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Stars shape their solar systems. It’s true of ours, and it’s true of others. But for some massive stars, their power to shape still-forming systems is fateful and final.

In their youth, stars are surrounded by a rotating mass of gas and dust called a protoplanetary disk. Planets form in these disks, and the process can take millions of years. But stars have different masses and different radiation outputs that affect how planets form, or if they form at all.

New research examines how the powerful UV radiation from massive stars affects planet formation in disks. The research article is “A far-ultraviolet–driven photoevaporation flow observed in a protoplanetary disk.” It’s published in the journal Science, and the lead author is Olivier Berne from the Institute for Research in Astrophysics and Planetology, University of Toulouse, France.

The research looks at large stars in their first million years of life, when they’re not only young but extremely luminous. The researchers focused on several stars in the Orion Nebula and its stellar nurseries. The stars are at least ten times more massive than the Sun and are 10,000 times more luminous. What effect does their luminosity and all that radiation have on disks where planets form?

These powerful young stars emit high levels of Far-Ultraviolet (FUV) radiation, which has the power to remove mass from planet-forming disks. This power extends beyond their own immediate surroundings into the disks around neighbouring low-mass stars.

“Most low-mass stars form in stellar clusters that also contain massive stars, which are sources of far ultraviolet (FUV) radiation,” the researchers explain. “Theoretical models predict that this FUV radiation produces photodissociation regions (PDRs) on the surfaces of protoplanetary disks around low-mass stars, which affects planet formation within the disks.” The PDRs can span several hundred astronomical units (AU).

The researchers examined one protoplanetary disk that’s within range of energetic, high-mass stars residing in the Trapezium Cluster in the heart of the Orion Nebula. The five brightest stars in that cluster range from 15 to 30 solar masses, making them prime candidates to study PDRs in neighbouring planet-forming disks. The Orion Bar PDR is an often-studied and prototypical PDR.

The Orion Nebula. The Trapezium Cluster is above and to the right of the three stars in Orion's Belt in this image. The stars in Trapezium are mostly responsible for illuminating Orion, and their powerful FUV energy can strip gas from the protoplanetary disks surrounding lower-mass stars nearby. Image Credit: NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team, Public domain, via Wikimedia Commons
The Orion Nebula. The Trapezium Cluster is above and to the right of the three stars in Orion’s Belt in this image. The stars in Trapezium are mostly responsible for illuminating Orion, and their powerful FUV energy can strip gas from the protoplanetary disks surrounding lower-mass stars nearby. Image Credit: NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team, Public domain, via Wikimedia Commons

The disk in the image, d203-506, is being bombarded by intense FUV radiation from the massive Trapezium stars. The FUV radiation is dispersing matter in the disk, inhibiting planet formation. According to the research, it’s impossible for a Jupiter-mass planet to form in this disk because the radiation is stripping matter away.

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Juno Reveals a Giant Lava Lake on Io

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NASA’s Juno spacecraft came within 1,500 km (930 miles) of the surface of Jupiter’s moon Io in two recent flybys. That’s close enough to reveal new details on the surface of this moon, the most volcanic object in the Solar System. Not only did Juno capture volcanic activity, but scientists were also able to create a visual animation from the data that shows what Io’s 200-km-long lava lake Loki Patera would look like if you could get even closer. There are islands at the center of a magma lake rimmed with hot lava. The lake’s surface is smooth as glass, like obsidian.

“Io is simply littered with volcanoes, and we caught a few of them in action,” said Juno principal investigator Scott Bolton during a news conference at the European Geophysical Union General Assembly in Vienna, Austria. “There is amazing detail showing these crazy islands embedded in the middle of a potentially magma lake rimmed with hot lava. The specular reflection our instruments recorded of the lake suggests parts of Io’s surface are as smooth as glass, reminiscent of volcanically created obsidian glass on Earth.”

This animation is an artist’s concept of Loki Patera, a lava lake on Jupiter’s moon Io, made using data from the JunoCam imager aboard NASA’s Juno spacecraft. With multiple islands in its interior, Loki is a depression filled with magma and rimmed with molten lava. Credit: NASA/JPL-Caltech/SwRI/MSSS

Just imagine if you could stand by the shores of this lake – which would be a stunning view in itself. But then, you could look up and see the giant Jupiter looming in the skies above you.

