Our planet orbits around the Sun at a distance of 93 million miles (150 million km), or eight and a half “light-minutes”—meaning that the Sun’s light takes eight and a half minutes to reach us. The next nearest stars are a few light-years away—or, just over half a million light-minutes. The closest galaxies to our Milky Way, the cosmic island of stars in which the Sun circles, lie millions of light-years out. And the farthest galaxies, faint specks that astronomers pick out as they peer across the universe through their telescopes, are billions of light-years distant—so far from us that we see them as they were billions of years in the past, long before human beings had even begun to evolve on Earth.
When I say space is big, I mean, it really is fucking enormous.
During the early 20th century, this became very apparent to a young German scientist named Albert Einstein, one of his country’s more affable exports of the time. He developed the theory of relativity—essentially a new take on the physics of motion and gravity, which was soon proven to roundly shit all over the ideas of the British polymath Sir Isaac Newton, who had laid the foundations of these fields more than 200 years earlier.
Don’t feel too sorry for Newton, though. Despite making stellar contributions to many areas of physics and mathematics, he’s generally regarded by historians of science as something of an all-round douchebag. He was renowned for stealing other scientists’ ideas, and dedicated much of his time and energy to sullying the reputations of those he viewed as rivals—of which there were many, perhaps most notably the German mathematician Gottfried Leibniz. He later became warden of the Royal Mint, in London, where he delighted in sending counterfeiters to their deaths at the end of a rope.
Had Newton been around to witness the publication of Einstein’s theory of relativity, he might have had Einstein killed and thrown from a train. As it happened, his loss was science’s considerable gain. It was relativity that gave scientists the means to construct the first decent mathematical models of the universe. These theories, together with the best astronomical observations, led to the conclusion that the universe started out some 14 billion years ago in a cataclysmic event that’s become known as the Big Bang. Matter and energy, as well as the very space and time in which they exist, were all brought into being at this moment.
The theory also predicted that the space of our universe was expanding. Distant galaxies on opposite sides of the night sky are literally rushing away from one another—a fact that was later confirmed by American astronomer Edwin Hubble.
Within our own galaxy, astronomers have found some distant stars to have planets in orbit around them. These worlds are known as extrasolar planets, sometimes shortened to just “exoplanets,” and they lie far beyond the confines of our own solar system.
It’s been conjectured that some of these faraway worlds may harbor life, and plans are now underway to build telescopes powerful enough to study their chemistry in more detail—aliens’ farts (and other chemical markers of life) leave a telltale signature in the atmosphere of a planet that can be detected from light-years away.
Closer to home, there are still hopes that we might find traces of extraterrestrial life within our own solar system. Our next-door neighbor Mars, and the ocean of liquid water thought to exist beneath the surface ice of Jupiter’s moon Europa are prime candidates. Sadly, however, this life is unlikely to be anything more complex or intelligent than microbes, or at best primitive multicelled blobs. I probably don’t need to add that diminutive gray-green humanoids landing saucer-shaped spacecraft on the White House lawn is about as probable as cloning Elvis or cold fusion.
Robot space probes are already looking for life on Mars and are due to get closer views of Europa over the coming decade. Robots are the explorers of choice for these far-flung destinations in the solar system, being much more robust than humans, and offering greater value for the money in terms of the scientific results they can deliver.
Crewed spaceflight to Earth orbit continues, but is becoming increasingly outsourced to commercial operators. Soon, Elon Musk’s private space launch company, SpaceX, is to begin ferrying crews to and from the International Space Station, while Virgin Galactic is to take paying space tourists on suborbital trips. And more power to them. Reality TV stars, bankers, entrepreneurs, and purveyors of ear-piss chart pop are all lining up to have themselves shot into the wild black yonder. It’s a good time to be alive.
