NITheP WITS node seminar
"Planet Formation in Dense Star Clusters"
to be presented by Dr. Henry Throop (University of Pretoria)
http://www.nithep.ac.za/4hu.htm
A presentation on the first cosmic explosions and how the Universe started to make heavy elements, by Monash University's Professor Alexander Heger from the Faculty of Science, School of Mathematical Science.
Astronomy - State of the Art - Life in the UniverseChris Impey
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the potential for life in the universe is covered, including extreme life on Earth, the Drake equation and SETI
A presentation on the first cosmic explosions and how the Universe started to make heavy elements, by Monash University's Professor Alexander Heger from the Faculty of Science, School of Mathematical Science.
Astronomy - State of the Art - Life in the UniverseChris Impey
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the potential for life in the universe is covered, including extreme life on Earth, the Drake equation and SETI
Astronomy - State of the Art - GalaxiesChris Impey
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the properties of galaxies are discussed, including supermassive black holes and dark matter.
NITheP WITS node Seminar by Dr Dr. Roland Cristopher F. Caballar (NITheP/UKZN)
TITLE: "One-Dimensional Homogeneous Open Quantum Walks"
ABSTRACT: In this talk, we consider a system undergoing an open quantum walk on a one-dimensional lattice. Each jump of the system between adjacent lattice points in a given direction corresponds to a jump operator, with these jump operators either commuting or not commuting. We examine the dynamics of the system undergoing this open quantum walk, in particular deriving analytically the probability distribution of the system, as well as examining numerically the behavior of the probability distribution over long time steps. The resulting distribution is shown to have multiple components, which fall under two general categories, namely normal and solitonic components. The analytic computation of the probability distribution for the system undergoing this open quantum walk allows us to determine at any instant of time the dynamical properties of the system.
Astronomy - State of the Art - GalaxiesChris Impey
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the properties of galaxies are discussed, including supermassive black holes and dark matter.
NITheP WITS node Seminar by Dr Dr. Roland Cristopher F. Caballar (NITheP/UKZN)
TITLE: "One-Dimensional Homogeneous Open Quantum Walks"
ABSTRACT: In this talk, we consider a system undergoing an open quantum walk on a one-dimensional lattice. Each jump of the system between adjacent lattice points in a given direction corresponds to a jump operator, with these jump operators either commuting or not commuting. We examine the dynamics of the system undergoing this open quantum walk, in particular deriving analytically the probability distribution of the system, as well as examining numerically the behavior of the probability distribution over long time steps. The resulting distribution is shown to have multiple components, which fall under two general categories, namely normal and solitonic components. The analytic computation of the probability distribution for the system undergoing this open quantum walk allows us to determine at any instant of time the dynamical properties of the system.
"Curved extra-dimensions" by Nicolas Deutschmann (Institut de Physique Nuclea...Rene Kotze
Abstract: Universal Extra-Dimension models provide a promising framework for model building as they naturally have rich phenomenological implications, not the least of which is a potential natural dark matter candidate. This candidate takes the form of a Kaluza-Klein excitation of some neutral Standard Model field whose stability is ensured by some isometry of the extra-space. In five dimensions, such a symmetry has to be enforced in an ad-hoc fashion, which is why six-dimensional models have started prompting the interest of model builders. If flat 6D models have been thoroughly surveyed and studied, the realm of curved extra-dimensional models remains mostly uncharted. This talk aims at showing the features of extra dimensional models on a curved background, focusing mostly on positively curved spaces. I will show that the main difficulty for constructing a convincing model revolves around the issue of chiral fermions in the 4D effective theory and how it can be overcome by the addition of a new gauge field which has to be hidden from experimental reach by a symmetry breaking. After going over the phenomenological consequences of a model built using these ingredients, I will briefly review hyperbolic extra-dimensions, for which several problems appearing on positively curved spaces are solved or alleviated.
