Three rings to bind them in ancient cosmic history

Asia's Tech News Daily

Three rings to bind them in ancient cosmic history

Astronomers have managed to link the properties of the inner planets of our solar system with our cosmic history: with the emergence of ring structures in the swirling disk of gas and dust in which these planets were formed. The rings are associated with basic physical properties such as the transition from an outer region where ice can form where water can only exist as water vapor. The astronomers made use of a spread of simulation to explore different possbilities of inner planet evolution. Our solar system’s inner regions are a rare, but possible outcome of that evolution. The results have been published in Nature Astronomy.

The broad-stroke picture of planet formation around stars has been unchanged for decades. But many of the specifics are still unexplained – and the search for explanations an important part of current research. Now, a group of astronomers led by Rice University’s Andre Izidoro, which includes Bertram Bitsch from the Max Planck Institute for Astronomy, has found an explanation for why the inner planets in our solar system have the properties we observe.

A swirling disk and rings that change everything
The broad-stroke picture in question is as follows: Around a young star, a “protoplanetary disk” of gas and dust forms, and inside that disk grow ever-larger small bodies, eventually reaching diameters of thousands of kilometers, that is: becoming planets. But in recent years, thanks to modern observational methods, the modern picture of planet formation has been refined and changed in very specific directions.

The most striking change was triggered by a literal picture: The first image taken by the ALMA observation after its completion in 2014. The image showed the protoplanetary disk around the young star HL Tauri in unprecedented detail, and the most stunning details amounted to a nested structure of clearly visible rings and gaps in that disk.

As the researchers involved in simulating protoplanetary disk structures took in these new observations, it became clear that such rings and gaps are commonly associated with “pressure bumps”, where the local pressure is somewhat lower than in the surrounding regions. Those localized changes are typically associated with changes in disk composition, mostly in the size of dust grains.

Three key transitions that produce three rings
In particular, there are pressure bumps associated with particularly important transitions in the disk that can be linked directly to fundamental physics. Very close to the star, at temperatures higher than 1400 Kelvin, silicate compounds (think “sand grains”) are gaseous – it is simply too hot for them to exist in any other state. Of course, that means that planets cannot form in such a hot region. Below that temperature, silicate compounds “sublimate”, that is, any silicate gases directly transition to a solid state. This pressure bump defines an overall inner border for planet formation.

Farther out, at 170 Kelvin (-100 degrees Celsius), there is a transition between water vapour on the one hand and water ice on the other hand, known as the water snowline. (The reason that temperature is so much lower than the standard 0 degrees Celsius where water freezes on Earth is the much lower pressure, compared to Earth’s atmosphere.) At even lower temperatures, 30 Kelvin (-240 degrees Celsius), is the CO snowline; below that temperature, carbon monoxide forms a solid ice.

Pressure bumps as pebble traps
What does this mean for the formation of planetary systems? Numerous earlier simulations had already shown how such pressure bumps facilitate the formation of planetesimals – the small objects, between 10 and 100 kilometers in diameter, that are believed to be the building blocks for planets. After all, the formation process starts much, much smaller, namely with dust grains. Those dust grains tend to collect in the low-pressure region of a pressure bump, as grains of a certain size drift inwards (that is, towards the star) until they are stopped by the higher pressure at the inner boundary of the bump.

As the grain concentration at the pressure bump increases, and in particular the ratio of solid material (which tends to aggregate) to gas (which tends to push grains apart) increases, it becomes easier for those grains to form pebbles, and for those pebbles to aggregate into larger objects. Pebbles are what astronomers call solid aggregates with sizes between a few millimeters and a few centimeters.

The role of pressure bumps for the (inner) solar system
But what had still be an open question was the role of those sub-structures in the overall shape of planetary systems, like our own Solar system, with its characteristic distribution of rocky, terrestrial inner planets and outer gaseous planets. This is the question that Andre Izidoro (Rice University), Bertram Bitsch of the Max Planck Institute for Astronomy and their colleagues took on. In their search for answers, they combined several simulations covering different aspects and different phases of planet formation.

Specifically, the astronomers constructed a model of a gas disk, with three pressure bumps at the silicates-become-gaseous boundary and the water and CO snow lines. They then simulated the way that dust grains grow and fragment in the gas disk, the formation of planetesimals, the growth from planetesimals to planetary embryos (from 100 km in diameter to 2000 km) near the location of our Earth (“1 astronomical unit” distance from the Sun), the growth of planetary embryos to planets for the terrestrial planets, and the accumulation of planetesimals in a newly-formed asteroid belt.

In our own solar system, the asteroid belt between the orbits of Mars and Jupiter is home to hundreds of smaller bodies, which are believed to be remnants or collision fragments of planetesimals in that region that never grew to form planetary embryos, let alone planets.

