- Astronomers, anthropologists, geologists, and many other scientists made mind-boggling breakthroughs in 2019.
- Some highlights include work that produced the first image of a black hole, traced the origins of modern humans, and predicted future sea-level rise.
- These are 26 of the biggest scientific accomplishments of the year.
In 2019, scientists around the world pulled off some impressive feats: They imaged a supermassive black hole for the first time, debuted two treatments for the Ebola virus, and launched a spacecraft into orbit that's powered by sunlight alone.
These and other accomplishments are improving scientists' understanding of our own biology, our planet, and the surrounding cosmos.
As a new year — and a new decade — approaches, here's a look back at some of the most mind-boggling scientific discoveries from 2019.
On New Year's Day, NASA's nuclear-powered New Horizons spacecraft flew past a mysterious, mountain-sized object 4 billion miles from Earth.
The object, called MU69, is nicknamed Arrokoth, which means "sky" in the Powhatan/Algonquian language (it was previously nicknamed Ultima Thule). It's the most distant object humanity has ever visited.
The New Horizons probe took hundreds of photographs as it flew by the space rock at 32,200 miles per hour.
Images revealed that Arrokoth is flat like a pancake, rather than spherical in shape. The unprecedented data will likely reveal new clues about the solar system's evolution and how planets like Earth formed, though scientists are still receiving and processing the information from the distant probe.
Just days after New Horizons' fly-by, China's Chang'e-4 mission put a rover and lander on the far side of the moon — the part we can't see from Earth.
Before Chang'e-4's success, no country or space agency had ever touched the far side of the moon.
The name "Chang'e" is that of a mythical lunar goddess, and the "4" indicates that this is the fourth robotic mission in China's decade-long lunar exploration program.
The rover landed in the moon's South Pole-Aitken Basin, which is the site of a cataclysmic collision that occurred about 3.9 billion years ago. The celestial smash-up left a 1,550-mile-wide impact site that likely punched all the way through the moon's crust. Landing the spacecraft in this crater could therefore enable scientists to study some of the moon's most ancient rocks.
Elsewhere in the solar system, NASA scientists learned about Mars quakes, the red planet's version of earthquakes.
NASA's InSight lander, which touched down on Mars in November 2018, has given scientists the unprecedented ability to detect and monitor Mars quakes.
The lander's built-in seismometer detected its first Mars quake in April. Since then, researchers have recorded more than 100 seismic events, about 21 of which were likely quakes. Reading the seismic waves on Mars, scientists hope, will reveal clues about what the planet's inside looks like.
Over 5.5 million miles from Earth, a Japanese spacecraft landed on the surface of an asteroid called Ryugu in July.
In order to collect samples from deep within the space rock, Hayabusa-2 blasted a hole in the asteroid before landing. The mission plan calls for it to bring those samples back to Earth. By studying Ryugu's innermost rocks and debris — which have been sheltered from the wear and tear of space — scientists hope to learn how asteroids like this may have seeded Earth with key ingredients for life billions of years ago.
NASA's Voyager 2 spacecraft left our solar system and entered the depths of interstellar space.
The probe beamed back unprecedented data about previously unknown boundary layers at the far edge of our solar system — an area known as the heliopause.
The discovery of these boundary layers suggests there are stages in the transition from our solar bubble to interstellar space that scientists did not know about until now.
In December, the European Space Agency launched a new space telescope into orbit to examine known exoplanets in more detail.
The CHaracterizing ExOPlanets Satellite (CHEOPS) has a foot-wide camera lens designed specifically to study the size and mass of known exoplanets smaller than Saturn.
CHEOPS will also look for atmospheres on those far-away worlds — a requirement for any planet to host life.
Kate Isaak, a physicist on the CHEOPS team, said in a press release that the telescope will "take us one step closer to answering one of the most profound questions we humans ponder: Are we alone in the universe?"
This was also a watershed year for the study of black holes. In April, the Event Horizon Telescope team published the first-ever image of a black hole.
