Here is the atmosphere of Jupiter in 3D for the first time (Planetary Science)

NASA’s Juno mission around the largest planet in the solar system, which also sees an important scientific and technological contribution from Italy, is revealing in unprecedented detail what happens under the huge clouds of the gas giant. Alessandro Mura (Inaf): “Crucial results for our understanding of giant planets like Jupiter”

The new findings from NASA’s Juno mission provide a more accurate view of the atmosphere of Jupiter, the largest and most massive planet in the Solar System. It is now clearer the inner workings not only of the bands that envelop the planet – which take the name of belts and zones – but also of the polar cyclones and the Great Red Spot that characterize the planet. Several articles on these findings were published today in the journal Science , the Journal of Geophysical Research: Planets , along with two recent publications in the journal Geophysical Research Letters.. Launched in 2011, Juno entered Jupiter’s orbit in 2016. During each scientific passage of the planet (37 to date), a series of instruments aboard the spacecraft peers under the turbulent cloud layer of the largest planet in the Solar System. .

“So far, Juno has surprised us by showing us that phenomena in Jupiter’s atmosphere develop at much greater depths than we thought,” said Scott Bolton , of the Southwest Research Institute in the United States, principal investigator of Juno and author of one of the articles. . “Now, we’re starting to put all these individual pieces together and get our first real understanding of how the fascinating and violent atmosphere of Jupiter works, in 3D.”

Juno, thanks to the Italian instrument Jovian Infrared Auroral Mapper ( Jiram ), made in Italy by Leonardo under the guidance of the Italian Space Agency and the scientific responsibility of the National Institute of Astrophysics, had already discovered polygonal dispositions of gigantic cyclonic storms on both Jupiter’s poles : a structure of eight cyclones to the north and one of five to the south. Now, five years later, thanks to new observations from Jiram, the mission scientists have discovered that these atmospheric cyclones are extremely persistent, even in their ability to maintain their peculiar polygonal shape.

“Like hurricanes on Earth, these cyclones want to move towards the pole but are repelled by the cyclone located in the center of the pole. This balance is valid for both the north and south poles of Jupiter and provides an explanation of where the cyclones reside and the different number at each pole “, says Alessandro Mura of the National Institute of Astrophysics in Rome, co-investigator by Juno. “The Juno / Jiram observations show that Jupiter’s cyclones perturb each other, just as if there were elastic forces in between. As a result, they slowly oscillate around an equilibrium position, a property that makes us believe that these cyclones develop much deeper than we observe. ‘

Data collected by the JunoCam and the Mwr aboard Juno during a pass over Jupiter’s Great Red Spot on July 11, 2017, offers us an insight into the inner workings of the giant planet’s most iconic structure in the atmosphere. Credits: Nasa / Jpl-Caltech / Swri / Mssi. Image processing: Kevin Gill Cc By

Juno’s microwave radiometer (Micro Wave Radiometer, Mwr ) is for the first time allowing mission scientists to peer beneath the cloud tops and probe the structure of its many vortices. The most famous of these is the iconic anticyclone which takes the name of the Great Red Spot. Larger than the size of the entire Earth, this bright red vortex has intrigued scientists since its discovery nearly two centuries ago.

The new results from Juno show that cyclones are warmer and with a lower atmospheric density in the upper layers and are cooler, with a higher density in the lower layers. The results also indicate that the vertical extent of these storms is much larger than expected, some extending 100km below cloud tops and others, including the Great Red Spot, extending over 350km. This unexpected discovery demonstrates that the eddies extend beyond the region where the water condenses and clouds form, below the boundary layer as far as sunlight can penetrate, heating the atmosphere.

The height and size of the Great Red Spot indicate that its mass could, in principle, be detectable in Jupiter’s gravitational field. Two close Juno flybys over Jupiter’s most famous spot provided an opportunity to search for the storm’s gravitational signature and corroborate the results of the Mwr instrument.

Artistic illustration combining an image of Jupiter taken by the Juno spacecraft’s JunoCam with a composition of the Earth superimposed to scale on the Great Red Spot. Credits: JunoCam Image data: Nasa / Jpl-Caltech / Swri / Msss. JunoCam Image processing by Kevin M. Gill (Cc By). Earth Image: Nasa

“The precision required to study the Great Red Spot during the July 2019 flyby is astounding,” says Marzia Parisi , of Juno’s science team at NASA’s Jet Propulsion Laboratory. “With Juno traveling low above Jupiter’s clouds at around 209,000 kilometers per hour, we were able to measure velocity changes of just 0.01 millimeters per second, using a tracking antenna from the Deep Space Network’s. Goldstone, California, from a distance of over 650 million kilometers. This has allowed us to understand that the depth of the Great Red Spot is at least 500 kilometers below the highest layers of the clouds ».

