NASA’s exoplanet count surges past 5,000

It’s official: The number of planets known beyond our solar system has just passed 5,000.

The exoplanet census surpassed this milestone with a recent batch of 60 confirmed exoplanets. These additional worlds were found in data from NASA’s now-defunct K2 mission, the “second life” of the prolific Kepler space telescope, and confirmed with new observations, researchers report March 4 at

As of March 21, these finds put NASA’s official tally of exoplanets at 5,005.

It’s been 30 years since scientists discovered the first planets orbiting another star — an unlikely pair of small worlds huddled around a pulsar (SN: 1/11/92). Today, exoplanets are so common that astronomers expect most stars host at least one (SN: 1/11/12), says astronomer Aurora Kesseli of Caltech.
“One of the most exciting things that I think has happened in the last 30 years is that we’ve really started to be able to fill out the diversity of exoplanets,” Kesseli says

Some look like Jupiter, some look — perhaps — like Earth and some look like nothing familiar. The 5,005 confirmed exoplanets include nearly 1,500 giant gassy planets, roughly 200 that are small and rocky and almost 1,600 “super-Earths,” which are larger than our solar system’s rocky planets and smaller than Neptune (SN: 8/11/15).
Astronomers can’t say much about those worlds beyond diameters, masses and densities. But several projects, like the James Webb Space Telescope, are working on that, Kesseli says (SN: 1/24/22). “Not only are we going to find tons and tons more exoplanets, but we’re also going to start to be able to actually characterize the planets,” she says.

And the search is far from over. NASA’s newest exoplanet hunter, the TESS mission, has confirmed more than 200 planets, with thousands more yet to verify, Kesseli says (SN: 12/2/21). Ongoing searches from ground-based telescopes keep adding to the count as well.

“There’s tons of exoplanets out there,” Kesseli says, “and even more waiting to be discovered.”

Levitating plastic beads mimic the physics of spinning asteroids

Some asteroids can barely hold it together.

Rather than solid lumps of rock, ‘rubble pile’ asteroids are loose collections of material, which can split apart as they rotate (SN: 3/16/20). To understand the inner workings of such asteroids, one team of scientists turned to levitating plastic beads. The beads clump together, forming collections that can spin and break up, physicist Melody Lim of the University of Chicago reported March 15 at a meeting of the American Physical Society in Chicago.

It’s an elegant dance that mimics the physics of asteroid formation, which happens too slowly to observe in real-life space rocks. “These ‘tabletop asteroids’ compress phenomena that take place over kilometers [and] over hundreds of thousands of years to just centimeters and seconds in the lab,” Lim said. The results are also reported in a paper accepted in Physical Review X.
Lim and colleagues used sound waves to levitate the plastic beads, which arranged themselves into two-dimensional clumps. Acoustic forces attract the beads to one another, mimicking the gravitational attraction between bits of debris in space. Separate clumps then coalesced similarly to how asteroids are thought to glom onto one another to grow.
When the experimenters gave the structures a spin using the sound waves, the clumps changed shape above a certain speed, becoming elongated. That could help scientists understand why ‘rubble pile’ asteroids, can have odd structures, such as the ‘spinning tops’ formed by asteroids Bennu and Ryugu (SN: 12/18/18).

Eventually, the fast-spinning clumps broke apart. This observation could help explain why asteroids are typically seen to spin up to a certain rate, but not beyond: Speed demons get split up.

Social media crackdowns during the war in Ukraine make the internet less global

Since Russia’s invasion of Ukraine in late February, people around the world have watched the war play out in jarring detail — at least, in countries with open access to social media platforms such as Twitter, Facebook, TikTok and the messaging app Telegram.

“The way that social media has brought the war into the living rooms of people is quite astounding,” says Joan Donovan, the research director of the Shorenstein Center on Media, Politics and Public Policy at Harvard University. Fighting and explosions play out nearly in real time, and video messages from embattled Ukrainian president Volodymyr Zelenskyy have stirred support across the West.

But that’s not all. Social media is actually changing the way wars are fought today, says political scientist Thomas Zeitzoff of American University in Washington, D.C., who is an expert on political violence.
The platforms have become important places to recruit fighters, organize action, spread news and propaganda and — for social scientists — to gather data on conflicts as they unfold.

As social platforms have become more powerful, governments and politicians have stepped up efforts to use them — or ban them, as in Russia’s recent blocking of Facebook, Twitter and Instagram. And in a first, the White House held a special briefing on the Ukraine war with TikTok stars such as 18-year-old Ellie Zeiler, who has more than 10 million followers. The administration hopes to shape the messages of young influencers who are already important sources of news and information for their audiences.

