The Sun has been imaged in unprecedented detail by a sophisticated solar laboratory in space, revealing new insights about the mysterious processes occurring in and around our star. 

The new pictures were captured on March 7 by the European Space Agency’s Solar Orbiter as it crossed directly between Earth and the Sun, at a distance of about halfway between the two bodies. From this special orbital vantagepoint, the orbiter was able to capture the highest-resolution image of the Sun and its surrounding atmosphere, known as the corona, ever taken (there’s an interactive zoom feature for the image at this link).

The final composite shot was stitched together from 25 images, totalling 83 million pixels, snapped by the spacecraft’s Extreme Ultraviolet Imager (EUI). 

The amazing mosaic, which has ten times the resolution of a 4K television screen, reveals tempestuous structures on the Sun’s surface that often erupt into flares and coronal mass ejections. These eruptions shoot wind and plasma out into the solar system, producing space weather that can fuel shimmering auroras in the night sky—or threaten electronics on satellites and Earth.

The Solar Orbiter also captured a dramatic image of the Sun, taken at the same wavelength of ultraviolet light emitted by hydrogen gas, with its Spectral Imaging of the Coronal Environment (SPICE) instrument. As with the EUI instrument, these were also compiled from multiple shots that show hydrogen color-coded at different temperatures around the Sun, from purple at 10,000°C to neon at 630,000°C.

First and foremost, these pictures offer never-before-seen views of our star that are stunning to behold. But the Solar Orbiter team also hopes to use them, and future images taken by the mission, to solve persistent riddles about the Sun. 

For instance, the spacecraft could help scientists understand why the surface of the Sun is about 5,000°C, whereas the corona can reach an astonishing 1,000,000°C. Nobody knows exactly why the corona can be so much hotter than the solar surface, but the answer will have implications for a host of other important processes, such as the creation of the solar wind.

The Solar Orbiter has now passed inside of the orbit of Mercury, and will settle into its permanent path around the Sun in the coming years. In addition to these detailed pictures, the mission is designed to capture rare glimpses of the Sun’s poles. Solar Orbiter is one of many next-generation missions that are peeling back the Sun’s layers, including NASA's Parker Solar Probe and the Inouye Solar Telescope. Together, these observatories stand to revolutionize our understanding of our star, and by extensions, star systems across the universe.

What happens to planets when they die?

For the first time ever, astronomers have directly witnessed the shredded remains of planetary bodies lighting up the sky as they are consumed by the corpse of their host star. The milestone detection offers an unprecedented glimpse into the guts of alien worlds while also providing a preview of what our own solar system might look like after the Sun has died.

For years, scientists have seen signs that asteroids, moons, and planets are getting ripped up and devoured by white dwarfs, which are the burned out remains of stars similar in mass to the Sun. For instance, many white dwarfs are surrounded by disks of debris or sport atmospheres that are polluted by metal elements heavier than hydrogen. These findings strongly suggest that the worlds that once orbited these stars when they were alive are being broken apart and eaten by their stellar corpses.

However, capturing the exact instant when a white dwarf feeds on the accreted remains of its planets, which is marked by a blast of energetic X-ray light, requires long exposure times and the right resolution to rule out other X-ray sources in the field of view. 

Now, astronomers led by Tim Cunningham, a postdoctoral research fellow at the University of Warwick, have at last snagged this elusive observation, leading to “the only direct measurement of the instantaneous accretion rate of any white dwarf accreting planetary debris,” according to a study published Wednesday in Nature. In other words: The team clocked the rate at which a white dwarf gulped down some planet dust.

“This is the first time that we've actually detected the moment that the material hits the surface” of a white dwarf, said Cunningham in a call. “It's the smoking gun of evidence that says: ‘Okay, we've got the disk. We've got the metals in the atmosphere. And now we've seen the moment that the material moves from the disk to the atmosphere of the star.’”

The team was able to capture this moment by training NASA’s sophisticated Chandra X-ray Observatory on a white dwarf named G29–38, which is about 44 light-years from Earth, for 32 hours in September 2020. During that long exposure, Chandra spotted the telltale X-ray emission produced when the dead star swallowed the remains of some ancient world that had been torn apart by the tidal forces of the hyper-dense white dwarf. This high-energy light is produced when electrons in the atoms of this lost world become excited during the impact with its dead host star.

“We know that there's iron, magnesium, calcium, and oxygen in the [white dwarf] atmosphere,” Cunningham explained. “What we're seeing is a magnesium atom that has been locked inside a planet or an asteroid for billions of years and then has been tidally disrupted and hit the surface and had its electron kick out a little X-ray which has been sent towards us.”

Scientists have already observed hundreds of polluted white dwarfs, which has led to comprehensive models of accretion rates based on indirect measurements. With this new study, Cunningham and his colleagues have provided the first direct measurement of this rate, and found that it neatly validates the consensus built by past observations. 

