Journal of the International Planetarium Society - Vol. 50, No. 3 September 2021
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Vol. 50, No. 3 September 2021
Journal of the International Planetarium Society
ISSN 2333-9063
September 2021 | Vol. 50, No. 3
ARTICLES
8 STAR OF BETHLEHEM: HOW TO TELL THE ASTRONOMY CORRECTLY By Susanne H. Hoffman
12 JAWAHARLAH NEHRU PLANETARIUM: IN A NEW AVATAR By Pradmod G. Galgali
16 SURFACE VS. VOLUME: NEBULAE, TAKE 2 By Nico Koning & Wolfgang Steffen
18 THE SOUND OF A CHILD REBORN: REVISITING AN OLD FRIEND By Charles Lawson
COLUMNS
6 In Front of the Console Shiloe Fontes
24 Immersive Matters Carolyn Collins Petersen
28 Under the Classdome Mark Percy
30 International News Lars Petersen
38 Tales from Dome Under Tom Callen
44 Mobile News Network Susan Reynolds Button ON THE COVER
48 LIP Service Karrie Berglund 5.3-Day old crescent Moon
50 A Different Point of View Ron Walker Adam Thanz
Captured April 17, 2021, 8:50 p.m. EDT
52 Book Reviews April Whitt Northeast Tennessee, USA
54 Debunking Education Myths Dr. Jenny Shipway Astro-Physics Gran Tourismo 130mm f/6.3
56 Misconception Ahead Dr. Jenny Shipway Sony A7II, ISO 100, 1/20 sec.
62 Technically Speaking Glenn Smith The image was
taken during one of
62 PARTYcles Alex Cherman
our live observing
76 Last Light April Whitt sessions for YouTube
hosted by the Dyer
ADVERTISERS Observatory in
IFC, 34-35, 47, 53, 59 Evans & Sutherland Nashville, TN. We
5 Clark Planetarium were a consortium
of live broadcast
6 SSIA telescopes in
7 Kwon O Chul Astrophotography Tennessee. I
15 Navitar covered East Tennessee from my home. The other
image is by Robin Byrne. You can see me on our
21 SkySkan
deck with the telescope, computer and light on me.
23 Bays Mountain That image was taken in February.
27 Loch Ness Production
During the April viewing, I was supposed to show
33 Bowen a live view of the Moon. Unfortunately, the clouds
40, 61, 63 Spitz/Spitz Creative Media were a real problem. Of course, after I did my first
46 You Can Do Astronomy bit for the broadcast, the skies opened up for a little
while. I captured this image and was able to share
55 Digitalis
it in my second part of the broadcast. The clouds
49 Ash Enterprises came in, but I was OK since I had this image. We
51 Metaspace were commenting on the sharpness of the image
59 ZEISS even with turbulent skies and shooting across our
roof. We were also able to answer a question about
65 American Natural History Museum color on the Moon as this image does reveal some
67 GOTO Inc. subtle color. Serendipity does happen. Or, should I
69 RSACosmos say selendipity?
BC Megastar
September 2021 Vol. 50, No. 3 Planetarian 1
PLANETARIAN CURRENT OFFICERS
Editor PRESIDENT EXECUTIVE SECRETARY
Shiloe Fontes
Flandrau Science Center & Planetarium Kaoru Kimura Patty Seaton
University of Arizona Japan Science Foundation/Science Howard B. Owens Science Center
Tucson, AZ., 85721, USA Museum 9601 Greenbelt Road
editor@ips-planetarium.org 2-1 Kitanomaru-koen Lanham, Maryland 20706 USA
Chiyoda-ku secretary@ips-planetarium.org
Research Editor Tokyo, Japan 102-0091
Julia Plummer +81 3-3212-8506
Dept. of Curriculum & Instruction president@ips-planetarium.org
Pennsylvania State University
University Park, PA 16802
jdp17@psu.edu PAST PRESIDENT TREASURER
Copy Editor Mark SubbaRao Mike Smail
Beth Moger NASA Adler Planetarium
Astra Ventures LLC Goddard Space Flight Center 1300 S. Lake Shore Drive
beth@astraventures.net 8800 Greenbelt Rd Chicago, Illinois USA 60605
Greenbelt, Maryland USA 20771 Phone: +1.312.294.0365
Director of Operations past-president@ips-planetarium.org treasurer@ips-planetarium.org
Jennie Benjamins
Managing Matters
411 Richmond Street PRESIDENT ELECT DIRECTOR OF OPERATIONS
Toronto, Ontario Canada M5A3S5
operations@ips-planetarium.org Michael McConville Jennie Benjamins
Evans & Sutherland/Spitz, Inc. Managing Matters
Webmaster 700 Brandywine Drive 411 Richmond Street East, Suite 200
Alan Gould Chadds Ford, PA 19317 Toronto, Ontario Canada M5A3S5
