George Herbig and Early Stellar Evolution

267 Pages·13.082 MB·English

by  Reipurth B.

G H
EORGE ERBIG
and Early Stellar Evolution
Bo Reipurth
Institute for Astronomy Special Publications No. 1
George Herbig in 1960
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G H
EORGE ERBIG
and Early Stellar Evolution
—————————————————————–
Bo Reipurth
Institute for Astronomy
University of Hawaii at Manoa
640 North Aohoku Place
Hilo, HI 96720
USA
.
Dedicated to Hannelore Herbig
(cid:13)c 2016 by Bo Reipurth
Version 1.0 – April 19, 2016
CoverImage: The HH 24 complexin the Lynds 1630 cloud in Orion was discov-
ered by Herbig and Kuhi in 1963. This near-infrared HST image shows several
collimated Herbig-Haro jets emanating from an embedded multiple system of
T Tauri stars. Courtesy Space Telescope Science Institute.
This book can be referenced as follows:
Reipurth, B. 2016, http://ifa.hawaii.edu/SP1
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FOREWORD
I first learned about George Herbig’s work when I was a teenager. I grew up in
Denmark in the 1950s, a time when Europe was healing the wounds after the
ravages of the Second World War. Already at the age of 7 I had fallen in love
with astronomy, but information was very hard to come by in those days, so
I scraped together what I could, mainly relying on the local library. At some
point I was introduced to the magazine Sky and Telescope, and soon invested
my pocket money in a subscription. Every month I would sit at our dining
roomtable with a dictionary and work my way through the latest issue. In one
issue I read about Herbig-Haro objects, and I was completely mesmerized that
these objects could be signposts of the formation of stars, and I dreamt about
some day being able to contribute to this field of study. As fate would have it,
Herbig-Haro objects did become my main focus after I became a professional
astronomer. But it was not until Iwas 40 that I gotto meet and talkto George
Herbig in person, when he attended a conference I was organizing at ESO in
Germany. Afterwards we had occasional correspondence.
After Herbig retired from the University of California in 1987, he moved to
Honolulu and took up a professorship at the Institute for Astronomy at the
University of Hawaii in order to focus exclusively on his research. Later, in
2001, I also moved to the University of Hawaii, and soon we developed strong
scientific andpersonalties, meeting frequentlyforlunchordinner totalkabout
the latest results in star formation.
During the last year of his life, when Herbig’s health started to decline, he
asked me to act as his scientific executor and to take care of his voluminous
writings, documents, notes, letters, and data. Herbig was a highly organized
and disciplined person, and his archives are full of meticulous notes on his
numerous projects, both completed and unfinished, from his entire career. Of
special interest is his carefully kept collection of thousands of letters exchanged
with essentially all of the leading astronomers of the 20th century.
Herbig never wrote a full length memoir, but he left extensive notes and com-
ments about his work and times. And sometime in his mid-seventies, he de-
cided to put together a brief account of his scientific endeavours up to that
time, notes meant only for his family. But shortly before his death, he gave
me a copy of these autobiographical sketches. With the permission of his wife,
Hannelore Herbig, I will throughout the present book cite from this mate-
rial, as well as from many other documents, letters, and extensive notes found
among Herbig’s archives. In doing so, I hope to give voice to Herbig on many
oftheepochal events andscientific results throughout hislife. Writtenby hand
on the cover of his autobiographical notes, Herbig added “... perhaps it may
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prove useful to that hapless soul who has to write my obituary.” Indeed I have
found it very useful, and quotes from Herbig’s various writings will appear in
italics throughout this book. The autobiographical notes are introduced thus:
“For reasons not entirely clear, I have thought it worthwhile to try to put
down a kind of inventory or outline of the various astronomical activities
that I have pursued, and how my involvement in each of them came about –
to the extent that I can remember or reconstruct reasons and motives at this
late date (January 1993). The scornful phrase ‘jack of all trades, master of
none’ has more than once come to my mind, for I recall old-timers speaking
with contempt of colleagues who frittered away their energies on a host of
activities, rather than spending theirlives bearing down hard in a single area.
Probably my uneasiness about the checkered nature of my own career arises
from recollectionof such scornful remarks by conservatives, Paul Merrill and
Joseph Moore in particular, who I heard on such matters in my early days.
Obviously, I did not hew closely to their examples or their admonitions.”
From this brief quote, two of Herbig’s characteristics are evident: his complete
lack of awe over his many and major contributions to science, and his unique
mastery of the written word.
This book attempts to give an overview of the scientific life of George Herbig.
Little will be said about Herbig’s personal life, mainly because scientists gen-
erally live dynamic lives in their minds, while living unremarkable daily lives.
Herbig was no exception, he enjoyed a quiet life, was happily married to his
wife Hannelore, and spent all of his time doing great intellectual voyages. In
the course of these journeys, he nearly singlehandedly built the foundation for
the observational study of infant stars. Almost all papers published today on
young stars rest in some way on the results established by Herbig.
The Danish philosopher Søren Kirkeg˚ard said “We live life forwards, but un-
derstand it backwards”. When new ideas are developed and refined over time,
what in hindsight appears as a gradual but ordered evolution of a subject
towards a correct answer in reality was often a chaotic process, with much
groping in darkness for answers, and with many explorations of blind alleys.
WhileHerbigultimatelysucceeded inestablishing thefoundationsforthemod-
ern view of early stellar evolution, also he from time to time embraced ideas
that he later realized were inconsistent with observations, his own or others.
This self-correcting process is at the heart of scientific progress. To the extent
that such forks in the road are reflected in the literature, I have attempted to
describe the wrong turns.
It should be emphasized that this book is not a general history of how star
formation studies have unfolded over time, and no attempt has been made to
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mention all important papers in the history of the field. The focus here is