Variations on a planetary theme
An interesting question for simulations is this: If the initial setup were just a little bit different, would the end result still be somewhat similar? Understanding these kinds of variations is important for understanding which of the ingredients are the key to the outcome of the simulation. That is why Bitsch and his colleagues analyzed a number of different scenarios with varying properties for the composition and for the temperature profile of the disk. In some of the simulations, they only the silicate and water ice pressure bumps, in others all three.

The results suggest a direct link between the appearance of our solar system and the ring structure of its protoplanetary disk. Bertram Bitsch of the Max Planck Institute for Astronomy, who was involved both in planning this research programme and in developing some of the methods that were used, says: “For me, it was a complete surprise how well our models were able to capture the development of a planetary system like our own – right down to the slightly different masses and chemical compositions of Venus, Earth and Mars.”

As expected, in those models, planetesimals in those simulations formed naturally near the pressure bumps, as a “cosmic traffic jam” for pebbles drifting inwards, which would then be stopped by the higher pressure at the inner boundary of the pressure bump.

Recipe for our (inner) solar system
For the inner parts of the simulated systems, the researchers identified the right conditions for the formation of something like our own solar system: If the region right outside the innermost (silicate) pressure bump contains around 2.5 Earth masses’ worth of planetesimals, these grow to form roughly Mars-sized bodies – consistent with the inner planets within the solar system.

A more massive disk, or else a higher efficiency of forming planetesimals, would instead lead to the formation of “Super-Earths,” that is, considerably more massive rocky planets. Those Super-Earths would be in close orbit around the host star, right up against that innermost pressure bump boundary. The existence of that boundary can also explain why there is no planet closer to the Sun than Mercury – the necessary material would simply have evaporated that close to the star.

The simulations even go so far as to explain the slightly different chemical compositions of Mars on the one hand, Earth and Venus on the other: In the models, Earth and Venus indeed collect most of the material that will form their bulk from regions closer to the Sun than the Earth’s current orbit (one astronomical unit). The Mars-analogues in the simulations, in contrast, were built mostly from material from regions a bit farther away from the Sun.

How to build an asteroid belt
Beyond the orbit of Mars, the simulations yielded a region that started out as sparsely populated with or, in some cases, even completely empty of planetesimals – the precursor of the present-day asteroid belt of our solar systems. However, some planetesimals from the zones inside of or directly beyond would later stray into the asteroid belt region and become trapped.

As those planetesimals collided, the resulting smaller pieces would form what we today observe as asteroids. The simulations are even able to explain the different asteroid populations: What astronomers call S-types asteroids, bodies that are made mostly of silica, would be the remnants of stray objects originating in the region around Mars, while C-type asteroids, which predominantly contain Carbon, would be the remnants of stray objects from the region directly outside the asteroid belt.

Outer planets and Kuiper belt
In that outer region, just outside the pressure bump that marks the inner limit for the presence of water ice, the simulations show the beginning of the formations of giant planets – the planetesimals near that boundary typically have a total mass of between 40 and 100 times the mass of the Earth, consistent with estimates of the total mass of the cores of the giant planets in our solar system: Jupiter, Saturn, Uranus and Neptune.

In that situation, the most massive planetesimals would quickly gather more mass. The present simulations did not follow up on the (already well-studied) later evolution of those giant planets, which involves an initially rather tight group, from which Uranus and Neptune later migrated outwards to their present positions.

Last but not least, the simulations can explain the final class of objects, and its properties: so-called Kuiper-belt objects, which formed outside the outermost pressure bump, which marks the inner boundary for the existence of carbon monoxide ice. It even can explain the slight differences in composition between known Kuiper-belt objects: again as the difference between planetesimals that formed originally outside the CO snowline pressure bump and stayed there, and planetesimals that strayed into the Kuiper belt from the adjacent inner region of the giant planets.

Two basic outcomes and our rare solar system
Overall, the spread of simulations led to two basic outcomes: Either a pressure bump at the water-ice snowline formed very early; in that case, the inner and outer regions of the planetary system went their separate ways rather early on within the first hundred thousand years. This led to the formation of low-mass terrestrial planets in the inner parts of the system, similar to what happened in our own solar system.

Alternatively, if the water-ice pressure bump forms later than that or is not as pronounced, more mass can drift into the inner region, leading instead to the formation of Super-Earths or mini-Neptunes in the inner planetary systems. Evidence from the observations of those exoplanetary systems astronomers have found so far shows that case is by far the more probable – and our own Solar system a comparatively rare outcome of planet formation.

In this research, the focus of the astronomers was on the inner solar system and the terrestrial planets. Next, they want to run simulations that include details of the outer regions, with Jupiter, Saturn, Uranus and Neptune. The eventual aim is to arrive at a complete explanation for the properties of ours and other solar systems.