Lawrence Hall of Science Planetarium Phone: +1.321-262-1190 operations@ips-planetarium.org
University of California president-elect@ips-planetarium.org
Berkeley, CA., 94720-5200, USA
adgould@comcast.net
Advertising Coordinator
Dale Smith BOARD
(See Publications Committee on page 3)
AFRICA
Membership Susan Murabana Owen LATIN AMERICA
Individual: $65 one year; $100 two years The Travelling Telescope’s Alexandre Cherman
Institutional: $125 for one year Nairobi Planetarium Rio de Janeiro City Hall
Library Subscriptions: $50 one year 105 Riverside Lane off Riverside Drive Rua Bento Lisboa, 106 BL1
All amounts in US currency Nairobi, Kenya
Direct membership requests and changes of
AP1005
address to the Treasurer/Membership Chairman
+254 722 218 267 Rio de Janeiro, RJ, Brazil 22221-
smurabana@travellingtelescope.co.uk 011
+55 21 993557100
Printed Back Issues of Planetarian alexandre.cherman@
IPS Back Publications Repository
maintained by the Treasurer/Membership Chair planetariodorio.com.br
(See contact information on next page) ASIA
Sumito Hirota
Associate Editors Kawasaki Science Museum
Book Reviews April S. Whitt
7-1-2 Masugata, Tama-ku NORTH AMERICA
Calendar Loris Ramponi
Kawasaki, Kanagawa Dayna Thompson
Cartoons Alexandre Cherman
214-0032 Japan Charles W. Brown Planetarium
Classroom Education Mark Percy and the
hirota@e23.jp Ball State University
Classdome Cadre
planetarium.jp Muncie, Indiana 47306 USA
Education Committee Shannon Schmoll +1 765-285-8963
Dr. Jenny Shipway
Jin Zhu dlthompson3@bsu.edu
Humor April S. Whitt
Honorary Director
Ron Walker
Beijing Planetarium Michele Wistisen
Immersive Media Carolyn Collins Petersen
138 Xiwaidajie Street Casper Planetarium
International News Lars Petersen
Xicheng District 904 North Poplar Street
Live Interactive Programs Karrie Berglund
Beijing 100044 China Casper, Wyoming
Mobile News Susan Reynolds Button
+86-10-51583002 82601 USA
Southern Hemisphere Haritina Mogoșanu
+86-13-601369613 +1 307-577-0310
History/Years ago Tom Callen
+86-10-51583312 fax mwistisen@gmail.com
Ron Walker
jinzhu@bjp.org.cn
OCEANIA
EUROPE Martin George
Jiri Dusek Launceston Planetarium
Hvězdárna a Planetárium Brno Queen Victoria Museum
Kraví hora 2, 616 00 Brno, Czechia 2 Invermay Road
+420 541 321 287 Launceston Tasmania 7250
International Planetarium Society home page: +420 775 35 45 55 (mobile) Australia
dusek@hvezdarna.cz +61 3 6323 3777
www.ips-planetarium.org +61 437 688824 (cell)
Martin.George@qvmag.tas.gov.au
Planetarian home page: Björn Voss
www.ips-planetarium.org/page/plntrn LWL-Museum für Naturkunde
Westphalian State Museum
of Natural History
Sentruper Str. 285
48161 Münster Germany
+49-251-591-6026
+49-251-591-6098 fax
bjoern.voss@lwl.org
www.facebook.com/InternationalPlanetariumSociety www.gdp-planetarium.org
twitter.com/IPS_Planetarium
2 Planetarian Vol. 50, No. 3 September 2021
ADVISORY COUNCIL
APA ABP APS PLANed APAS APLF AMPAC APLE APS BAP CASC CPS EMPA
GDP GLPA GPPA PlanIt JPA MAPS NPA PPA RMPA RPA GDP SEPA SWAP
African Planetarium Association (APA) Association of Mexican Planetariums Society of German-Speaking Planetariums (GDP) Pacific Planetarium Association (PPA)
Susan Murabana Owen AMPAC Dr. Andreas Schmidt Benjamin Mendelsohn
The Travelling Telescope’s Nairobi Ignacio Castro Pinal Planetarium “Stellarium Erkrath” West Valley Community College
Planetarium Ave. San Bernabé, 723, Casa 7 Sternwarte Neanderhöhe Hochdahl e.V. 14000 Fruitvale Avenue
105 Riverside Lane off Riverside Drive San Jerónimo Lídice, C.P. 10200 Sedentaler Str. 150 Saratoga, California
Nairobi, Kenya México City, D.F. México 40699 Erkrath 95070-5698 USA
+254 722 218 267 +52 (55) 5500 0562 Germany +1 408-741-4018
smurabana@travellingtelescope.co.uk +52 (55) 5500 0583 fax +49-2104-947-668 +1 408-741-4072 fax
icastrop@hotmail.com schmidt@snh.nrw Benjamin.Mendelsohn@wvm.edu
Association of Brazilian Planetariums (ABP) www.gdp-planetarium.org sites.csn.edu/planetarium/PPA
Alexandre Cherman Association of Spanish Planetariums (APLE)