Juno’s findings on polar cyclones, atmospheric circulation, and the iconic Great Red Spot are influencing our understanding of giant planets throughout the Solar System and beyond. “These results are crucial to our understanding of giant planets like Jupiter,” concludes Mura.  These recent discoveries once again demonstrate the very high scientific quality of the data obtained by the Juno spacecraft,” reiterates Giuseppe Sindoni , head of the Jiram project for the Italian Space Agency. “For the first time in history we are scrutinizing the deeper layers of Jupiter’s atmosphere. The analysis of the new data acquired during the extension of the mission will help us to reveal the ‘deep’ secrets of these mysterious cyclones ».

To know more:

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Hazy infrared monsters (Cosmology)

A nebula on the plane of the Milky Way, a luminous region 7800 light years from Earth and two stars of unknown distance: these are the dots to connect to draw a frightening cosmic Godzilla. To see it, the fantasy of an astronomer from NASA’s Spitzer mission, who shot these and other spectacular nebulae in our galaxy

You know when you see the clouds take the shape of animals? Or when you stare at a wooden beam ceiling and in the knots can you see faces and constellations? Here, the constellations, they too were born because someone was able to see gods, heroes and mythological figures hidden inside a simple juxtaposition of luminous dots in the sky. All this is not a simple fantasy game, it has a scientific name: it is called pareidolia .

Let’s take the image here on the right now. It is a nebula – a cloud of gas and dust like there are many in space – in the constellation of Sagittarius and immortalized, in this case, by the Spitzer Space Telescope.of NASA. Over the course of billions of years, it has given rise to countless stars, which in turn have colored, modified and shaped the cloud itself with their radiation. When the most massive stars die, they often become supernovae, in an explosion that often wipes out a lot of material, and creates more. To observe such an environment, however, the human eye is not enough: the visible light is completely obscured by the clouds of dust that pervade the space. Infrared light, on the other hand – that observed by Spitzer, at wavelengths greater than what our eyes can perceive – can penetrate the clouds, revealing hidden details and colors like those we can appreciate in this image. Actually, there are four images we are seeing, one in each of the four dominant colors (blue, cyan, green and red), corresponding to different and suitably superimposed infrared wavelengths: yellow and white are combinations of these, while blue and cyan represent the wavelengths emitted mainly by stars; dust and organic molecules called hydrocarbons appear green; finally, hot dust that has been heated by stars or supernovae appears red.

But let’s go back to the imagination because, if at first glance the nebula seems just an immense spectacle of nature, by sliding the cursor to the left , we will be able to see that someone, punctual as on Halloween night, has seen something else: it is the godzilla monster . The two small bright spots in the upper right – two stars whose distance is unknown but which are within our galaxy – draw the eyes, while the brightest region in the lower left is about 7800 light-years from Earth. (it’s called W33) and shapes the cosmic monster’s right hand. Finally, with a little more imagination, under the two stars at the top, you can see the dark shadow of the jaws.

“I wasn’t looking for monsters,” says Robert Hurt , astronomer responsible for most of the public images created by Spitzer data since the observatory’s launch in 2003. “I just happened to take a look at a region of the sky I had browsed through. many times before, but I had never zoomed in. Sometimes, if you crop an area differently, something that wasn’t seen before comes out. It was my eyes and mouth that made me scream ‘Godzilla’. ‘

“It’s one of the ways we want people to connect with the amazing work Spitzer has done,” continues Hurt. “I’m looking for compelling areas that can really tell a story. Sometimes it’s a story about how stars and planets are formed, and sometimes it’s a giant monster raging in Tokyo. “

If you are not convinced of the similarity identified by Spitzer’s astronomer, you can draw your own cosmic creature with the Spitzer Artistronomy web app . New nebulae, including this one, were added to the app this month. Thanks to its infrared eyes, Spitzer can easily find nebulae that are too cold to radiate visible light, or whose visible light cannot reach because it is hidden behind clouds of dust.

Featured image: Click to open the interactive version. Credits: Nasa / Jpl-Caltech

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Building Planets from Protoplanetary Disks (Planetary Science)

Planets and their stars form from the same reservoir of nebular material and their chemical compositions should therefore be correlated but the observed compositions of planets do not match completely those of their central stars. In our Solar system, for example, all the rocky planets and planetesimals contain near-solar proportions of refractory elements (elements like aluminum that condense from a gas when the temperature falls below about 1500 kelvin) but are depleted in volatile elements (those that evaporate easily, like nitrogen). Astronomers think that this was the result of planets forming by the coalescence of already-condensed mineral dust.