Wits Node Seminar: Dr Sunandan Gangopadhyay (NITheP Stellenbosch)
TITLE: Path integral action of a particle in the noncommutative plane and the Aharonov-Bohm effect
NITheP UKZN Seminar: Prof. Alexander Gorokhov (Samara State University, Russi...Rene Kotze
NITheP UKZN Seminar: Prof. Alexander Gorokhov (Samara State University, Russia)
TITLE: Dynamical Groups, Coherent States and Some of their Applications in Quantum Optics and Molecular Spectroscopy
Stochastic Gravity in Conformally-flat SpacetimesRene Kotze
The National Institute for Theoretical Physics, and the Mandelstam Institute for Theoretical Physics, School of Physics, would like to invite to its coming talk in the theoretical physics seminar series, entitled:
"Stochastic Gravity in Conformally-flat Spacetimes"
to be presented by Prof. Hing-Tong Cho (Tamkang University, Taiwan)
Abstract: The theory of stochastic gravity takes into account the effects of quantum field fluctuations onto the classical spacetime. The essential physics can be understood from the analogous Brownian motion model. We shall next concentrate on the case with conformally-flat spacetimes. Our main concern is to derive the so-called noise kernels. We shall also describe our on-going program to investigate the Einstein-Langevin equation in these spacetimes.
Dates: Tuesday, 17th February 2015
Venue: The Frank Nabarro lecture theatre, P216
Time: 13.20 - 14.10 - TODAY
Presentation to Bangkok Scientifique Meetup group on August 27, 2014.
Overview of galaxies and introduction to dark matter, spanning the Milky Way to the Local Group to rich clusters of galaxies. Simple galaxy morphologies, various ways in which we see the gravitational influence of dark matter.
WE LIVE IN A STRANGE SOLAR SYSTEM
There's a lot to wonder about space. The fact is we don't know all the answers about it. We know it's vast and beautiful, but we're not really sure how vast (or how beautiful, for that matter).
Some of the things we do know, however, are downright mind-boggling. Below, I've collected some of the most amazing facts about space, so when you look up at the stars you can be ever more wowed by what you're looking at.
1. Neutron stars can spin at a rate of 600 rotations per second
Neutron stars are one of the possible evolutionary end-points of high mass stars. They're born in a core-collapse supernova star explosion and subsequently rotate extremely rapidly as a consequence of their physics. Neutron stars can rotate up to 60 times per second after born. Under special circumstances, this rate can increase to more than 600 times per second.
2. Space is completely silent
Sound waves need a medium to travel through. Since there is no atmosphere in the vacuum of space, the realm between stars will always be eerily silent.
That said, worlds with atmospheres and air pressure do allow sound to travel, hence why there's plenty of noise on Earth and likely other planets as well.
3. There is an uncountable number of stars in the known universe
We basically have no idea how many stars there are in the universe. Right now we use our estimate of how many stars there are in our own galaxy, the Milky Way. We then multiply that number by the best guesstimate of the number of galaxies in the universe. After all that math, NASA can only confidently say that say there all zillions of uncountable stars. A zillion is any uncountable amount.
An Australian National University study put their estimate at 70 sextillion. Put another way, that's 70,000 million million million
4. The Apollo astronauts' footprints on the moon will probably stay there for at least 100 million years
Since the moon doesn't have an atmosphere, there's no wind or water to erode or wash away the Apollo astronauts' mark on the moon. That means their footprints, roverprints, spaceship prints, and discarded materials will stay preserved on the moon for a very long time.
They won't stay on there forever, though. The moon still a dynamic environment. It's actually being constantly bombarded with "micrometeorites," which means that erosion is still happening on the moon, just very slowly.
5. 99 percent of our solar system's mass is the sun
Our star, the sun, is so dense that it accounts for a whopping 99 percent of the mass of our entire solar system. That's what allows it to dominate all of the planets gravitationally.
Technically, our sun is a "G-type main-sequence star" which means that every second, it fuses approximately 600 million tons of hydrogen to helium. It also converts about 4 million tons of matter to energy as a byproduct.
When the sun dies, it will become a red giant and envelop the Earth and everything on it. But don't worry: That won't happen for another
Professor’s Questions Set 5Provide comprehensive answers to th.docxwkyra78
Professor’s Questions Set 5
Provide comprehensive answers to the following questions. Remember to support your arguments where necessary by websites and pictures.
