爱上海419论坛|阿拉爱上海同城|上海后花园论坛|夜上海419论坛|上海419龙凤

We’ve now seen farther, deeper and more clearly into space than ever before.

A stellar birthplace, a nebula surrounding a dying star, a group of closely interacting galaxies, the first spectrum of an exoplanet’s light. These are some of the first images from the James Webb Space Telescope, released in a NASA news briefing on July 12. This quartet of cosmic scenes follows on the heels of the very first image released from the telescope, a vista of thousands of distant galaxies, presented in a White House briefing on July 11.
“First of all, it’s really gorgeous. And it’s teeming with galaxies,” said JWST Operations Scientist Jane Rigby at the July 12 briefing. “That’s been true of every image we’ve taken with Webb. We can’t take [an image of] blank sky. Everywhere we look, there’s galaxies everywhere.”

Going deep
The galaxies captured in the first released image lie behind a cluster of galaxies about 4.6 billion light-years away. The mass from those closer galaxies distorts spacetime in such a way that objects behind the cluster are magnified, giving astronomers a way to peer more than 13 billion years into the early universe.

Even with that celestial assist, other existing telescopes could never see so far. But the James Webb Space Telescope, also known as JWST, is incredibly large — at 6.5 meters across, its mirror is nearly three times as wide as that of the Hubble Space Telescope. It also sees in the infrared wavelengths of light where distant galaxies appear. Those features give it an edge over previous observatories.

“There’s a sharpness and a clarity we’ve never had,” said Rigby, of NASA’s Goddard Space Flight Center in Greenbelt, Md. “You can really zoom in and play around.”
Although that first image represents the deepest view of the cosmos to date, “this is not a record that will stand for very long,” astronomer Klaus Pontoppidan of the Space Telescope Science Institute in Baltimore said in a June 29 news briefing. “Scientists will very quickly beat that record and go even deeper.”

But JWST wasn’t built only to peer deeper and farther back in time than ever before. The cache of first images and data showcases space scenes both near and far, glimpses of single stars and entire galaxies, and even a peek into the chemical composition of a far-off planet’s atmosphere.

“These are pictures just taken over a period of five days. Every five days, we’re getting more data,” European Space Agency science advisor Mark McCaughrean said at the July 12 briefing. (JWST is an international collaboration among NASA, ESA and the Canadian Space Agency.) “It’s a culmination of decades of work, but it’s just the beginning of decades. What we’ve seen today with these images is essentially that we’re ready now.”
Cosmic cliffs
This image shows the “Cosmic Cliffs,” part of the enormous Carina nebula, a region about 7,600 light-years from Earth where many massive stars are being born. Some of the most famous Hubble Space Telescope images feature this nebula in visible light, but JWST shows it in “infrared fireworks,” Pontoppidan says. JWST’s infrared detectors can see through dust, so the nebula appears especially spangled with stars.
“We’re seeing brand new stars that were previously completely hidden from our view,” said NASA Goddard astrophysicist Amber Straughn.

But molecules in the dust itself are glowing too. Energetic winds from baby stars in the top of the image are pushing and sculpting the wall of gas and dust that runs across the middle. “We see examples of bubbles and cavities and jets that are being blown out from newborn stars,” Straughn said. And gas and dust are the raw material for new stars — and new planets.

“It reminds me that our sun and our planets, and ultimately us, were formed out of this same stuff that we see here,” Straughn said. “We humans really are connected to the universe. We’re made out of the same stuff.”
Foamy nebula
The Southern Ring nebula is an expanding cloud of gas that surrounds a dying star about 2,000 light-years from Earth. In previous Hubble images, the nebula looks like an oblong swimming pool with a fuzzy orange deck and a bright diamond, a white dwarf star, in the middle. JWST expands the view far beyond that, showing more tendrils and structures in the gas than previous telescopes could see.
“You see this bubbly, almost foamy appearance,” said JWST astronomer Karl Gordon, of the Space Telescope Science Institute. In the left hand image, which captures near-infrared light from JWST’s NIRCam instrument, the foaminess traces molecular hydrogen that formed as dust expanded away from the center. The center appears blue due to hot ionized gas heated by the leftover core of the star. Rays of light escape the nebula like the sun peeking through patchy clouds.

In the right-hand image, taken by the MIRI mid-infrared camera, the outer rings look blue and trace hydrocarbons forming on the surface of dust grains. The MIRI image also reveals a second star in the nebula’s core.

“We knew this was a binary star, but we didn’t see much of the actual star that produced this nebula,” Gordon said. “Now in MIRI this star glows red.”
A galactic quintet
Stephan’s Quintet is a group of galaxies about 290 million light-years away that was discovered in 1877. Four of the galaxies are engaged in an intimate gravitational dance, with one member of the group passing through the core of the cluster. (The fifth galaxy is actually much closer to Earth and just appears in a similar spot on the sky.) JWST’s images show off more structure within the galaxies than previous observations did, revealing where stars are being born.

