Did Powerful Asteroid Impacts Make Venus So Different From Earth?

Venus and Earth have several things in common. Both are terrestrial planets composed of silicate minerals and metals that are differentiated between a rocky mantle and crust and a metal core. Like Earth, Venus orbits within our Sun’s circumsolar habitable zone (HZ), though Venus skirts the inner edge of it. And according to a growing body of evidence, Venus has active volcanoes on its surface that contribute to atmospheric phenomena (like lightning). However, that’s where the similarities end, and some rather stark differences set in.

In addition to Venus’ hellish atmosphere, which is about 100 times as dense as Earth’s and hot enough to melt lead, Venus has a very “youthful” surface. Compared to other bodies in the Solar System (like Mercury, the Moon, and Mars), Venus’ surface retains little evidence of the many bolides impacts it experienced over billions of years. According to new research from the Southwest Research Institute (SwRI) and Yale University, this may result from bolide impacts that provided a high-energy, rejuvenating boost to the planet in its early years.

The research was conducted by Simone Marchi, a staff scientist at the SwRI who specializes in planetary formation and the geology of asteroids and terrestrial planets. He was joined by Raluca Rufu, a postdoctoral researcher of space sciences at SwRI, and Jun Korenaga, a professor of Earth and planetary sciences at Yale University. The paper that describes their research, “Long-lived volcanic resurfacing of Venus driven by early collisions,” recently appeared in Nature Astronomy.

Thanks to missions like the Magellan probe and the extensive radar mapping it conducted in the 1990s, scientists began mapping the surface of Venus in detail. To their surprise, the surface appeared far smoother than expected, which suggested that a certain mechanism was responsible for “recycling” the surface. On Earth, impact craters are largely removed by resurfacing events caused by tectonic activity, but Venus has no such activity to explain its smooth features. Said Professor Korenaga in a Yale News release:

“We would expect Venus to be heavily cratered, but surprisingly, it is much less cratered than the moon or Mars. Many scientists have tried to explain this young surface age of Venus. One popular idea is that Venus used to have plate tectonics, but somehow it stopped about 500 million years ago. This explanation is admittedly ad hoc, so others have tried to come up with models that are physically more sound, with limited success.”

For their study, Marchi, Rufu, and Korenaga considered the possibility that Venus experienced more powerful bolide impacts than Earth during the Hadean period (ca. 4.5 billion years ago). At this time, the newly-formed planets experienced a high rate of high-magnitude impacts due to the abundance of leftover material floating around space. Similarly, astronomers have noted another period of intense bombardment between 4.1 and 3.8 billion years ago known as the Late Heavy Bombardment. This period is attributed to planetary instability, possibly involving the migration of the gas giants.

Over time, the intensity of the bombardment declined as the planets achieved more stable orbits. While Earth and Venus formed in the same general area of the inner Solar System, the differences in their distances from the Sun mean that they have different impact histories – i.e., the number of impacts and their outcomes were slightly different. “One of the mysteries of the inner solar system is that, despite their similar size and bulk density, Earth and Venus operate in strikingly different ways, particularly affecting the processes that move materials through a planet,” explained Marchi.

Artist’s illustration of Quetzalpetlatl Corona on Venus displaying both active volcanism and a subduction zone. (Credit: NASA/JPL-Caltech/Peter Rubin)

To test this theory, the team ran simulations of Venus experiencing more systemic bolide impacts billions of years ago. These revealed a trend where successive impacts blasted deeper into Venus, leading to the superheating of the planet’s core. Said Korenaga, this would account for higher than normal volcanic activity, which could explain why the surface appears young and uncratered:

“This superheated core could have a long-lasting influence on the volcanic history of Venus It could keep heating up the mantle for a few billion years, with sufficient volcanic activity to cover up most of the craters and reduce the apparent surface age to only a few hundred million years.”

The team looks forward to upcoming missions that will explore Venus in the coming years and provide insight into the planet’s tectonic and bolide impact history (allowing them to test their theory). These include NASA’s Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy (VERITAS) and Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission, scheduled to launch by 2027 and 2029 (respectively). They will be joined by the ESA/NASA EnVision satellite by the early 2030s.

These missions will perform atmospheric studies and high-resolution radar mapping of Venus’ surface, building on the work of previous missions – like the Soviet Venera Program, NASA’s Pioneer Venus and Magellan missions, and the ESA’s Venus Express – and delivering deeper into the mysteries and evolutionary history of “Earth’s Sister Planet.”

Further Reading: YaleNews

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Computer Algorithm Finds a “Potentially Hazardous” Asteroid

Humanity has been on an asteroid-finding spree as of late. Those close to Earth, known as Near Earth Objects (NEOs), have been particularly interesting for two reasons. One is they offer potentially lucrative economic opportunities with asteroid mining. The other is they are potentially devastating if they hit the Earth, so we’d like to find them with some advance warning. Those that fall into the latter category are known as potentially hazardous asteroids, or PHAs. Now, thanks to some ingenious programmers from the University of Washington, we have a new algorithm to detect them.

Of the 30,000 total NEOs found so far, about 2,300 of them are PHAs. However, researchers think there are at least that many left to be discovered. PHAs typically come within 5 million miles of Earth and must be large enough to be a potential threat, not just burn up in our atmosphere as a shooting star.

Finding these dim objects, even when they are on their closest approach, can be a daunting challenge. Scientists typically use specialized telescopes like Asteroid Terrestrial Impact Last Alert System (ATLAS) at the University of Hawai’i. However, these massive telescopes usually have to image the same patch of sky four times in a single night to catch a glimpse of a PHA on the edge of its detection range.

Video describing how the HelioLinc3D algorithm found its first PHA.
Credit – DiRAC Institute, University of Washington YouTube Channel

That’s where the new algorithm comes in. Developed by Ari Heinze, a researcher at UW, and Siegfried Eggl, now a professor at the University of Illinois Urbana-Champaign, the algorithm, known as HelioLinc3D, is capable of finding data on asteroids that might be spread throughout observations of multiple days from a single satellite.

Which is precisely what happened when it found its first new PHA. Now known as 2022 SF289, ATLAS originally picked it up during observations on September 19th, 2022, but it was only captured once that night. Luckily, it was captured three more times by ATLAS on two separate nights as well, and HelioLinc3D could piece together the puzzle to find the asteroid hiding in plain sight.

2022 SF289 is not a threat – while its orbital path will take it within 140,000 miles of Earth, it appears unlikely to impact the planet at any point in the foreseeable future. And, at 600 in length, it likely would be devastating, but not catastrophic, like the asteroid that contributed to the dinosaurs’ downfall.