Chapter 7 and 8 Readings
1. Why is Jupiter so much richer in hydrogen and helium than Earth?
2. Why do astronomers conclude that none of the Jovian planets’ rings can be left over from the formation of the planets?
3. How can Jupiter have a liquid interior and not have a definite liquid surface?
4. Why are Uranus and Neptune respectively green-blue and blue?
5. What evidence indicates that catastrophic impacts have occurred in the solar system’s past?
6. Why do astronomers refer to carbonaceous chondrites as unmodified or “primitive” materials?
7. What evidence indicates that the asteroids are mostly fragments of larger bodies?
8. What is the difference between condensation and accretion?
9. Why does the solar nebula theory predict that planetary systems are common?
10. Why is the evidence of “hot Jupiters” puzzling? What is the current hypothesis of how they formed?
Michael Seeds
Dana Backman
Chapter 8
Origin of the Solar System and Extrasolar Planets
*
The solar system is our home in the universe. As humans are an intelligent species, we have the right and the responsibility to wonder what we are. Our kind has inhabited this solar system for at least a million years. However, only within the last hundred years have we begun to understand what a solar system is.
*
You are linked through a great chain of origins that leads backward through time to the first instant when the universe began 13.7 billion years ago.The gradual discovery of the links in that chain is one of the most exciting adventures of the human intellect.
The Great Chain of Origins
*
Earlier, you have studied some of that story:Origin of the universe in the big bangFormation of galaxiesOrigin of starsProduction of the chemical elementsHere, you will explore further and consider the origin of planets.
The Great Chain of Origins
*
By the time the universe was three minutes old, the protons, neutrons, and electrons in your body had come into existence. You are made of very old matter.
The History of the Atoms in Your Body
*
Although those particles formed quickly, they were not linked together to form the atoms that are common today.Most of the matter was hydrogen and about
25 percent was helium. Very few of the heavier atoms were made in
the big bang.
The History of the Atoms in Your Body
*
Although your body does not contain helium, it does contain many of those ancient hydrogen atoms that have remained unchanged since the universe began.
The History of the Atoms in Your Body
*
During the first few hundred million years after the big bang, matter collected to form galaxies containing billions of stars. You have learned how nuclear reactions inside stars combine low-mass atoms, su ...
Hands on instructions for NITheCS August mini - school Rene Kotze
For all students participating in the NITheCS Mini-School (continuing tomorrow 17 August 2021) - please follow these simple instructions to setup the software environment for the hands-on session for tomorrow.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Instructions for Submissions thorugh G- Classroom.pptx
"Planet Formation in Dense Star Clusters" presented by Dr. Henry Throop (University of Pretoria)
1. Henry Throop!!
University of Pretoria !
&!
Planetary Science Institute!
Tucson, Arizona!
!
Collaborators:!
!
John Bally (U. Colorado)!
Nickolas Moeckel (Cambridge)!
!
!
University of the Witwatersrand, Johannesburg
April 8, 2014
Planet Formation in
Dense Star Clusters
9. Orion Star Forming Region!
!
• Closest bright star-forming region to Earth!
• Distance ~ 1500 ly!
• Age ~ 10 Myr!
• Radius ~ few ly!
• Mean separation ~ 104 AU
13. • Largest Orion disk: 114-426, D ~ 1200 AU !
• Dust grains in disk are grey, and do not redden light as they extinct it!
• Dust grains have grown to a few microns or greater in < 1 Myr!
Largest Orion disk: 114-426, diameter 1200 AU !
14. Star Formation
17
1961 view:!
“Whether we've ever seen a star form or not is still debated. The next
slide is the one piece of evidence that suggests that we have. Here's
a picture taken in 1947 of a region of gas, with some stars in it. And
here's, only two years later, we see two new bright spots. The idea is
that what happened is that gravity has...”!
!
Richard Feynman, Lectures on Physics
2000s view: !