In this chapter you’ll find some of the more astounding discoveries concerning the universe and our place in it—things that we’ve just learned in recent years. Find out why we haven’t seen any evidence of intelligent extraterrestrials, even though many scientists believe the universe is teeming with life. Discover why sunsets on Mars are blue, not red (Total Recall fans, rejoice). And read about the closest Earth-like planet, now known to be just six light-years away (a hop and a skip in galactic terms). And more. Plus, naturally, you can find some of the madder celestial observations to grace the news, like why Uranus really does smell of farts—and why male genitalia could be the first thing to greet visiting aliens.
18
WHY ARE MARS’S SUNSETS BLUE?
by Alfredo Carpineti
EARTH AND MARS ARE A BIT LIKE MIRROR WORLDS. Mars is the Red Planet. Earth is the pale blue dot. Mars is a frigid desert. Earth is full of water and life. But there’s another curious difference. The sky on Mars is red, while its sunsets are blue.
The reason behind this is similar to why our sky is blue and our sunsets are red. The light from the Sun scatters based on what chemicals and particles are in the atmosphere. Sunlight comprises light of many different colors, and molecules and dust particles only interact with a specific range of these. The scattering of light by these particles is key to the color that we see.
Mars’s atmosphere is very tenuous—its pressure is equivalent to about 1 percent of Earth’s. It is made of carbon dioxide and has a lot of dust. This fine dust tends to scatter red light, which is why the diffuse glow of the sky appears reddish, whereas blue light is allowed to pass straight through. On Earth, it is the other way around. Blue light bounces off air molecules, giving our sky its characteristic hue.
At sunset, light has a longer distance to travel within the atmosphere, so it scatters more (picture the Sun low in the sky—its light has to pass through a greater length of atmosphere to reach you than it does when it’s directly overhead). What is left is the color that we see.
During sunset on Earth, this means that most of the blue light is scattered away and what’s left to reach our eyes is a fierce red. The reddening effect is amplified further by dust in the air, ash from volcanoes, and smoke particles from fires. On Mars, the opposite is true and the daytime sky is salmon-colored, giving way to a cool blue color at sunset.
Curiosity, Spirit, and Opportunity, the robotic rovers we’ve sent to the Red Planet, have witnessed and recorded the curious phenomenon. Interestingly, Earth and Mars are the only two places in the solar system that have sunsets we can observe.
Mercury lacks an atmosphere so we would see the Sun disappear instantaneously at sundown while the temperature goes from 801°F (427°C) to—279°F (–173°C), as night falls. It also has a very long day, rotating on its axis once every 58 and a bit Earth days. But going to Venus would be even worse. The thick cloud cover and extremely dense atmosphere blocks the Sun’s light altogether. And the high temperature and acid rain would melt our spacesuits—and eventually our bodies.
Maybe Titan, the largest moon of the faraway ringed planet Saturn, could offer a rare sunset, within its dense, murky atmosphere. But, for the time being, we must content ourselves with our earthly sunsets and the haunting images of those on Mars.
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COLOSSAL DRAWING OF A PENIS THAT CAN BE SEEN FROM SPACE PROVES HUMANITY WILL NEVER CHANGE
by Robin Andrews
IT’S HARD NOT TO WONDER WHAT IT’D BE LIKE IF advanced aliens were tuning in to our planet right now, downloading the latest news and gossip in an attempt to understand just where our civilization is at. Hopefully, they’d gloss over a few details, like the movie Geostorm, the current US federal government—and the colossal penis currently splashed across part of Australia.
Yes, you read that correctly. It appears that a rather sizable phallic drawing has appeared in the dry lake bed in Bellarine, a rural part of the state of Victoria.
The Geelong Advertiser, Victoria’s oldest morning newspaper, noted: “Popular Facebook group Take the Piss Geelong shared images of the crass crop circle creation on Monday night, but it is understood locals have been aware of it for months.”
The phallus is so large that it’s been spotted on Google Maps, where it’s labeled the “Aussie Weiner.” Indeed, if the scale provided by Google Maps is to be believed, then it would appear to be in excess of 200 feet (60 meters) long—or roughly the length of four buses parked end to end.