“This is a very important image and area to study,” because it shows the sort of interactions that drive the evolution of galaxies, said JWST scientist Giovanna Giardino of the European Space Agency.

In an image from the MIRI instrument alone, the galaxies look like wispy skeletons reaching towards each other. Two galaxies are clearly close to merging. And in the top galaxy, evidence of a supermassive black hole comes to light. Material swirling around the black hole is heated to extremely high temperatures and glows in infrared light as it falls into the black hole.
An exoplanet’s sky
This “image” is clearly different from the others, but it’s no less scientifically exciting. It shows the spectrum of light from the star WASP 96 as it passes through the atmosphere of its gas giant planet, WASP 96b.

“You get a bunch of what looks like bumps and wiggles to some people but it’s actually full of information content,” said NASA exoplanet scientist Knicole Colón. “You’re actually seeing bumps and wiggles that indicate the presence of water vapor in the atmosphere of this exoplanet.”
The planet is about half the mass of Jupiter and orbits its star every 3.4 days. Previously astronomers thought it had no clouds in its sky, but the new data from JWST show signs of clouds and haze. “There is evidence of clouds and hazes because the water features are not quite as large as we predicted,” Colón said.
A long time coming
These first images and data have been a very long time coming. The telescope that would become JWST was first dreamed up in the 1980s, and the planning and construction suffered years of budget issues and delays (SN: 10/6/21).

The telescope finally launched on December 25. It then had to unfold and assemble itself in space, travel to a gravitationally stable spot about 1.5 million kilometers from Earth, align its insectlike primary mirror made of 18 hexagonal segments and calibrate its science instruments (SN: 1/24/22). There were hundreds of possible points of failure in that process, but the telescope unfurled successfully and got to work.

“We are so thrilled that it works because there’s so much at risk,” says JWST senior project scientist John Mather of NASA’s Goddard Space Flight Center. “The world has trusted us to put our billions into this and make it go, and it works. So it’s an immense relief.”
In the months following, the telescope team released teasers of imagery from calibration, which already showed hundreds of distant, never-before-seen galaxies. But the images now being released are the first full-color pictures made from the data scientists will use to start unraveling mysteries of the universe.

“It sees things that I never dreamed were out there,” Mather says.

For the telescope team, the relief in finally seeing the first images was palpable. “It was like, ‘Oh my god, we made it!’” says image processor Alyssa Pagan, also of Space Telescope Science Institute. “It seems impossible. It’s like the impossible happened.”

In light of the expected anticipation surrounding the first batch of images, the imaging team was sworn to secrecy. “I couldn’t even share it with my wife,” says Pontoppidan, leader of the team that produced the first color science images.

“You’re looking at the deepest image of the universe yet, and you’re the only one who’s seen that,” he says, of the first picture released July 11. “It’s profoundly lonely.” Soon, though, the team of scientists, image processors and science writers was seeing something new every day for weeks as the telescope downloaded the first images. “It’s a crazy experience,” Pontoppidan says. “Once in a lifetime.”

For Pagan, the timing is perfect. “It’s a very unifying thing,” she says. “The world is so polarized right now. I think it could use something that’s a little bit more universal and connecting. It’s a good perspective, to be reminded that we’re part of something so much greater and beautiful.”

JWST is just getting started as it now begins its first round of full science operations. “There’s lots more science to be done,” Mather says. “The mysteries of the universe will not come to an end anytime soon.”

There is a galaxy spinning like a record in the early universe — far earlier than any others have been seen twirling around.

Astronomers have spotted signs of rotation in the galaxy MACS1149-JD1, JD1 for short, which sits so far away that its light takes 13.3 billion years to reach Earth. “The galaxy we analyzed, JD1, is the most distant example of a rotational galaxy,” says astronomer Akio Inoue of Waseda University in Tokyo.
“The origin of the rotational motion in galaxies is closely related to a question: how galaxies like the Milky Way formed,” Inoue says. “So, it is interesting to find the onset of rotation in the early universe.”

JD1 was discovered in 2012. Due to its great distance from Earth, its light had been stretched, or redshifted, into longer wavelengths, thanks to the expansion of the universe. That redshifted light revealed that JD1 existed just 500 million years after the Big Bang.

Astronomers used light from the entire galaxy to make that measurement. Now, using the Atacama Large Millimeter/submillimeter Array in Chile for about two months in 2018, Inoue and colleagues have measured more subtle differences in how that light is shifted across the galaxy’s disk. The new data show that, while all of JD1 is moving away from Earth, its northern part is moving away slower than the southern part. That’s a sign of rotation, the researchers report in the July 1 Astrophysical Journal Letters.

JD1 spins at about 180,000 kilometers per hour, roughly a quarter the spin speed of the Milky Way. The galaxy is also smaller than modern spiral galaxies. So JD1 may be just starting to spin, Inoue says.

The James Webb Space Telescope will observe JD1 in the next year to reveal more clues to how that galaxy, and others like ours, formed (SN: 10/6/21).