The unprecedented photo shows the supermassive black hole at the center of the Messier 87 galaxy, which is about 54 million light-years away from Earth. The black hole's mass is equivalent to 6.5 billion suns.
Though the image is somewhat fuzzy, it showed that, as predicted, black holes look like dark spheres surrounded by a glowing ring of light.
Scientists struggled for decades to capture a black hole on camera, since black holes distort space-time, ensuring that nothing can break free of their gravitational pull — even light. That's why the image shows a unique shadow in the form of a perfect circle at the center.
That wasn't the only black hole breakthrough this year: For the first time, scientists detected a black hole devouring a nearby neutron star.
In August, astrophysicists detected the aftermath of a collision between a black hole and a neutron star (the super-dense remnant of a dead star).
This was the third event scientists observed using gravitational-wave detectors. In 2015, researchers detected waves from the collision of two black holes, and in 2017 they observed two neutron stars merging.
Einstein predicted the existence of gravitational waves in 1915, but thought they'd be too weak to ever pick up on Earth. New tools have proved otherwise.
This year saw many innovations in space-travel technology, too. In March, SpaceX launched Crew Dragon, a commercial spaceship designed for NASA astronauts, into orbit for the first time.
The maiden flight of Crew Dragon marked the first time that a commercial spaceship designed for humans has left Earth.
It was also the first time in eight years that any American spaceship made for people launched into orbit. Crew Dragon's successful test flight was a critical milestone for the US. Since NASA retired its fleet of space shuttles in 2011, the US has relied on Russian rockets and ships to taxi astronauts to and from the ISS.
Scientists also successfully harnessed the power of sunlight to propel a spacecraft.
This summer, the Planetary Society — led by science communicator Bill Nye — launched a satellite called LightSail 2 into orbit, where it then unfurled a 344-square-foot solar sail.
As light particles reflect off that sail, they transfer momentum to the spacecraft.
A spacecraft that utilizes a solar sail in this way has an almost unlimited supply of energy. Advancing this type of propulsion technology could one day help spacecraft reach nearby star systems that aren't currently accessible due to the finite amount of fuel we can launch off the planet.
On Earth, scientists have made monumental — though often troubling — discoveries. Climate researchers found that the Antarctic and Greenland ice sheets are melting at unprecedented rates.
In April, a study revealed that the Greenland ice sheet is sloughing off an average of 286 billion tons of ice per year. Two decades ago, the annual average was just 50 billion.
In 2012, Greenland lost more than 400 billion tons of ice.
Antarctica, meanwhile, lost an average of 252 billion tons of ice per year in the last decade. In the 1980s, by comparison, Antarctica lost 40 billion tons of ice annually.
What's more, parts of Thwaites Glacier in western Antarctica are retreating by up to 2,625 feet per year, contributing to 4% of sea-level rise worldwide. A study published in July suggested that Thwaites' melting is a time bomb that is likely approaching an irreversible point after which the entire glacier could collapse into the ocean. If that happened, global sea levels would rise by more than 1.5 feet.
Researchers' predictions about coming sea-level rise are getting more accurate — and scarier. Estimates suggest the world's oceans could rise 3 feet by 2100.
A September report from the United Nations Intergovernmental Panel on Climate Change projected that sea levels could rise by more than 3 feet by the end of the century. The rising water could affect hundreds of millions of people who live on small islands and in coastal regions.
Another study suggested that the number of people displaced by sea-level rise could reach 630 million if greenhouse-gas emissions continue to rise through 2100.
Another landmark UN report revealed that between 500,000 and 1 million plant and animals species face extinction, many within decades.
The report, published in April, estimated that 40% of amphibian species, more than 33% of all marine mammals and reef-forming corals, and at least 10% of insect species are threatened, largely as a result of human actions. Researchers also found that more than 500,000 land species already don't have enough natural habitat left to ensure their long-term survival.
This finding contributes to a rapidly growing body of evidence that suggests Earth is the midst of a sixth mass extinction — the sixth time in the planet's history that species are experiencing a major global collapse in numbers.