Etching out a todger of such proportions actually goes well above the call of duty. Earth-orbiting satellites—and even handheld photography equipment aboard the International Space Station—are so good these days they can zoom in on the tiniest of details. Though fair play, it is quite impressive that someone took the time and effort to actually carve out a sedimentological member so large.
In case you’ve been living in a cave for your entire life, you’ll be aware that humanity has obsessed over all things phallic since time immemorial. From the murals of Pompeii and Herculaneum to toilet walls in pretty much any country on Earth today, a dangly, two-dimensional rendering of the male thingamajig is never far away.
When it comes to making penises you can see from space, though, those lewd, snickering Brits have a long and distinguished history. Centuries ago, a man with a ludicrous erection (now known as the Cerne Abbas Giant) was carved into the chalk on the side of a hill in the English county of Dorset, where it is maintained to this very day. In 2007, students in Southampton, in the south of the UK, used weed killer to create a more viridian-colored penis on their school lawn that you could also see from space. So the Aussie Weiner is just the latest “member” of the club, so to speak.
Perhaps, when it comes to giant geoglyphs, passing aliens will pay more attention to features like the Nazca Lines of southern Peru. These ancient trenches, many of which are hundreds of yards (meters) long, depict dozens of animals and shapes. Constructed around 2,000 years ago, they are quite rightfully a UNESCO World Heritage Site.
Then again, the aliens might take stock of our dickish doodlings and conclude that, in the last few thousand years, human beings as a species really haven’t achieved very much at all.
21
ELON MUSK’S TESLA ROADSTER COULD CRASH BACK INTO EARTH
by Jonathan O’Callaghan
RESEARCHERS HAVE FOUND THAT ELON MUSK’S TESLA Roadster car, launched toward the orbital plane of Mars in early 2018, has a small but not insignificant chance of hitting Earth in the next few million years.
Writing in a paper published in Aerospace, the team, from the University of Toronto in Canada, said there was a 6 percent chance of it hitting Earth in the next million years. That rises to 10 percent over 3 million years.
The team, who specialize in orbital mechanics, used their existing models to simulate 240 future possible paths for the car, launched on SpaceX’s Falcon Heavy rocket on February 6, 2018. Although they note that it is hard to calculate exact figures, due to its chaotic orbit, it is possible to determine statistical probabilities of collisions far into the future.
“We have all the software ready, and when we saw the launch last week we thought, ‘Let’s see what happens,’” Hanno Rein, the study’s lead author, said in Science magazine.
“So we ran the [Tesla’s] orbit forward for several million years.”
The car is on an elliptical orbit lasting 1.5 years that takes it out to roughly 1.7 AU (astronomical units, where 1 AU is the Earth-Sun distance) from the Sun, about the same size as the orbit of Mars. It then swings inward to about 0.99 AU before heading out again.
The team found that the car’s first close encounter with Earth occurs in 2091, when it will approach to about the same distance as the Moon and will possibly be visible to telescopes on Earth. After that, there are a number of possibilities, depending on what happens to its orbital path as a result of interactions with other bodies.
Some of the outcomes gave the car a 2.5 percent chance of hitting Venus within the next million years, while there was a tiny chance of it hitting the Sun in 3 million years. There’s a 50 percent chance the car will survive for a few tens of millions of years. Earth seemed to be the most likely target, although in reality we probably don’t have too much to worry about.
“It will either burn up or maybe one component will reach the surface,” Rein said. “There is no risk to health and safety whatsoever.”
And that’s even if the car survives that long in its current form. By some predictions, it will have been mostly stripped away by radiation within just a year. So even if it ever does make it back to the vicinity of Earth, it might not look very recognizable.
23
URANUS HAS EXPERIENCED A COLOSSAL POUNDING
by Alfredo Carpineti
URANUS IS A FUNNY PLANET. AND NOT JUST BECAUSE it has a vaguely innuendo-y name in the English language; it is absolutely peculiar in its own right. One of its weirdest features is its tilt. Uranus rotates around the Sun on its side, with each pole facing the Sun for 42 years before switching. The cause of this weird tilt is long suspected to have been a collision with another planet-sized object, and a study published in July 2018 calculated the details of the impact.