No beast on Earth is tougher than the tiny tardigrade. It can survive being frozen at -272° Celsius, being exposed to the vacuum of outer space and even being blasted with 500 times the dose of X-rays that would kill a human.

In other words, the creature can endure conditions that don’t even exist on Earth. This otherworldly resilience, combined with their endearing looks, has made tardigrades a favorite of animal lovers. But beyond that, researchers are looking to the microscopic animals, about the size of a dust mite, to learn how to prepare humans and crops to handle the rigors of space travel.
The tardigrade’s indestructibility stems from its adaptations to its environment — which may seem surprising, since it lives in seemingly cushy places, like the cool, wet clumps of moss that dot a garden wall. In homage to such habitats, along with a pudgy appearance, some people call tardigrades water bears or, adorably, moss piglets.

But it turns out that a tardigrade’s damp, mossy home can dry out many times each year. Drying is pretty catastrophic for most living things. It damages cells in some of the same ways that freezing, vacuum and radiation do.

For one thing, drying leads to high levels of peroxides and other reactive oxygen species. These toxic molecules chisel a cell’s DNA into short fragments — just as radiation does. Drying also causes cell membranes to wrinkle and crack. And it can lead delicate proteins to unfold, rendering them as useless as crumpled paper airplanes. Tardigrades have evolved special strategies for dealing with these kinds of damage.
As a tardigrade dries out, its cells gush out several strange proteins that are unlike anything found in other animals. In water, the proteins are floppy and shapeless. But as water disappears, the proteins self-assemble into long, crisscrossing fibers that fill the cell’s interior. Like Styrofoam packing peanuts, the fibers support the cell’s membranes and proteins, preventing them from breaking or unfolding.

At least two species of tardigrade also produce another protein found in no other animal on Earth. This protein, dubbed Dsup, short for “damage suppressor,” binds to DNA and may physically shield it from reactive forms of oxygen.

Emulating tardigrades could one day help humans colonize outer space. Food crops, yeast and insects could be engineered to produce tardigrade proteins, allowing these organisms to grow more efficiently on spacecraft where levels of radiation are elevated compared with on Earth.

Scientists have already inserted the gene for the Dsup protein into human cells in the lab. Many of those modified cells survived levels of X-rays or peroxide chemicals that kill ordinary cells (SN: 11/9/19, p. 13). And when inserted into tobacco plants — an experimental model for food crops — the gene for Dsup seemed to protect the plants from exposure to a DNA-damaging chemical called ethyl methanesulfonate. Plants with the extra gene grew more quickly than those without it. Plants with Dsup also incurred less DNA damage when exposed to ultraviolet radiation.
Tardigrades’ “packing peanut” proteins show early signs of being protective for humans. When modified to produce those proteins, human cells became resistant to camptothecin, a cell-killing chemotherapy agent, researchers reported in the March 18 ACS Synthetic Biology. The tardigrade proteins did this by inhibiting apoptosis, a cellular self-destruct program that is often triggered by exposure to harmful chemicals or radiation.

So if humans ever succeed in reaching the stars, they may accomplish this feat, in part, by standing on the shoulders of the tiny eight-legged endurance specialists in your backyard.

Pig hearts beat for three days inside the chests of two brain-dead patients who were kept alive using ventilators. The feat helps researchers prepare for future clinical trials of pig-to-human transplants, surgeons at the NYU Langone Health in New York City announced at a news conference on July 12.

In mid-June, surgeons transplanted a heart from a genetically modified pig into Lawrence Kelly — a 72-year-old Vietnam veteran with a history of heart problems. A second patient received a porcine heart on July 6. The team monitored both patients for 72 hours before taking them off life support.

For those three days, the hearts kept the recently deceased patients’ blood flowing. “We learned a tremendous amount from the first operation,” surgeon Nader Moazami said at the news conference. The new heart was too small for Kelly’s chest. So surgeons had to adjust blood vessels to account for the size mismatch and blood flow wasn’t perfect.
Last year, another team at NYU Langone Health transplanted a pig kidney into a brain-dead woman (SN: 10/22/21). The first pig-to-human heart transplant happened in a living patient in January: 57-year-old David Bennet survived two months with a pig heart before dying of heart failure (SN: 1/31/22). All the organs had been genetically modified to avoid immediate rejection by the body and make them safe for people.

It’s unclear why Bennet’s new heart ultimately failed. Transplanting organs into brain-dead people allows for in-depth analyses that aren’t possible in living patients, NYU Langone surgeon Robert Montgomery said. Researchers can take tissue samples and pictures of the organ immediately following the procedure, while the focus for living people is on keeping them alive and comfortable.

Next, the team plans to do longer-term transplants in more brain-dead patients to determine how long pig hearts might last.

Bees that land on short, wide flowers can fly away with an upset stomach.