The Ukraine war is shining a spotlight on social media’s role as a political tool, says Donovan, whose Technology and Social Change Project team has been following the spread of disinformation in the conflict. “This is a huge moment in internet history where we’re starting to see the power of these tech companies play out against the power of the state.” And that, she says, “is actually going to change the internet forever.”

Science News interviewed Donovan and Zeitzoff about social media’s influence on the conflict and vice versa. The following conversations have been edited for length and clarity.

SN: When did social media start to play a role in conflicts?

Zeitzoff: Some people would say the Zapatista uprising in Mexico, way back in the 1990s, because the Zapatistas used the internet [to spread their political message]. But I think the failed Green Revolution in Iran in 2007 and 2008 was one of the first, and especially the Arab Spring in the early 2010s. There was this idea that social media would be a “liberation technology” that allows people to hold truth to power.

But as the Arab Spring gave way to the Arab Winter [and its resurgence of authoritarianism], people started challenging that notion. Yes, it makes it easy to get a bunch of people out on the street [to protest], but it also makes it easier for governments to track these folks.
SN: How do you see social media being used in the Ukrainian conflict, and what’s different now?
Donovan: Some of the platforms that are more well-known, like Facebook and Twitter, are not as consequential as newer platforms like Telegram and TikTok. For instance, Ukrainian groups on Facebook started to build other channels for communication right before the Russian invasion because they felt that Facebook might get compromised. So Telegram has been a very important space for getting information and sharing news.

Telegram has also become a hot zone for propaganda and misinformation, where newer tactics are emerging such as fake debunked videos. These are videos that look like they’re news debunks showing that Ukraine is participating in media manipulation efforts, but they’re actually manufactured by Russia to make Ukraine look bad.

Zeitzoff: I think social media has probably afforded the Ukrainians an easier ability to communicate to their diaspora communities, whether in Canada, the United States or across Europe. It’s also increasingly affording unprecedented battlefield views.

But I think the bigger thing is to think about what these new suites of technology allow, like Volodymyr Zelenskyy holding live videos that basically allow him to show proof of life, and also put pressure on European leaders.

SN: Despite Russia’s big investments in disinformation, is Ukraine winning the social media war?

Zeitzoff: Up to the beginning of the conflict, many Ukrainians were skeptical of Zelenskyy’s ability to lead. But you look back at his presidential campaign, and he was doing Facebook videos where he would talk into the camera, in a very sort of intimate style of campaigning. So he knew how to use social media beforehand. And I think that has allowed Ukraine to communicate to Western audiences, basically, ‘give me money, give me weapons,’ and that has helped. There is an alternative scenario where perhaps if Russia’s military were slightly better organized and had a better social media campaign, it would become very difficult for Ukraine to hold.

And I would say that Russia’s propaganda has been sloppier. It’s not as good of a story. Ukraine already has the underdog sympathy, and they’ve been very good at capitalizing on it. They show their battlefield successes and highlight atrocities committed by Russians.

And the other thing is that social media has helped to organize foreign fighters and folks who have volunteered to go to Ukraine.

SN: Social media is also an enormous source of misinformation and disinformation. How is that playing out?

Donovan: We’re seeing recontextualized media [on TikTok and elsewhere], which is the reuse of content in a new context. And it usually also misrepresents the time and place of the content.

For instance, we’ve seen repurposed video game footage as if it was the war in Ukraine. While we [in the United States] don’t need real-time information to understand what’s happening in Ukraine, we do need access to the truth. Recontextualized media gets in the way of our right to truth.

And we want to make sure the information getting to people in Ukraine is as true and correct and vetted as possible, because they’re going to make a life-or-death decision that day about going out in search of food or trying to flee a certain area. So those people do need real-time accurate information.

There’s one other story about the way in which hope and morale can be decimated by disinformation. Among Ukrainians, there’s a lot of talk about when or if the United States or NATO will send planes. And there were these videos going around suggesting that the United States had already sent planes, and showing paratroopers jumping out. People were sharing these until they got to a reputable news source and heard the news that NATO was still not sending planes. So it can be something as innocent as a video that provides a massive amount of hope to people who share it, and then it’s all snatched away.

SN: What aren’t we seeing on social media?

Donovan: There’s a missing piece, which is that many social media algorithms are set to remove things that are torturous or gory. And so the very violent and vicious aftermath of war is something that the platforms are suppressing, just by virtue of their design.