Fraser details how hard it is to find asteroids in the first place

Other observatories also missed discovering it, as it was located in a region of the Milky Way that is awash with background stars, making it difficult to make out a faint, fast-moving rock, even if it is much closer to us. Once discovered, though, it was quickly confirmed by other specialist asteroid hunters like the Catalina Sky Survey and Pan-STARRS. 

So, chalk one up for the new algorithm. But that’s just the beginning of its contributions. HelioLinc3D was originally developed to work on a much more powerful telescope. The Vera C. Rubin observatory, planned to come online in Chile in early 2025, is expected only to require two captures a night to detect asteroids like 2022 SF289 rather than the four currently needed. And HelioLinc3D will help it do that. But until then, it appears it will have plenty of work cut out for it searching through the back catalogs of ATLAS and other asteroid hunters. For our own sakes, we should all wish it the best of luck.

Learn More:
UW – New algorithm ensnares its first ‘potentially hazardous’ asteroid
UT – Astronomers Have Found More Than 30,000 Near-Earth Asteroids… so far
UT – Astronomers Want Your Help to Identify Risky Asteroids
UT – Three New Potentially Hazardous Asteroids Discovered, Including a big one That Measures 1.5 km Across

Lead Image:
Four separate images from ATLAS run through the algorithm with 2022 SF289 highlighted in red boxes.
Credit – ATLAS / University of Hawai’i Institute for Astronomy / NASA

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Oops. NASA Accidentally Points Voyager 2’s Antenna Away from Earth, Temporarily Losing Contact

It’s every space mission’s nightmare: losing contact with the spacecraft. In the best case, you recover it right away. Worst case, you never hear from your hardware again. On July 21, controllers lost contact with Voyager 2, out in the depths of space. Now they’re waiting for a reset to catch Voyager 2’s next message when it “phones home”.

So, what happened? The spacecraft, which is nearly 20 billion kilometers away, seems to be doing fine. It’s probably sending all kinds of communications back to Earth. But, the stream of data is bounding off into space instead of linking up with the Deep Space network. That’s because a series of planned commands to Voyager 2 inadvertently caused the spacecraft to point its antenna 2 degrees away from Earth. Essentially, Voyager 2 and Earth are not in communication. They’re “talking past” each other.

This artist’s concept depicts one of NASA’s Voyager spacecraft, including its high-gain antenna. The cosmic ray subsystem is highlighted, too. Voyager 2 is out of communications until October. Credit: NASA/JPL-Caltech

Regaining Contact with Voyager 2

All is not lost. Yet. That’s because the spacecraft is programmed to reset its orientation several times a year to keep the antenna pointed toward Earth. The next reset isn’t for several months—on October 15th. Until then, Voyager 2 is speeding along on its planned trajectory. If all goes well, the control team should hear from the spacecraft again on October 15th. At this point, they’re characterizing this loss of signal as a temporary communications pause. There’s nothing to indicate any other problems with Voyager 2, beyond the mistaken commands.

The spacecraft is equipped with a high-gain antenna measuring 3.7 meters across. It communicates with the Deep Space Network via the S band (13 cm wavelength) channel as well as in the X band (3.6 cm wavelength). At its current distance, the spacecraft’s signals take about 17.5 hours to get back to Earth. That time increases as the spacecraft gets farther away.

A Glorious History

Currently, Voyager 2 and its twin Voyager 1 are exploring space beyond the solar system. They launched in 1977 and for the past decades, they’ve made huge discovieres at planets and the outermost bounds of the heliosphere. Their images and data opened up a whole new way of looking at the outer solar system.

Now, they’re in the Voyager Interstellar Mission phase, where their data helps characterize the “limits” of the solar system lie and where deep space begins. Voyager 2 probably entered interstellar space a few years ago, although it still reports on conditions at the “edge” of the solar system. Interestingly, while Voyager 2 is out of communications with Earth, Voyager 1 is still talking with the Deep Space Network. It’s about 24 billion kilometers from Earth.

This illustration shows the position of NASA’s Voyager 1 and Voyager 2 probes, outside of the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto. Voyager 1 exited the heliosphere in August 2012. Voyager 2 exited at a different location in November 2018. Credit: NASA/JPL-Caltech

Ultimately, they’re headed out on two very different trajectories through the stars. They have enough power to operate for a few more years (2025 or thereabouts) to send back information to Earth about their environments. Engineers on the project have figured out a way to extend spacecraft power for perhaps a couple more years by tapping some specific onboard reserves. Eventually, however, the spacecraft will fall silent as their power supplies run out. This current outage on Voyager 2 is giving mission engineers an early taste of what that experience will be like, after “talking” with these distant spacecraft for nearly five decades.

For More Information

Mission Update: Voyager 2 Communications Pause
Voyagers Mission Status

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NASA is Working on Technology to 3D Print Circuits in Space

A collaboration of engineers from NASA and academia recently tested hybrid printed electronic circuits near the edge of space, also known as the Kármán line. The space-readiness test was demonstrated on the Suborbital Technology Experiment Carrier-9, or (SubTEC-9), sounding rocket mission, which was launched from NASA’s Wallops Flight Facility on April 25 and reached an altitude of approximately 174 kilometers (108 miles), which lasted only a few minutes before the rocket descended to the ground via parachute.

Image of a Terrier-Improved Malamute sounding rocket launching from NASA’s Wallops Flight Facility for the SubTEC-9 mission on April 25, 2023. The brief flight carried 14 new technology development experiments, including 3D-printed circuits, a faster telemetry link, and a new star tracker. (Credit: NASA/Kyle Hoppes)

The test consisted of humidity and electronic sensors that were printed on two attached panels along with the payload door, all of which transmitted data to the ground during the brief flight. The mission was deemed a success and holds the potential to help scientists and engineers improve design efficiency for smaller spacecraft.

“The uniqueness of this technology is being able to print a sensor actually where you need it,” said Dr. Margaret Samuels, who is an electronics engineer at NASA’s Goddard Space Flight Center and co-led the experiment with Goddard aerospace engineer, Beth Paquette. “The big benefit is that it’s a space saver. We can print on 3-dimensional surfaces with traces of about 30 microns – half the width of a human hair – or smaller between components. It could provide other benefits for antennas and radio frequency applications.”  

The humidity-sensing printing ink was produced at NASA’s Marshall Space Flight Center while the circuits were created at the University of Maryland’s Laboratory for Physical Sciences (LPS), who each coordinated their efforts with Dr. Samuels and Paquette, demonstrating the collaborative effort undertaken for the project.

Brian Banks, who is an electronics engineer at Wallops, noted the printed circuits provide a new framework for designing smaller spacecraft, for both near-Earth and deep space mission.