Common eastern bumblebees (Bombus impatiens) are more likely to catch a diarrhea-inducing gut parasite from purple coneflowers, black-eyed Susans and other similarly shaped flora than other flowers, researchers report in the July Ecology. Because parasites and diseases contribute to bee decline, the finding could help researchers create seed mixes that are more bee-friendly and inform gardeners’ and land managers’ decisions about which flower types to plant.
The parasite (Crithidia bombi) is transmitted when the insects accidentally ingest contaminated bee feces, which “tends to make the bees dopey and lethargic,” says Rebecca Irwin, a community and evolutionary ecologist at North Carolina State University in Raleigh. “It isn’t the number one bee killer out there,” but bees sickened with it can struggle with foraging.

In laboratory experiments involving caged bees and 16 plant species, Irwin and her colleagues studied how different floral attributes affected transmission of the gut parasite. They focused on three factors of transmission: the amount of poop landing on flowers when bees fly and forage, how long the parasite survives on the plants and how easily the parasite is transmitted to new bees. Multiplied together, these three factors show the overall transmission rate.

Compared with plants with long, narrow flowers like phlox and bluebeards, short, wide flowers had more feces land on them and transmitted the parasite more easily to the pollinators, increasing the overall parasite transmission rate for these flowers. However, parasite survival times were reduced on these blooms. This is probably due to the open floral shapes increased exposure to ultraviolet light, speeding the drying out of parasite-laden “fecal droplets,” Irwin says.

The findings confirm a new theory suggesting that traits, such as flower shape, are better predictors of disease transmission than individual species of plants, says Scott McArt, an entomologist focusing on pollinator health at Cornell University who wasn’t involved with the study. Therefore, “you don’t need to know everything about every plant species when designing your pollinator-friendly garden or habitat restoration project.”

Instead, to limit disease transmission among bees, it’s best to choose plants that have narrower, longer flowers, he says. “Wider and shorter flowers are analogous to the small, poorly ventilated rooms where COVID is efficiently transmitted among humans.”

If ripping out coneflowers or black-eyed Susans isn’t palatable, don’t fret. Irwin recommends continuing to plant a diversity of flower types. This helps if one type of flower is “a high transmitting species,” she notes. In the future, she plans to conduct field experiments examining other factors that could influence parasite transmission, such as whether bees are driven to visit certain types of flowers more often in nature.

As a journalist covering COVID-19, I’ve had a front-row seat to the pandemic. I’ve been overwhelmed with despair over the death and suffering. I’ve been numb, trying to keep up with the deluge of COVID-19 studies. One balm has been the understanding of colleagues who also report on COVID-19.

I found solace too in Virology, microbiologist Joseph Osmundson’s book of 11 wide-ranging essays, in which he writes of the pandemic and calls for “a new rhetoric of care.” Osmundson includes journal entries from the pandemic, and some of his experi­ences are similar to mine. He dreams he’s at a gathering where no one is masked. He too felt the “density” of the pandemic: “Emotionally dense, with loss and struggle and even some­times joy,” he writes. “Scientifically dense, with papers and pre-prints out every day that need reading and some analysis.”

Osmundson doesn’t just focus on the coronavirus. He jumps from other viruses and the immune system to illness and metaphors for illness, to sex and HIV, to archiving history and whose stories get told. Parts of the book feel like an anthology, with quotes from many writers who have weighed in on these topics. Parts are a call to care for everyone, regardless of race, ethnicity, wealth or who one loves.
Overall, Osmundson questions how society thinks about viruses. “Viruses … are not evil, they don’t invade. They just are,” he writes. “The meaning we give a virus affects how we live with it.” When we describe viruses as enemies and illness as a war, it “assumes the necessity of casualties.” He argues instead to focus resources on caring for one another.

Born in the early 1980s, Osmundson, a gay man, is acutely aware of the messages that come with viruses. “Our generation of gay men came after the plague,” he writes. “HIV didn’t just kill bodies. It killed a type of sex as well, a type of pleasure.” But new therapies have saved lives and altered perceptions. Pre-exposure prophylaxis can prevent infection, while treatment can render HIV untransmissible (SN: 11/15/19). These advances changed our relationship with the virus, Osmundson writes. “I used to think that HIV would make it harder to find love and sex. Now we know that HIV-positive and undetectable is safe. It’s sexy.”

But the biomedicine that can change our relationship with viruses has not been wielded equitably, Osmundson observes. He returns throughout the book to our common humanity. “That fact of all our bodies, vulnerable together, necessitates mutual care.”

Modern mammals are known for their big brains. But new analyses of mammal skulls from creatures that lived shortly after the dinosaur mass extinction show that those brains weren’t always a foregone conclusion. For at least 10 million years after the dinosaurs disappeared, mammals got a lot brawnier but not brainier, researchers report in the April 1 Science.

That bucks conventional wisdom, to put it mildly. “I thought, it’s not possible, there must be something that I did wrong,” says Ornella Bertrand, a mammal paleontologist at the University of Edinburgh. “It really threw me off. How am I going to explain that they were not smart?”

