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.

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.

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..