One nearly long-lost species, however, emerged from the wilderness this year. In June, scientists spotted a giant squid in its deep-sea habitat in the Gulf of Mexico.
The giant squid, which inspired the legend of the Kraken monster, has only been caught on video one other time. The creatures almost never leave the icy depths of their habitat, up to 3,300 feet (about 1,000 meters) beneath the waves.
In 2012, scientists from Japan's National Museum of Nature and Science filmed a giant squid in its natural habitat in the Ogasawara archipelago.
Another hidden part of nature — a lost continent — was found hiding under Europe.
Hundreds of millions of years ago, Earth had one giant supercontinent named Pangea, which eventually broke up into our modern-day continents. A recent study showed that in that process, an eighth continent slid under what is now southern Europe about 120 million years ago.
It's still hidden deep within the Earth.
The researchers named this continent Greater Adria. Its uppermost regions formed mountain ranges across Europe, like the Alps.
Anthropologists dug deep into the Earth to make incredible discoveries in 2019. In August, researchers announced they'd found the oldest skull ever seen from one of our human ancestors.
The nearly-intact skull, which belonged to the species Australopithecus anamensis, is 3.8 million years old. The fossil, nicknamed "MRD," revealed that these ancient people had protruding faces with prominent foreheads and cheek bones, much like other Australopithecus species in the fossil record.
"The MRD find is an iconic cranium," paleoanthropologist Tim White told Nature.
MRD's age also suggested that these human ancestors coexisted with another species of human ancestor, Australopithecus afarensis, for at least 100,000 years. The nearly complete skeleton "Lucy" was a member of the latter group, which roamed Africa between 3.9 million and 3 million years ago.
In April, anthropologists discovered teeth and a finger bone from a new species of human ancestor.
The new species, named Homo luzonensis after the Philippine island on which it was discovered, lived between 50,000 and 67,000 years ago.
Researchers also used DNA analysis to pinpoint where anatomically modern humans originated: modern-day Botswana.
An October study suggested that every person alive today descended from a woman who lived in an area of modern-day Botswana south of the Zambezi River about 200,000 years ago. Researchers narrowed in on that area using genetic analysis of DNA that gets passed down the female line.
This finding supports the theory that modern human ancestors migrated out of Africa then populated the world, rather than evolving in different pockets around the globe simultaneously.
Physicists, engineers, and biologists made big breakthroughs this year, too. This summer, researchers captured quantum entanglement on camera for the first time.
According to quantum mechanics, two particles can be paired and separated, yet remain intimately and instantly connected across vast distances. One particle will affect the other no matter how far apart they are.
This is "quantum entanglement," and the strange phenomenon rattled Albert Einstein so much that he died disbelieving it could exist.
"The image we've managed to capture is an elegant demonstration of a fundamental property of nature, seen for the very first time in the form of an image," Paul-Antoine Moreau, a physicist at the University of Glasgow, said in a press release.
In October, engineers at Google announced they had created a quantum computer that could perform a computation in just over 3 minutes that would take the world's fastest supercomputer 10,000 years to achieve.
This achievement in quantum computing — a field of study that strives to enable computers to perform exponentially faster than today's machines — could be used to improve artificial intelligence or assist in the development of new drugs.
Google described the milestone in a paper published in the journal Nature. The authors said the company had achieved "quantum supremacy," meaning their computer did something a conventional computer could never do.
Researchers at St. Jude's hospital also found a cure for a severe genetic disease called "bubble boy" syndrome.
Babies who are born with X-linked severe combined immunodeficiency (XSCID) don't have disease-fighting immune cells. For them, the outside world is an intensely dangerous place.
XSCID was nicknamed "bubble-boy" disease because of a young boy named David Vetter, who famously lived his entire life in a protective plastic bubble. Vetter died more than 30 years ago at age 12 after a failed treatment.
In April, St. Jude scientists announced that they had successfully cured babies with XSCID using a new experimental gene therapy.
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