As the initial, cold molecular cloud core collapses and a disc forms, heating from the new star (plus the viscosity of the disc) can vaporize some of the primordial condensed material – forcing the condensation sequence to begin anew but now under higher temperature and pressure conditions that evolve relatively rapidly. Astronomers also analyze meteorites of various types to determine their chemical compositions. Depending upon the properties of the initial molefular cloud core and the disc, the temperatures produced during planet formation may not have been sufficient to vaporize the most refractory of the pre-existing material. Since different minerals in planetesimals condense under different conditions, times, and places, the overall situation is complex, making it hard to understand the observed chemistry of planets.

CfA geologist Michail Petaev and his colleagues simulated the collapse of a molecular cloud core and the formation of the star, disk and planets, and analyzed the evolving distribution of temperatures across the disk to infer the mineral condensation sequence. They find that the properties of the initial cloud core significantly affect the maximum temperatures reached in the disk and the resultant compositions of the planets and asteroids; the maximum temperature occurs around the end of the collapse phase, after a few hundreds of thousands of years. They also find that while the composition of the star is similar to that of the molecular cloud core, the star might be slightly depleted in some of the most refractory elements – and thus the stellar composition may not be a good approximation to the initial composition of the core. Only cloud cores with high initial temperatures (or low disk rotation) will produce refractory-rich planets. Significantly, they conclude that in order to reproduce the composition seen in Solar system meteorites and the terrestrial planets either the initial core had rare properties like temperatures near 2000 kelvin (well above the expected median value of 1250 kelvin), or else some other source of heating must have raised the protoplanetary disk’s temperature.

Featured image: An artist’s conception of the early solar nebulae, illustrating material in the disk as it cools and coalesces, ultimately evolving into rocky planets. The composition of the rocky planets and meteorites in the Solar system differs from that of the Sun, a puzzle since both emerge from the same molecular cloud material. Astronomers have simulated the complex temperature evolution of the young planetary disk and conclude that the Solar nebula appears to have developed under rare conditions, either forming from a parent molecular core with unusally high temperatures or with some other energy source heating the young disk. © USRA/LPI

Reference: “Maximum Temperatures in Evolving Protoplanetary Discs and Composition of Planetary Building Blocks,” Min Li, Shichun Huang, Zhaohuan Zhu, Michail I. Petaev and Jason H. Steffen, Monthly Notices of the Royal Astronomical Society, 503, 5254, 2021.

Provided by CFA Harvard

Did a Black Hole Eating a Star Generate a Neutrino? Unlikely, New Study Shows (Cosmology)

New calculations show that a black hole slurping down a star may not have generated enough energy to launch a neutrino.

In October 2019, a high-energy neutrino slammed into Antarctica. The neutrino, which was remarkably hard to detect, piqued astronomers’ interest: what could generate such a powerful particle?

Researchers traced the neutrino back to a supermassive black hole that had just ripped apart and swallowed a star. Known as a tidal disruption event (TDE), AT2019dsg occurred just months earlier — in April 2019 — in the same region of the sky where the neutrino had come from. The monstrously violent event must have been the source of the powerful particle, astronomers said.

But new research casts doubt on that claim.

In a study published this month in The Astrophysical Journal, researchers at the Center for Astrophysics | Harvard & Smithsonian and Northwestern University, present extensive new radio observations and data on AT2019dsg, allowing the team to calculate the energy emitted by the event. The findings show AT2019dsg generated nowhere near the energy needed for the neutrino; in fact, what it spewed out was quite “ordinary,” the team concludes.

Black Holes are Messy Eaters

While it may seem counterintuitive, black holes do not always swallow everything in reach.

“Black holes are not like vacuum cleaners,” says Yvette Cendes, a postdoctoral fellow at the Center for Astrophysics who led the study.

When a star wanders too close to a black hole, gravitational forces begin to stretch, or spaghettify, the star, Cendes explains. Eventually, the elongated material spirals around the black hole and heats up, creating a flash in the sky that astronomers can spot from millions of light years away.

“But when there’s too much material, black holes can’t eat it all smoothly at once,” says Kate Alexander, a study co-author and postdoctoral fellow at Northwestern University who calls black holes ‘messy eaters.’ “Some of the gas gets spewed back out during this process — like when babies eat, some of the food ends up on the floor or the walls.”

These leftovers get flung back into space in the form of an outflow, or jet — which, if powerful enough, could theoretically generate a subatomic particle known as a neutrino.

An Unlikely Source for Neutrinos

Using the Very Large Array in New Mexico and Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the team was able to observe AT2019dsg, some 750 million light years away, for more than 500 days after the black hole had started consuming the star. The extensive radio observations make AT2019dsg the most well-studied TDE to date and revealed that the radio brightness peaked around 200 days after the event began.