As reported in the Astrophysical Journal, an international team used sophisticated computer simulations to try to reproduce the current configuration of the ice giant planet. After examining the results from 50 different impact scenarios, they believe that Uranus was hit by an object roughly twice as massive as Earth, most likely made of rock and ice. This happened around 4 billion years ago when the solar system was still quite young.
The impact didn’t just influence the planet’s tilt. The researchers believe that it can also explain its surprisingly low temperature. They say debris from the impactor may have acted as a thermal shield, trapping the heat from the planet’s interior and making the outer atmosphere extremely cold.
“Uranus spins on its side, with its axis pointing almost at right angles to those of all the other planets in the solar system,” lead author Jacob Kegerreis, a PhD researcher at Durham University, said in a statement. “This was almost certainly caused by a giant impact, but we know very little about how this actually happened and how else such a violent event affected the planet.
“Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today.”
Based on the simulation results, the most likely scenario has the impactor delivering a grazing blow to Uranus. This affected the planet’s tilt but left most of its atmosphere in place. The impact might also have played a role in the formation of the planet’s rings and moons. Such an impact could have thrown enough material into orbit to coalesce into some of its inner moons, and could also have affected the orbits of preexisting moons.
Large impacts were a frequent occurrence in the early solar system. Our own Moon is the result of a cataclysmic impact between the Earth and a planetoid roughly the size of Mars. Uranus is similar to the most common type of exoplanet we have discovered so far, so this gives us a better understanding of distant planetary systems and the likelihood that they can host life.
24
FIRST RESULTS FROM NASA’S TWINS EXPERIMENT SURPRISE SCIENTISTS
by Jonathan O’Callaghan
IN 2015 AND 2016, NASA CONDUCTED A UNIQUE EXPERIMENT on twin astronauts, where one was monitored while in space and the other remained on the ground.
The experiment involved astronaut Scott Kelly and his brother Mark, a former astronaut. Scott spent a year at the International Space Station (ISS) between March 2015 and March 2016, while his brother Mark remained on Earth. During that time, tests were performed on each of them.
One of the main reasons for doing the study was to see how long-term spaceflight affects the human body. Although we’ve been sending humans into space for decades now, the exact physical and mental changes that take place still aren’t clear. Getting to the bottom of this will be crucial for future long-term missions, like trips to Mars.
The first results from the study were presented on January 26, 2017, in Galveston, Texas, at a NASA Human Research Program meeting. Researchers found that Scott’s telomeres—caps on the end of each DNA chromosome that prevent the genetic material from unraveling—grew longer than his brother’s, which was a surprise to the scientists.
“That is exactly the opposite of what we thought,” Susan Bailey, a radiation biologist at Colorado State University in Fort Collins, told the science journal Nature.
The length of Scott’s telomeres returned to normal quite quickly after he returned to Earth, for reasons unknown at the moment.
Changes were also spotted in the DNA of the twins. Specifically, Scott went through less DNA methylation, a process where molecules called methyl groups are added to DNA; this alters how the information contained in genes is expressed as actual biological traits.
The researchers also found changes in gut microbe balance between the flight twin and his earthbound sibling.
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A Super-Earth Has Been Discovered Just Six Light-Years Away, the Second-Closest Planet to Our Solar System
by Jonathan O’Callaghan
Scientists have discovered a super-Earth, a large Earth-like planet, roughly 3.2 times the mass of the Earth, orbiting a red dwarf called Barnard’s star. This is located just six light-years away, making this the second-closest planet to our solar system. The findings were published in Nature in November 2018.
FOR DECADES WE HAVE SEARCHED FOR WATER ON MARS, and we’ve found very little, either in the form of trickles on the surface or frozen as ice. But an incredible discovery may change everything.
Researchers, led by Dr. Roberto Orosei from the National Institute of Astrophysics (INAF) in Rome, reported in 2018, in the journal Science, that they have found a vast reservoir of water beneath Mars’s south pole. So vast, in fact, that it looks similar to a subglacial lake on Earth—one where life could arise.
