Winds of change: James Webb Space Telescope reveals elusive details in young star systems | University of Arizona News
This description is so far removed from reality that none of it can plausibly be described as allegorical or metaphorical, or even a simplistic description intended to inform simple, uneducated people incapable of understanding anything more complicated. It is simply and laughably wrong; but exactly what parochial pastoralists might think from their limited perspective.
And these same parochial, naïve people came up with the notion of gods to explain the world around them whose working were so mysterious as to look like magic - and magic requires a magician. Where better to locate that magician? Above the dome over the Earth, obviously.
And so religions were built on the best guesses of people who knew no better; people whose best guess was that the Universe consisted of a small flat planet with a dome over it to keep the water above the sky out; people who saw no contradiction in describing the creation of light before the creation of the source of light, or the creation of green plants before the sun!
But how could they, with no technology more complicated than a potter's wheel and the visual acuity of the human eye, possibly know what was really going on as they looked up at the 'little lights stuck to the dome'? How could they possibly have been aware that this Earth is in orbit round the sun, that the sun is but one of half a trillion suns in one of half a trillion galaxies, all existing in a vast, expanding universe in which more than 3000 new stars are being born every second, most of them with an accretion disc from which planets will eventually coalesce?
Had they done so, and had they told us about it, then, and only then, would the notion that a creator god was inspiring them to explain the magnificence of its creation be even a plausible explanation for how they knew that stuff. As it is, all we are left to explain is why they were so ignorant of reality that they needed to invent stories to fill the gaps in their understanding, and of course, the gods they created exactly fitted those gaps, just as todays gods are precisely tailored to fill the gaps in the understanding of ignorant people.
So, how do we know they got things so badly wrong?
Describe the Universe as it would have been 4.6 billion years ago, please. The Universe at 4.6 Billion Years AgoBecause we now have the technology to look into deep space and see in far greater detail, in a wider range of spectra, than is possible with the unaided human eye.
This period aligns with the early formation of our Solar System, around 4.6 billion years ago. However, the broader universe had already existed for about 9 billion years at that time. Galaxies, stars, and other cosmic structures were already well-established. The process of star formation and galaxy evolution was ongoing, but the conditions of the universe were far more settled than in its early years.
Cosmic Context
- Galaxies: The universe had a rich structure of galaxies, some of which resembled our modern Milky Way, while others were still evolving. Star formation in galaxies was more vigorous than it is today, but the universe was already starting to transition to a more "mature" state.
- Stars and Elements: Many stars had lived and died in supernovae, enriching the universe with heavier elements like carbon, oxygen, and iron. These elements are crucial for the formation of rocky planets and life as we know it. The earlier universe (within the first few billion years after the Big Bang) consisted mainly of hydrogen and helium, but by 4.6 billion years ago, heavier elements were abundant in places where new solar systems were forming.
The Solar Nebula and Solar System Formation
- Solar Nebula: A key event was happening in a region of the Milky Way where a molecular cloud—composed of dust and gas—was collapsing due to gravity. This collapse was triggered by some external force, possibly a nearby supernova explosion. This collapse would give birth to our Solar System.
- Protostar (Sun): As the cloud collapsed, the central region formed a protostar, which would become the Sun. Nuclear fusion hadn’t started yet, so it wasn’t fully formed as a star. The protostar was surrounded by a rotating disk of gas and dust known as the protoplanetary disk.
Formation of the Planets
- Planetesimals: In the disk surrounding the young Sun, particles of dust began to collide and stick together, forming small bodies called planetesimals. Over time, these planetesimals grew larger, forming protoplanets through accretion.
- The Early Earth: Earth, at this time, was in its molten state, formed through the accumulation of matter in this chaotic, colliding environment. It was a hot, unstable world with frequent volcanic activity, no solid crust, and no atmosphere similar to today’s. Over millions of years, Earth would gradually cool and form a solid surface.
Wider Universe Conditions
- Star Formation: Across the universe, star formation was still active, especially in galaxies where new stars were born from molecular clouds. However, star formation rates had started to decline compared to the universe’s earlier eras.