Rua Bento Lisboa, 106 BL1 AP1005 Javier Armentia Great Lakes Planetarium Association (GLPA)
Rio de Janeiro, RJ Planetario de Pamplona Mike Smail
22221-010 Brazil Sancho Ramirez, 2 Adler Planetarium
alexandre.cherman@ E-31008 Pamplona Navarra Spain 1300 S Lake Shore Drive Rocky Mountain Planetarium Association
planetariodorio.com.br +34 948 260 004 Chicago, Illinois 60612 USA (RMPA)
www.planetarios.org.br +34 948 260 056 +1 312-294-0365 Michele Wistisen
www.planetariodorio.com.br +34 948 261 919 fax msmail@adlerplanetarium.org Casper Planetarium
javarm@pamplonetario.org www.glpa.org 904 North Poplar Street
Arab Planetarium Society (APS) www.planetarios.org Casper, Wyoming
Marwan Anwar Shwaiki Great Plains Planetarium Association (GPPA) 82601 USA
Planetarium Director; President of APS Australasian Planetarium Society (APS) Jack L. Northrup +1 307-577-0310
Sharjah Academy for Astronomy, Oana Jones Sci-Tech Instructional Facilitator mwistisen@gmail.com
Space Sciences and Technology (SAASST) Perpetual Guardian Planetarium –Otago Museum Omaha, Nebraska USA
University of Sharjah 419 Great King Street jlnorthrup@fbx.com Russian Planetariums Association (RPA)
P.O. Box 27272, United Arab Emirates Dunedin Yaroslav Gubchenko
Mobile phone: 00971 56 44 57 202 Otago 9016 Italian Association of Planetaria (PlanIt) Fulldome Film Society
arab.planetariums@gmail.com New Zealand Loris Ramponi PO Box 103
mshwaiki@sharjah.ac.ae +64 (3) 4793233 National Archive of Planetaria 60310 Nizhny Novgorod, Russia
oana.jones@otagomuseum.nz c/o Centro Studi e Ricerche gubchenko@fulldomefilm.org
Association of Dutch-Speaking Planetariums Serafino Zani www.apr.planetariums.ru
(PLANed) British Association of Planetaria (BAP) via Bosca 24, C.P. 104
Marlies van de Weijgaert Nina Cameron I 25066 Lumezzane (Brescia) Italy Society of the German-Speaking Planetariums
Kapteyn Astronomical Institute Glasgow Science Centre +39 30 872 164 (GDP)
University of Groningen 50 Pacific Quay +39 30 872 545 fax Björn Voss
P.O. Box 800 Glasgow, Scotland G51 1EA megrez58@gmail.com LWL-Museum für Naturkunde
9700 AV Groningen +44 (0) 141 420 5010 osservatorio@serafinozani.it Westphalian State Museum
The Netherlands nina.cameron@glasgowsciencecentre.org www.planetari.org of Natural History
+31 50 363 7027 www.planetaria.org.uk Sentruper Str. 285
m.weijgaert@astro.rug.nl Japan Planetarium Association (JPA) 48161 Münster Germany
www.astronomie.nl Canadian Association of Science Centres (CASC) Sumito Hirota +49-251-591-6026
Frank Florian Kawasaki Science Museum +49-251-591-6098 fax
Association of Planetariums of South America TELUS World of Science 7-1-2 Masugata, Tama-ku bjoern.voss@lwl.org
(APAS) 11211 142 Street NW Kawasaki, Kanagawa www.gdp-planetarium.org
Diego Bagú Edmonton, Alberta T5M 4A1 Canada 214-0032 Japan
Director Planetario Ciudad de La Plata fflorian@twose.ca hirota@e23.jp Southeastern Planetarium Association (SEPA)
Secretario de Extensión www.canadiansciencecentres.ca planetarium.jp John Hare
Fac. Ciencias Astronómicas y Geofísicas Ash Enterprises
Paseo del Bosque s/n - La Plata Chinese Planetarium Society (CPS) Middle Atlantic Planetarium Society (MAPS) 29 Riverside Drive, Apt 402
Universidad Nacional de La Plata - Argentina Professor Xiaofeng Wang April Whitt Cocoa, Florida 32922 USA
+54 0221 4236593 Director, Beijing Planetarium Jim Cherry Memorial Planetarium +1 941 730 3434
diegobagu@gmail.com 138 Xiwaidajie Street Fernbank Science Center johnhare@earthlink.net
Xicheng District Atlanta, Georgia 30307 USA www.sepadomes.org
Association of French-Speaking Planetariums Beijing 100044 China april.whitt@dekalbschoolsga.org
(APLF) +86-18-911028682 www.mapsplanetarium.org Southwestern Association of Planetariums (SWAP)
Milène Wendling wang_xf@mail.tsinghua.edu.cn Levent Gurdemir
Université de Strasbourg Nordic Planetarium Association (NPA) Planetarium at the University of Texas at Arlington
Jardin des Sciences European/ Mediterranean Planetarium Association Kai Santavuori Chemistry Physics Building