According to the data, the total amount of energy in the outflow was equivalent to the energy radiated by the Sun over the course of 30 million years. While that may sound impressive, the powerful neutrino spotted on Oct. 1, 2019 would require a source 1,000 times more energetic.

“Instead of seeing the bright jet of material needed for this, we see a fainter radio outflow of material,” Alexander explains. “Instead of a powerful firehose, we see a soft wind.”

Cendes adds, “If this neutrino somehow came from AT2019dsg, it begs the question: Why haven’t we spotted neutrinos associated with supernovae at this distance or closer? They are much more common and have the same energy velocities.”

The team concludes it’s unlikely that the neutrino came from this particular TDE. If it did, however, astronomers are far from understanding TDEs and how they launch neutrinos.

“We’re probably going to check-in on this one again,” says Cendes, who believes there’s still much to learn. “This particular black hole is still feeding.”

TDE AT2019dsg was first discovered on April 9, 2019 by the Zwicky Transient Facility in Southern California. The neutrino, known as IceCube-191001A, was detected by the IceCube Neutrino Observatory in the South Pole six months later.

Additional study co-authors are Edo Berger and Peter Williams of the Center for Astrophysics; Tarraneh Eftekhari of Northwestern University; and Ryan Chornock of the University of California, Berkeley.

Featured image: DESY, Science Communication Lab

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Why Nearly No Adhesive Interaction Forces Between the Asteroid Fragments? (Planetary Science)

Most asteroids with a diameter larger than ∼300 m are rubble piles i.e. consisting of more than one solid object. All asteroids are rotating but almost all asteroids larger than ∼300 m rotate with a period longer than 2.3 hours, which is the critical period where the centrifugal force equals the gravitational force. This indicates that there are nearly no adhesive interaction forces between the asteroid fragments. Now, Persson and Biele showed that this is due to the surface roughness of the asteroid particles which reduces the van der Waals interaction between the particles by a factor of 100 for micrometer sized particles and even more for larger particles.

“This means that the dependence of cohesive strength of the granular medium on particle size is due to the, increase in the number of particle-particle contacts (per unit area) alone. A decrease in particle size only increases the number of contacts without changing the strength of the particle-particle adhesive bond.”

FIG. 1. A big particle (fragment) bound to an asteroid via a matrix of smaller particles © Persson and Biele

They showed that surface roughness results in an interaction force which is independent of the size of the particles, in contrast to the linear size dependency expected for particles with smooth surfaces. Thus, two stone fragments of size 100 nm attract each other with the same non-gravitational force as two fragments of size 10 m.

FIG. 2. The big particles (fragments) in an asteroid are assumed to be kept together by a matrix of smaller particles. Analysis of experimental data gives an effective yield stress of rubble pile asteroids of order (or less than) σY ≈ 25 Pa © Persson and Biele

“In order for the small particles to act like a cement or glue for the bigger particles in asteroids it is important that there are enough of them to fill out all cavity regions between the bigger particles. If this is not the case then the effective adhesive force keeping the big fragments together will be strongly reduced.”

For more:

B.N.J. Persson and J. Biele, “On the stability of spinning asteroids”, Arxiv, pp. 1-24, 2021.

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Making Martian Rocket BioFuel on Mars (Astronomy)

Researchers have developed a concept that would make Martian rocket fuel, on Mars, that could be used to launch future astronauts back to Earth.

Researchers at the Georgia Institute of Technology have developed a concept that would make Martian rocket fuel, on Mars, that could be used to launch future astronauts back to Earth.

The bioproduction process would use three resources native to the red planet: carbon dioxide, sunlight, and frozen water. It would also include transporting two microbes to Mars. The first would be cyanobacteria (algae), which would take COfrom the Martian atmosphere and use sunlight to create sugars. An engineered E. coli, which would be shipped from Earth, would convert those sugars into a Mars-specific propellant for rockets and other propulsion devices. The Martian propellant, which is called 2,3-butanediol, is currently in existence, can be created by E. coli, and, on Earth, is used to make polymers for production of rubber.  

The process is outlined in a paper, “Designing the bioproduction of Martian rocket propellant via a biotechnology-enabled in situ resource utilization strategy,” published in the journal Nature Communications.

Rocket engines departing Mars are currently planned to be fueled by methane and liquid oxygen (LOX). Neither exist on the red planet, which means they would need to be transported from Earth to power a return spacecraft into Martian orbit. That transportation is expensive: ferrying the needed 30 tons of methane and LOX is estimated to cost around $8 billion. To reduce this cost, NASA has proposed using chemical catalysis to convert Martian carbon dioxide into LOX, though this still requires methane to be transported from Earth.