- Cosmic Scale: Galaxies were still interacting and merging. These galactic collisions played a critical role in shaping the structure of galaxies. The universe’s expansion continued, with distances between galaxies increasing.
Summary
The universe 4.6 billion years ago was a dynamic place, where galaxies, stars, and solar systems like ours were evolving. The elements for life were present, but Earth and its neighboring planets were just beginning to form, and the Solar System was emerging from the debris of previous stellar generations.
Would you like to explore any specific aspect of this era in more detail?
Tell me more about the formation of suns and their accretion disks, please.
The formation of suns (stars) and their accretion disks is a fascinating process, central to the creation of solar systems like ours. Here’s a detailed breakdown of how this process unfolds, starting from a massive molecular cloud to the birth of a star and its accompanying disk:
- Molecular Cloud Collapse Stars form in regions of space called molecular clouds (also known as stellar nurseries). These clouds are dense with gas (mostly hydrogen and helium) and dust, and they can span light-years across. Under normal conditions, these clouds are in a delicate balance between internal pressure and gravitational forces. However, if something disturbs this balance—such as a nearby supernova explosion or internal instabilities—gravity can cause part of the cloud to collapse.
As the cloud collapses under its own gravity, it begins to fragment into smaller and smaller clumps of material. Each clump can form an individual star.
- Formation of a Protostar
As the collapsing region shrinks, the gravitational energy is converted into heat, and the core of the clump becomes hotter and denser. This forms a protostar, which is the early, developing stage of a star. The surrounding material in the cloud continues to fall inward, feeding the growing protostar.
At this stage:
- The protostar is not yet hot enough for nuclear fusion to start (which is the process that powers fully formed stars), but it’s getting closer to that point.
- The surrounding gas and dust in the cloud form a rotating accretion disk around the protostar.
- The Accretion Disk
The material around the protostar doesn’t fall straight in; instead, it forms a rotating disk due to the conservation of angular momentum. This disk is crucial for the formation of the star and its planets, and it’s called a protoplanetary disk when planets are likely to form within it.
- Accretion: Material in the disk slowly spirals inward, adding mass to the growing protostar. This process is known as accretion.
- Size and Composition: The disk is made of gas, primarily hydrogen and helium, with heavier elements (such as carbon, silicon, oxygen, and iron) mixed in. Dust particles within the disk will eventually coalesce to form larger structures, like planets, moons, and asteroids.
- Angular Momentum and Disk Structure
One reason why the material forms a disk rather than just falling directly into the star is due to angular momentum. As the cloud contracts, any small amount of rotation is amplified, causing the material to flatten into a disk around the central protostar. This same principle is why ice skaters spin faster when they pull in their arms—conservation of angular momentum.
The inner part of the disk (closer to the protostar) spins faster and is hotter due to the stronger gravitational forces, while the outer part is cooler and moves more slowly. This temperature gradient is important for determining what kinds of materials can condense and form planets at different distances from the protostar.
- Birth of the Star (Main Sequence)
As more and more material from the accretion disk falls onto the protostar, the core of the protostar becomes increasingly hot and dense. When the temperature at the core reaches around 10 million Kelvin, nuclear fusion ignites. This marks the transition from a protostar to a fully-fledged main sequence star.
At this point, the star enters the longest phase of its life, during which hydrogen in the core is fused into helium, releasing energy and creating the outward pressure needed to balance the force of gravity. Our Sun, for instance, is in this main sequence stage.
- Clearing the Disk and Planet Formation
While the star is forming, material in the surrounding disk is still present. Over the next few million years, much of this material either:
In our Solar System, for example, rocky planets like Earth and Mars formed from the material in the hotter, inner part of the disk, while gas giants like Jupiter formed farther out, where cooler temperatures allowed for the accumulation of lighter gases like hydrogen and helium.
- Falls into the star, adding to its mass.
- Clumps together to form planetesimals (small bodies of rock, ice, or metal), which can eventually grow into planets through a process called accretion.
Eventually, the intense radiation and stellar winds from the young star blow away the remaining gas and dust in the disk, leaving behind a system of planets, moons, and other debris orbiting the newly formed star.