Modern mammals have the largest brains in the animal kingdom relative to their body size. How and when that brain evolution happened is a mystery. One idea has been that the disappearance of all nonbird dinosaurs following an asteroid impact at the end of the Mesozoic Era 66 million years ago left a vacuum for mammals to fill (SN: 1/25/17). Recent discoveries of fossils dating to the Paleocene — the immediately post-extinction epoch spanning 66 million to 56 million years ago — does reveal a flourishing menagerie of weird and wonderful mammal species, many much bigger than their Mesozoic predecessors (SN: 10/24/19). It was the dawn of the Age of Mammals.
Before those fossil finds, the prevailing wisdom was that in the wake of the mass dino extinction, mammals’ brains most likely grew apace with their bodies, everything increasing together like an expanding balloon, Bertrand says. But those discoveries of Paleocene fossil troves in Colorado and New Mexico, as well as reexaminations of fossils previously found in France, are now unraveling that story, by offering scientists the chance to actually measure the size of mammals’ brains over time.

Bertrand and her colleagues used CT scanning to create 3-D images of the skulls of different types of ancient mammals from both before and after the extinction event. Those specimens included mammals from 17 groups dating to the Paleocene and 17 to the Eocene, the epoch that spanned 56 million to 34 million years ago.

What the team found was a shock: Relative to their body sizes, Paleocene mammal brains were relatively smaller than those of Mesozoic mammals. It wasn’t until the Eocene that mammal brains began to grow, particularly in certain sensory regions, the team reports.

To assess how the sizes and shapes of those sensory regions also changed over time, Bertrand looked for the edges of different parts of the brains within the 3-D skull models, tracing them like a sculptor working with clay. The size of mammals’ olfactory bulbs, responsible for sense of smell, didn’t change over time, the researchers found — and that makes sense, because even Mesozoic mammals were good sniffers, she says.

The really big brain changes were to come in the neocortex, which is responsible for visual processing, memory and motor control, among other skills. But those kinds of changes are metabolically costly, Bertrand says. “To have a big brain, you need to sleep and eat, and if you don’t do that you get cranky, and your brain just doesn’t function.”
So, the team proposes, as the world shook off the dust of the mass extinction, brawn was the priority for mammals, helping them swiftly spread out into newly available ecological niches. But after 10 million years or so, the metabolic calculations had changed, and competition within those niches was ramping up. As a result, mammals began to develop new sets of skills that could help them snag hard-to-reach fruit from a branch, escape a predator or catch prey.

Other factors — such as social behavior or parental care — have been important to the overall evolution of mammals’ big brains. But these new finds suggest that, at least at the dawn of the Age of Mammals, ecology — and competition between species — gave a big push to brain evolution, wrote biologist Felisa Smith of the University of New Mexico in Albuquerque in a commentary in the same issue of Science.
“An exciting aspect of these findings is that they raise a new question: Why did large brains evolve independently and concurrently in many mammal groups?” says evolutionary biologist David Grossnickle of the University of Washington in Seattle.

Most modern mammals have relatively large brains, so studies that examine only modern species might conclude that large brains evolved once in mammal ancestors, Grossnickle says. But what this study uncovered is a “much more interesting and nuanced story,” that these brains evolved separately in many different groups, he says. And that shows just how important fossils can be to stitching together an accurate tapestry of evolutionary history.

Researchers have finally deciphered a complete human genetic instruction book from cover to cover.

The completion of the human genome has been announced a couple of times in the past, but those were actually incomplete drafts. “We really mean it this time,” says Evan Eichler, a human geneticist and Howard Hughes Medical Institute investigator at the University of Washington in Seattle.

The completed genome is presented in a series of papers published online March 31 in Science and Nature Methods.

An international team of researchers, including Eichler, used new DNA sequencing technology to untangle repetitive stretches of DNA that were redacted from an earlier version of the genome, widely used as a reference for guiding biomedical research.

Deciphering those tricky stretches adds about 200 million DNA bases, about 8 percent of the genome, to the instruction book, researchers report in Science. That’s essentially an entire chapter. And it’s a juicy one, containing the first-ever looks at the short arms of some chromosomes, long-lost genes and important parts of chromosomes called centromeres — where machinery responsible for divvying up DNA grips the chromosome.

“Some of the regions that were missing actually turn out to be the most interesting,” says Rajiv McCoy, a human geneticist at Johns Hopkins University, who was part of the team known as the Telomere-to-Telomere (T2T) Consortium assembling the complete genome. “It’s exciting because we get to take the first look inside these regions and see what we can find.” Telomeres are repetitive stretches of DNA found at the ends of chromosomes. Like aglets on shoelaces, they may help keep chromosomes from unraveling.

Data from the effort are already available for other researchers to explore. And some, like geneticist Ting Wang of Washington University School of Medicine in St. Louis, have already delved in. “Having a complete genome reference definitely improves biomedical studies.… It’s an extremely useful resource,” he says. “There’s no question that this is an important achievement.”

But, Wang says, “the human genome isn’t quite complete yet.”