As an alternative, Georgia Tech researchers propose a biotechnology based in situ resource utilization (bio-ISRU) strategy that can produce both the propellant and LOX from CO2. The researchers say making the propellant on Mars using Martian resources could help reduce mission cost. Additionally, the bio-ISRU process generates 44 tons of excess clean oxygen that could be set aside to use for other purposes, such as supporting human colonization.

“Carbon dioxide is one of the only resources available on Mars. Knowing that biology is especially good at converting CO2 into useful products makes it a good fit for creating rocket fuel,” said Nick Kruyer, first author of the study and a recent Ph.D. recipient from Georgia Tech’s School of Chemical and Biomolecular Engineering (ChBE).

The paper outlines the process, which begins by ferrying plastic materials to Mars that would be assembled into photobioreactors occupying the size of four football fields. Cyanobacteria would grow in the reactors via photosynthesis (which requires carbon dioxide). Enzymes in a separate reactor would break down the cyanobacteria into sugars, which could be fed to the E. coli to produce the rocket propellant. The propellant would be separated from the E. coli fermentation broth using advanced separation methods.

The team’s research finds that the bio-ISRU strategy uses 32% less power (but weighs three times more) than the proposed chemically enabled strategy of shipping methane from Earth and producing oxygen via chemical catalysis.

Because the gravity on Mars is only a one-third of what is felt on Earth, the researchers were able to be creative as they thought of potential fuels.

“You need a lot less energy for lift-off on Mars, which gave us the flexibility to consider different chemicals that aren’t designed for rocket launch on Earth,” said Pamela Peralta-Yahya, a corresponding author of the study and an associate professor in the School of Chemistry & Biochemistry and ChBE who engineers microbes for the production of chemicals. “We started to consider ways to take advantage of the planet’s lower gravity and lack of oxygen to create solutions that aren’t relevant for Earth launches.”

“2,3-butanediol has been around for a long time, but we never thought about using it as a propellant. After analysis and preliminary experimental study, we realized that it is actually a good candidate,” said Wenting Sun, associate professor in the Daniel Guggenheim School of Aerospace Engineering, who works on fuels.

The Georgia Tech team spans campus. Chemists, chemical, mechanical, and aerospace engineers came together to develop the idea and process to create a viable Martian fuel. In addition to Kruyer, Peralta-Yahya, and Sun, the group included Caroline Genzale, a combustion expert and associate professor in the George W. Woodruff School of Mechanical Engineering, and Matthew Realff, professor and David Wang Sr. Fellow in ChBE, who is an expert in process synthesis and design.

The team is now looking to perform the biological and materials optimization identified to reduce the weight of the bio-ISRU process and make it lighter than the proposed chemical process. For example, improving the speed at which cyanobacteria grows on Mars will reduce the size of the photobioreactor, significantly lowering the payload required to transport the equipment from Earth.

“We also need to perform experiments to demonstrate that cyanobacteria can be grown in Martian conditions,” said Realff, who works on algae-based process analysis. “We need to consider the difference in the solar spectrum on Mars both due to the distance from the Sun and lack of atmospheric filtering of the sunlight. High ultraviolet levels could damage the cyanobacteria.”

The Georgia Tech team emphasizes that acknowledging the differences between the two planets is pivotal to developing efficient technologies for the ISRU production of fuel, food, and chemicals on Mars. It’s why they’re addressing the biological and materials challenges in the study in an effort to contribute to goal of future human presence beyond Earth.

“The Peralta-Yahya lab excels at finding new and exciting applications for synthetic biology and biotechnology, tackling exciting problems in sustainability,” added Kruyer. “Application of biotechnology on Mars is a perfect way to make use of limited available resources with minimal starting materials.”

The research was supported by a NASA Innovative Advanced Concepts (NIAC) Award.

Citation: Kruyer, et al. “Designing the bioproduction of Martian rocket propellant via a biotechnology-enabled in situ resource utilization strategy” Nature Communications. 10.1038/s41467-021-26393-7.

Featured image: Artist’s conception of astronauts and human habitats on Mars. Courtesy: NASA

Provided by Georgia Institute of Technology

The Upside-down Orbits Of A Multi-planetary System (Planetary Science)

Astronomers have discovered exoplanets that orbit in planes at 90 degrees from each other.

When planets form, they usually continue their orbital evolution in the equatorial plane of their star. However, an international team, led by astronomers from the University of Geneva (UNIGE), Switzerland, has discovered that the exoplanets of a star in the constellation Pisces orbit in planes perpendicular to each other, with the innermost planet the only one still orbiting in the equatorial plane. Why so? This radically different configuration from our solar system could be due to the influence of a distant companion of the star that is still unknown. This study, to be read in the journal Astronomy & Astrophysics, was made possible by the extreme precision achieved by ESPRESSO and CHEOPS, two instruments whose development was led by Switzerland.

