible. Sleep tight!

Part of Einstein's theory of gravity concerns a "cosmological constant," the idea that seemingly empty space is filled with its own energy. This energy would be produced by space, so as the universe expands and creates more space, that extra energy would make the universe move even faster. But since we have no clue how space could make its own energy (interstellar photosynthesis?) this is just one unproven theory among many more.

How will the universe end?

Eventually, the Earth will die, almost certainly because the Sun will scorch it when expanding into a Red Giant. This won't be for another 6 billion-ish years, so keep paying your taxes. What's less certain, however, is when the universe itself will die, and how. All we know for sure is that it's going to happen.

According to the BBC, some scientists feel the universe will perish via "heat death," where the differences in heat among separate objects will become nil. Since everything we know operates thanks to heat differences, uniform temperatures would mean nothing will work anymore. Eventually, heat itself will die, and the entire universe will freeze just a tick above absolute zero (-459.67 Fahrenheit). We end not with a bang, but a very heavy winter jacket.

Then there's the "Big Crunch" theory, positing that the universe will continue expanding until that's all it can expands, it can't expands no more. Then, everything will contract and collapse onto itself, coming together in a massively hot pig-pile of matter, much like it was pre-Big Bang. There's also the "Big Change" theory, where bubbles of dark energy consume our universe. They would transform matter at the molecular level, rendering everything inhospitable to the point where even atoms might not form anymore. Or how about the "Big Rip," where dark energy would expand, become more massive, and just tear galaxies to pieces? We have no proof the universe will end in any of these ways, so all we can do is hope we're dead before it does.

Gamma-ray bursts

Gamma-ray bursts (GRBs) don't happen very often, and considering they're basically giant, super-long explosions of energy (the most recent one, 2013's GRB 130427A, lasted 20 hours), that's a good thing. However, their rarity means we don't know too much about them, even though one may wind up killing us all some day.

We don't know exactly what GRBs are or how they happen. As NASA explains, GRBs might be caused by low-energy gamma rays that, once exposed to space, explode into high-energy rays. But even NASA admits that's just a theory, as are any other idea beyond "the Horrendous Space Kablooie come to life." And they are horrendous indeed — a 2014 study showed frequent GRB explosions have left swaths of the universe completely inhospitable. That study also said there's a good chance a GRB caused at least one mass-extinction event in Earth's history. And while we probably won't have a follow-up GRB (according to the BBC, our area isn't really vulnerable to one), it's still possible. The more we know about these things, the easier it might become to detect them before they explode and kill everything in sight. But that knowledge may be a long way off.

Eridanus Supervoid

Space is pretty big, and although there are lots of stars and galaxies and such flying about, there's also a lot of, well, space—that's why it's called that. And while astronomers are used to talking about large gaps between objects, one has been found that leaves even space experts speechless.

The first hint of the Eridanus Supervoid's existence turned up during a survey of the Cosmic Microwave Background, which is the electromagnetic remnants of the earliest moments of the Universe still whizzing about in space. When the clever people were looking at their results, they noticed a "cold spot" in the direction of the Eridanus constellation. Subsequent observations identified the Eridanus Supervoid as an unexpectedly large — and very empty — bit of space, around one billion light years in diameter. Even by astronomical standards, that's a pretty large piece of real estate … or real vacuum, if you prefer. Other voids have been found before, though this supervoid is so large that it can't be explained by current theories of the universe, which is pretty worrying.

Nevertheless, scientists love the opportunity to propose a new theory, and some of them are quite creative. The most straightforward idea proposes the existence of a super, super, super-massive black hole with the mass of thousands of galaxies. This would have the power to suck in all stars, planets, dust, light, dark matter, and cosmic microwave background radiation for huge distances, growing ever stronger with each meal. Black holes are always exciting, and incredibly massive ones even more so, but science has an even more terrifying theory cooked up too.

See, instead of a black hole, some researchers have proposed that the void is actually evidence of a parallel universe, no doubt with hordes of technologically advanced and ruthless aliens just waiting for a chance to evict us. More work is required to give greater credence to this theory (the parallel universe, not the aliens), but let's hope it's not true. One universe is quite enough to feel insignificant in — we don't need a few thousand more around the edges to devalue our life goals even further.

Zombie stars

Does anything sound more metal than "zombie stars"? Amazingly, they're real. Maybe. Few examples, even hypothetical ones, of zombie stars exist, but enough are out there to make you wonder if they're real. Space is pretty weird, remember.

In August 2014, NASA announced it had discovered a star system that had fallen victim to a weak supernova explosion, one dubbed SN 2012Z because scientists are not typically novelists. Usually, when stars supernova, it's game over, but in this case, scientists discovered that a part of the system's dwarf star may have survived as a sort of zombie star. If true, this would likely be because the supernova was a weak one, appropriately enough called a Type Lax supernova. The explosion would damage a star beyond repair but not outright destroy it, leaving behind a "zombie star." No such zombie has officially been confirmed yet, but it's currently the best explanation for how some stars can get blown to bits but still hang on.

Here's another reason they're called "zombie stars": they apparently scream as they eat other stars. As NASA explained, several seemingly dead stars are emitting high energy X-rays that could well be their "howls" or screams. If that's not freaky enough, they "scream" while siphoning energy off other nearby stars, essentially feasting on them. But NASA doesn't yet know how they emit these X-rays, considering they're supposedly dead. Perhaps they don't want to know, because an undead star basically eating the brains of a living one isn't a reality many of us are strong enough to face.

Dark flow

The observable universe is about 90 billion light years across, but experts feel the entire cosmos is at least 250 times larger. And apparently, something there is influencing the galaxies we can see, making some disappear like cosmic dust in the wind.

In 2008, a NASA team discovered weird, unexpected movements in far-off galaxy clusters. These movements seemed to be sending these galaxies in a single direction, away from anywhere we can see. The team's lead scientist, Alexander Kashlinsky, isn't sure what's causing these oddball movements, only that it doesn't seem to be anything observable. So he's theorized that forces beyond what we can see are controlling these clusters, dubbing whatever it is the "dark flow." There's no better name for an invisible force pulling entire galaxies into a mysterious void we can't even begin to see.

Amazingly, not only do we not know what the "dark flow" is, we're not even sure if it exists. As New Scientist reported, 2013 data from the Planck spacecraft seemingly disproved the flow, based on a high-res map showing no galaxy clusters flowing away from us like a single-line marching band. But even some Planck scientists insist that data was flawed, and in 2015 Kashlinsky and his team returned with a vengeance. They claimed follow-up studies proved consistent with their original findings, and the same "dark flow" dipole marker appeared in all their tests. This tells them dark flow is real, though we still don't know for certain. Hopefully it's not, because if so, our Milky Way might be next in line to join the Black Parade.