12 rue de l’Université (EMPA) Sweco Structures LTD 700 Planetarium Place
Strasbourg F-67000 France Manos Kitsonas Viitankruununtie 34 B 11 Arlington, Texas 76019-0059 USA
+33 (0)3 68 85 05 32 Eugenides Planetarium 00970 Helsinki gurdemir@uta.edu
+33 (0)3 68 85 04 88 fax 387 Syngrou Avenue Finland www.swapskies.org
milene.wendling@unistra.fr 17564 P. Faliro +358 44 9867 630
www.aplf-planetariums.org Athens, Greece KaiSantavuori@gmail.com
+30 210 946 9633
+30 210 941 7372 fax
mak@eef.edu.gr
September 2021 Vol. 50, No. 3 Planetarian 3
STANDING COMMITTEES IPS PERMANENT
MAILING ADDRESS
AWARDS ELECTIONS FINANCE
Manos Kitsonas, Chair Martin George, Chair Current Officers
Eugenides Planetarium Launceston Planetarium International Planetarium Society
387 Syngrou Avenue Queen Victoria Museum MEMBERSHIP c/o Mike Smail, Treasurer
17564 P. Faliro Wellington Street Mike Murray, Chair Adler Planetarium
Athens, Greece Launceston Tasmania 7250 Delta College Planetarium
+30 210 946 9633 Australia Bay City, Michigan 48708 USA
1300 S. Lake Shore Drive
+30 210 941 7372 fax +61 3 6323 3777 +1 989-667-2270 Chicago, Illinois 60605 USA
mak@eef.edu.gr +61 3 6323 3776 fax mikemurray@delta.edu
Martin.George@qvmag.tas.gov.au
IPS Web Site:
CONFERENCE PUBLICATIONS
Current Officers EQUITY, DIVERSITY AND Dale W. Smith, Chair www.ips-planetarium.org
Upcoming conference host, past conference INCLUSION BGSU Planetarium
host, any IPS member Danielle Khoury LeBlanc, Co-chair Physics &Astronomy Department Please notify the Editor and Secretary of any
appointed by the President Charles Hayden Planetarium Bowling Green State University
Museum of Science Bowling Green, Ohio 43403 USA changes on these two pages.
Boston, Massachusetts 02114 USA +1 419-372-8666
dleblanc@mos.org +1 419-372-9938 fax Contact the Treasurer/Membership Chair for
dwsmith@bgsu.edu
Dayna Thompson, Co-chair individual member address changes and general
Director, Brown Planetarium circulation and billing questions. Addresses also may
Ball State University be changed online on the IPS Web Site.
Muncie, Indiana, 47306 USA
dlthompson3@bsu.edu
edi@ips-planetarium.org
PROFESSIONAL PARTNERS
AD HOC COMMITTEES/TASK FORCES/WORKING GROUPS
Armand Spitz Indigeneous Astronomy Working Group Planetarium Design and Operations
Planetarium Education Fund Annette Lee, Co-Chair Ian McLennan, Chair
Finance Committee St. Cloud State University Vancouver, British Columbia
St. Cloud, Minnesota 56301-4498 USA V6E 1G1 Canada
COVID-19 Task Force aslee@stcloudstate.edu +1 604-681-4790 phone + fax
Thomas Kraupe and Mark SubbaRao, ian@ianmclennan.com
Ka’iu Kimura, Co-Chair
Co-Chairs ian.mclennan@gmail.com
‘Imiloa Astronomy Center
www.ianmclennan.com
Hilo, Hawaii 96720 USA
Education
Shannon Schmoll, Chair
lesliek@hawaii.edu
Portable Planetariums
We are gathered together from all
Abrams Planetarium Milagros Vasquez, Co-Chair Susan Reynolds Button, Chair corners of this globe, inspired by the
Michigan State University Quarks to Clusters
East Lansing, Michigan 48824 USA
Cha’an Ka’an Planetario de Cozumel
Cozumel, Quintana Roo Mexico 8793 Horseshoe Lane world and the universe we inhabit.
1-517-355-0039
schmolls@msu.edu
milagrosvarguez@gmail.com Chittenango, New York 13037
+1 315-687-5371
Our society draws its strength
Immersive Audio
Charles Morrow, Chair
sbuttonq2c@twcny.rr.com from our predecessors and from
Emerging Communities sbuttonq2c@gmail.com
Dave Weinrich, Chair 1961 Roaring Brook Road the wide diversity of our present
S250 State Road 35 S Barton, Vermont 05822 USA Science & Data Visualization Task Force
Nelson, Wisconsin 54756 USA Phone: +1-212-989-2400 NASA membership. Building on our past
cm@cmorrow.com
dave.l.weinrich@gmail.com Goddard Space Flight Center
8800 Greenbelt Rd
heritage, we are inspired to dream
History International Relations
Martin George, Chair
Greenbelt, Maryland USA 20771 of future accomplishments, working
John Hare, IPS Historian past-president@ips-planetarium.org
Ash Enterprises Launceston Planetarium together as a worldwide society.