Juno made the two close flybys of Io in December 2023 and February 2024. Images from Juno’s JunoCam included the first close-up images of the moon’s northern latitudes. Undoubtedly, Io looks like a pizza – which has been the conclusion since our first views of this moon, when Voyager 1 flew through the Jupiter system in March 1979. The mottled and colorful surface comes from the volcanic activity, with hundreds of vents and calderas on the surface that create a variety of features. Volcanic plumes and lava flows across the surface show up in all sorts of colors, from red and yellow to orange and black. Some of the lava “rivers” stretch for hundreds of kilometers.

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Io’s sub-Jovian hemisphere is revealed in detail for the first time since Voyager 1 flew through the Jupiter system in March 1979, during the Juno spacecraft’s 58th perijove, or close pass, on February 3, 2024. This image shows Io’s nightside illuminated by sunlight reflected off Jupiter’s cloud tops. Several surface changes are visible include a reshaping of the compound flow field at Kanehekili (center left) and a new lava flow to the east of Kanehekili. This image has a pixel scale of 1.6 km/pixel. Credit : NASA/SwRI/JPL/MSSS/Jason Perry.

Juno scientists were also able to re-create a spectacular feature on Io, a spired mountain that has been nicknamed “The Steeple.” This feature is between 5 and 7 kilometers (3-4.3 miles) in height. It’s hard to comprehend the type of volcanic activity that could have created such a stunning landform.

Created using data collected by the JunoCam imager aboard NASA’s Juno during flybys in December 2023 and February 2024, this animation is an artist’s concept of a feature on the Jovian moon Io that the mission science team nicknamed “Steeple Mountain.” Credit: NASA/JPL-Caltech/SwRI/MSSS

Speaking of volcanic activity, two recent papers have come to a jaw-dropping conclusion about Io: this moon has been erupting since the dawn of the Solar System.

All the volcanic on Io is activity is driven by tidal heating. Io is in an orbital resonance with two other large moons of Jupiter, Europa and Ganymede.

“Every time Ganymede orbits Jupiter once, Europa orbits twice, and Io orbits four times,” explained the authors of a paper published in the Journal of Geophysical Research: Planets, led by Ery Hughes of GNS Science in New Zealand. “This situation causes tidal heating in Io (like how the Moon causes ocean tides on Earth), which causes the volcanism.”

However, scientists haven’t known how long this resonance has been occurring and whether what we observe today is what has always been happening in the Jupiter system. This is because volcanism renews Io’s surface almost

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Artemis Astronauts Will Deploy New Seismometers on the Moon

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Back in the 1960s and 1970s, Apollo astronauts set up a collection of lunar seismometers to detect possible Moon quakes. These instruments monitored lunar activity for eight years and gave planetary scientists an indirect glimpse into the Moon’s interior. Now, researchers are developing new methods for lunar quake detection techniques and technologies. If all goes well, the Artemis astronauts will deploy them when they return to the Moon.

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Fiber optic cable is the heart of a seismology network to be deployed on the Moon by future Artemis astronauts.

The new approach, called distributed acoustic sensing (DAS), is the brainchild of CalTech geophysics professor Zhongwen Zhan. It sends laser beams through a fiber optic cable buried just below the surface. Instruments at either end measure how the laser light changes during the shake-induced tremors. Basically Zhan’s plan turns the cable into a sequence of hundreds of individual seismometers. That gives precise information about the strength and timing of the tremors. Amazingly, a 100-kilometer fiber optic cable would function as the equivalent of 10,000 seismometers. This cuts down on the number of individual seismic instruments astronauts would have to deploy. It probably also affords some cost savings as well.

A seismometer station deployed on the Moon during the Apollo 15 mission. Courtesy NASA.
A seismometer station deployed on the Moon during the Apollo 15 mission. Courtesy NASA.

DAS and Apollo on the Moon

Compare DAS the Apollo mission seismometer data and it becomes obvious very quickly that DAS is a vast improvement. In the Apollo days, the small collection of instruments left behind on the Moon provided information that was “noisy”. Essentially, when the seismic waves traveled through different parts of the lunar structure, they got scattered. This was particularly true when they encountered the dusty surface layer. The “noise” basically muddied up the signals.