“This is potentially the first habitat we know of on Mars,” Dr. Orosei told IFLScience. “It’s the first place where microorganisms like those that exist today on Earth could survive.”
The large reservoir of water was found by a radar instrument, the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument, onboard ESA’s Mars Express orbiter. The team used data collected by the spacecraft from May 2012 to December 2015.
The data showed that 0.9 miles (1.5 km) below the surface, in a region called Planum Australe, there was a source of liquid water spanning about 12 miles (20 km) across. The team do not know exactly how deep this reservoir of water is, but note that it is deeper than a few tens of centimeters.
It was detected by sending 29 sets of radar pulses under the surface, with reflections showing a radar signal almost identical to that from lakes of liquid water found beneath the ice of Antarctica and Greenland on Earth. This strongly suggests that it is not only water, but that it is in liquid form.
“It’s very difficult to say what we’re really looking at,” Dr. Anja Diez, from the Norwegian Polar Institute in Tromsø, Norway, told IFLScience. Dr. Diez wrote an accompanying perspective on the research. “It could either be a thin layer of water, a large layer, or water in sediments.”
The team said they considered some other possibilities for the signal, including a layer of carbon dioxide ice or very low-temperature water ice. They believe these explanations are unlikely, however, because they would not have caused such a strong radar reflection.
The characteristics of this suspected water are complicated by the conditions it is in. On Earth, subglacial lakes reach temperatures of about–76°F (–60°C). The intense pressure caused by the ice pressing down from above lowers the melting point of the water, allowing it to remain liquid.
Under this region on Mars, however, it’s thought that the temperature drops further, to around–90°F (–68°C). In order for the water to remain liquid here, it is likely full of salts, like magnesium, calcium, and sodium, and thus quite briny—different from the freshwater lakes often found on Earth.
“Underneath the Antarctic ice sheet, water can be at its melting point because of the ice above,” said Dr. Diez. “On Mars it’s a bit different, as really cold temperatures are expected under the ice. Water can only exist because it’s briny.”
A handful of subglacial lakes have been drilled into on Earth, including Lake Vostok in Antarctica. These projects are not easy and it can take years to dig below several kilometers of ice. But the scientific payoff is huge—and every time we drill down into these lakes, we find life.
Previously on Mars, we have found evidence for water trickling on the surface, known as recurring slope lineae (RSL). These features are short-lived, however, with the water quickly evaporating in the low-pressure environment on the Martian surface.
It’s long been theorized that there may be more stable bodies of liquid beneath the surface. And if that really is the case, it will provide an exciting new habitat for microorganisms of the past or present on Mars.
“It’s very important to know if this [reservoir] is a unique thing,” said Dr. Orosei. “If it’s regional, not local, then you can have a whole system of subglacial lakes similar to what you see on Earth. You would have ways for living organisms, if they existed, to have a much larger environment and perhaps move around.”
The team hope to investigate further, using more data from the Mars Express orbiter over the coming years. The spacecraft is aging, though, and it’s running out of fuel, so time is of the essence.
Getting to these sources of liquid water in the future may also be difficult. Drilling operations on Earth require complicated machinery, something we simply don’t have on Mars. The upcoming European ExoMars rover in 2021 will be able to drill about 6.6 feet (2 meters) below the surface, but that may not be enough to get close to subsurface reservoirs of water like this.
On Earth, liquid water almost always means life. Coupled with the recent discovery of the chemical building blocks of life on Mars, and the possibility that it once had a more habitable environment, evidence is building that the Red Planet may not be so dead after all.
“It’s likely that this is what we would describe as a habitat,” said Dr. Orosei. “It has at least some of the conditions that terrestrial microorganisms would need to survive.”
27
A NASA SPACECRAFT MAY HAVE DETECTED A GIANT WALL AT THE EDGE OF THE SOLAR SYSTEM
by Jonathan O’Callaghan
NASA’S NEW HORIZONS SPACECRAFT HAS HELPED scientists study a mysterious phenomenon at the edge of the solar system, where particles from the Sun and interstellar space interact.