So in order to get a complete picture of what has happened in Ukraine, people are going to have to see those videos [from other news sources] and be a global witness to the atrocity.

SN: Where is this all heading?

Zeitzoff: I think the biggest thing that’s changing is this decoupling of social media networks across great powers. So you have the Great Firewall [that censors the internet] in China, and I think Russia will be doing something very similar. And how does that influence the free flow of information?

Donovan: We try to understand how information warfare plays out as kind of a chess match between different actors. And what’s been incredible about the situation in Russia is you have this immense titan, the tech industry, pushing back on Russia by removing state media from their platforms. And then Russia counters by removing Facebook and Instagram in Russia.

This is the first time that we’ve seen these companies take action based on the request of other governments. In particular, Nick Clegg [the president of global affairs at Meta, the parent company of Facebook, Instagram and the messaging service WhatsApp] said that they were complying with Ukrainian asks. That means that they are taking some responsibility for the content that is being aired on their platforms. Whatever outcome happens over the next month, I don’t think the internet is going to be as global as it once was.

Here’s the best timeline yet for the Milky Way’s big events

A new analysis of nearly a quarter million stars puts firm ages on the most momentous pages from our galaxy’s life story.

Far grander than most of its neighbors, the Milky Way arose long ago, as lesser galaxies smashed together. Its thick disk — a pancake-shaped population of old stars — originated remarkably soon after the Big Bang and well before most of the stellar halo that envelops the galaxy’s disk, astronomers report March 23 in Nature.

“We are now able to provide a very clear timeline of what happened in the earliest time of our Milky Way,” says astronomer Maosheng Xiang.
He and Hans-Walter Rix, both at the Max Planck Institute for Astronomy in Heidelberg, Germany, studied almost 250,000 subgiants — stars that are growing larger and cooler after using up the hydrogen fuel at their centers. The temperatures and luminosities of these stars reveal their ages, letting the researchers track how different epochs in galactic history spawned stars with different chemical compositions and orbits around the Milky Way’s center.

“There’s just an incredible amount of information here,” says Rosemary Wyse, an astrophysicist at Johns Hopkins University who was not involved with the study. “We really want to understand how our galaxy came to be the way it is,” she says. “When were the chemical elements of which we are made created?”

Xiang and Rix discovered that the Milky Way’s thick disk got its start about 13 billion years ago. That’s just 800 million years after the universe’s birth. The thick disk, which measures 6,000 light-years from top to bottom in the sun’s vicinity, kept forming stars for a long time, until about 8 billion years ago.

During this period, the thick disk’s iron content shot up 30-fold as exploding stars enriched its star-forming gas, the team found. At the dawn of the thick disk era, a newborn star had only a tenth as much iron, relative to hydrogen, as the sun; by the end, 5 billion years later, a thick disk star was three times richer in iron than the sun.

Xiang and Rix also found a tight relation between a thick disk star’s age and iron content. This means gas was thoroughly mixed throughout the thick disk: As time went on, newborn stars inherited steadily higher amounts of iron, no matter whether the stars formed close to or far from the galactic center.

But that’s not all that was happening. As other researchers reported in 2018, another galaxy once hit our own, giving the Milky Way most of the stars in its halo, which engulfs the disk (SN: 11/1/18). Halo stars have little iron.

The new work revises the date of this great galactic encounter: “We found that the merger happened 11 billion years ago,” Xiang says, a billion years earlier than thought. As the intruder’s gas crashed into the Milky Way’s gas, it triggered the creation of so many new stars that our galaxy’s star formation rate reached a record high 11 billion years ago.

The merger also splashed some thick disk stars up into the halo, which Xiang and Rix identified from the stars’ higher iron abundances. These “splash” stars, the researchers found, are at least 11 billion years old, confirming the date of the merger.

The thick disk ran out of gas 8 billion years ago and stopped making stars. Fresh gas around the Milky Way then settled into a thinner disk, which has given birth to stars ever since — including the 4.6-billion-year-old sun and most of its stellar neighbors. The thin disk is about 2,000 light-years thick in our part of the galaxy.

“The Milky Way has been quite quiet for the last 8 billion years,” Xiang says, experiencing no further encounters with big galaxies. That makes it different from most of its peers.

If the thick disk really existed 13 billion years ago, Xiang says, then the new James Webb Space Telescope (SN: 1/24/22) may discern similar disks in galaxies 13 billion light-years from Earth — portraits of the Milky Way as a young galaxy.