Infrared detectors have allowed us to directly see thousands of star
forming -- nearly everywhere that we see an IR source. 1000+ young
stars in Orion alone.!
!
Whether we’ve ever seen a planet form or not is the current question!
Star Cluster Formation Star Formation Planet Formation
15. Circumstellar Disks In
Orion
• 100+ disks directly observed, diameters 100-1200 AU!
• 80%+ of stars in Orion show evidence for having disks!
!
These stars are too distant and young to directly search for planets… but we
want to study the environment and processes to understand the planets which
would be produced in these dense clusters -- and therefore throughout the
galaxy.
16. Regions of Star Formation
Large Dense Clusters:!
Orion
Small Sparse Clusters: !
Taurus
# of stars 103
104
(Orion)
10 -
OB stars Yes No
Distance 450 pc (Orion) 140 pc (Taurus)
Fraction of stars that
form here
70-90% 10-30%
Distance between
stars
5000 AU 20,000 AU
Dispersal lifetime Few Myr
% of stars with disks > 80%
Orion: Hot,
Dense,
Massive!
!
Most stars
form in large
clusters.
Taurus:!
Dark, Small,
Cold!
!
Most planet
formation
models study
small clusters.
17. Where did our Sun form?
• We don’t know! The Sun is an isolated star today.!
• 90% of stars formed in clusters!
• But just 1% remain in clusters now.!
• Stellar motions can be back-integrated for 100 Myr, but not 10 Gyr.!
• 60Fe isotopes suggest Sun was born in a large cluster, few pc away
from a supernova
18. Planet Formation - Classical Model
21
!
Cloud core collapses due to self-gravity!
10,000 AU, 1 Msol!
!
!
!
Disk flattens; grains settle to midplane!
Planet cores grow!
Disk Mass: ‘Minimum Mass Solar Nebula’!
MMSN = 0.01 Msol!
Star Mass: ~ 1 Msol!
!
Terrestrial planets form!
Jovian planets accrete gas!
!
!
Disk disperses!
Solar System complete after ~ 5-10 Myr!
! W. Hartmann
19. Work we have done involves ...!
!
!
– UV photo-evaporation from massive stars!
!
!
– Interaction with cluster gas!
!
!
– Close stellar encounters!
!
!
– Organics and UV photolysis from massive stars
How does Cluster Environment affect Disk
Evolution?
Throop 2000; Bally et al 2005; Throop & Bally 2005; Throop & Bally 2008; Moeckel & Throop 2009;
Throop & Bally 2010; Pichardo et al 2010; Throop 2011.
20.
21. Bondi-Hoyle Accretion
• Cool molecular H2 from cluster ISM accretes onto disks!
• Accretion flow is onto disk, not star.!
• Accretion is robust against stellar winds, radiation pressure, turbulence.!
• This accretion is not considered by existing Solar System formation
models!!
1 MMSN = 1 ‘Mimimum Mass Solar Nebula’ = 0.01 MSol
26
Accretion radius ~ 1000 AU Accretion rate ~ 10-8 M! yr-1
Accretion rate ~ 1 MMSN / Myr
2 RB
24. 29
Following trajectory of one star of 3000 from N-body simulation...
BH Accretion: History of individual star
25. • Star+disk accretes 5% of own mass in 5 Myr.!
• Accretion is episodic!
– Highest at core: High velocity but high
density
BH Accretion: History of individual star
26. Results of N-Body sims
!
!
• Typical mass accreted by disks surrounding
Solar-mass stars is 1 MMSN per Myr!
• Accretion occurs for several Myr, until cluster
disperses or cloud is ionized!
27. Observations of accretion in young stars
• Accretion is seen onto hundreds
young stars in molecular clouds.!
!
• Varies with stellar mass: dM/dt ~ M2 !
!
• Accretion is ~ 0.01 M! Myr-1 for 1M!!
!
• Source of the accretion is unknown!
28. Observations of accretion in young stars
Text
We propose: accretion onto young stars may be due
to ISM accretion onto their disks
• Accretion is seen onto hundreds
young stars in molecular clouds.!
!
• Varies with stellar mass: dM/dt ~ M2 !