To understand why and what this new volume of the human genetic encyclopedia tells us, here’s a closer look at the milestone.
What did the researchers do?
Eichler is careful to point out that “this is the completion of a human genome. There is no such thing as the human genome.” Any two people will have large portions of their genomes that range from very similar to virtually identical and “smaller portions that are wildly different.” A reference genome can help researchers see where people differ, which can point to genes that may be involved in diseases. Having a view of the entire genome, with no gaps or hidden DNA, may give scientists a better understanding of human health, disease and evolution.

The newly complete genome doesn’t have gaps like the previous human reference genome. But it still has limitations, Wang says. The old reference genome is a conglomerate of more than 60 people’s DNA (SN: 3/4/21). “Not a single individual, or single cell on this planet, has that genome.” That goes for the new, complete genome, too. “It’s a quote-unquote fake genome,” says Wang, who was not involved with the project.

The new genome doesn’t come from a person either. It’s the genome of a complete hydatidiform mole, a sort of tumor that arises when a sperm fertilizes an empty egg and the father’s chromosomes are duplicated. The researchers chose to decipher the complete genome from a cell line called CHM13 made from one of these unusual tumors.

That decision was made for a technical reason, says geneticist Karen Miga of the University of California, Santa Cruz. Usually, people get one set of chromosomes from their mother and another set from their father. So “we all have two genomes in every cell.”

If putting together a genome is like assembling a puzzle, “you essentially have two puzzles in the same box that look very similar to each other,” says Miga, borrowing an analogy from a colleague. Researchers would have to sort the two puzzles before piecing them together. “Genomes from hydatidiform moles don’t present that same challenge. It’s just one puzzle in the box.”

The researchers did have to add the Y chromosome from another person, because the sperm that created the hydatidiform mole carried an X chromosome.

Even putting one puzzle together is a Herculean task. But new technologies that allow researchers to put DNA bases — represented by the letters A, T, C and G — in order, can spit out stretches up to more than 100,000 bases long. Just as children’s puzzles are easier to solve because of larger and fewer pieces, these “long reads” made assembling the bits of the genome easier, especially in repetitive parts where just a few bases might distinguish one copy from another. The bigger pieces also allowed researchers to correct some mistakes in the old reference genome.

What did they find?
For starters, the newly deciphered DNA contains the short arms of chromosomes 13, 14, 15, 21 and 22. These “acrocentric chromosomes” don’t resemble nice, neat X’s the way the rest of the chromosomes do. Instead, they have a set of long arms and one of nubby short arms.

The length of the short arms belies their importance. These arms are home to rDNA genes, which encode rRNAs, which are key components of complex molecular machines called ribosomes. Ribosomes read genetic instructions and build all the proteins needed to make cells and bodies work. There are hundreds of copies of these rDNA regions in every person’s genome, an average of 315, but some people have more and some fewer. They’re important for making sure cells have protein-building factories at the ready.

“We didn’t know what to expect in these regions,” Miga says. “We found that every acrocentric chromosome, and every rDNA on that acrocentric chromosome, had variants, changes to the repeat unit that was private to that particular chromosome.”

By using fluorescent tags, Eichler and colleagues discovered that repetitive DNA next to the rDNA regions — and perhaps the rDNA too — sometimes switches places to land on another chromosome, the team reports in Science. “It’s like musical chairs,” he says. Why and how that happens is still a mystery.

The complete genome also contains 3,604 genes, including 140 that encode proteins, that weren’t present in the old, incomplete genome. Many of those genes are slightly different copies of previously known genes, including some that have been implicated in brain evolution and development, autism, immune responses, cancer and cardiovascular disease. Having a map of where all these genes lie may lead to a better understanding of what they do, and perhaps even of what makes humans human.

One of the biggest finds may be the structure of all of the human centromeres. Centromeres, the pinched portions which give most chromosomes their characteristic X shape, are the assembly points for kinetochores, the cellular machinery that divvies up DNA during cell division. That’s one of the most important jobs in a cell. When it goes wrong, birth defects, cancer or death can result. Researchers had already deciphered the centromeres of fruit flies and the human 8, X and Y chromosomes (SN: 5/17/19), but this is the first time that researchers got a glimpse of the rest of the human centromeres.

The structures are mostly head-to-tail repeats of about 171 base pairs of DNA known as alpha satellites. But those repeats are nestled within other repeats, creating complex patterns that distinguish each chromosome’s individual centromere, Miga and colleagues describe in Science. Knowing the structures will help researchers learn more about how chromosomes are divvied up and what sometimes throws off the process.
Researchers also now have a more complete map of epigenetic marks — chemical tags on DNA or associated proteins that may change how genes are regulated. One type of epigenetic mark, known as DNA methylation, is fairly abundant across the centromeres, except for one spot in each chromosome called the centromeric dip region, Winston Timp, a biomedical engineer at Johns Hopkins University and colleagues report in Science.

Those dips are where kinetochores grab the DNA, the researchers discovered. But it’s not yet clear whether the dip in methylation causes the cellular machinery to assemble in that spot or if assembly of the machinery leads to lower levels of methylation.

Examining DNA methylation patterns in multiple people’s DNA and comparing them with the new reference revealed that the dips occur at different spots in each person’s centromeres, though the consequences of that aren’t known.

