Our solar system narrowly escaped an explosive death

Welcome back to the Abstract! These are the studies this week that got hosed with star spray, mounted a failed invasion, declined to comment, and achieved previously unknown levels of adorability.  

First, a study about how the solar system wasn’t destroyed 4.5 billion years ago (phew!). Then: a human touch on an ancient boat, the duality of posters and lurkers, and an important update on toadlets.

As always, for more of my work, check out my book First Contact: The Story of Our Obsession with Aliens or subscribe to my personal newsletter the BeX Files. 

Sink into a warm cosmic-ray bath

Sawada, Ryo et al. “Cosmic-ray bath in a past supernova gives birth to Earth-like planets.” Science Advances.

Earth was cosmically conceived in part by a massive shockwave from a nearby supernova, which seeded our home world and neighboring rocky planets with telltale radioactive signatures, according to a new study.

The solar system’s rocky planets contain short-lived radionuclides (SLRs), which are ancient elements that were likely barfed out from exploding stars. For this reason, scientists have long suspected that stars must’ve detonated next to the gassy disk that gave rise to the solar system. The heat generated from these radioactive elements helped the building blocks of the rocky planets—Mercury, Venus, Earth, and Mars—melt together so they could become whole worlds, which means we owe our existence to these ancient supernovas.

Now, a team has developed a new model to explain how the primordial pyrotechnics didn’t just blow up the nascent solar system. The results suggest that rocky Earth-like worlds may be common in the universe, with potential implications for the search for extraterrestrial life.

“A key question in astronomy is how ubiquitous Earth-like rocky planets are,” said researchers led by Ryo Sawada of the University of Tokyo. “The formation of terrestrial planets in our Solar System was strongly influenced by the radioactive decay heat of SLRs, particularly aluminum-26, likely delivered from nearby supernovae.”

“However, the supernova injection scenario faces an unresolved problem in that existing supernova models could not reproduce both the relative and absolute abundances of SLRs without disrupting the protosolar disk,” an event that “would likely prevent the Solar System formation altogether,” the team added.

In other words, it’s hard to explain how the solar system got its high abundance of SLRs without killing it in the cradle. Sawada and his colleagues propose a solution that involves at least one star exploding about three light years of the disk, sparking a shockwave that created a cosmic-ray “bath.”  

Schematic picture of the system assumed in this study. Image: Sawada et al., Sci. Adv. 11, eadx7892

In this “immersion mechanism,” energetic cosmic rays trapped in the bath triggered SLR-producing reactions directly within the disk. This contrasts with the hypothesis that the SLRs were largely injected and then mixed up in the disk through some unknown process. This new solution can account both for the high abundance of certain SLRs, like aluminum-26, and the fact that the solar system was not destroyed, as evidenced by its apparent continued existence.

“Our results suggest that Earth-like, water-poor rocky planets may be more prevalent in the 

Galaxy than previously thought,” the team said, noting that many disks are rocked by similar supernova-shockwaves. “This challenges previous interpretations that classified the Solar System as an outlier with a particularly high [aluminum-26] abundance.”

In addition to offering a new hypothesis for an old astronomical problem, the study gets bonus points for its extremely poetic title: “Cosmic-ray bath in a past supernova gives birth to Earth-like planets.” If you say this enchanted phrase three times, somewhere an Earth-like world will be born.

In other news…

The biometrics of a Baltic boatsman

Fauvelle, Mikael et al. “New investigations of the Hjortspring boat: Dating and analysis of the cordage and caulking materials used in a pre-Roman iron age plank boat.” PLOS One

Stars aren’t the only things leaving their dirty fingerprints in unexpected places this week. Archeologists working on the mysterious Hjortspring boat, a 2,400-year-old Scandinavian vessel, discovered a tantalizing partial human fingerprint in its caulking, providing “a direct link to the ancient seafarers who used this boat,” according to the study.

Photo of caulking fragment showing fingerprint on the left and high-resolution x-ray tomography scan of fingerprint region on the right. Image: Photography by Erik Johansson, 3D model by Sahel Ganji

The ridges of the fingerprint “fall within average distributions for both adult male and females as well as for juvenile adults, making it difficult to say much about the individual who produced the print,” said researchers led by Mikael Fauvelle of Lund University. “The most likely interpretation, however, is that it was made during repairs by one of the crew members on the boat itself, providing a direct link to the seafarers of the ancient vessel.”

Regardless of this person’s identity, their voyage didn’t end well. Researchers think the crew of the Hjortspring boat probably sailed from the eastern Baltic Sea to attack the Danish island of Als, where they were defeated. “The victors [deposited] the weapons of their vanquished foes together with one of their boats into the bog,” where they remained for millennia until they were rediscovered in the 1880s, the team said. 

It’s a timeless reminder for would-be invaders: Don’t get caulky.

Long-time lurker, first-time poster

Oswald, Lisa et al. “Disentangling participation in online political discussions with a collective field experiment.” Science Advances.

At last, scientists have investigated the most elusive online demographic: the humble lurker. A team recruited 520 Redditors in the U.S. to participate in small subreddits focused on a variety of political topics during the summer of 2024. The aim was to probe why some people became prolific “power-users” that post with voluminous confidence, while others remained wallflowers.

“Online political discussions are often dominated by a small group of active users, while most remain silent,” said researchers led by Lisa Oswalt of the Max Planck Institute for Human Development. “This visibility gap can distort perceptions of public opinion and fuel polarization.” 

The team found that “lurking (posting nothing) was most common among users who perceived discussions as toxic, disrespectful, or unconstructive.” Lurkers were offered small payments to post in the experiment, which succeeded in motivating some to contribute to discussions. As a result, the study concluded that “future interventions may be able to make online political discussions more representative by offering more positive social rewards for lurkers to post.”

At last, an opportunity to unionize the lurkers of the world. Solidarity (in silence) forever.

It’s the great pumpkin toadlet, Charlie Brown 

Bornschein, Marcos R. et al. “A new species of Brachycephalus (Anura: Brachycephalidae) from Serra do Quiriri, northeastern Santa Catarina state, southern Brazil, with a review of the diagnosis among species of the B. pernix group and proposed conservation measures.” PLOS One.

We will close, as we have before, with an impossibly cute toadlet. Scientists have discovered this new species of “pumpkin toadlet” in the “cloud forests” of Brazil, a sentence so twee that it’s practically its own fairy tale. The tiny toad Brachycephalus lulai, pictured below on a pencil tip, belongs to a family of “flea toads” that are among the smallest vertebrates on Earth. 

Basically it is very smol: Brachycephalus lulai is a tiny pumpkin toadlet measuring less than 14 mm in length. Photo: Luiz Fernando Ribeiro. Image credit 1: Luiz Fernando Ribeiro, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

“Our team sought to better document the individual variation of all Brachycephalus species in southern Brazil, looking for them in the field over the past seven years,” said researchers led by Marcos R. Bornschein of São Paulo State University. “As a result of this work, we discovered and herein described a population collected on the eastern slope of Serra do Quiriri as a new species.”

The team also reported that the toads are actively colonizing newly formed cloud forests, which are high-altitude woods shrouded in mist. The researchers propose making these unique habitats into refuges for the adorable anurans. 

Thanks for reading! See you next week.