!
• Accretion is ~ 0.01 M! Myr-1 for 1M!!
!
• Source of the accretion is unknown!
Throop & Bally 2008
29. Consequences of Tail-End Accretion
• Disks may accrete many times their own mass in a few Myr. !
• Disks may still be accreting gas at >5 Myr, after
planetesimals form, and maybe after giant planet cores form.!
• Disk may be ‘rejuvenated’ after being partially lost!
• Final composition of disk may be different than star!
– There may be no ‘Solar Nebula Composition’!
– Isotopes may not be diagnostic of solar vs. extrasolar material
34
Throop & Bally 2008, AJ!
30. Accretion of ‘polluted’ ISM
• Stars of same age/position/
type in Orion show metallicities
that vary by up to 10x in Fe, O,
Si, C!
• Could stars have accreted
metallic ‘veneers’ by passing
through nearby molecular
clouds, contaminated with
supernova ejecta?!
• 20 MSol SN produces 4 MSol O
35
Late accretion may cause the composition of a stars and their
disks to be different! There may be no ‘Solar Nebula
Composition.’ Even in our Solar System, there is a lot of
variation : isotope ratios.
Cunha et al 2000
46. Jupiter vs. the Sun
If the Sun and Jupiter both formed from the same cloud,
why are they made of such different stuff?
47. Jupiter’s Atmosphere
• Mass Spectrometer aboard Galileo Probe!
• Measured to ~20 bars!
• Found Jupiter atmosphere to be 2-6x
higher in metals vs. Sun, when normalized
to H.!
– C, S, Ar, Kr, Xe!
– All these are stable and long-lived: enrichment
was a complete surprise!!
– vesc = 45 km/sec!
• GPMS likely passed through ‘dry spot’ on
Jupiter.!
• Several explanations proposed:!
– Noble gases may be enhanced by
freeze-out onto ices. But requires
extremely cold disk < 30K (Guillot,
Hersant, Lunine).!
– Jupiter may be H-depleted, and S
could be a better reference (Lodders
2004). 53
48. Jupiter ‘Polluted Accretion’ model
We propose a crazy idea for Jupiter’s composition:!
!
!
1. Solar System forms in a large star cluster.!
!
2. Massive stars pollute ISM with heavy elements.!
SNs and massive stellar winds convert H into C, N, S, etc.!
!
3. ‘Pollution’ from massive stars is accreted onto Jupiter.!
Accretion from ISM -> Solar Nebula Disk -> Jupiter!
Sun’s metallicity is not affected, only Jupiter’s
54
Throop & Bally 2010 (Icarus)
50. Jupiter ‘Polluted Accretion’ model
• Data: Galileo Probe!
• Model: Accretion from ISM!
– 87% Solar nebula material!
– 9% Stellar winds from 20 M! star (provides C, N)!
– 4% SN from 25 M! star (provides S, Ar, Kr, Xe)!
– Requires total of ~0.13 MJ of accretion to explain Jupiter’s
current metallicity.!
– Bondi-Hoyle accretion supplies 10 MJ of accretion per Myr --
plenty of mass, and with the right chemistry!
51. • Evidence for a heterogeneous nebula is not new!!
!
!
!
!
!
!
!
!
!
!
• Heterogeneity between Jupiter and Sun is a natural extension
to that already observed in meteorites (but much bigger).
Jupiter ‘Polluted Accretion’ model
Dauphas et al 2002:!
“'Mb isotope abundances were heterogeneously distributed in
the Solar System’s parental molecular cloud, and the large-
scale variations we observed were inherited from the
interstellar environment where the Sun was born.”
Ranen & Jacobsen 2006:!
“There are resolvable differences between the Earth and
carbonaceous chondrites that are most likely caused by
incomplete mixing of r- and s-process nucleosynthetic
components in the early Solar System.”
Trinquier et al 2007:!
“Preservation of the 54Cr heterogeneity in space and time
(several Myr) motivates us to speculate that late stellar input(s)
could have been significant contributions to inner nebular Cr
reservoirs...”