For the inner solar system, at least, we now know that key properties of Earth and its nearest neighbouring planet can be traced to some rather basic physics: the boundary between frozen water and water vapour and its associated pressure bump in the swirling disk of gas and dust that surrounded the young Sun.

Research Report: “Planetesimal rings as the cause of the Solar System’s planetary architecture”

Internet Explorer Channel Network
Asia's Tech News Daily
News Related


Plato exoplanet mission gets green light for next phase

Plato, ESA’s next-generation planet hunting mission, has been given the green light to continue with its development after the critical milestone review concluded successfully on 11 January 2022. The review ... Read more »

Earth's interior is cooling faster than expected

The evolution of our Earth is the story of its cooling: 4.5 billion years ago, extreme temperatures prevailed on the surface of the young Earth, and it was covered by ... Read more »

New DAF software factory aims to digitally transform AFRL

The chief software officer for the Air Force recently designated Hangar 18 as a Department of the Air Force software factory. Hangar 18 joins 16 other DAF software factories-including the ... Read more »

Arase uncovers Geospace coupling between plasma waves and charged particles

In a new study published in Physical Review Letters, researchers from Japan show that high-frequency plasma waves in the Geospace can generate low-frequency plasma waves through wave-particle interactions by heating ... Read more »

Chile court freezes multi-million dollar lithium deal

A Chilean appeals court on Friday suspended a million-dollar state lithium tender issued two days earlier that had generated controversy for coming just two months before the end of conservative ... Read more »

Understanding the "cold spot" in the cosmic microwave background

After the Big Bang, the universe, glowing brightly, was opaque and so hot that atoms could not form. Eventually cooling down to about minus 454 degrees Fahrenheit (-270 degrees Celsius), ... Read more »

Evidence for a second supermoon beyond our solar system

Astronomers have reported a second, super-sized moon orbiting a Jupiter-sized planet beyond our solar system. If confirmed, the sighting could mean that exomoons are as common in the universe as ... Read more »

Virgin Orbit mission success brings UK satellite launch one step closer

Satellite launch from Spaceport Cornwall is a step closer following Virgin Orbit’s successful ‘Above the Clouds’ mission in the US. The UK Space Agency welcomes the news that Virgin Orbit ... Read more »

OMEGA joins ClearSpace to clean up space

ClearSpace SA is working to rid space of dangerous debris comprising left-over rockets and defunct satellites. Now, Swiss watchmaker OMEGA, manufacturer of the first watch worn on the Moon, is ... Read more »

Iran tests solid-fuel satellite carrier rocket

Iran’s Revolutionary Guards tested last week a solid-fuel satellite carrier rocket, state media has reported quoting the force’s aerospace commander as saying. Reports carried footage released by the elite force ... Read more »

SpaceX launches 44 SuperDove satellites for Planet Labs

Planet Labs reports the successful launch of its 4x Flock, consisting of 44 SuperDove satellites, into orbit on a SpaceX Falcon 9 rocket. The company has established contact with all ... Read more »

Ironing out the interiors of exoplanets

The discovery of more than 4,500 extra-solar planets has created a need for modelling their interior structure and dynamics. As it turns out, iron plays a key role. Lawrence Livermore ... Read more »

New insights into seasons on a planet outside our solar system

Imagine being in a place where the winds are so strong that they move at the speed of sound. That’s just one aspect of the atmosphere on XO-3b, one of ... Read more »

Citizen Scientists Spot Jupiter-like Planet in NASA TESS Data

Tom Jacobs of Bellevue, Washington, loves treasure hunts. Since 2010, the former U.S. naval officer has participated in online volunteer projects that allow anyone who is interested – “citizen scientists” ... Read more »

Team of astronomers finds widest separation of brown dwarf pair to date

A team of astronomers, led by Arizona State University undergraduate student Emma Softich, has discovered a rare pair of brown dwarfs that has the widest separation of any brown dwarf ... Read more »

Pandora mission to study stars and exoplanets continues toward flight

The Pandora mission, co-led by a national laboratory and a NASA flight center, has passed a crucial step on its path to study stars and planets outside our solar system, ... Read more »

Unusual team finds gigantic planet hidden in plain sight

Riverside CA (SPX) Jan 14, 2022 A UC Riverside astronomer and a group of eagle-eyed citizen scientists have discovered a giant gas planet hidden from view by typical stargazing tools. ... Read more »

Photon pairs are more sensitive to rotations than single photons

In the field of quantum metrology, scientists are developing novel measurement schemes that benefit from quantum features and are more precise and sensitive than classical conventional methods. The team of ... Read more »

Newly-Found Planets On The Edge Of Destruction

Three newly-discovered planets have been orbiting dangerously close to stars nearing the end of their lives. Out of the thousands of extrasolar planets found so far, these three gas giant ... Read more »