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The layout for the Apollo Lunar Seismic Profiling Experiment for the Apollo 17 mission. Courtesy Nunn, et al.

What DAS Does to Detect Quakes on the Moon

The DAS system stations laser emitters and data collectors at each end of a fiber optic cable. This allows for multiple widely spaced installations that measure light as it transits the network. The cable consists of glass strands, and each strand contains tiny imperfections. That sounds bad, but each imperfection provides a useful “waypoint” that reflects a little bit of the light back to the source. That information gets recorded as part of a larger data set. Setting up such a system of
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Ice Deposits on Ceres Might Only Be a Few Thousand Years Old

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The dwarf planet Ceres has some permanently dark craters that hold ice. Astronomers thought the ice was ancient when they were discovered, like in the moon’s permanently shadowed regions. But something was puzzling.

Why did some of these shadowed craters hold ice while others did not?

Ceres was first discovered in 1801 and was considered a planet. Later, it was thought to be the first asteroid ever discovered, since it’s in the main asteroid belt. Since then, our expanding knowledge has changed its definition: we now know it as a dwarf planet.

Even though it was discovered over 200 years ago, it’s only in the last couple of decades that we’ve gotten good looks at its surface features. NASA’s Dawn mission is responsible for most of our knowledge of Ceres’ surface, and it found what appeared to be ice in permanently shadowed regions (PSRs.)

New research shows that these PSRs are not actually permanent and that the ice they hold is not ancient. Instead, it’s only a few thousand years old.

The new research is titled “History of Ceres’s Cold Traps Based on Refined Shape Models,” published in The Planetary Science Journal. The lead author is Norbert Schorghofer, a senior scientist at the Planetary Science Institute.

“The results suggest all of these ice deposits must have accumulated within the last 6,000 years or less.”

Norbert Schorghofer, senior scientist, Planetary Science Institute.

Dawn captured its first images of Ceres while approaching the dwarf planet in January 2015. At that time, it was close enough to capture images as good as Hubble’s. Those images showed craters and a high-albedo site on the surface. Once captured by Ceres, Dawn followed a polar orbit with decreasing altitude. It eventually reached 375 km (233 mi) above the surface, allowing it to see the poles and surface in greater detail.

“For Ceres, the story started in 2016, when the Dawn spacecraft, which orbited around Ceres at the time, glimpsed into these permanently dark craters and saw bright ice deposits in some of them,” Schorghofer said. “The discovery back in 2016 posed a riddle: Many craters in the polar regions of Ceres remain shadowed all year – which on Ceres lasts 4.6 Earth years – and therefore remain frigidly cold, but only a few of them harbor ice deposits.”

As scientists continued to study Ceres, they made another discovery: its massive Solar System neighbours make it wobble.

“Soon, another discovery provided a clue why: The rotation axis of Ceres oscillates back and forth every 24,000 years due to tides from the Sun and Jupiter. When the axis tilt is high and the seasons strong, only a few craters remain shadowed all year, and these are the craters that contain bright ice deposits,” said lead author Schorghofer.

This figure from the research shows how Ceres' obliquity has changed over the last 25,000 years. As the obliquity varies, sunlight reaches some crater floors that were thought to be PSRs. Image Credit: Schorghofer et al. 2023.
This figure from the research shows how Ceres’ obliquity has changed over the last 25,000 years. As the obliquity varies, sunlight reaches some crater floors that were thought to be PSRs. Image Credit: Schorghofer et al. 2023.

Researchers constructed digital elevation maps (DEMs) of the craters to uncover these facts. They wanted to find out how large and deep the shadows in the craters were, not just now but thousands of years ago. But that’s difficult to do since portions of these craters were in deep shadow when Dawn visited. That made it difficult to see how deep the craters were.

Robert Gaskell, also from the Planetary Science Institute, took on the task. He developed a new technique to create more accurate maps of the craters with data from Dawn’s sensitive Framing Cameras, contributed to the mission by Germany. With improved accuracy, these maps of the crater floors could be used in ray tracing to show sunlight penetrated the shadows as Ceres wobbled over thousands of years.

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