̽��ֱ�� of Cambridge - Cathie Clarke

Neon sign identified by JWST gives clue to planet formation

Anonymous — Tue, 05 Mar 2024 15:06:11 +0000

Planetary systems like our Solar System seem to contain more rocky objects than gas-rich ones. Around our sun, these include the inner planets, the asteroid belt and the Kuiper belt. But scientists have known for a long time that planet-forming discs start with 100 times more mass in gas than in solids, which leads to a pressing question; when and how does most of the gas leave the disc/system?

JWST is helping scientists uncover how planets form, by advancing understanding of their birthplaces, the circumstellar discs surrounding young stars. In a new study published in the Astronomical Journal, a team of scientists including those from the ̽��ֱ�� of Leicester, the ̽��ֱ�� of Cambridge and led by the ̽��ֱ�� of Arizona, image for the first time an old planet-forming disc (still very young relative to the Sun) which is actively dispersing its gas content.

Knowing when the gas disperses is important as it constrains the time that is left for nascent planets to consume the gas from their surroundings.

During the very early stages of planetary system formation, planets coalesce in a spinning disc of gas and tiny dust around the young star. These particles clump together, building up into bigger and bigger chunks called planetesimals. Over time, these planetesimals collide and stick together, eventually forming planets. ̽��ֱ��type, size, and location of planets that form depend on the amount of material available and how long it remains in the disc. So, the outcome of planet formation depends on the evolution and dispersal of the disc.

At the heart of this discovery is the observation of T Cha, a young star (relative to the Sun) enveloped by an eroding disc notable for its vast dust gap, approximately 30 astronomical units in radius. For the first time, astronomers have imaged the dispersing gas (aka winds) using the four lines of the noble gases neon (Ne) and argon (Ar), one of which is the first detection in a planet-forming disc. ̽��ֱ��images of [Ne II] show that the wind is coming from an extended region of the disc. ̽��ֱ��team is also interested in knowing how this process takes place, so they can better understand the history and impact on our solar system.

Scientists have been trying to understand the mechanisms behind the winds in protoplanetary discs for over a decade. ̽��ֱ��observations by JWST represent a huge step-change in the data they have to work with, compared to previous data from ground-based telescopes.

“We first used neon to study planet-forming discs more than a decade ago, testing our computational simulations against data from Spitzer, and new observations we obtained with the ESO VLT,” said co-author Professor Richard Alexander from the ̽��ֱ�� of Leicester. “We learned a lot, but those observations didn’t allow us to measure how much mass the discs were losing.

“ ̽��ֱ��new JWST data are spectacular, and being able to resolve disc winds in images is something I never thought would be possible. With more observations like this still to come, JWST will enable us to understand young planetary systems as never before.”

“These winds could be driven either by high-energy stellar photons (the star's light) or by the magnetic field that weaves the planet-forming disc,” said Naman Bajaj from the ̽��ֱ�� of Arizona, the study’s lead author.

To differentiate between the two, the same group, this time led by Dr Andrew Sellek of Leiden Observatory and previously of the Institute of Astronomy at the ̽��ֱ�� of Cambridge, performed simulations of the dispersal driven by stellar photons. They compare these simulations to the actual observations and find dispersal by high-energy stellar photons can explain the observations, and hence cannot be excluded as a possibility.

“ ̽��ֱ��simultaneous measurement of all four lines by JWST proved crucial to pinning down the properties of the wind and helped us to demonstrate that significant amounts of gas are being dispersed,” said Sellek.

To put it into context, the researchers calculate that the mass dispersing every year is equivalent to that of the moon! These results will be published in a companion paper, currently under review at the Astronomical Journal.

̽��ֱ��[Ne II] line was discovered towards several planet-forming discs in 2007 with the Spitzer Space Telescope and soon identified as a tracer of winds by team member Professor Ilaria Pascucci at the ̽��ֱ�� of Arizona; this transformed research efforts focused on understanding disc gas dispersal. Now the discovery of spatially resolved [Ne II] - as well as the first detection of [Ar III] - using the James Webb Space Telescope, could become the next step towards transforming our understanding of this process.