Kleos' Patrol Mission satellites to launch in April

Kleos Space S.A, a space-powered Radio Frequency Reconnaissance data-as-a- service (DaaS) company, announces the Kleos Patrol Mission (KSF2) satellites, planned to launch in January 2022, have been remanifested to launch ... Read more »

Virgin Orbit launches a rocket carrying 7 satellites

Virgin Orbit kicked off an ambitious launch schedule for 2022 on Thursday by sending seven small satellites into space aboard a rocket launched from a jet high above the Pacific ... Read more »

Black hole at center of Milky Way unpredictable and chaotic

An international team of researchers, led by postgraduate student Alexis Andres, has found that the black hole at the centre of our galaxy, Sagittarius A*, not only flares irregularly from ... Read more »

SES Government Solutions Launches On-Demand X-band Service Platform

SES Government Solutions, a wholly-owned subsidiary of SES, announced the launch of tactiXs, a mission-specific managed service platform in partnership with Network Innovations and GovSat, a public-private joint venture between ... Read more »

Pixxel Partners with Rio Tinto to investigate benefits of hyperspectral satellite technology

Earth imaging company Pixxel has announced an early adoption partnership with Rio Tinto. Pixxel’s imaging satellites, capable of 5 meter hyperspectral imaging, will help Rio Tinto assess the benefits the ... Read more »

Are astronomers seeing a signal from giant black holes?

An international team of astronomers has discovered what could be the early sign of a background signal arising from supermassive black holes, observed through low-frequency gravitational waves. These scientists are ... Read more »

New theory finds upcoming satellite mission will be able to detect more than expected

The upcoming satellite experiment LiteBIRD is expected to probe the physics of the very early Universe if the primordial inflation happened at high energies. But now, a new paper in ... Read more »

How the Webb telescope could ultimately help protect Earth

The James Webb Space Telescope, the most complex and expensive space laboratory ever created, is less than two weeks away from its ultimate destination a million miles from Earth. Once ... Read more »

Watch live: Virgin Orbit plans to launch a rocket carrying 7 satellites

Virgin Orbit kicked off an ambitious launch schedule for 2022 on Thursday by sending seven small satellites into space aboard a rocket launched from a jet high above the Pacific ... Read more »

Oxygen ions in Jupiter's innermost radiation belts

Planets like Earth, Jupiter, and Saturn with global magnetic fields of their own are surrounded by so-called radiation belts: Trapped in the magnetic field, fast moving charged particles such as ... Read more »

It all comes down to the first electron

Every living thing requires energy. This is also true of microorganisms. This energy is frequently generated in the cells by respiration, that is by the combustion of organic compounds, in ... Read more »

Cosmic explosions offer new clue to how stars become Black Holes

Scientists have witnessed for the first time exactly what happens to the most massive stars at the end of their lives. Most very large stars explode in a fiery supernova ... Read more »

A cosmic romance written in the stars

An international team of astronomers has taken a step forward in understanding the evolution of galaxies, and in so doing, told a story written in the heavens. It has long ... Read more »

Copper-based chemicals may be contributing to ozone depletion

Copper released into the environment from fungicides, brake pads, antifouling paints on boats and other sources may be contributing significantly to stratospheric ozone depletion, according to a new study from ... Read more »

ALMA Catches "Intruder" Redhanded in Rarely Detected Stellar Flyby Event

Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA) made a rare detection of a likely stellar flyby event in the Z ... Read more »

New spheres of knowledge on the origin of life

The shape of a cell affects its physical and chemical properties. Different cell types have developed different shapes to enable effective functioning. But what shape were the very first cells, ... Read more »

Too much heavy metal stops stars producing

Stars are giant factories that produce most of the elements in the Universe – including the elements in us, and in the Earth’s metal deposits. But what stars produce changes ... Read more »

Deciphering conditions around the Sun five million years ago

Using high-resolution data obtained from the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope, Wesleyan University Professor of Astronomy Seth Redfield can show the conditions the Sun encountered traveling ... Read more »

Researchers Observe Massive CME on Distant, Sun-Like Star

EK Draconis illuminates an unimagined picture of how superflares may affect interplanetary space through coronal mass ejections Welcome to the New Year! While Earth celebrated 2022’s arrival with displays of ... Read more »

North Pole solar eclipse excited auroras on the other side of the world

A solar eclipse over the Arctic created changes in auroras in both of Earth’s hemispheres due to connections through the planet’s magnetic field, according to a new study. The new ... Read more »

Increased space missions risk extraterrestrial contamination

The days of the U.S.-Soviet Space Race are over, and the domain of space exploration is expanding daily to include more countries than ever before. With the advent of private ... Read more »
On you will find lots of free English exam practice materials to help you improve your English skills: grammar, listening, reading, writing, ielts, toeic