- Types of Stars and Their Accretion Disks
Not all stars form in the same way or have the same kind of accretion disks. For instance:
- Massive stars (more than 8 times the mass of the Sun) form much faster than lower-mass stars. They can form in a few hundred thousand years compared to a few million years for stars like the Sun.
- Low-mass stars have less material in their disks and form planets more slowly, often resulting in smaller systems with fewer planets.
Key Concepts in Star and Disk FormationFinal Stages: A New Solar System
- Accretion: This is the process by which material from the disk falls onto the growing star. Accretion is a slow process, and it’s how the protostar gathers most of its mass.
- Angular Momentum: This principle explains why the collapsing cloud forms a disk rather than collapsing directly into the star.
- Protoplanetary Disk: The disk surrounding the star is where planets, moons, and other small bodies eventually form through accretion.
By the end of the star formation process, the accretion disk has mostly cleared away, and the young star is surrounded by planets, moons, and other smaller objects. This is how the Solar System—and countless other star systems—are born.
Would you like to dive deeper into any particular aspect, such as how planets form within the accretion disk or how stars evolve after their formation?
And we now know that the further we look into deep space, the further back we are looking in time, because we now know that light travels at a finite velocity so takes time to reach us, and the vastness of space is such that some of the light reaching us has taken billions of years to get here.
That brings me to today's news that a team of cosmologists, led by scientists from the University of Arizona, have used the James Webb Space Telescope (JWST) to see the creation of suns and their planetary systems at about the time the solar system was being formed - descriptions of which no amount of twisting of words and creative re-writing of Genesis comes even close to achieving.
The cosmologists have just published their findings in Nature Astronomy and describe it in a University of Arizona News item:
Winds of change: James Webb Space Telescope reveals elusive details in young star systems
Every second, more than 3,000 stars are born in the visible universe. Many are surrounded by what astronomers call a protoplanetary disk – a swirling "pancake" of hot gas and dust from which planets form. The exact processes that give rise to stars and planetary systems, however, are still poorly understood.
A team of astronomers led by University of Arizona researchers has used NASA's James Webb Space Telescope to obtain some of the most detailed insights into the forces that shape protoplanetary disks. The observations offer glimpses into what our solar system may have looked like 4.6 billion years ago.
Specifically, the team was able to trace so-called disk winds in unprecedented detail. These winds are streams of gas blowing from the planet-forming disk out into space. Powered largely by magnetic fields, these winds can travel tens of miles in just one second. The researchers' findings, published in Nature Astronomy, help astronomers better understand how young planetary systems form and evolve.
According to the paper's lead author, Ilaria Pascucci, a professor at the U of A Lunar and Planetary Laboratory, one of the most important processes at work in a protoplanetary disk is the star eating matter from its surrounding disk, which is known as accretion.
How a star accretes mass has a big influence on how the surrounding disk evolves over time, including the way planets form later on. The specific ways in which this happens have not been understood, but we think that winds driven by magnetic fields across most of the disk surface could play a very important role.
Professor Ilaria Pascucci, lead author
Lunar and Planetary Laboratory
The University of Arizona, Tucson, AZ, USA
Young stars grow by pulling in gas from the disk that's swirling around them, but in order for that to happen, gas must first shed some of its inertia. Otherwise, the gas would consistently orbit the star and never fall onto it. Astrophysicists call this process "losing angular momentum," but how exactly that happens has proved elusive.
To better understand how angular momentum works in a protoplanetary disk, it helps to picture a figure skater on the ice: Tucking her arms alongside her body will make her spin faster, while stretching them out will slow down her rotation. Because her mass doesn't change, the angular momentum remains the same.
For accretion to occur, gas across the disk has to shed angular momentum, but astrophysicists have a hard time agreeing on how exactly this happens. In recent years, disk winds have emerged as important players funneling away some gas from the disk surface – and with it, angular momentum – which allows the leftover gas to move inward and ultimately fall onto the star.
Because there are other processes at work that shape protoplanetary disks, it is critical to be able to distinguish between the different phenomena, according to the paper's second author, Tracy Beck at NASA's Space Telescope Science Institute.
While material at the inner edge of the disk is pushed out by the star's magnetic field in what is known as X-wind, the outer parts of the disk are eroded by intense starlight, resulting in so-called thermal winds, which blow at much slower velocities.