̽��ֱ��implications of these findings offer new insights into the complex interactions that lead to the dispersal of the gas and dust critical for planet formation. By understanding the mechanisms behind disc dispersal, scientists can better predict the timelines and environments conducive to the birth of planets. ̽��ֱ��team's work demonstrates the power of JWST and sets a new path for exploring planet formation dynamics and the evolution of circumstellar discs.

Reference:
Naman S Bajaj et al. ‘JWST MIRI MRS Observations of T Cha: Discovery of a Spatially Resolved Disk Wind.’ ̽��ֱ��Astronomical Journal (2024). DOI: 10.3849/1538-3881/ad22e1

Adapted from a ̽��ֱ�� of Leicester press release.

̽��ֱ��winds that help to form planets in the gaseous discs of early solar systems have been imaged for the first time by the James Webb Space Telescope (JWST) using the noble gases neon and argon.

ESO/M. Kornmesser

Artist's impression of the surroundings of the supermassive black hole in NGC 3783

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Exceptional scientists elected as Fellows of the Royal Society 2023

lw355 — Wed, 10 May 2023 10:52:57 +0000

̽��ֱ��Royal Society is a self-governing Fellowship of many of the world’s most distinguished scientists drawn from all areas of science, engineering and medicine.

̽��ֱ��Society’s fundamental purpose, as it has been since its foundation in 1660, is to recognise, promote and support excellence in science and to encourage the development and use of science for the benefit of humanity.

This year, a total of 80 researchers, innovators and communicators from around the world have been elected as Fellows of the Royal Society for their substantial contribution to the advancement of science. These include 59 Fellows, 19 Foreign Members and two Honorary Fellows.

Sir Adrian Smith, President of the Royal Society said: “I am delighted to welcome our newest cohort of Fellows. These individuals have pushed forward the boundaries of their respective fields and had a beneficial influence on the world beyond. This year’s intake have already achieved incredible things, and I have no doubt that they will continue to do so. I look forward to meeting them and following their contributions in future.”

̽��ֱ��Fellows and Foreign Members join the ranks of Stephen Hawking, Isaac Newton, Charles Darwin, Albert Einstein, Lise Meitner, Subrahmanyan Chandrasekhar and Dorothy Hodgkin.

̽��ֱ��Cambridge Fellows are:

Professor Cathie Clarke FRS

Professor of Theoretical Astrophysics, Institute of Astronomy, and Fellow of Clare College

Clarke studies astrophysical fluid dynamics, including accretion and protoplanetary discs and stellar winds. She was the first to demonstrate how protoplanetary disc formation around low-mass young stars is determined by their radiation field. In 2017 she became the first woman to be awarded the Eddington Medal by the Royal Astronomical Society and in 2022 she became director of the Institute of Astronomy.

She said: “It's a great honour to join the many Cambridge astrophysicists who have held this title. I would like to particularly pay tribute to the many junior colleagues, PhD students and postdocs who have contributed to my research.”

Professor Christopher Jiggins FRS

Professor of Evolutionary Biology (2014), Department of Zoology, and Fellow of St John's College

Jiggins studies adaption and speciation in the Lepidoptera (butterflies and moths). In particular he is interested in studying how species converge due to mimicry as a model for understanding the predictability of evolution and the genetic and ecological causes of speciation. He demonstrated the importance of hybridisation and movement of genes between species in generating novel adaptations. He also works on the agricultural pest cotton bollworm and carries out genomic studies of the insect bioconversion species, black soldier fly.

He said: “I am amazed and delighted to receive this honour, and would thank all the amazing students, and postdocs that I have been lucky enough to work with over the years.”