This region, about 100 times farther from the Sun than Earth, is where uncharged hydrogen atoms from interstellar space meet charged particles from our Sun. The latter extend out from the Sun in a bubble called the heliosphere.
At the point where the two interact, known as the heliopause, it’s thought there is a buildup of hydrogen from interstellar space. This creates a sort of “wall,” which scatters incoming ultraviolet light.
In the early 1990s, NASA’s Voyager 1 and 2 spacecraft detected the first hint of this wall, and now New Horizons has found additional evidence for it. A paper describing the discovery was published in the journal Geophysical Research Letters, in August 2018.
“We’re seeing the threshold between being in the solar neighborhood and being in the galaxy,” Dr. Leslie Young from the Southwest Research Institute in Colorado, one of the co-authors on the paper, told Science News.
New Horizons made the detection using its Alice UV spectrometer, taking measurements from 2007 to 2017. It found an ultraviolet glow, known as a Lyman-alpha line, which is made when ultraviolet light gets scattered by hydrogen atoms.
We see this ultraviolet glow all over the solar system. But, at the heliopause, there appears to be an additional source caused by the wall of hydrogen, creating a larger glow. Beyond the wall there’s more ultraviolet light compared to in front of it, suggesting that the light is being scattered by the wall.
“This distant source could be the signature of a wall of hydrogen, formed near where the interstellar wind encounters the solar wind,” the researchers wrote in their paper.
The theory is not definitive yet. To find out for sure, New Horizons will continue looking for the wall about twice a year. If our estimates are correct, then the spacecraft should have reached where the wall is thought to lie by the time the mission ends in the mid-2030s. At that point, we should finally know for sure whether it’s there or not.
EARTH IS PASSING THROUGH A DARK MATTER “HURRICANE” RIGHT NOW
by Jonathan O’Callaghan
Hurricanes on Earth could be left looking like gentle gusts, according to scientists who have suggested that a dark matter “hurricane” in space may be whipping past the Sun, at speeds of up to 310 miles (500 km) per second.
Published in Physical Review D, the study, led by Ciaran O’Hare from the University of Zaragoza in Spain, looked at 30,000 nearby stars known as the S1 stream, believed to be a remnant of a dwarf galaxy that was swallowed by the Milky Way billions of years ago.
The researchers noted that, in addition to stars, the stream might also harbor about 10 billion solar masses of dark matter from the original dwarf galaxy, “blowing” past us. And this may produce noticeable effects near us, creating turbulence and eddies in the flow of dark matter around our galaxy.
No direct detection of dark matter has ever been made, despite numerous efforts. But this violent dark matter hurricane may provide astronomers with an intriguing opportunity to do so.
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A PHYSICIST CLAIMS HE’S FIGURED OUT WHY WE HAVEN’T MET ALIENS YET, AND IT’S PRETTY WORRYING
by Alfredo Carpineti
THE QUESTION “WHERE IS EVERYONE?” IS THE CRUX OF the Fermi paradox, originally asked by the Italian-American physicist Enrico Fermi. If life on Earth is not particularly special, he mused, then where are all the alien civilizations? Many explanations have been proposed to explain why we seem to be alone in the vast universe. None have been 100 percent convincing, and people continue to puzzle over a solution.
Russian physicist Alexander Berezin, from the National Research University of Electronic Technology (MIET), has another idea. He calls it the “First in, last out” solution of the Fermi paradox. He suggests that once a civilization becomes capable of spreading across the stars, it will inevitably wipe out all other civilizations.
This doesn’t mean that all alien races are necessarily evil. Simply put, they might not know we’re here, and their exponential expansion across the galaxy might be more important to them than whatever the consequences might be for other, inferior races, such as ourselves.
“They simply won’t notice, the same way a construction crew demolishes an anthill to build real estate because they lack incentive to protect it,” he wrote in a paper exploring the idea, which is available on the arXiv pre-print website.