29 Riverside Drive, Apt 402 Queen Victoria Museum Vision 2020 Initiative
Cocoa, Florida 32922 USA Wellington Street Jon Elvert, Chair
+1 941 730 3434 Launceston, Tasmania 7250 jelvert1@gmail.com IPS President Dave Weinrich
johnhare@earthlink.net Australia Welcome to the 2012
+61 3 6323 3777
+61 3 6323 3776 fax
IPS Conference
History of the Planetarium Working Group
Pedro Raposo, Chair Martin.George@qvmag.tas.gov.au Baton Rouge, Louisiana
Adler Planetarium
Chicago, Illinois 60605 USA Planetarium Centennial Task Force
praposo@adlerplanetarium.org Björn Voss, Chair
LWL-Museum für Naturkunde
Westphalian State Museum Of Natural History Planetarian (ISSN 0090-3213) is published quarterly by the
48161 Munster, Germany International Planetarium Society. ©2021 International
+49-251-591-6026 Planetarium Society, Inc., all rights reserved.
+49-251-591-6098 fax
bjoern.voss@lwl.org Also known as The Planetarian from Vol. 1 No. 1 through
Vol. 6 No. 4. Titled Planetarian starting with Vol. 7 No. 1
forward.
Guidelines for contributors Opinions expressed by authors are personal opinions
and are not necessarily the opinions of the International
• Planetarian welcomes submissions of interest to the planetarium community. Preference is given to articles that closely relate to the philosophy, Planetarium Society, its officers, or agents.
management, technical aspects, educational aspects, or history of planetariums, and to ideas that can readily be incorporated into planetarium
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• Research articles dealing with educational aspects of the planetarium and other topics are highly desirable and will be refereed if applicable and material does not imply endorsement by the International
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the editor with questions. The online PDF version holds ISSN 2333-9063
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4 Planetarian Vol. 50, No. 3 September 2021
COLONIZE
MARS
INTER ACTIVE EXHIBIT Collect Resources
Complete each stage to develop a
sustainable colony on Mars.
Construct Base
Maintain Habitance
clarkplanetariumproductions.org
September 2021 Vol. 50, No. 3 Planetarian 5
COLUMNS Shiloe Fontes
Flandrau Science Center
DEJA-VU, ANYONE?
& Planetarium
University of Arizona
Tucson, Arizona
editor@ips-planetarium.org
IN FRONT OF THE CONSOLE
Seriously. (And not just because that’s only one degree of separation (or fewer) in this thinking? What helps you get
how I started by calling last time.) between ourselves and somebody with a through these kinds of things, and what
The past few months have been very breakthrough COVID infection. steps might you and your planetarium
surreal. We have been reopened for six I find myself constantly waiting for be taking to be prepared for what
months, and to my pleasant surprise, the other shoe to drop and asking “this comes next? I would love to share some
things have been going well! I can’t time around, what will that shoe-drop responses and open a dialogue about
lie, I was worried – would people have mean for us?” what we can do to help support each in
missed coming to the planetarium? this as we move forward.
I don’t mean “us” as in myself and
Would they still want to come inside I would also like to thank the many
my Science Center and Planetarium,
and explore science? Turns out the planetarium facebook groups that have
but yours, everyones. All the Museums,
answer is a resounding “yes”! Shows popped up, especially the meme ones.
Science Centers, Planetarium Theaters,
are busy, requests for field trips are They are a vital source of levity in my day.
etc. The spaces where people come to
pouring in, and visitors are exploring
learn. Many were able to find ways to Also, unrelated to all of that. I would
the exhibits again.
subsist through closure, but many lost like to apologize to Tom Callen for
Still, I have a feeling of constant good people due to the lack of revenue mis-titling his column, and to anyone
uneasiness. COVID-19 case numbers are and audience. whom has dealt with the growing
almost where they were a year ago at the pains of the transition over the last few
peak. Hospitals are getting full again. I worry that we might be heading in
issues. I appreciate your patience, and I
For legal reasons, many places cannot that direction again; honestly, it keeps
appreciate you letting me know what I
require masks to protect those who are me up at night.
can do better.
unable to be vaccinated. Many of us So, to you, my fellow planetarians, I
are having deja vu, returning to having ask, what keeps you at night? Am I alone
6 Planetarian Vol. 50, No. 3 September 2021
September 2021 Vol. 50, No. 3 Planetarian 7
PLANETARIUM RESEARCH
STAR OF BETHLEHEM
HOW TO TELL THE ASTRONOMY CORRECTLY
By Susanne H. Hoffman
Abstract morning twilight. Therefore, Jupiter and the
Moon were clearly visible but, because it is only as
The star of Bethlehem is a popular and standard
bright as the brightest stars (around +0.5 mag), it
topic in many planetaria all over the (Christian)
was hard to see Saturn. 1° separation means that
world. Since the production of dome planetariums
started in the 1920s, the most common story that the two planets (which appear very close in our
is told deals with a great conjunction of Jupiter small picture) had a visible distance of roughly two
and Saturn. Alternatives are hardly discussed apparent Moon diameters.