on Herbig’s pioneering work, and other studies are discussed only as context
for the development of his ideas, or to show how a subject has later evolved.
Herbig tended to open up a new field, work on it only long enough to establish
thefoundationandthekeyfacts, andthenmoveontonewideasandendeavors,
often leaving it to others to polish the details.
While efforts have been made to write this bookso it is also understandable for
a more general readership, the audience that the book targets is drawn from
researchers and advanced students, who know the terminology of the field of
star formation, and who understand the underlying scientific issues. Other
readers who may wish to first get an overview of the field of star formation
can read the popular-level book by Bally & Reipurth ‘The Birth of Stars and
Planets’ from Cambridge University Press.
Many people have contributed to the present book, for a full list see the Ac-
knowledgements, and I am grateful to all. First and foremost I wish to thank
HanneloreHerbig,whohasbeenindefatigableinansweringmymanyquestions,
in finding photos, and in facilitating my work with Herbig’s major collections
of documents.
Bo Reipurth
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CONTENTS
1 The Budding Astronomer ................................. 1
1.1 Early Years ........................................................ 1
1.2 UCLA and Griffith Observatory .................................... 5
1.3 Assistantship at Lick Observatory .................................. 8
1.4 Alfred Joy ........................................................ 11
1.5 PhD at Berkeley .................................................. 12
1.6 Pasadena, Yerkes, McDonald Observatory ......................... 15
1.7 Lick Observatory .................................................. 19
2 The T Tauri Stars ........................................ 20
2.1 Joy’s 1945 paper .................................................. 20
2.2 RW Aur and V380 Ori ............................................ 21
2.3 Thesis ............................................................ 23
2.4 Are T Tauri Stars Young? ........................................ 25
2.5 Objective-prism and Grism Surveys ............................... 30
2.6 The Herbig-Rao and Herbig-Bell Catalogs ......................... 35
2.7 Spectral Properties of T Tauri Stars ............................... 37
2.8 Lithium ........................................................... 43
2.9 Rotation of Young Stars ........................................... 48
2.10 Radial Velocities and Proper Motions of T Tauri Stars ............ 49
2.11 Variability of T Tauri Stars and Flare Stars........................ 51
2.12 Binarity of T Tauri Stars ......................................... 54
2.13 The Post-T Tauri Problem ........................................ 56
2.14 The Early Solar System ........................................... 61
2.15 Peculiar Young Stars .............................................. 63
2.16 Putting it All Together: Accretion Disks .......................... 70
3 Herbig-Haro Objects ..................................... 73
3.1 Discovery ......................................................... 73
3.2 The Nature of HH Objects ........................................ 76
3.3 Proper Motions ................................................... 82
3.4 The Jet Phenomenon .............................................. 87
4 The Herbig Ae/Be Stars ................................. 91
4.1 Defining Young Intermediate Mass Stars .......................... 91
4.2 Three Herbig Ae/Be Stars ......................................... 94
4.3 Development of the Field .......................................... 98
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5 FUors and EXors ....................................... 102
5.1 The Eruption of FU Orionis ...................................... 102
5.2 The Hertzsprung Symposium ..................................... 102
5.3 The Russell Lecture .............................................. 105
5.4 The Grand Debate ............................................... 109
5.5 The Winds of FUors ............................................. 118
5.6 Triggering the FUor Outbursts ................................... 119
5.7 EX Lupi and the EXors .......................................... 122
6 Clustered Star Formation ............................... 129
6.1 The Orion Nebula Cluster ........................................ 129
6.2 IC 348 ........................................................... 133
6.3 IC 5146 .......................................................... 135
6.4 NGC 1579 ....................................................... 137
6.5 Lynds 988 ....................................................... 138
6.6 IC 1274 .......................................................... 140
7 The Interstellar Medium ................................ 142
7.1 The Diffuse Interstellar Bands .................................... 142
7.2 Absorption Lines of Interstellar Gas ...............................148
7.3 Formation of Interstellar Dust .................................... 150
7.4 Globules ......................................................... 151
7.5 AE Aur .......................................................... 153
7.6 Merope and IC 349 .............................................. 154
8 Molecular Spectroscopy ................................. 157
9 Variable and Exotic Stars ............................... 162
9.1 R Coronae Borealis – A Double Degenerate Merger ............... 162
9.2 S Sagittae – A Cepheid Binary ................................... 164
9.3 VV Puppis – A Cataclysmic Binary .............................. 166
9.4 V Sagittae – A Super-Soft X-ray Source .......................... 167
9.5 FG Sagittae – A Thermal Pulse in a Post-AGB Star .............. 169
9.6 VY Canis Majoris – A Disk Around a Massive Young Star ....... 170
9.7 IX Ophiuchi – A High-Velocity Interloper in Ophiuchus .......... 171
9.8 UV Aurigae – Intercepting Shells from a Carbon Star ............ 172
10 From Astronomer to Professor .......................... 174
11 Instruments and Telescopes ............................. 190
12 Closing Remarks ....................................... 200
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12.1 Administrative Work ............................................ 200
12.2 Awards, Recognitions, Travels ................................... 200
12.3 Impact .......................................................... 201
13 References .............................................. 204
14 Bibliography ............................................ 223
15 Notes ................................................... 240
16 Acknowledgements ..................................... 247
17 Index ................................................... 249