“One of the extremely exciting things is that the accretion rate that we derived from the X-rays—which is a completely different method because the production of the emission is different physics—agrees extremely well with what's been done previously,” Cunningham said. “It provides an independent test of those white dwarf models.”

With this finding, the team has bolstered our understanding of the often messy afterlives of star systems like our own. The results open a window into the future of our solar system, in which the corpse of the Sun potentially tears up and eats its planets, including Earth. Moreover, the new study yields new insights about the contents of planetary bodies in other star systems, which can shed light on some of the most intractable questions in science, such as whether life exists elsewhere in the universe.

“When you have a white dwarf that is accrediting the ground-down constituents of a planetary system, it's like putting all of your planetary bodies into a blender,” Cunningham said. “You can use the white dwarf models, then, to really infer what the composition of that planetary system was.”

“These different elements that we have in our own solar system, which are crucial for life—white dwarfs definitely offer a tool to probe that,” he concluded. “Being able to do that accurately is super-important and this observation is a very good step towards even more accurate models.”

For a brief period in Earth’s tumultuous early history, a mineral that no longer exists on our planet may have safeguarded the ingredients of water long enough to enable the emergence of oceans that eventually nurtured life.

That’s the conclusion of a recent study led by Xiao Dong, a materials scientist at Nankai University, that presents a new possible origin story for Earth’s water—the most essential ingredient for life as we know it. In addition to yielding new insights into Earth’s ancient oceans, the new study also has implications in the search for water, and therefore alien life, on other planets.

As our young planet was bombarded by asteroids and comets more than four billion years ago, a “now-extinct” permutation of magnesium silicate might have kept hydrogen and oxygen atoms securely locked away deep underground so that they could eventually survive and upwell as liquid water at the surface, according to the study, which appears in Physical Review Letters.

“The origin of water on the Earth is a long-standing mystery, requiring a comprehensive search for hydrous compounds, stable at conditions of the deep Earth and made of Earth-abundant elements,” said Dong and his colleagues in the study. 

The team undertook just such a search with the help of an algorithm called Universal Structure Predictor: Evolutionary Xtallography (USPEX) developed by study co-author Artem Oganov, who is a professor at the Skolkovo Institute of Science and Technology. USPEX is able to predict exotic crystal structures to fit a variety of parameters, including compounds that would have existed within the extreme conditions in the interior of our infant planet.

The researchers used USPEX to search for compounds that contain hydrogen and oxygen, the two constituents of water, that would be stable at the high temperatures and pressures that existed hundreds of miles under our planet’s ancient surface. The results revealed a magnesium silicate that is two parts magnesium, one part silicon, five parts oxygen, and two parts hydrogen. This compound “must have existed in the Earth, hosting much of Earth’s water” during “the first 30 million years of Earth’s history, before the Earth’s core was formed, according to the study.

In an email, Oganov noted that his team’s hypothesis presents an alternate origin of Earth’s oceans that might explain some of the mysteries of another popular explanation that suggests our planet’s early water was delivered by comet impacts. 

“Only a minor fraction of Earth's water can be from comets,” Oganov said. “This follows from very different isotope compositions of Earth's water and water in comets.”

According to the team, the magnesium silicates would have disintegrated as Earth’s core formed, a process that released hydrous constituents as water. Over the course of 100 million years, this water made its way to Earth’s surface, where it became the life-sustaining force that still exists today. In this way, these silicates “likely contributed in a major way to the evolution of our planet,” the team said.

“Now we are asking ourselves whether other components could be brought to the Earth during this or similar process,” Oganov said.

These now-extinct compounds may also contribute to the evolution of other planets, which makes them relevant to the search for extraterrestrial life. 

Planets that are smaller than Earth, such as Mars, cannot achieve the interior pressures necessary to create these magnesium silicates, which means any water on these worlds had to have a different origin. Meanwhile, planets larger than Earth, such as the tantalizing “Super-Earths” observed in other star systems, would likely support pressures that could preserve huge volumes of these hydrous compounds. 

“For large Earth-like planets (Super-Earths) the ‘window’ of habitability is wider than previously thought,” Oganov said. “Previously, it was shown that if a planet contains more than 0.2 weight percent of water, its surface will be completely flooded, which will result in an unstable climate and will be adverse for emergence of life.”

“With the new hydrosilicates, a planet can contain a lot more water ‘hidden’ in the interior of the planet and not flooding its surface,” he added. “Such water-rich planets are therefore still suitable for life.”

While some scientists have speculated that Earth’s water may have been delivered from outer space by comets, the new study shows that our precious oceans may have emerged from the opposite direction—as byproducts of long-lost compounds hidden deep underground. 

Update: This article has been updated to include comments from study co-author Artem Oganov.

An object from another star system crashed into Earth in 2014, the United States Space Command (USSC) confirmed in a newly-released memo. 