Throop & Bally 2010
52. SPH Sims: BH Acc onto 100 AU disk
58
10,000 years!
0.01 solar masses!
v ~ 1 km/sec!
!
!
Moeckel & Throop
2009 (AJ)
53. Close Stellar Encounters
• Typical distances today ~ 10,000 AU!
!
• C/A strips disks to 1/3 the closest-
approach distances (Hall et al 1996)!
!
• Question: What is the minimum C/A
distance a disk encounters as it moves
through the cluster for several Myr?
HST 16
200 AU diameter
! 0.3 ly to O star
54. Close Approach History - Typical 1 M! Star
• Star has 5 close approaches at < 2000 AU.!
• Closest encounter is 300 AU at 8 Myr!
• Too late to do any damage
Throop & Bally 2008;
also Adams et al
2006
55.
56.
57. Photo-Evaporation in Orion
• Disks surrounding solar-type stars are
heated by UV-bright stars.!
!
• Gas is heated and removed from disk on
1-10 Myr timescales.!
!
• If disk is removed quickly, we can’t form
planets!!
!
59. Effects of Photo-Evaporation on Planet
Formation
Solar System-like disks are removed in
1-10 Myr. Effects on...!
!
• Kuiper Belt (> 40 AU): UV removes
volatiles and small grains. Kuiper belts
and Oort clouds may be rare! Or, they
may be formed easily and quickly thru
triggering.!
!
• Giant Planets (5-40 AU): Gas is rapidly
removed from disk: If you want to build
Jupiters in Orion, do it quickly! (e.g.,
Boss models).!
!
• Terrestrial Planets (1-5 AU): Safe
against photo-evaporation since it’s hard
to remove gas from 1 AU.
60. Flux Received onto a Disk vs. Time
Punctuated equilibrium
• Flux received by disk varies by 1000x as it moves
through the cluster : Freeze-Broil-Freeze-Broil!
• Peak flux approaches 107 G0.!
• Most of the flux is deposited during brief but intense
close encounters with core.!
• There is no ‘typical UV flux.’!
• Photo-evap models assume steady UV flux. But if UV is
not steady, then other processes (viscous, grain growth)
can dominate at different times and dramatically change
the disk. Throop, in prep
61. Planet Formation - Classical Model
67
!
Cloud core collapses due to self-gravity!
10,000 AU, 1 M!!
!
!
!
!
Disk flattens; grains settle to midplane!
Planet cores grow!
!
!
Terrestrial planets form!
Jovian planets accrete gas!
!
!
Disk disperses!
Solar System complete after ~ 5-10 Myr!
!
!
W. Hartmann
62. Planet Formation - Classical Model
68
Cloud is heterogeneous and polluted!
Cloud core collapses due to self-gravity!
10,000 AU, 1 M!!
Cloud inherits composition from nearby SN!
!
!
!
Disk flattens; grains settle to midplane!
Planet cores grow!
Disk is photo-evaporated by UV stars!
Disk is injected with 60Fe from nearby SNs!
Terrestrial planets form!
Jovian planets accrete gas!
(Disk is stripped due to close approaches)!
Disk accretes gas from environment!
Disk disperses and is photo-evaporated!
Solar System complete after ~ 5-10 Myr!
!
!
W. Hartmann
modified
63. Randomness as a factor in Disk
Evolution
• Disk outcome depends not just on its ingredients, but on its
individual history.!
• If we try to predict what will form around individual stars or disks,
we’re doomed to fail!!
• Disk systems are individuals, they interact with their environment,
and random events and timing matter:!
– How much stuff was photo-evaporated by UV?!
– How hot was the disk, and how viscous, and how did its
surface density evolve?!
– How strong, when, and how many times did UV hit it?!
– What SN events occurred? How did they contaminate the
disk?!
– What molecular clouds did disk pass through? What material
was accreted? Onto inner disk, or outer?!
– Do planetesimals form before, or after, photo-evaporation
starts?!
• There is no ‘typical’ disk, and no ‘typical’ planetary system, even if
starting from the same initial disk structure and ingredients.