Theories of the origin of planetary systems predict that planets form in the equatorial plane of their star and continue to evolve there, unless disturbed by special events. This is not the case in the solar system, where our planets lie close to the solar equatorial plane. In this case, the planets are said to be aligned with their star. However, a study showed in 2019 that two of the three planets around the star HD3167 are not aligned with it. HD3167c and HD3167d, two mini-Neptunes that orbit in 8.5 and 29.8 days, actually pass over the star’s poles, nearly 90 degrees from its equatorial plane.

Synergies between instruments

By re-observing this system with more efficient instruments, a team led by astronomers from UNIGE was able to measure the orientation of the third planet’s orbital plane, the super earth HD3167b, which orbits in less than a day (23 hours exactly). When a planet transits its star, the orientation of its orbit can be determined with a spectrograph, which allows measuring the motion of the stellar regions occulted by the planet and thus deducing its trajectory. The smaller the planet, the more difficult this motion is to detect. It is therefore with ESPRESSO on one of the four 8.2m telescopes of the VLT in Chile that the researchers were able to determine the orbit of HD3167b, which happens to be aligned with the star and perpendicular to the orbital plane of its two siblings. “We needed a maximum of light and a very precise spectrograph to be able to measure the signal of such a small planet”, comments Vincent Bourrier, researcher at the Department of Astronomy of the Faculty of Science of the UNIGE. “Two conditions that are met by the precision of ESPRESSO, combined with the collecting power of the VLT.”

This result could not have been obtained without a precise knowledge of when HD3167b transits its star, which was not possible with the time predicted by the literature with a precision of 20 minutes – an eternity for a transit that lasts 97 minutes. The researchers therefore turned to the CHEOPS satellite consortium, whose main mission is precisely to measure transits with very high precision. “CHEOPS allowed us to know the time of transit with a precision better than one minute. This is a good illustration of the synergy there can be between different instruments, here CHEOPS and ESPRESSO, and the teams that operate them”, says Christophe Lovis, a researcher in the Department of Astronomy of the UNIGE and member of the two consortia.

An unknown celestial body responsible for this disorder

These new measurements seem to confirm the prediction made in 2019 on the presence of a fourth body orbiting HD3167. In this scenario, HD3167b’s proximity to the star kept it under its influence, forcing the small planet to orbit in the plane in which it formed. On the contrary, the two more distant mini-Neptunes were able to free themselves from the star only to fall under the influence of this fourth body, which would have gradually misaligned their orbits. The path is therefore clear for the researchers, who are now setting out in search of this elusive companion.

This research is published in
Astronomy & Astrophysics
DOI:  10.1051/0004-6361/202141527

Featured image: The perpendicular orbits of the HD3167 planets: jewels of the Pisces constellation. © Gilliane Devidal

Reference: V. Bourrier et al, The Rossiter-McLaughlin effect Revolutions: an ultra-short period planet and a warm mini-Neptune on perpendicular orbits, Astronomy & Astrophysics (2021). DOI: 10.1051/0004-6361/202141527

Provided by University of Geneve

Astronomers Discover Massive Galaxy ‘Shipyard’ in the Distant Universe (Cosmology)

Astronomers have discovered a structure thought to be a “protocluster” of galaxies on its way to developing into a galaxy supercluster. Observations show the protocluster, which is located 11 billion light-years from Earth, as it appeared when the universe was 3 billion years old, when stars were produced at higher rates in certain regions of the cosmos.

Even galaxies don’t like to be alone. While astronomers have known for a while that galaxies tend to congregate in groups and clusters, the process of going from formation to friend groups has remained an open question in cosmology.

In a paper published in the journal Astronomy & Astrophysics, an international team of astronomers reports the discovery of a group of objects that appear to be an emerging accumulation of galaxies in the making – known as a protocluster.

“This discovery is an important step toward reaching our ultimate goal: understanding the assembly of galaxy clusters, the most massive structures that exist in the universe,” said Brenda Frye, an associate professor of astronomy at the University of Arizona’s Steward Observatory and a co-author of the study.

The Milky Way, home to our solar system, belongs to a galaxy cluster known as the Local Group, which is part of the Virgo supercluster. But what did a supercluster such as Virgo look like 11 billion years ago? 

“We still know very little about protoclusters, in part because they are so faint, too faint to be detected by optical light,” Frye said. “At the same time, they are known to radiate brightly in other wavelengths such as the sub-millimeter.”