Dr Philip Jones FRS

Senior Group Leader, Wellcome Sanger Institute and Professor of Cancer Development, ̽��ֱ�� of Cambridge, and Fellow of Clare College

Jones studies how normal cell behaviour is altered by mutation in aging and the earliest stages of cancer development. He focuses on normal skin and oesophagus, which become a patchwork of mutant cells by middle age. He has found that different mutations can either promote or inhibit cancer development giving hope of new ways to prevent cancer in the future. He is also a Consultant in Medical Oncology at Addenbrooke’s Hospital in Cambridge.

He said: “I am delighted to be elected to the Fellowship of the Royal Society. This honour is a tribute to the dedication of my research team and collaborators and support of my mentors and scientific colleagues over many years.”

Dr Lori Passmore FRS

Group Leader, Structural Studies Division, MRC Laboratory of Molecular Biology, and Fellow of Clare Hall

Passmore a cryo-electron microscopist and structural biologist who works at the Medical Research Council (MRC) Laboratory of Molecular Biology and at the ̽��ֱ�� of Cambridge. She is known for her work on multiprotein complexes involved in gene expression and the development of new supports for cryo-EM studies. She also studies the molecular mechanisms underlying Fanconi anemia, a rare genetic disease resulting in an impaired response to DNA damage.

She said: “I am so honoured to be recognised alongside such an exceptional group of scientists. I am grateful to all the trainees, collaborators and colleagues whom I have worked with over the past years - science is truly collaborative and this is a recognition of all the courageous work of many people.”

Professor Peter Sewell FRS

Professor of Computer Science, Department of Computer Science and Technology, and Fellow of Wolfson College

Sewell’s research aims to put the engineering of the real-world computer systems that we all depend on onto better foundations, developing techniques to make systems that are better-understood, more robust and more secure. He and his group are best known for their work on the subtle relaxed-memory concurrency behaviour and detailed sequential semantics of processors and programming languages. He co-leads the CHERI cybersecurity project, for which his team have established mathematically-proven security properties of Arm's Morello industrial prototype architecture.

He said: “This honour is a testament to the work of many excellent colleagues over the years, without whom none of this would have been possible.”

Professor Ivan Smith FRS

Professor of Geometry, Centre for Mathematical Sciences, and Fellow of Caius College

Smith is a mathematician who deals with symplectic manifolds and their interaction with algebraic geometry, low-dimensional topology and dynamics. In 2007, he received the Whitehead Prize for his work in symplectic topology, highlighting the breadth of applied techniques from algebraic geometry and topology, and in 2013 the Adams Prize.

He said: “I am surprised, delighted and hugely honoured to be elected a Fellow of the Royal Society. I’ve been very fortunate to work in a rapidly advancing field, learning it alongside many inspirational and generous collaborators, who should definitely share this recognition.”

Professor William Sutherland CBE FRS

Miriam Rothschild Chair of Conservation Biology, Department of Zoology and Professorial Fellow of St Catharine’s College

Sutherland is a conservation scientist who is interested in improving the processes by which decisions are made. This has involved horizon scanning to identify future issues to reduce the surprises of future developments. His main work has been the industrial-scale collation of evidence to determine which interventions are effective and which are not and then establishing processes for embedding evidence in decision making. He has developed a free, online resource, Conservation Evidence, summarising evidence for the effectiveness of conservation actions to support anyone making decisions about how to maintain and restore biodiversity and an open access book Transforming Conservation: a practical guide to evidence and decision making.

He said: “I am delighted that our work on the means of improving decision making in conservation and elsewhere has been recognised in this way and thank my numerous collaborators.”

Seven outstanding Cambridge researchers have been elected as Fellows of the Royal Society, the UK’s national academy of sciences and the oldest science academy in continuous existence.