in the public, although it has long been known During that summer, the two planets first
amongst researchers that there was no special moved away from each other and then approached
astronomical phenomenon that coincides exactly. again. They re-met at the beginning of October
Here, I present a brief discussion of all suggestions, with a minimum separation of 54’ (almost 1°) on
including an analysis of the nova question with October 5th and had another close approach at
my recently developed, data-driven method that the beginning of December with a separation
was successfully presented to the public. The goal of a bit more than 1° on the 5th to 8th (Fig. 2).
is not to present an explanation, because there The astrological narrative for why this triple
is no historical proof that the star existed at all. conjunction would have led to the voyage of three
This paper is dedicated only to the suggestion of a Babylonian astral scientists is, in most cases, the
narrative in the planetarium that communicates following: Jupiter is the planet of the king, Saturn
that this star is a symbol with a function in the is the planet of the Jews, and when they meet,
story. Additionally, it provides the possibility to something happens to the king of the Jews. This
demonstrate a huge variety of astronomical objects triple conjunction took place in the constellation
and their appearance to the naked eye. of Pisces and, as we know, this constellation shows
two fish that are connected by an umbilical cord,
INTRODUCTION: THE POPULARLY thus representing birth. Ferrari d’Occhieppo (1999)
“KNOWN” EXPLANATION combines this story with zodiacal light.
For decades, it has been demonstrated in public
talks and planetarium shows (e.g. Letsch, 1953: 62;
Mucke, 1967) that the asterism that (according to
Matthew’s gospel) guided three scholars (magi)
from the East (Babylon) to the place where Jesus was
born, refers to the above-mentioned conjunction.
CRITICAL POINTS IN THE POPULAR
EXPLANATION
2.1 The constellation
In Greek antiquity, the two fish were connected
by an unexplained cord that was metaphorical and
never explained. Only Aratos (362-370) describes
it as the ribbon binding the two fish together,
reaching to the comb of the sea monster, and that
the two parts meet at an acute angle.
Eratosthenes reports that the two fish are
Figure 1 Morning
twilight in 7
In the year -6 (7 BCE), there was a Great descendants of Pisces Austrinus (PsA), a comment
BCE: Jupiter, conjunction between Jupiter and Saturn: Within which might have led to the interpretation of the
Saturn and the seven months, these two planets met three times. constellation as a sign of birth.
Moon met on the
23rd. Simulation: On May 23rd, Jupiter and Saturn were separated However, the gospel of Matthew reports that
Stellarium 0.20.3. by only 1° and the lunar crescent stood close to it was Babylonian, not Greek, astrologers who
them (Fig. 1). Yet, the scenario took place in the travelled to Israel. In Babylonian astrology, the
8 Planetarian Vol. 50, No. 3 September 2021The idea of the Star of Bethlehem
as a planet conjunction goes back
to Johannes Kepler. He observed
Supernova 1604 in an area of the sky
where a conjunction of Mars and Jupiter
had taken place one year prior. Thus,
he suggested that it was possible that
planetary conjunctions could create
new objects. In his time, the weekday
on which the Jews closed their shops
and went to the synagogue was the day
named after the planet Saturn (since
Vettius Valens, +2nd c.). Thus, in the
modern era, Saturn may have been
considered somehow related to the
Jews, but not in Antiquity.
In Kepler’s time, Babylonian
divination and the omen handbooks we
have today were unknown. Cuneiform
was only recently decrypted in the 19th
century. Afterwards, it took some time
before our understanding of Babylonian
Figure 2 (Top): Two further conjunctions in October (Hunger and Sachs, 1988-2014). This culture, astral divination, and practise
(left) and December (right) 7 BCE, Simulation and mathematical astronomy became
Stellarium 0.20.3.
is an abbreviation of the “Tails of the
Swallow,” which is the part of the huge complete enough to judge whether the
Figure 3 (Below): Babylonian constellations in the
constellation that intersects the zodiac suggested interpretation had merit.
2nd millennium (left) and the re-interpretation
of the 1st millennium (right). Photos taken in (cf. Hoffmann, 2017).
Planetarium Jena (installation and photos: SMH). WAS IT A NOVA?
Obviously, the Babylonian constellation
Transients are rarely reported in
did not depict any descendants.
constellation was not considered to Greco-Roman and Babylonian astrology
be two fish. In the 2nd millennium, 2.2 The planets but there was a strong focus on them in
the astronomical compendium, MUL. Chinese divination (Pankenier, 2013).