While the picture he paints is quite grim, there’s an even less cheery aspect to his argument. He suggests that the reason we are still here is that we are not likely to be the ants. Instead, he believes that humans may be future destroyers of countless civilizations.
“Assuming the hypothesis above is correct, what does it mean for our future? The only explanation is the invocation of the anthropic principle. We are the first to arrive at the [interstellar] stage. And, most likely, will be the last to leave,” Berezin explained.
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BIBLICAL CITY OF SIN DESTROYED BY “SULFUR AND FIRE” MAY HAVE BEEN FLATTENED BY ASTEROID
by Madison Dapcevich
A CATACLYSMIC DISASTER OF BIBLICAL PROPORTIONS MAY have wiped out the ancient “city of sin” mentioned in the Christian Bible.
Located in the modern-day Jordan Valley, it’s told in the Book of Genesis that the notoriously sinful city of Sodom, and its neighbor Gomorrah, were destroyed by “sulfur and fire” because of their wickedness. A team of researchers who have spent more than a decade carrying out archaeological excavation work in the Holy Land say there may be some truth to this story after all. Presenting their work at the 2018 annual meeting of the American Schools of Oriental Research, they say a meteor explosion in the atmosphere instantly obliterated the city and a 15.5-mile-wide (25-km-wide) region around it.
“We’re unearthing the largest Bronze Age site in the region, likely the site of biblical Sodom itself,” said the excavation team on its website.
Analyses of the site, known as Tall el-Hamman and located just northeast of the Dead Sea, suggest that the area was occupied continuously for 2,500 years before suddenly collapsing at the end of the Bronze Age. Radiocarbon dating shows the mud-brick walls of almost every structure disappeared 3,700 years ago, leaving behind just their stone foundations. Outer layers of some pottery samples also show signs of melting—zircon crystals found inside them would have been formed within one second at high temperatures, possibly as hot as the surface of the Sun.
Ground surveys indicate more than 100 other small settlements in the area were also exposed to the disaster, killing the estimated 40,000 to 65,000 people who lived there.
Such an event has also occurred in recent history. In 1908, a blast near the Stony Tunguska River in Siberia flattened 772 square miles (2,000 km2) of woodland. The lack of any crater suggests this was also an airburst, the meteor exploding between 3 and 6 miles (5–10 km) above ground.
And a similar explosion in 2013 over Chelyabinsk, Russia, injured more than 1,600 people—mainly by flying glass, blown from windows by the force of the explosion.
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ASTRONOMERS HAVE SPOTTED A MYSTERIOUS “GHOST” GALAXY NEXT TO THE MILKY WAY
by Alfredo Carpineti
THE MILKY WAY IS NOT ALONE IN OUR CORNER OF THE universe. Our home galaxy is surrounded by dozens of small companion galaxies, some orbiting very close and some farther away. In 2018, researchers announced the discovery of a new dwarf galaxy and it doesn’t look quite how we would expect.
The object is called Antlia 2, or Ant 2, and it doesn’t seem to be quite there. It is comparable in size to the Large Magellanic Cloud (LMC), one of our two galactic companions visible to the naked eye, and yet it’s 10,000 times fainter. Basically, it is either far too large for its luminosity or far too dim for its size. A paper reporting the discovery is available on the e-print archive site arXiv.
“This is a ghost of a galaxy,” Gabriel Torrealba, the paper’s lead author from the University of Cambridge, said in a statement. “Objects as diffuse as Ant 2 have simply not been seen before. Our discovery was only possible thanks to the quality of the Gaia data.”
Gaia is the flagship European space observatory mission that is mapping the position of billions of stars in the Milky Way and beyond. Its first whiff of Ant 2 came when it detected a distant group of stars all moving together.
Together with the Anglo Australian Telescope, Gaia was able to estimate the distance and mass of Ant 2. It is located 130,000 light-years from the Milky Way and is over 13 million times heavier than the Sun. For a galaxy, though, that is definitely on the light side. The LMC, for example, weighs almost 1,000 times as much.