About half of genes implicated in the evolution of humans’ large, wrinkly brains are found in multiple copies in the newly uncovered repetitive parts of the genome (SN: 2/26/15). Overlaying the epigenetic maps on the reference allowed researchers to figure out which of many copies of those genes were turned on and off, says Ariel Gershman, a geneticist at Johns Hopkins University School of Medicine.

“That gives us a little bit more insight into which of them are actually important and playing a functional role in the development of the human brain,” Gershman says. “That was exciting for us, because there’s never been a reference that was accurate enough in these [repetitive] regions to tell which gene was which, and which ones are turned on or off.”

What is next?
One criticism of genetics research is that it has relied too heavily on DNA from people of European descent. CHM13 also has European heritage. But researchers have used the new reference to discover new patterns of genetic diversity. Using DNA data collected from thousands of people of diverse backgrounds who participated in earlier research projects compared with the T2T reference, researchers more easily and accurately found places where people differ, McCoy and colleagues report in Science.

The Telomere-to-Telomere Consortium has now teamed up with Wang and his colleagues to make complete genomes of 350 people from diverse backgrounds (SN: 2/22/21). That effort, known as the pangenome project, is poised to reveal some of its first findings later this year, Wang says.

McCoy and Timp say that it may take some time, but eventually, researchers may switch from using the old reference genome to the more complete and accurate T2T reference. “It’s like upgrading to a new version of software,” Timp says. “Not everyone is going to want to do it right away.”

The completed human genome will also be useful for researchers studying other organisms, says Amanda Larracuente, an evolutionary geneticist at the University of Rochester in New York who was not involved in the project. “What I’m excited about is the techniques and tools this team has developed, and being able to apply those to study other species.”

Eichler and others already have plans to make complete genomes of chimpanzees, bonobos and other great apes to learn more about how humans evolved differently than apes did. “No one should see this as the end,” Eichler says, “but a transformation, not only for genomic research but for clinical medicine, though that will take years to achieve.”

It doesn’t have to be this way.

The world already has the know-how and tools to dramatically reduce emissions from fossil fuels — but we need to use those tools immediately if we hope to forestall the worst impacts of climate change. That’s the message of the third and final installment of the massive sixth assessment of climate science by the United Nations’ Intergovernmental Panel on Climate Change, which was released April 4.

“We know what to do, we know how to do it, and now it’s up to us to take action,” said sustainable energy researcher Jim Skea of Imperial College London, who cochaired the report, at a news event announcing its release.
Earth is on track to warm by an average of about 3.2 degrees Celsius above preindustrial levels by the end of the century (SN: 11/26/19). Altering that course and limiting warming to 1.5 degrees or even 2 degrees means that global fossil fuel emissions will need to peak no later than the year 2025, the new report states.

Right now, meeting that goal looks extremely unlikely. National pledges to reduce fossil fuel emissions to date amount to “a litany of broken climate promises,” said United Nations Secretary-General António Guterres at the event.

The previous two installments of the IPCC’s sixth assessment described how climate change is already fueling extreme weather events around the globe — and noted that adaptation alone will not be enough to shield people from those hazards (SN: 8/9/21; SN: 2/28/22).

The looming climate crisis “is horrifying, and I don’t want to sugarcoat that,” says Bronson Griscom, a forest ecologist and the director of Natural Climate Solutions at the environmental organization Conservation International, based in Arlington, Va.

But Griscom, who was not an author on the new IPCC report, says its findings also give him hope. It’s “what I would call a double-or-nothing bet that we’re confronted with right now,” he says. “There [are] multiple ways that this report is basically saying, ‘Look, if we don’t do anything, it’s increasingly grim.’ But the reasons to do something are incredibly powerful and the tools in the toolbox are very powerful.”

Tools in the toolbox
Those tools are strategies that governments, industries and individuals can use to cut emissions immediately in multiple sectors of the global economy, including transportation, energy, building, agriculture and forestry, and urban development. Taking immediate advantage of opportunities to reduce emissions in each of those sectors would halve global emissions by 2030, the report states.

Consider the transportation sector, which contributed 15 percent of human-related greenhouse gas emissions in 2019. Globally, electric vehicle sales have surged in the last few years, driven largely by government policies and tougher emissions laws for the auto industry (SN: 12/22/21).

If that surge continues, “electric vehicles offer us the greatest potential [to reduce transportation emissions on land], as long as they’re combined with low or zero carbon electricity sources,” Diana Ürge-Vorsatz, the vice chair of the IPCC’s Working Group III, said at the news event. But for aviation and long-haul shipping, which are more difficult to electrify, reduced carbon emissions could be achieved with low-carbon hydrogen fuels or biofuels, though these alternatives require further research and development.

Then there are urban areas, which are contributing a growing proportion of global greenhouse gas emissions, from 62 percent in 2015 to between 67 and 72 percent in 2020, the report notes. In established cities, buildings can be retrofitted, renovated or repurposed to make city layouts more walkable and provide more accessible public transportation options.