Image of the engineering team from NASA and the University of Maryland’s Laboratory for Physical Sciences (LPS) (from left to right): Team lead and Goddard aerospace engineer, Beth Paquette; Wallops electronics engineer Brian Banks; Jason Fleischer of LPS; and Donghun Park, also with LPS. They are displaying the curved metal plate with their printed electronics test assembly in a NASA Wallops Flight Facility laboratory prior to the SubTEC-9 technology test flight from Wallops in April 2023. This flight marked the first hybrid printed electronic circuits to fly into space. (Credit: NASA/Berit Bland)

“The hybrid technology allows for circuits to be fabricated in locations that would typically not be available for conventional electronics modules,” said Banks. “Printing on curved surfaces could also be helpful for small, deployable sub-payloads where space is very limited.”

The circuits were both designed and printed by LPS engineer, Jason Fleischer, who said the SubTEC-9 mission establishes a “turning point” for the evolution and validation of printed-circuit technology at LPS.

According to Paquette, temperature sensors could be printed all over the vehicle’s surface interiors on future missions. For example, that type of mission could analyze the heating and cooling of a spacecraft as it travels close to the Sun.

Image of a 3D-printed circuit on display during the Goddard Field Day event that launched on the Suborbital Technology Experiment Carrier-9 (SubTEC-9) technology test flight from NASA’s Wallops Flight Facility in April 2023. (Credit: NASA/Karl B. Hille)

Along with testing the 3D-printed electronic circuits, the SubTEC-9 mission tested a total of 14 different types of technologies. These include a faster telemetry link, a new antenna, a low-cost gyro, a new high-density battery, and a new smaller star tracker, which, as its name implies, is a sensor built to align an object of importance in space, like a star, and is built for altitude control systems.

The SubTEC missions are only a small piece of NASA’s Sounding Rockets Program (NRSP), which started in 1959 with the goal of providing research activities for space and earth sciences. During its tenure, NRSP has launched approximately 3,000 missions to suborbital space, achieving a greater than 90 percent mission success rate over the last two decades along with a launch success rate of 97 percent.

The SubTEC-9 sounding rocket mission is the most recent of NASA’s SubTEC program, whose first launch was in 2005 with recent flights including SubTEC-7, which occurred on May 16, 2017, and SubTEC-8, which occurred on October 24, 2019.

What new discoveries will scientists and engineers make about 3D-printed electronic circuits in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

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The PLATO Mission Could be the Most Successful Planet Hunter Ever

In 2026, the European Space Agency (ESA) will launch its next-generation exoplanet-hunting mission, the PLAnetary Transits and Oscillations of stars (PLATO). This mission will scan over 245,000 main-sequence F, G, and K-type (yellow-white, yellow, and orange) stars using the Transit Method to look for possible Earth-like planets orbiting Solar analogs. In keeping with the “low-hanging fruit” approach (aka. follow the water), these planets are considered strong candidates for habitability since they are most likely to have all the conditions that gave rise to life here on Earth.

Knowing how many planets PLATO will likely detect and how many will conform to Earth-like characteristics is essential to determining how and where it should dedicate its observation time. According to a new study that will be published shortly in the journal Astronomy & Astrophysics, the PLATO mission is likely to find tens of thousands of planets. Depending on several parameters, they further indicate that it could detect a minimum of 500 Earth-sized planets, about a dozen of which will have favorable orbits around G-type (Sun-like) stars.

The study was conducted by researchers from the Institute of Planetary Research (IFP) and Institute of Optical Sensor Systems at the German Aerospace Center (DLR), the Department of Geological Sciences at the Freie Universität Berlin (FU Berlin), and the Center for Astronomy and Astrophysics at the Technical University Berlin (TUB). Filip Matuszewski, a Ph.D. candidate with the Grenoble Planetary and Astrophysics Institute (IPAG) at the Université Grenoble Alpes, led the study as part of his thesis while studying at FU Berlin and the Extrasolar Planets and Atmospheres.

To assess the number of exoplanets PLATO could detect, Matuszewski and his team developed a tool named the Planet Yield for PLATO Estimator (PYPE). This tool combines a statistical approach with occurrence rates from planet formation models and data obtained by the Kepler space telescope. This allowed them to estimate how many exoplanets PLATO will detect during four years based on a fraction of the observation fields selected for the all-sky PLATO stellar input catalog (PIC). As Matuszewski explained to Universe Today via email:

“First, we needed a synthetic population of planets (our own little universe, if you will). To do this, we took a planetary population model, which is basically a simulation of 1000 protoplanetary discs evolving into planetary systems (Christoph Mordasini of the University of Bern, Switzerland, provided us with these planetary systems). Since the resulting systems are quite different from what we currently know about exoplanets, we wanted to include data from Kepler. Based on the occurrence rates from Kepler, we formed our own two-planet populations to use as a comparison.”

The second step, said Matuszewski, consisted of the team estimating how many stars PLATO will observe in just one field of view (~125,000) and assigning a planetary system (based on our own) to each. Next, they considered how many of these planets would have the proper orientation to make transits relative to PLATO (is it edge-on to the telescope?), thus producing a visible dip in brightness. For a plant orbiting a star the same size as our Sun with an orbital period of 365 days, the probability of this happening (aka. transit probability) is just 0.47%.

But when one considers the number of stars PLATO will observe, that still leaves tens of thousands of candidates available for study. Last, they employed a detection efficiency model that accounts for the performance of PLATOs cameras and various noise sources to see if the transit signal would be stronger than the background noise. “That is the basic function of PYPE,” said Matuszewski. “From there, we can tweak the program to give us results for various false scenarios and time periods. How many planets do we find looking here for two years and there for two years? What if we look at a particular field for longer?”

Artist’s impression of the Planetary Transits and Oscillations of stars (PLATO) mission. Credit: ESA

When they applied the PYPE to the observatory’s 4-year primary mission, the team obtained some very encouraging results. Depending on what fields it observes and for how long, the orbital period of the planets, the orientation of the planets, and other factors, they found that PLATO is likely to detect thousands or tens of thousands of exoplanets. Even more encouraging, they found that a statistically significant number of these planets are likely to be similar to Earth. As Matuszewski explained:

“Using the most conservative planet population model and mission scenario, we estimate a minimum of 500 Earth-sized planets to be detected in the nominal mission duration of 4 years. That includes every type of star and every distance to the star. If we look at Earth-sized planets with an orbital period range of 250-500 days around G stars (Earth-Sun analogs), we estimate up to 12 detections. This is for the 2+2 year observation with the most optimistic planet model.”