It is true that, since the beginning
APIN, reports that the Great Swallow of written astrological records There is one record from China, with a
constellation sits in place of the Greek on significance, Jupiter has been copy in Korea, dated 24 April 4 BCE
constellations Pisces and Cetus (Hunger considered the King’s planet (Hunger that reports “a fuzzy star in Hegu.”
and Pingree, 1999). A fuzzy star could be anything, e.g.
and Pingree, 1989; Hunger and Steele,
a comet or a stellar transient that is
2018). Around the time of Jesus’ birth, The interpretation of Saturn as the blurred by the atmosphere or that has
this huge constellation had probably planet of the Jews seems to not be of rays due to its brightness.
been forgotten and replaced by the ancient origin, but rather modern.
constellation of the Swallow-Fish, an Handbooks on omen writing have been To exclude the possibility of a nova
unexplained creature that we can see preserved from Babylon showing that or supernova, we probed the area
depicted on seals from that time (Fig. Saturn was known as the planet that of the Hegu asterism for modern
stands for evil. It was so evil, in fact, that counterparts of such high amplitude
3). It is possible that the term originally
one should not call it by its name, but stellar transients. Hegu is an asterism of
designated a certain species of fish but
rather by the euphemism “the Sun of three stars among which the brightest is
was transformed into a strange image in
the Night” (Reiner and Pingree, 1998). Altair, α Aql.
the sky.
The interpretation of asterisms being The record is listed among the
In Babylon, since the 7th century,
associated with certain geographical possible “guest stars” in Xu et al. (2000:
there were astronomical `diaries’
regions exists in Babylon (Horowitz, 130), which strengthens the hypothesis
that were created monthly to record
1998), but it is relatively rare in that this could be a stellar transient
happenings in the sky. Up to fourteen
divination and not a concept of zodiac rather than a comet.
astronomers worked simultaneously
on observations, computations of astrology. It was not used to determine The map in Fig. 4 shows the little
phenomena, and the development of the fate of single people. asterism surrounded by a circle with
algorithms for those computations. Result 1: Neither the constellation a radius of 4°. This is the main search
In the astronomical diaries, the great (Pisces) nor the planet (Saturn) fit field for possible counterparts. In the
conjunction is described as occurring Babylonian omens and concepts whole area, there are a few pulsars
in the constellation of “the Tails” of divination. but no supernova remnants – not even
September 2021 Vol. 50, No. 3 Planetarian 9PLANETARIUM RESEARCH
theoretically, become months suggest a comet in preference
visible to the naked of a nova, which is why Pankenier et
eye. They are PS1-3PI al. (2008) and Xu et al. (2000) did not
J195042.77+082545.3, include it in their list of potential guest
MASTER OT stars. However, since the list by Clark
J194850.95+102828.1, and Stephenson (1977) included it, we
MGAB-V850, V0725 are sometimes asked to discuss it as well
Aql and MGAB-V1275. in public presentations.
The Master optical As terminology in chronicles could
transient has been be wrong or misleading, we did search
detected only one for possible nova remnants in this field.
time and is, thus, No further records are preserved, i.e.
assumed a dwarf no movement is reported. A stellar
nova at peak. The transient with the duration of 70 days
quiescence magnitude could have been a slowly declining
is unknown. Both classical nova (Hoffmann, Vogt and
MGAB objects and the Protte 2020; Hoffmann and Vogt 2020a,
PS1 have quiescence Hoffmann and Vogt 2020b). In the
brightness of ~20 mag zodiac (Capricorn), it would likely be
observed by any astronomer - in Rome
and, thus, turn out
and Alexandria as well as in Jerusalem
to be too faint in this
or Babylon. Whatever this was, a nova
area of bright celestial
in this area of the sky appears unlikely
background (within regarding the possible counterparts
the Milky Way) to that are known from surveys on
become visible. cataclysmic variables.
V725 Aql is the only Result 2b: The suggested transient in
Figure 4 Map of cataclysmic and symbiotic binaries remaining candidate 5 BCE was likely a comet.
around Altair (coded in Wolfram Language: SMH). for a nova in Hegu. Its quiescence
magnitude is 16.2 mag and typical nova IS AN ALTERNATIVE SUGGESTION
just outside the search circle. This area amplitudes are 11 to 13 mag. If this MORE LIKELY?
includes part of the Milky Way, and system permits a classical nova, it could There is another suggestion of a
thus, we expect a possible supernova become 5 or even 3 mag. In case of a possible conjunction of two planets
relatively close (inside our Galaxy). A fast nova, the time of decline by 2 mag that makes more sense in the thinking
pulsar without a gaseous supernova would be a few days, in which time it style of Antiquity: a close conjunction
remnant was found but appears much of Venus and Jupiter. Both planets have
would fade to invisibility for naked eye
older than ~2000 years. Therefore, a generally positive connotations in
observers.
supernova observation is not probable Babylonian astrology and are therefore
in this case. However, a “new” 5 mag star could more likely to serve as a good omen.