And growing cities can incorporate energy-efficient infrastructure and construct buildings using zero-emissions materials. Additionally, urban planners can take advantage of green roofs, urban forests, rivers and lakes to help capture and store carbon, as well as provide other climate benefits such as cleaner air and local cooling to counter urban heat waves (SN: 4/3/18).

Meanwhile, “reducing emissions in industry will involve using materials and energy more efficiently, reusing and recycling products and minimizing waste,” Ürge-Vorsatz said.

As for agriculture and forestry, these and other land-use industries contribute about 22 percent of the world’s greenhouse gas emissions, with half of those emissions coming from deforestation (SN: 7/13/21). So reforestation and reduced deforestation are key to flipping the balance between CO₂ emissions and removal from the atmosphere (SN: 7/9/21; SN: 1/3/22). But there are a lot of other strategies that the world can employ at the same time, the report emphasizes. Better management of forests, coastal wetlands, grasslands and other ecosystems, more sustainable crop and livestock management, soil carbon management in agriculture and agroforestry can all bring down emissions (SN: 7/14/21).

The report also includes, for the first time in the IPCC’s reports, a chapter on the “untapped potential” of lifestyle changes to reduce emissions. Such changes include opting for walking or cycling or using public transportation rather than driving, shifting toward plant-based diets and reducing air travel (SN: 5/14/20).

Those lifestyle changes could reduce emissions by 40 to 70 percent by 2050, the report suggests. To enable those changes, however, government policies, infrastructure and technology would need to be in place.

Government policies are also key to financing these transformational changes. Globally, the investment in climate-related technologies needs to ramp up, and quickly, to limit warming below 2 degrees C, the report states. Right now, investments are three to six times lower than they need to be by 2030. And a combination of public and private investments will be essential to aiding the transition away from fossil fuels and toward renewable energy in developing nations (SN: 1/25/21).

Future strategies
Still, reducing emissions alone won’t be enough: We will need to actively remove carbon from the atmosphere to achieve net zero emissions and keep the planet well below 2 degrees C of warming, the report notes. “One thing that’s clear in this report, as opposed to previous reports, is that carbon removal is going to be necessary in the near term,” says Simon Nicholson, director of the Institute for Carbon Removal Law and Policy at American University in Washington, D.C., who was not involved in the report.

Such strategies include existing approaches such as protecting or restoring carbon dioxide–absorbing forests, but also technologies that are not yet widely available commercially, such as directly capturing carbon dioxide from the air, or converting the gas to a mineral form and storing it underground (SN: 12/17/18).

These options are still in their infancy, and we don’t know how much of an impact they’ll have yet, Nicholson says. “We need massive investment now in research.”

An emphasis on acting “now,” on eliminating further delay, on the urgency of the moment has been a recurring theme through all three sections of the IPCC’s sixth assessment report released over the last year. What impact these scientists’ stark statements will have is unclear.

But “the jury has reached a verdict, and it is damning,” U.N. Secretary-General Guterres said. “If you care about justice and our children’s future, I am appealing directly to you.”

A chance alignment may have revealed a star from the universe’s first billion years.

If confirmed, this star would be the most distant one ever seen, obliterating the previous record (SN: 7/11/17). Light from the star traveled for about 12.9 billion years on its journey toward Earth, about 4 billion years longer than the former record holder, researchers report in the March 30 Nature. Studying the object could help researchers learn more about the universe’s composition during that early, mysterious time.

“These are the sorts of things that you only hope you could discover,” says astronomer Katherine Whitaker of the University of Massachusetts Amherst, who was not part of the new study.
The researchers found the object while analyzing Hubble Space Telescope images of dozens of clusters of galaxies nearer to Earth. These clusters are so massive that they bend and focus the light from more distant background objects, what’s known as gravitational lensing (SN: 10/6/15).

In images of one cluster, astronomer Brian Welch of Johns Hopkins University and colleagues noticed a long, thin, red arc. The team realized that the arc was a background galaxy whose light the cluster had warped and amplified.

Atop that red arc is a bright spot that is too small to be a small galaxy or a star cluster, the researchers say. “We stumbled into finding that this was a lensed star,” Welch says.

The researchers estimate that the star’s light originates from only 900 million years after the Big Bang, which took place about 13.8 billion years ago.

Welch and his colleagues think that the object, which they poetically nicknamed “Earendel” from the old English word meaning “morning star” or “rising light,” is a behemoth with at least 50 times the mass of the sun. But the researchers can’t pin down that value, or learn more about the star or even confirm that it is a star, without more detailed observations.

The researchers plan to use the recently launched James Webb Space Telescope to examine Earendel (SN: 10/6/21). The telescope, also known as JWST, will begin studying the distant universe this summer.

JWST may uncover objects from even earlier times in the universe’s history than what Hubble can see because the new telescope will be sensitive to light from more distant objects. Welch hopes that the telescope will find many more of these gravitationally lensed stars. “I’m hoping that this record won’t last very long.”