Initially discovered by the European Space Agency’s Planck telescope as part of an all-sky survey, the protocluster described in the new paper showed up prominently in the far-infrared region of the electromagnetic spectrum. Sifting through a sample of more than 2,000 structures that could be in the process of becoming clusters, researchers came across a protocluster designated as PHz G237.01+42.50, or G237 for short. The observations looked promising, but to confirm its identity required follow-up observations with other telescopes.

Led by Mari Polletta at the National Institute for Astrophysics in Milan, Italy, the team conducted observations using the combined power of the Large Binocular Telescope in Arizona, which is managed by UArizona, and the Subaru Telescope in Japan. The team identified 63 galaxies belonging to the G237 protocluster. The original discovery was published in a previous paper, and follow-up observations were obtained using archival data, the Herschel Space Observatory and the Spitzer Space Telescope.

“You can think of galaxy protoclusters such as G237 as a galaxy shipyard in which massive galaxies are being assembled, only this structure existed at a time when the universe was 3 billion years old,” Frye said. “At the same time, the genealogy may be closer than you think. Because the universe is homogeneous and the same in all directions, we think that the Milky Way may have docked at a protocluster node similar to G237 when it was very young.”

simulation of the cosmic web
A simulation of the cosmic web – a vast, three-dimensional “spider web” of gas filaments crisscrossing in the cosmos. Rather than being randomly distributed, galaxies tend to cluster at the nodes of the cosmic web, depicted by the red regions, forming protoclusters such as G237. International Gemini Observatory-NOIRLab-NSF-AURA-G. L. Bryan-M. L. Norman

At first, observations of G237 implied a total star formation rate that was unrealistically high, and the team struggled to make sense of the data. The G237 protocluster seemed to be forming stars at a rate of 10,000 times that of the Milky Way. At that rate, the protocluster would be expected to rapidly use up its stellar fuel and subsequently settle down into a complex system similar to the Virgo supercluster.

“Each of the 63 galaxies discovered so far in G237 was like a star factory in overdrive,” Frye said. “It’s as if the galaxies were working on overtime to the assemble stars. The rate of production was unsustainable. At such a pace, the supply chains are expected to break in the near future, and in a way that permanently shuts down the galaxy shipyard.”

Such high yields could only be maintained by a continuous injection of fuel, which for stars is hydrogen gas. Frye said that would require an efficient and unbroken supply chain that drew in unreasonably large amounts of fresh gas to fuel the star-forming factories.

“We don’t know where that gas was coming from,” she said. 

Later, the team discovered that some of what it was seeing came from galaxies unrelated to the protocluster, but even after the irrelevant observations were removed, the total star formation rate remained high, at least 1,000 solar masses per year, according to Polletta. In comparison, the Milky Way produces about one solar mass each year.

“The picture we have pieced together now is that of a successful galaxy shipyard, which is working at high efficiency to assemble galaxies and the stars within them and has an energy supply that is more sustainable,” Frye said. 

All galaxies in the universe are part of a giant structure that resembles a three-dimensional spider web shape called the cosmic web. The filaments of the cosmic web intersect at the nodes, which equate to the galaxy shipyards in the analogy.

“We believe that the filaments mediate the transfer of hydrogen gas from the diffuse medium of intergalactic space onto these hungry, newly forming protocluster structures in the nodes,” Frye said.

Pointing to future research, Polletta said: “We are in the process of analyzing more observations on this and other Planck protoclusters with the goal of tracing the gas that gives birth to these newly forming stars and feeds the supermassive black holes, to determine its origin and explain the observed extraordinary activity.”

Frye said she is looking forward to combining data from the Large Binocular Telescope with observations from NASA’s the James Webb Space Telescope, to be launched in December.

“Protoclusters offer an opportunity to investigate key questions in astronomy that only this new observatory can answer,” she said, “such as what mechanisms drive the prodigious star formation, and when will the hydrogen supply run out, forcing this galaxy shipyard to close its doors and turn into a supercluster similar to the one our Milky Way is in?”

Featured image: Several instruments joined forces to produce this image of the G237 protocluster, identifying its galaxies in different colors representing different wavelengths of observations. The image on the right zooms in on the central region of this massive galaxy “shipyard.”ESA/Herschel and XMM-Newton; NASA/Spitzer; NAOJ/Subaru; Large Binocular Telescope; ESO/VISTA. Polletta, M. et al. 2021; Koyama, Y. et al. 2021

Provided by University of Arizona

How to Find Hidden Oceans on Distant Worlds? Use Chemistry (Planetary Science)

A new study shows how the chemicals in an exoplanet’s atmosphere can, in some cases, reveal whether or not the temperature on its surface is too hot for liquid water.