In the past twenty years, the number of known exoplanets has grown exponentially, with 5,483 confirmed detections in 4,087 systems (and another 9,770 candidates awaiting confirmation) as of July 30th, 2023. The discovery and characterization of these exoplanets have informed (and challenged) prevailing theories about planet formation and occurrence rates. However, there remain some unanswered questions and a significant margin of uncertainty regarding how common certain types of planets are (related to gaps in the exoplanet census).

The purpose of this study, and those like it, is to establish estimates that can be compared to observational data. The way the results deviate from the estimates will help inform planet formation models and provide scientists with a better idea of how common exoplanets are – accounting for size, mass, composition, orbital period, etc. In particular, PLATO’s results will show just how common Earth-like planets orbiting G-type solar analogs are, which will help narrow the search for worlds that are likely to be habitable – and inhabited.

Further Reading: arXiv

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New Simulation Reveals the Churning Interiors of Giant Stars

On a basic level, a star is pretty simple. Gravity squeezes the star trying to collapse it, which causes the inner core to get extremely hot and dense. This triggers nuclear fusion, and the heat and pressure from that pushes back against gravity. The two forces balance each other while a star is in its main sequence state. Easy peasy. But the details of how that works are extremely complex. Modeling the interior of a star accurately requires sophisticated computer models, and even then it can be difficult to match a model to what we see on the surface of a star. Now a new computer simulation is helping to change that.

Although the internal pressure and gravitational weight of a star are generally in equilibrium, the flow of heat is not. All the heat and energy generated in a stellar core has to escape in time, and there are two general ways in which it happens. The first is through a radiative exchange. High-energy gamma rays scatter against nuclei in the core, gradually losing some energy as they migrate to the surface and escape. The interior of a star is so dense that this can take thousands of years.

The second method is through convective flow. Hot material near the center of a star tries to expand, pushing its way toward the surface. Meanwhile, cooler material near the surface condenses and sinks towards the core. Together this creates a cyclic flow of material that transfers heat energy to the star’s surface. This convection churns the interior of a star, and because of things such as viscosity and turbulent vortices, it is extremely difficult to model.

How heat is transferred within a star. Credit: Wikipedia

Stars generally have a radiative zone and a convective zone. The location and size of these zones depend on a star’s mass. Small stars are almost entirely convective, while stars like the Sun have an inner radiative zone and an outer convective zone. For massive stars, this is flipped, with an inner convective zone and an outer radiative one. One of the things we know about convection is that it can cause the surface of a star to fluctuate like a simmering pot of water. This in turn causes the overall brightness of a star to flicker slightly.

In this new study, the team has shown how convection regions in a star are connected to the way in which a star flickers. What they found was that sound waves rippling through a star are affected by convective flows, which in turn change the way a star flickers. This means in principle we can study the interior of a star by observing its flicker of light, allowing astronomers to better understand stars.

Right now the flickers are too small for current telescopes to observe. But with larger and more sensitive telescopes we should be able to study them. We are already able to study the effects of sound waves in the Sun, through what is known as helioseismology. In the coming decades, we should be able to do this with nearby stars.

Reference: Anders, Evan H., et al. “The photometric variability of massive stars due to gravity waves excited by core convection.” Nature Astronomy (2023).

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Chinese Scientists Complete a Concept Study for a 6-Meter Space Telescope to Find Habitable Exoplanets

We have discovered more than 5,400 planets in the universe. These worlds range from hot jovians that closely orbit their star to warm ocean worlds to cold gas giants. While we know they are there, we don’t know much about them. Characteristics such as mass and size are fairly straightforward to measure, but other properties such as temperature and atmospheric composition are more difficult. So the next generation of telescopes will try to capture that information, including one proposed telescope from the Chinese National Space Administration.

Known as the Tianlin Mission, the proposed telescope would have a 6-meter primary mirror. That’s roughly the size of the primary mirror for the Webb Space Telescope. The goal of Tianlin, which means “Neighbors of Heaven”, would be to study the atmospheres of potentially habitable Earth-sized worlds.

It’s very difficult to study the atmospheres of distant worlds. There are only a few cases of exoplanets we can see directly, and these are large gas giants far from their star. We have yet to be able to see Earth-sized worlds close enough to their star to be in the habitable zone. That doesn’t necessarily mean we can’t study their atmospheres, just that we have to do it indirectly.

One way is to look at the spectra of light from a star as a planet transits the star. The planet blocks some of the starlight, and if it has an atmosphere that will also block some light. But the atmosphere will only block certain wavelengths of light. By studying the light absorbed by the atmosphere, we can understand the composition of the atmosphere, such as water vapor or oxygen. This is extremely difficult to do since only the tiniest portion of starlight will pass through the atmosphere to reach us.

The Tainlin proposal takes a different approach. Rather than waiting for a planet to transit its star, the Tainlin telescope would utilize a coronagraph. This is a small barrier in the telescope’s field of view that blocks the light of a star. Coronagraphs were first used to study the Sun’s atmosphere, acting as a kind of artificial solar eclipse. By blocking direct light from a star, Tainlin could better capture light from orbiting planets. Even if a planet was too small to image, Tainlin could capture its spectra of light.

As outlined in a recent paper, the Tainlin Mission could be ready to launch within the next 10-15 years with proper funding and could observe hundreds of Earth-like worlds during its five-year mission. Based on simulations, the Tainlin Mission could observe molecules such as water, oxygen, methane, and even chlorophyll. Taken together, this could confirm the presence of life on an exoplanet.

The proposal is still in the early stages, and there are many other planned missions, such as NASA’s LUVIOR mission and the European Space Agency’s PLATO and ARIEL missions. The race is on to discover new Earths and possibly even extraterrestrial life. With Tainlin, China hopes to ensure they are in the race as well.

Reference: Wang, Wei, et al. “The Tianlin Mission: a 6m UV/Opt/IR space telescope to explore the habitable worlds and the universe.” Research in Astronomy and Astrophysics (2023).

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Astronomers are Watching a Planet Get its Atmosphere Blasted Away into Space

What do you get when a hot young world orbits a wildly unstable young red dwarf? For AU Microsopii b, the answer is: flares from the star tearing away the atmosphere. That catastrophic loss happens in fits and starts, “hiccuping” out its atmosphere at one point and then losing practically none the next.

That frenetic activity is kind of shocking. Usually, interactions between stars and their planets are more constant. But not this one. “We’ve never seen atmospheric escape go from completely not detectable to very detectable over such a short period when a planet passes in front of its star,” said Keighley Rockcliffe of Dartmouth College in Hanover, New Hampshire. “We were really expecting something very predictable, repeatable. But it turned out to be weird. When I first saw this, I thought ‘That can’t be right.'”