The meteor ignited in a fireball in the skies near Papua New Guinea, the memo states, and scientists believe it possibly sprinkled interstellar debris into the South Pacific Ocean. The confirmation backs up the breakthrough discovery of the first interstellar meteor—and, retroactively, the first known interstellar object of any kind to reach our solar system—which was initially flagged by a pair of Harvard University researchers in a study posted on the preprint server arXiv in 2019. 

Amir Siraj, a student pursuing astrophysics at Harvard who led the research, said the study has been awaiting peer review and publication for years, but has been hamstrung by the odd circumstances that arose from the sheer novelty of the find and roadblocks put up by the involvement of information classified by the U.S. government. 

The discovery of the meteor, which measured just a few feet wide, follows recent detections of two other interstellar objects in our solar system, known as ‘Oumuamua and Comet Borisov, that were much larger and did not come into close contact with Earth.

“I get a kick out of just thinking about the fact that we have interstellar material that was delivered to Earth, and we know where it is,” said Siraj, who is Director of Interstellar Object Studies at Harvard’s Galileo Project, in a call. “One thing that I'm going to be checking—and I'm already talking to people about—is whether it is possible to search the ocean floor off the coast of Papua New Guinea and see if we can get any fragments.”

Siraj acknowledged that the odds of such a find are low, because any remnants of the exploded fireball probably landed in tiny amounts across a disparate region of the ocean, making it tricky to track them down. 

“It would be a big undertaking, but we're going to look at it in extreme depth because the possibility of getting the first piece of interstellar material is exciting enough to check this very thoroughly and talk to all the world experts on ocean expeditions to recover meteorites,” he noted.

Siraj and study co-author Avi Loeb, who serves as Frank B. Baird, Jr. Professor of Science at Harvard University, were inspired to search for potential interstellar fireballs in the wake of the discovery of ‘Oumuamua, an interstellar object measuring about a quarter mile that was spotted hurtling out of the solar system in 2017. Loeb, who has famously speculated that ‘Oumuamua might have been a piece of alien technology, suggested that Siraj comb through a database of fireballs and meteor impacts run by NASA’s Center for Near Earth Object Studies (CNEOS).

There are nearly 1,000 impacts logged in the database, but a fireball that exploded near Manus Island on January 8, 2014 jumped out at Siraj due to an unusually swift speed exceeding 130,000 miles per hour. This breakneck pace hinted at “a possible origin from the deep interior of a planetary system or a star in the thick disk of the Milky Way galaxy,” according to the team’s 2019 study.

“It was really fast, and so I was like: ‘Oh my God, this could be an interstellar meteor,’” Siraj said. “It was hiding in plain sight. It wasn't that we had to dig to find this database. It was more that there hadn't been an interstellar object until 2017. As a result, no one had a reason to think that there could be meteors that were from outside of the solar system.” 

Siraj and Loeb submitted the discovery to The Astrophysical Journal Letters, but the study became snarled during the review process by missing information withheld from the CNEOS database by the U.S. government. 

Some of the sensors that detect fireballs are operated by the U.S. Department of Defense, which uses the same technologies to monitor the skies for nuclear detonations. As a result, Siraj and Loeb couldn’t directly confirm the margin of error on the fireball’s velocity. 

The secret data threw the paper into limbo as the researchers sought to get confirmation from the U.S. government. Siraj called the multi-year process a “whole saga” as they navigated a bureaucratic labyrinth that wound its way though Los Alamos National Laboratory, NASA, and other governmental arms, before ultimately landing at the desk of Joel Mozer, Chief Scientist of Space Operations Command at the U.S. Space Force service component of USSC.

The newly released memo, which is dated March 1 of this year, reveals that Mozer at last “confirmed that the velocity estimate reported to NASA is sufficiently accurate to indicate an interstellar trajectory.” Siraj found out about the results this week due to a tweet from a NASA scientist, and is now renewing the effort to get the original discovery published so that the scientific community can follow-up with more targeted research into the implications of the find. 

For instance, Siraj noted that any information about the light emitted by the object as it burned up in the atmosphere could yield insights about the interior composition of the interstellar visitor. Indeed, scientists may have already glimpsed the spectral trace of an intergalactic meteor particle—yes, a particle from beyond the Milky Way—according to a study published in 2007. 

While this was an incredibly small object, it indicates that the solar system may be awash in material from other star systems, and indeed even other galaxies, that could be turned up by future searches. Such efforts could offer a glimpse of the worlds beyond the Sun right here on Earth, and perhaps even unearth bonafide interstellar meteorites.  

“Given how infrequent interstellar meteors are, extra-galactic meteors are going to be even rarer,” Siraj cautioned. ”But the fact of the matter is, going forward, we won't find anything unless we look for it. We might as well take it upon ourselves as scientists to build a network as extensive as the U.S government's sensor network, and use it for the purposes of science and fully use the atmosphere.” 

“The atmosphere is already a sensor for these things,” he concluded. “We're just not paying attention to the signals. So we might as well use the whole atmosphere and see what comes our way.”