In our solar system, planets are either small and rocky (like Earth) or large and gaseous (like Neptune). But around other stars, astronomers have found planets that fall in between – worlds slightly larger than Earth but smaller than Neptune. These planets may have rocky surfaces or liquid-water oceans, but most are likely to be topped with atmospheres that are many times thicker than Earth’s and opaque.

In the new study, accepted in the Astrophysical Journal Letters, researchers show how the chemistry of those atmospheres could reveal clues about what lies beneath – specifically, which planets are too hot to support liquid-water oceans. Since liquid water is a necessary ingredient for life as we know it, this technique could help scientists narrow their search for potentially habitable exoplanets, or planets beyond our solar system. More than 4,500 exoplanets have been confirmed in our galaxy, with over 7,700 candidates yet to be confirmed, but scientists estimate that hundreds of billions of exoplanets exist in our galaxy.

Some NASA space telescopes equipped with spectrometers can reveal the chemical makeup of an exoplanet’s atmosphere. A chemical profile of Earth wouldn’t be able to reveal pictures of, say, cows or humans on the planet’s surface, but it would show carbon dioxide and methane produced by mammals, and oxygen produced by trees. None of these chemicals alone would be a sign of life, but in combination they would point to the possibility that our planet is inhabited.

The new paper shows which chemicals might point to hidden oceans on exoplanets between 1.7 and 3.5 times the diameter of Earth. Since Neptune is about four times Earth’s diameter, these planets are sometimes called “sub-Neptunes.”

Video: To help understand the incredible variety of exoplanets that exist in our galaxy, scientists sometimes use terms like “hot Jupiter” and “sub-Neptune” to indicate the similarities and differences between exoplanets (planets beyond our solar system) and planets within in our solar system. Credit: NASA/JPL-Caltech

A thick atmosphere on a sub-Neptune planet would trap heat on the surface and raise the temperature. If the atmosphere reaches a certain threshold – typically about 1,430 degrees Fahrenheit (770 degrees Celsius) – it will undergo a process called thermochemical equilibrium that changes its chemical profile. After thermochemical equilibrium occurs – and assuming the planet’s atmosphere is composed mostly of hydrogen, which is typical for gaseous exoplanets – carbon and nitrogen will predominantly be in the form of methane and ammonia.

Those chemicals would largely be missing in a cooler, thinner atmosphere where thermochemical equilibrium has not occurred. In that case, the dominant forms of carbon and nitrogen would be carbon dioxide and molecules of two nitrogen atoms.

A liquid-water ocean underneath the atmosphere would leave additional signs, according to the study, including the absence of nearly all stray ammonia, which would be dissolved in the ocean. Ammonia gas is highly soluble in water, depending on the pH of the ocean (its level of acidity). Over a wide range of plausible ocean pH levels the researchers found the atmosphere should be virtually free of ammonia when there is a massive ocean underneath.

In addition, there would be more carbon dioxide than carbon monoxide in the atmosphere; by contrast, after thermochemical equilibrium, there should be more carbon monoxide than carbon dioxide if there are detectable amounts of either.

“If we see the signatures of thermochemical equilibrium, we would conclude that the planet is too hot to be habitable,” said Renyu Hu, a researcher at NASA’s Jet Propulsion Laboratory, who led the study. “Vice versa, if we do not see the signature of thermochemical equilibrium and also see signatures of gas dissolved in a liquid-water ocean, we would take those as a strong indication of habitability.”

NASA’s James Webb Space Telescope, set to launch Dec. 18, will carry a spectrometer capable of studying exoplanet atmospheres. Scientists like Hu are working to anticipate what kinds of chemical profiles Webb will see in those atmospheres and what they could reveal about these distant worlds. The observatory has the capabilities to identify signs of thermochemical equilibrium in sub-Neptune atmospheres – in other words, signs of a hidden ocean – as identified in the paper.

As Webb discovers new planets or does more in-depth studies of known planets, this information could help scientists decide which of them are worthy of additional observations, especially if scientists want to target planets that might harbor life.

“We don’t have direct observational evidence to tell us what the common physical characteristics for sub-Neptunes are,” said Hu. “Many of them may have massive hydrogen atmospheres, but quite a few could still be ‘ocean planets.’ I hope this paper will motivate many more observations in the near future to find out.”

JPL is managed for NASA by Caltech in Pasadena, California.

Featured image: Planets that are between 1.7 and 3.5 times the diameter of Earth are sometimes called “sub-Neptunes.” There are no planets in this size range in Earth’s solar system, but scientists think many sub-Neptunes have thick atmospheres, potentially cloaking rocky surfaces or liquid oceans. Credit: NASA/JPL-Caltech

Provided by JPL