An artist’s impression of the red dwarf star AU Microscopii (AU Mic.) it’s losing some of its atmosphere each time its star flares. Image Credit: By NASA/ESA/G. Bacon (STScI)

Rockcliffe and her team are working on scenarios for this weirdly variable atmospheric loss. Such activity is important to understand as astronomers find more planets close to their stars, particularly red dwarfs. “We want to find out what kinds of planets can survive these environments. What will they finally look like when the star settles down? And would there be any chance of habitability eventually, or will they wind up just being scorched planets?” said Rockcliffe. “Do they eventually lose most of their atmospheres and their surviving cores become super-Earths? We don’t really know what those final compositions look like because we don’t have anything like that in our solar system.”

How Red Dwarf Stars Affect Planet Atmospheres

AU Microscopii b (AU Mic b) is a Neptune-sized planet with a hydrogen atmosphere. It was first discovered orbiting its parent star by NASA’s Spitzer Space Telescope and the Transiting Exoplanet Survey Satellite) in 2020. They spotted the planet as it transited (passed in front of) the star.

The star and its planet lie 32 light-years from Earth. AU Microscopii (AU Mic) itself is a very young star—only about 32 million years old. This stellar baby is a red dwarf and shows an amazing amount of flaring activity and variability. That affects its planets, particularly AU Mic b, which orbits only 9.6 million kilometers away.

An artist’s conception of a violent flare erupting from the red dwarf star Proxima Centauri. Such flares can obliterate the atmosphere of a nearby planet. Credit: NRAO/S. Dagnello.

Red dwarfs like AU Mic are the most abundant stars in our Milky Way galaxy. It seems likely that they host many of the planets in our galaxy. But, there’s a catch. These stars blast out ferocious stellar flares that blast any nearby planets with radiation. The flares stem from activity in the strong magnetic fields in the stellar atmospheres. The fields break from time to time and then reconnect. That releases huge amounts of energy that send torrential stellar winds, flares, and X-rays out to space. Any planets that get in the way get baked. “This creates a really unconstrained and frankly, scary, stellar wind environment that’s impacting the planet’s atmosphere,” said Rockcliffe. Young planets around these young stars lose their atmosphere, sometimes completely.

What Happens to AU Microscopii’s Neptune-Sized Planet

To understand the weirdly hiccupy atmospheric loss at AU Mic b, Rockcliff’s team used observations made by Hubble Space Telescope’s Space Telescope Imaging Spectrograph (HST/STIS). It’s sensitive to ultraviolet light, which is given off as the escaping atmosphere is photoionized by the parent star’s extreme heat and flare activity. The STIS instrument captured enough data to allow the science team to at least theorize about what’s happening in this system as the star heats its immediate environment with flares and other activity.

Changes in atmospheric outflow from AU Mic b may indicate rapid extreme variability in the star’s outbursts. Astronomers attribute that variability to roiling magnetic field lines. It’s possible that a powerful stellar flare photoionized the hydrogen escaping from the planet to the point where it became transparent to light. That rendered it undetectable.

Most puzzling is the escape of hydrogen ahead of the planet as it orbits its parent star. It’s possible that the high-energy radiation from the star is shaping the atmospheric hydrogen into a “leading tail” that precedes the star. To prove that, astronomers will need to do more follow-up observations of AU Mic b as it transits its star in the future. Not only will that pin atmospheric loss to stellar variability, but further observations will help explain atmospheric loss in such planets.

For More Information

Hubble Sees Evaporating Planet Getting the Hiccups
The Variable Detection of Atmospheric Escape around the Young, Hot Neptune AU Mic b

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JWST Pierces Through a Thick Nebula to Reveal Newly Forming Binary Stars

In 1985, the physicist Heinz Pagels wrote that star birth was a “veiled and secret event.” That’s because the stellar crêches hide the action. But, ever since the advent of infrared astronomy, astronomers have been able to lift that veil. In particular, the Hubble Space Telescope has studied these systems and now, the Webb Telescope (JWST) gives regular detailed views of stellar nurseries.

Recently, JWST took a look at the Herbig-Haro 46/47 system. It’s a pair of still-forming binary stars hidden inside a nebula that lies about 1,470 light-years away from us. Normally in visible light, this scene appears as a black cloud with a bright streak of light beaming away from it. But, in the JWST view, we can see a lot more detail.

This image from ESO’s New Technology Telescope at the La Silla Observatory in Chile shows the Herbig-Haro object HH 46/47 as jets emerging from a star-forming dark cloud containing newly forming binary stars. This object was the target of a study using ALMA during the Early Science phase.

What’s Happening to These Binary Stars

In the JWST image, the newborn binary stars are in the orange-white blob in the center of the nebula. JWST couldn’t see past that smaller cloud of gas and dust because it was so thick. Indeed, it’s still “feeding” the young stars. They gain mass until the birth cloud gets used up.

Look for the HH 46/47 details in this annotated JWST image. Six near-infrared images from NIRCam (the Near-Infrared Camera) aboard JWST make up this composite of Herbig-Haro 46/47. The north and east compass arrows show the orientation of the image on the sky. It shows invisible near-infrared wavelengths of light that have been translated into visible-light colors. The scale bar is labeled in arcminutes. Targets like this show how stars gather mass over time and show how our own Sun may have formed. The two-sided orange lobes were created by earlier ejections from these stars. The stars’ more recent ejections appear as blue, thread-like features. Courtesy NASA/ESA/JWST.

Each of the binary stars sends out jets of superheated material across thousands of light-years. They carry material that formed two orange-colored lobes of material on either side of the star-birth crêche. As these baby binary stars gobble up the gas in the birth cloud, they also eject gas and dust out to space. That’s what built up the lobes of material. Their presence influences the shapes of the jets. As ejected material rams into the nebula, the jets interact with molecules within the nebula, causing them both to light up.

Jets are a major part of the star-birth process. They regulate how much mass the young stars can gather up. As the jets move material out, that ejected “stuff” collides with the rest of the nebula. All these details make this JWST image one of the most detailed looks to date at the action inside a star-birth nursery.

Herbig-Haro Objects

The HH 46/47 system is one of many such star-birth sites around the galaxy. They all have the same types of features: glowing clouds of gas and dust associated with newborn stars that shoot jets of material across space. Astronomers have known about them for more than 100 years. However, astronomers didn’t associate them with star birth until the 1940s. That’s when George Herbig and Guillermo Haro studied and wrote about them as possible sites of star formation.