To distinguish between the magnetic field-driven wind, the thermal wind and X-wind, we really needed the high sensitivity and resolution of JWST (the James Webb Space Telescope)
Tracy L. Beck, co-author
Instruments Division
Space Telescope Science Institute, Baltimore, MD, USA.
Unlike the narrowly focused X-wind, the winds observed in the present study originate from a broader region that would include the inner, rocky planets of our solar system – roughly between Earth and Mars. These winds also extend farther above the disk than thermal winds, reaching distances hundreds of times the distance between Earth and the sun.
Our observations strongly suggest that we have obtained the first images of the winds that can remove angular momentum and solve the longstanding problem of how stars and planetary systems form.
Professor Ilaria Pascucci.
For their study, the researchers selected four protoplanetary disk systems, all of which appear edge-on when viewed from Earth.
Their orientation allowed the dust and gas in the disk to act as a mask, blocking some of the bright central star's light, which otherwise would have overwhelmed the winds.
Naman S. Bajaj
Lunar and Planetary Laboratory
The University of Arizona, Tucson, AZ, USA.
By tuning JWST's detectors to distinct molecules in certain states of transition, the team was able to trace various layers of the winds. The observations revealed an intricate, three-dimensional structure of a central jet, nested inside a cone-shaped envelope of winds originating at progressively larger disk distances, similar to the layered structure of an onion. An important new finding, according to the researchers, was the consistent detection of a pronounced central hole inside the cones, formed by molecular winds in each of the four disks.
Next, Pascucci's team hopes to expand these observations to more protoplanetary disks, to get a better sense of how common the observed disk wind structures are in the universe and how they evolve over time.
We believe they could be common, but with four objects, it's a bit difficult to say. We want to get a larger sample with James Webb, and then also see if we can detect changes in these winds as stars assemble and planets form.
Professor Ilaria Pascucci.
Funding for this work was provided by NASA and the European Research Council.
AbstractAmazingly, there are people living in technologically advanced economies who still believe the description of a small flat planet with a dome over it, complete with stars and galaxies as small lights that can be shaken loose during earthquakes, is a far more accurate and reliable description of the real universe than anything science can produce. They conclude therefore that the description is so accurate it can only have been written by the creator god who made it.
Radially extended disk winds could be the key to unlocking how protoplanetary disks accrete and how planets form and migrate. A distinctive characteristic is their nested morphology of velocity and chemistry. Here we report James Webb Space Telescope near-infrared spectrograph spectro-imaging of four young stars with edge-on disks, three of which have already dispersed their natal envelopes. For each source, a fast collimated jet traced by [Fe ii] is nested inside a hollow cavity within wider lower-velocity H2. In one case, a hollow structure is also seen in CO ro-vibrational (v = 1 → 0) emission but with a wider opening angle than the H2, and both of those are nested inside an Atacama Large Millimeter Array CO (J = 2 → 1) cone with an even wider opening angle. This nested morphology, even for sources with no envelope, strongly supports theoretical predictions for wind-driven accretion and underscores the need for theoretical work to assess the role of winds in the formation and evolution of planetary systems.
Pascucci, I., Beck, T.L., Cabrit, S. et al. The nested morphology of disk winds from young stars revealed by JWST/NIRSpec observations. Nat Astron (2024). https://doi.org/10.1038/s41550-024-02385-7
© 2024 Springer Nature Ltd.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.
These people claim to know this by 'faith' and think their faith is something to be admired as the best available measure of reality.
And they elect politicians who agree with them!
Ten Reasons To Lose Faith: And Why You Are Better Off Without It
This book explains why faith is a fallacy and serves no useful purpose other than providing an excuse for pretending to know things that are unknown. It also explains how losing faith liberates former sufferers from fear, delusion and the control of others, freeing them to see the world in a different light, to recognise the injustices that religions cause and to accept people for who they are, not which group they happened to be born in. A society based on atheist, Humanist principles would be a less divided, more inclusive, more peaceful society and one more appreciative of the one opportunity that life gives us to enjoy and wonder at the world we live in.
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