Spinosaurus’ dense bones fuel debate over whether some dinosaurs could swim

A fierce group of predatory dinosaurs may have done much of their hunting in the water.

An analysis of the bone density of several sharp-toothed spinosaurs suggests that several members of this dino group were predominantly aquatic, researchers report March 23 in Nature.

That finding is the latest salvo in an ongoing challenge to the prevailing view that all dinosaurs were land-based animals that left the realms of water and air to marine reptiles such as Mosasaurus and flying reptiles such as Pteranodon. But, other researchers say, it still doesn’t prove that Spinosaurus and its kin actually swam.
Back in 2014, Nizar Ibrahim, a vertebrate paleontologist now at the University of Portsmouth in England, and colleagues pieced together the fossil of a 15-meter-long Spinosaurus from what’s now Morocco. The dinosaur’s odd collection of features — a massive sail-like structure on its back, short and muscular legs, nostrils set well back from its snout and needlelike teeth seemingly designed for snagging fish — suggested to the researchers that the predator might have been a swimmer (SN: 9/11/14). In particular, it had very dense leg bones, a feature of some aquatic creatures like manatees that need the bones for ballast to stay submerged.

In the new study, Ibrahim and his team returned to that question of bone density to assess whether it’s a reliable proxy for how much time a creature spends in the water. The team assembled “a massive dataset” of femur and dorsal rib bone densities from “an incredible menagerie of extinct and living animals, reaching out to museum curators all around the world,” Ibrahim says.

That menagerie includes spinosaurs like showy, sail-backed Spinosaurus as well as its equally sharp-toothed cousins Baryonyx and Suchomimus. It also includes other groups of dinosaurs, extinct marine reptiles, pterosaurs, birds, modern crocodiles and marine mammals.

The team then compared these bone analyses with the water-dwelling habits of the various creatures in the study. That work confirms that density is “an excellent indicator” for species in the early stages of a transition from land-dwelling to water-dwelling, the team reports. Those compact bones can aid such transitional creatures, which might not yet have features like fins or flippers to help them maneuver in the water more easily, in hunting underwater — what the team calls “subaqueous foraging.”

The analyses also show that not only did Spinosaurus have very dense bones, but Baryonyx did too. That suggests that both of these dinos were subaqueous foragers, the team says. That idea builds on previous work by Ibrahim and colleagues that proposed that Spinosaurus didn’t just spend much of its time in the water, but could actually swim in pursuit of prey, thanks to its odd, paddle-shaped tail (SN: 4/29/20).
The idea of a swimming Spinosaurus hasn’t been convincing to all. In 2021, a study in Palaeontologia Electronica examined Spinosaurus’ anatomy in detail and came to a different conclusion. The dinosaur was not a highly specialized aquatic predator, wrote David Hone, a zoologist and paleobiologist at Queen Mary University of London, and Thomas Holtz Jr., a vertebrate paleontologist at the University of Maryland in College Park. Instead, Spinosaurus may have just waded in the shallows, heronlike, to do its fishing.

The new study has not convinced those skeptics. Spinosaurus has “clearly got very dense bones. This is really good evidence that they’re hanging around in water — but we kind of knew that,” Hone says. “It’s not clear what they’re doing in the water. That’s the contentious part.”

Take hippos, which spend much of their time mostly submerged, Hone says. “Hippos have bone densities entirely comparable to Spinosaurus and Baryonyx, but they don’t eat in the water” and they don’t swim, he adds.

“Everyone has been in agreement that Spinosaurus was more aquatic than other big theropods” like Tyrannosaurus rex, Holtz says. That Baryonyx also had dense bones was a bit of an interesting surprise, he adds.

But dense bones or not, Holtz says, “it still doesn’t turn them into aquatic hunters.” He describes several anatomical features — Spinosaurus’ long slender neck, tilted head and arrangement of neck muscles that suggest a downward striking motion — that point more to a wading creature that hunted from above the water surface than one that chased its prey underwater.

Kiersten Formoso, a vertebrate paleobiologist at the University of Southern California in Los Angeles, says that the new comparison of bone densities among a wide variety of creatures is a valuable addition, one that she anticipates referring to in her own work studying the transition of ancient creatures from land to water. But she too is not convinced that it proves that Spinosaurus and Baryonyx could actually swim.

“I would never detach Spinosaurus from the water,” Formoso says. But, she adds, more work needs to be done on its biomechanics — how it might have moved — to understand how adroitly aquatic the dinosaur might have been.