Herbig-Haro object HH 24 is seen by Hubble Space Telescope as it imaged a star-birth nursery in the constellation Orion. Astronomers know of more than a thousand in the Milky Way Galaxy.

HH objects usually are associated with so-called H II regions and often lie near dark clouds called Bok globules. There are more than a thousand known (so far) and they offer a way to study star formation from its early stages. Typically in star formation, a cloud of material collapses, and eventually stellar cores, called protostars, form in the cloud. The protostars continue to accrete material—and shoot it out along the axis of rotation in bipolar jets. The jets collide with material around the star and that triggers the bright emissions that characterize HH objects.

What Will Happen to These Newborn Binary Stars?

JWST’s image captures a single moment in the long evolutionary process of creating new stars. Eventually, HH 46/47 will have gathered enough material and the jets will eventually die away. The birth crêche will be largely (or maybe even completely) eaten away and replaced by the hot young stars. Interestingly, most of the stars associated with HH objects will be binary stars or in multiple-star systems. That raises questions about the mechanisms that give rise to the jets flowing away from the stars. Many stars in the galaxy are born in these multiple systems, so the existence and evolution of HH systems give interesting insights into the whole star birth process.

Studying these systems in infrared light is a whole new ballgame in understanding the origin and evolution of stars. Hubble Space Telescope and the JWST are showing incredibly detailed views of the jets and clouds surrounding the newly forming stars in these systems. From the ground, radio and submillimeter instruments such as ALMA study them, too. Thanks to these observatories, the veiled and secret process, except for the most densely packed clouds, is no longer so hidden or secret.

For More Information

Webb Snaps Detailed Infrared Image of Actively Forming Stars (image and caption)
Webb Snaps Highly Detailed Infrared Image of Actively Forming Stars (longer story)

Herbig-Haro Objects

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If Rogue Planets are Everywhere, How Could We Explore Them?

At one time, astronomers believed that the planets formed in their current orbits, which remained stable over time. But more recent observations, theory, and calculations have shown that planetary systems are subject to shake-ups and change. Periodically, planets are kicked out of their star systems to become “rogue planets,” bodies that are no longer gravitationally bound to any star and are adrift in the interstellar medium (ISM). Some of these planets may be gas giants with tightly bound icy moons orbiting them, which they could bring with them into the ISM.

Like Jupiter, Saturn, Uranus, and Neptune, these satellites could have warm water interiors that might support life. Other research has indicated that rocky planets with plenty of water on their surfaces could also support life through a combination of geological activity and the decay of radionuclides. According to a recent paper by an international team of astronomers, there could be hundreds of rogue planets in our cosmic neighborhood. Based on their first-ever feasibility analysis, they also indicate that deep space missions could explore these unbound objects more easily than planets still bound to their stars.

The research was led by Manasvi Lingam, an assistant professor at the Department of Aerospace, Physics, and Space Sciences at the Florida Institute of Technology and the Institute for Fusion Studies at the University of Texas at Austin. Joining him were Andreas M. Heinc, a researcher with the Interdisciplinary Centre for Security, Reliability, and Trust (SnT) at the University of Luxembourg and the Initiative for Interstellar Studies (i4is); and T. Marshall Eubanks, the chief scientist at Space Initiatives Inc. The preprint of their paper recently appeared online and is being considered for publication in Elsevier.

As Lingam and his colleagues note in their paper, interstellar objects (ISO) are a time-honored field of study that was already quite active by the 1970s. However, the detection of ‘Oumuamua in 2017, the first recorded encounter with an ISO, followed by the detection of 2I/Borisov in 2019, has brought this field to the forefront of scientific research. Subsequent research has revealed previous instances where smaller interstellar objects and meteors came to Earth, allowing their abundances to be constrained.

One such object (CNEOS 2014-01-08) was found in the meteor catalog of NASA’s Center for Near Earth Object Studies (CNEOS) by Harvard astrophysicists Amir Siraj and Professor Avi Loeb (Manasavi’s former mentor). According to CNEOS, this interstellar meteor landed in the South Pacific off the coast of Papua New Guinea in 2014. The Galileo Project (led by Prof. Loeb) mounted a sample retrieval campaign last year, which retrieved hundreds of metallic spherules from the meteor’s remains on the ocean floor (360 and counting!).

However, Lingam and his colleagues investigate the possibility of studying much larger objects. Research from the 1990s predicted that gravitational microlensing experiments could enable the detection of extrasolar planets, including those unbound to any stars. This has since been confirmed by surveys that have gauged the distribution of rogue planets, indicating that they are likely prevalent within our galaxy. This includes a pair of studies led by David Bennett, a Senior Research Scientist with the Science Mission Directorate (SMD) at NASA Goddard.

The study papers, which are scheduled to appear in The Astronomical Journal, suggest that there could be trillions of rogue planets wandering the Milky Way. As Prof. Lingam told Universe Today via email, the prolific nature of rogue objects and their potential to support life presents tremendous opportunities for future exploration:

“It is estimated that there might be as many as 1000 Moon-sized and larger nomadic worlds per star. Hence, even if a small fraction of them possess conditions amenable to life, they would be among the most common abodes for life. This is why they may represent a promising target for astrobiology.”

An illustration of an ice-covered rogue planet. Credit: NASA’s Goddard Space Flight Center

The subject of rogue planets, satellites, and smaller objects’ potential for habitability was explored extensively in Prof. Lingam’s 2021 book Life in the Cosmos: From Biosignatures to Technosignatures (co-authored by Prof. Loeb). For the sake of this study, Prof. Lingam and his colleagues focused on objects significantly larger than meteorites or ‘Oumuamua and 2I/Borisov – which measured between 100 and 1000 meters (~330 to 3300 ft) in diameter. They also cast a wide net that extended for two orders of magnitude, ranging from bodies comparable to Main Belt Asteroids to planets with radii between Earth and Mars.

“We focused on objects in the radius range of 100 to 10,000 km. These worlds can be rocky/icy and may potentially support liquid water in the (sub)surface for up to 100 Myr or more. The number of these objects depends on their size; as many as 1000 Moon-sized and larger nomadic worlds may exist per star.”

In addition, they determined that smaller objects are likely to be far more numerous than larger rocky bodies and that they are statistically more likely to be found closer to the inner Solar System. Their results also suggest that tens of thousands of planet-sized nomadic worlds could be within a spherical volume centered on Earth and extending to the nearest star system (Proxima Centauri). Whereas Proxima Centauri has three confirmed exoplanets, one of them rocky and located within the star’s habitable zone (Proxima b), these rogue planets constitute the nearest exoplanets beyond our Solar System.