These individuals have pushed forward the boundaries of their respective fields and had a beneficial influence on the world beyond

Sir Adrian Smith, President of the Royal Society

Courtesy of ̽��ֱ��Royal Society

̽��ֱ��Royal Society, London

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Giant planets around young star raise questions about how planets form

sc604 — Mon, 15 Oct 2018 11:01:28 +0000

̽��ֱ��system has also set a new record for the most extreme range of orbits yet observed: the outermost planet is more than a thousand times further from the star than the innermost one, which raises interesting questions about how such a system might have formed.

̽��ֱ��star is just two million years old – a ‘toddler’ in astronomical terms – and is surrounded by a huge disc of dust and ice. This disc, known as a protoplanetary disc, is where the planets, moons, asteroids and other astronomical objects in stellar systems form.

̽��ֱ��star was already known to be remarkable because it contains the first so-called hot Jupiter - a massive planet orbiting very close to its parent star – to have been discovered around such a young star. Although hot Jupiters were the first type of exoplanet to be discovered, their existence has long puzzled astronomers because they are often thought to be too close to their parent stars to have formed in situ.

Now, a team of researchers led by the ̽��ֱ�� of Cambridge have used the Atacama Large Millimeter/submillimeter Array (ALMA) to search for planetary ‘siblings’ to this infant hot Jupiter. Their image revealed three distinct gaps in the disc, which, according to their theoretical modelling, were most likely caused by three additional gas giant planets also orbiting the young star. Their results are reported in ̽��ֱ��Astrophysical Journal Letters.

̽��ֱ��star, CI Tau, is located about 500 light years away in a highly-productive stellar ‘nursery’ region of the galaxy. Its four planets differ greatly in their orbits: the closest (the hot Jupiter) is within the equivalent of the orbit of Mercury, while the farthest orbits at a distance more than three times greater than that of Neptune. ̽��ֱ��two outer planets are about the mass of Saturn, while the two inner planets are respectively around one and 10 times the mass of Jupiter.

̽��ֱ��discovery raises many questions for astronomers. Around 1% of stars host hot Jupiters, but most of the known hot Jupiters are hundreds of times older than CI Tau. “It is currently impossible to say whether the extreme planetary architecture seen in CI Tau is common in hot Jupiter systems because the way that these sibling planets were detected - through their effect on the protoplanetary disc – would not work in older systems which no longer have a protoplanetary disc,” said Professor Cathie Clarke from Cambridge’s Institute of Astronomy, the study’s first author.

According to the researchers, it is also unclear whether the sibling planets played a role in driving the innermost planet into its ultra-close orbit, and whether this is a mechanism that works in making hot Jupiters in general. And a further mystery is how the outer two planets formed at all.

“Planet formation models tend to focus on being able to make the types of planets that have been observed already, so new discoveries don’t necessarily fit the models,” said Clarke. “Saturn mass planets are supposed to form by first accumulating a solid core and then pulling in a layer of gas on top, but these processes are supposed to be very slow at large distances from the star. Most models will struggle to make planets of this mass at this distance.”

̽��ֱ��task ahead will be to study this puzzling system at multiple wavelengths to get more clues about the properties of the disc and its planets. In the meantime, ALMA – the first telescope with the capability of imaging planets in the making – will likely throw out further surprises in other systems, re-shaping our picture of how planetary systems form.

̽��ֱ��research has been supported by the European Research Council.

Reference:
C.J. Clarke et al. ‘High resolution millimetre imaging of the CI Tau protoplanetary disc – a massive ensemble of protoplanets from 0.1 – 100 AU.’ ̽��ֱ��Astrophysical Journal Letters (2018). DOI: 10.3847/2041-8213/aae36b

Inset image: Synthesized image of the CI Tau continuum observation.

Researchers have identified a young star with four Jupiter and Saturn-sized planets in orbit around it, the first time that so many massive planets have been detected in such a young system.

Planet formation models tend to focus on being able to make the types of planets that have been observed already, so new discoveries don’t necessarily fit the models.

Cathie Clarke

Amanda Smith, Institute of Astronomy

Artist's impression of CI Tau

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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