In the near future, multiple organizations and non-profits want to mount the first interstellar missions to the nearest stars to investigate their planetary systems. Examples include Breakthrough Starshot, a proposed mission architecture combining gram-scale watercraft and directed-energy propulsion (DEP) to achieve interstellar missions in our lifetimes. However, as Lingam and his team noted, these missions would save time and money by directing their efforts to explore potentially-habitable rogue planets nearer to the Solar System.

An artist’s illustration of Breakthrough Starshot, a light-sail powered by a laser array generated on Earth’s surface. Credit: M. Weiss/CfA

To this end, they investigated several proposed propulsion methods that are currently being investigated for interstellar mission architectures. Specifically, they sought concepts that could accomplish missions to study Earth-sized planets with a 50-year flight timescale. Said Lingam:

“We considered many propulsion systems such as electric and magnetic sails, solar and laser sails, nuclear fusion, laser and nuclear electric propulsion, and chemical propulsion. Among the various candidates, we determined that laser sails (spacecraft propelled by laser arrays) are the most promising for reaching nomadic worlds in a reasonable time frame.”

These findings present opportunities for existing and next-generation space telescopes. In the coming years, astronomers hope to expand the search for rogue planets and further constrain the number of unbound objects that are out there right now. In 2027, NASA will launch the next-generation Nancy Grace Roman Space Telescope, the true successor of Hubble and named after NASA’s first chief astronomer who played a foundational role in the telescope’s creation (hence her nickname, “The Mother of Hubble“).

According to the same papers led by NASA Goddard’s David Bennett, Roman could find as many as 400 Earth-like rogue planets during its primary mission. The technique key to this process is known as Gravitational Microlensing, typically used for hunting exoplanets bound to stars. This technique combines elements of the Transit Method and Gravitational Lensing, relying on the gravitational force of massive objects to bend and focus light coming from a distant star. As a planet passes in front of this star relative to the observer (aka. transits), there is a measurable dip in brightness that can be used to infer the presence of a planet.

According to Lingam, microlensing surveys performed by Nancy Grace Roman will help confirm their results and determine the locations of rogue planets in our stellar neighborhood, all of which could be targets for future exploration missions:

“Through the technique of gravitational microlensing, missions like the Nancy Grace Roman Space Telescope and Euclid are expected to empirically constrain the abundances of nomadic worlds, because these telescopes may detect worlds smaller than the Earth (e.g., Moon-sized).”

By exploring rogue objects kicked from their systems, scientists can conduct lucrative astrobiology missions without having to travel to distant stars. These efforts are likely to happen in parallel with missions to the outer Solar System, where robotic explorers will travel to icy moons like Europa, Ganymede, Titan, Callisto, etc., and either collect samples from the surface or drill/melt through the surface ice to look for evidence of biosignatures. Even in instances where biosignatures are not evident, the study of rogue bodies will provide considerable insight into the formation and evolution of other planetary systems.

Any way you slice it, studying rogue planets and objects will tell us things about star systems that could only be learned by going there. Given the time, energy, and expense of mounting interstellar voyages, this option is faster, cheaper, and ultimately preferable. Moreover, exploring rogue objects could serve as “pathfinder missions,” providing scientists with a taste of what we are likely to find out there in the galaxy and pointing the way toward the most promising locations.

Further Reading: arXiv

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How Will We the Find First Signs of Alien Life — and When?

When will we find evidence for life beyond Earth? And where will that evidence be found? University of Arizona astronomer Chris Impey, the author of a book called “Worlds Without End,” is betting that the first evidence will come to light within the next decade or so.

But don’t expect to see little green men or pointy-eared Vulcans. And don’t expect to get radio signals from a far-off planetary system, as depicted in the 1992 movie “Contact.”

Instead, Impey expects that NASA’s James Webb Space Telescope — or one of the giant Earth-based telescopes that’s gearing up for observations — will detect the spectroscopic signature of biological activity in the atmosphere of a planet that’s light-years away from us.

“Spectroscopic data is not as appealing to the general public,” Impey admits in the latest episode of the Fiction Science podcast. “People like pictures, and so spectroscopy never gets its fair due in the general talk about astronomy or science, because it’s slightly more esoteric. But it is the tool of choice here.”

“Worlds Without End” is the 14th book written by Impey, who has been an author for 200 peer-reviewed publications focused on observational cosmology, galaxies and quasars. His previous books have taken on subjects ranging from the universe’s origin (“How It Began”) to its expected demise (“How It Ends”).

Impey says it’s the right time for a book about the search for worlds beyond Earth, and the search for life on those worlds.

“It’s still less than 30 years since the first exoplanet was detected, and now we have over 5,000,” he says. The raw numbers of newfound planets are no longer all that interesting, but Impey is intrigued by the different strategies that are being used to look for life on those planets.

Some researchers are putting their money on SETI, the search for extraterrestrial intelligence. That quest involves looking for radio signals from faraway star systems that may carry messages from alien civilizations. Twenty years ago, a couple of SETI astronomers predicted that such signals would be detected by 2025 — but although there are still a couple of years of shelf life left for that prediction, scientists aren’t counting on that timetable as a sure thing.

There was a time when Impey thought the first signs of alien life would be found on Mars, thanks to NASA’s plans to bring samples back to Earth for detailed study. But those plans have run into a budgetary buzzsaw, and Impey suspects it will take longer to nail down the evidence of biological activity on the Red Planet, if it exists.

Life may also lurk in the hidden oceans of a Jovian moon called Europa and a Saturnian moon called Enceladus. But the next mission designed to study the outer solar system’s icy frontier — NASA’s Europa Clipper — won’t start looking for evidence until the 2030s.

By then, Impey expects scientists to be analyzing the spectroscopic signs of life they’ll pick up from telescopic observations of exoplanets.

Chris Impey is an astronomer at the University of Arizona. (U. of Ariz. Photo)

Those observations won’t be easy to come by: Teams of researchers will have to identify the chemical signatures of compounds detected in exoplanet atmospheres. But scientists have already shown that the James Webb Space Telescope is up to the job. Other telescopes that are due to come online within the next seven years — including the Rubin Observatory, the Giant Magellan Telescope and the Extremely Large Telescope — could do an even better job of sniffing alien air.

If an exoplanet is found to have, say, a higher-than-expected percentage of oxygen in its atmosphere, that could be a clue pointing to biological activity. Other types of detections might represent technosignatures rather than biosignatures. For example, if scientists see elevated levels of chlorofluorocarbons or anomalous heat emissions, that could signal that an alien civilization is facing the same environmental challenges we’ve been going through.

In any case, it’ll take more than one promising data point.

“It’ll be a set of spectra,” Impey says. “It’ll maybe be half a dozen, or a dozen planets, saying the same thing. Or maybe saying different things. Maybe it turns out that a lot of the habitable planets are dead, and that’s a possibility everyone has to be prepared for.”

Everyone will also have to be prepared for a debate over whether the spectroscopic evidence of biological activity is sufficiently persuasive.

“It’s a hard experiment, and so the data will be ambiguous,” Impey acknowledges. “It won’t be enough to convince some people, maybe. And it depends of what the data says, of course. So, beyond that, it is hard to do much better.”

No-go for UFOs

What about the idea that the aliens are already here? This week, a House subcommittee heard sworn testimony from a witness claiming that the U.S. government has been aware of extraterrestrial connections to UFOs (now known as unidentified anomalous phenomena, or UAPs) going as far back as the 1930s. Impey doesn’t buy it, however.

“That’s something that most astronomers just don’t subscribe to, because of the Saganism of ‘extraordinary claims require extraordinary evidence,’” he says. “That bar has never been cleared. Extraordinary evidence is not anecdotal evidence. It’s not video or images, because, well, you know how they can be altered. And even if they’re not altered, even if it’s video from an Air Force pilot, the interpretation of that data is very ambiguous.”

Impey is a bit more intrigued by Harvard astronomer Avi Loeb’s claims that an interstellar object known as ‘Oumuamua might have been an alien artifact, or that metallic spherules recovered from the seafloor might be the remains of an extraterrestrial alloy.

“Worlds Without End” by Chris Impey (MIT Press)

“These particular cases that he’s picking out are interesting, because you learn something either way,” he says. “You either learn something new about planetary science, for example, or you learn a dramatic thing about interstellar visitors and artifacts that come into the solar system from elsewhere. But I think the strong bet is still that these are natural phenomena.”

In the latter chapters of his book, Impey turns his attention to future trends in space exploration. Will humanity make a second home on Mars, as SpaceX founder Elon Musk hopes?

“I don’t think it’s the future of humanity,” Impey says. “It’s almost a deflection or a distraction to think of us leaving the Earth, because we’re never going to do that in large numbers or sufficiently to make it a Plan B. I just think it’s coming from a different place.”

The way Impey sees it, the drive to explore space comes from the same place that has driven humans to set up outposts in Antarctica. But if humans decide to push outward from Earth someday, Impey says it would mark the start of “an extraordinary biological experiment.”

“The bottleneck effect in genetics means they will diverge as a population, more rapidly than normal,” he says. “And so you’ll speciate, and at some point they won’t be humans anymore. They’ll be the next thing. And that’s extraordinary.”

What will we find by 2073?

Impey goes into detail about what could happen over the decades to come in his book, and in our podcast. Perhaps the biggest question for the next 50 years will be whether intelligent life — as opposed to mere microbes — exists beyond Earth.

This month, a nationwide survey suggested that 40 percent of Americans think intelligent life will be discovered on another planet by the year 2073. “I probably will go in on a bet like that,” Impey says.

And if we don’t find intelligent life in the next 50 years?

“This is very tricky, because the methods you use involve technologies like radio and lasers and so on,” Impey says. “What if they don’t have radio or lasers? Well, some of them will, you imagine. But the sensitivity of those methods is going to be so good by then, and there’ll have been so much searching and listening by then, that if any of our types of technologies exist on millions and millions of planets around millions and millions of stars, then we would see them.”

If we don’t see them by 2073, that may have to serve as the answer to one of humanity’s ultimate questions: Are we alone?

“At some point, the null result becomes meaningful,” Impey says. “It just says they’re either not there, or they’re exceptionally rare. And that’s what could happen on a 50-year timescale.”

Check out the original version of this report on Cosmic Log for reading recommendations from the Cosmic Log Used Book Club — and stay tuned for future episodes of the Fiction Science podcast via Apple, Google, Overcast, Spotify, Player.fm, Pocket Casts, Radio Public and Podvine. Alan Boyle’s co-host for the Fiction Science podcast is Dominica Phetteplace, an award-winning science-fiction writer who currently lives in San Francisco. To learn more about Phetteplace, visit her website, DominicaPhetteplace.com.

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Clumps Around a Young Star Could Eventually Turn Into Planets Like Jupiter

From the dust, we rise. Vortices within the disks of young stars bring forth planets that coalesce into worlds. At least that’s our understanding of planetary evolution, and new images from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Very Large Telescope’s Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) further support this.

We know that most stars have planetary systems and that these systems form with their star via protoplanetary disks. But there are still plenty of smaller details we don’t fully understand. What causes the initial clumping of material from which planets grow, and how do planets clear the debris of a disk to become a fully-fledged planetary system?

Studying the early period of a star system is difficult because the same gas and dust that forms planets also obscure them from view. But in recent years advanced infrared and radio observatories have yielded high-resolution images of many young stars. We can now see large protoplanets in many of these disks and gaps where planets have cleared debris. Now observations of a young star 5,000 light-years away have given us a glimpse of the earliest moments of planetary formation.

The star is known as V960 Mon, and it attracted the attention of astronomers in 2014 after it suddenly brightened by a factor of 20. This outburst showed that the star’s protoplanetary disk had intricate spiral arms. Astronomers are still not entirely sure how these spirals form, but they seem to be connected to early planet formation. So a team of astronomers wanted to take a closer look.

Gravitational clumps forming withing the spiral arms of V960 Mon. Credit: ESO/ALMA (ESO/NAOJ/NRAO)/Weber et al

There are two broad models of planetary formation. The first model argues that planets form gradually through what is known as core accretion. Small clumps form within a debris disk, which grows over time as it captures nearby material. The second model argues that the seeds of planets form quickly through gravitational instabilities within the disk. Astronomers have found evidence of core accretion in some disks, but most of the young planets we’ve observed are already sizable, suggesting the latter model.

In this new study, the team found evidence of a nearby star that is triggering gravitational clumps within the spiral arms of V960 Mon. This suggests that planetary cores can form quickly within a spiral arm due to gravitational perturbations. It is the first strong evidence in support of the gravitational instability model.

We still do not know if one or both models play significant roles in planetary formation, but it is clear the process can be complex. It is clear that change can happen quickly, so it will be important to look for transient brightening among young stars to better understand the process. As new observatories such as the Vera Rubin Telescope come online, astronomers will be able to see how planets rise from the spiral arms of stars.

Reference: Philipp Weber et al. “Spirals and Clumps in V960 Mon: Signs of Planet Formation via Gravitational Instability around an FU Ori Star?” The Astrophysical Journal Letters 952 (2023): L17.

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