likely be overlooked, and a “new” 3 For instance, the clay tablet BM 75228
A nova should also have produced a
mag star would be easily visible, but not from the British Museum preserves a
remnant in the shape of a nebula, but it
really bright in, or next to, a crowded list of Venus omens with the schema `If
is unknown on which timescales these
star field. Venus …, then …’. Of particular note is
objects evolve and vanish and if it would
still be visible. There is no suspicious Result 2a: It is demonstrated that sentence number 9, which reads:
nebula in the field. Thus, we checked there are no convincing candidates. dDil-bat u dGAL it-te-mi-du LUGAL
the field for all cataclysmic variables A nova in Aquila in 4 BCE is not BE-ma BALA KUR2-ir dSAG,ME.GAR
and symbiotic stars, which are depicted excluded, but highly unlikely. dDilbat ina iti […]
in green and orange, respectively, in There is one further possibility for “If Venus and the Great Star meet: the
our figure. Most of them are much too a nova. In 5 BCE (year -4) a transient king will die, the dynasty will change –
faint to flare up to naked-eye visibility, is reported in the Chinese asterism of Jupiter Venus in month […].”
according to predictive methods and Qianniu (the Draught Ox), 6 stars with Citations: Reiner and Pingree
criteria defined in Hoffmann, Vogt and β Cap as the principal star (western (1998:68,69). It should be mentioned
Protte (2020). most). Only the records from the month that dGAL designates an asterism (the
The five cataclysmic variables in of its appearance, March, is preserved Great God). This shows that there
our figure (highlighted with filled and the duration of visibility of 70 days are omens of the required type that
diamonds) passed our brightness (Ho, 1962). The terminology “broom announce a change of dynasty in
filter of first instance and could, star” and the duration of more than two connection with Venus and others.
10 Planetarian Vol. 50, No. 3 September 2021images of this Venus Genetrix as his
own ancestor on coins. In his old age,
Augustus again applied these images
to his designated heirs to the throne
(Zanker, 2009: 218-227).
Augustus’ usage of Caesar’s comet.
Since 42 BCE, Octavian had already
started to promote himself as the divi
filius (son of a god or of the deified
dictator) and the newly appeared
comet as sign of the saeculum aureum
(the golden age) that was subsequently
dawning. Therefore, he also used
images of the Julian comet on temple
Figure 5 Apparent merger of the two brightest planets, Venus and Jupiter, in -1 (2 BCE) next to Regulus, the
king’s star. Simulation with Stellarium 0.20.3.
walls and on his helmet, as it was
considered extraordinarily positive by
Interestingly, there had been two 94). Because Theogenes predicted an the public.
extraordinarily close conjunctions of extraordinarily great fate for him, and Augustus in Alexander’s tradition. In
Venus and Jupiter in the years -1 and a comet appeared a year later during Hellenism, it had always been tradition
-2 (2 and 3 BCE), both in northern the funeral games of Gaius Julius, to depict a successful warrior king as
summer, which does not fit the Augustus put strong focus on astral Zeus/Jupiter. This tradition started
time of celebration of Christmas. signs. In contrast to the normal concept with Alexander the Great when he
Both conjunctions took place in the of comets as a bad omen, Caesar’s
was considered deified in Egypt and
constellation of Leo the Lion, whose comet was commonly connected with
his own entourage adopted this view.
brightest star, Regulus, had been the deification of the dead dictator
The depiction of Augustus as Jupiter
considered the king’s star since the and a sign of hope. During this period,
on the Gemma Augustea is most
early times of Mesopotamian astrology astrology flourished in the Roman
empire and Augustus was a master at famously known, but the tradition was
(Hunger and Pringree, 1999). Its widespread (Zanker, 2009: 232-239).
using this in his propaganda.
Sumerian name, LUGAL, the King, was
Augustus’ sign: According to the In summary, Caesar Augustus was
also used later in Akkadian.
oracle of Theogenes, Caesar Augustus, equated with the god Jupiter and
We can conclude that a conjunction of legitimized himself by claiming the
who was born in September, considered
Jupiter and Regulus is a meeting of the goddess Venus as his ancestor. An
the sign where the Sun stood during
king’s star with the king’s planet, and a apparent merger of the planets of
his conception (in January) as “his”
conjunction (apparent merger) of Venus Venus and Jupiter was, therefore, yet
sign (Schumacher, 1988: 324). Thus,
and Jupiter means something really another great propaganda tool for him,
the strange creature of Capricorn
good and strong for the king – at least in demonstrating his legitimate claim of
decorated many coins, seals, art and
Babylonian astrology. autocratic rule.
official documents during the whole
Result 3: The conjunctions of Jupiter epoch of Caesar Augustus (Schütz, As it was visible all over the empire
and Venus appear more attractive to 1991). Capricorn is a Babylonian figure, and easily recognisable by everybody,
explain the “Star of Bethlehem” in a so-called Goat-Fish that was not this was a welcome `confirmation’ by
regard to i) visibility, ii) concepts of understandable in Greek culture but the gods of Augustus’s claim.
divination in Babylon. had always been considered a good Result 4: The conjunction of Venus
4.1 Astrology in the epoch of and helpful daemon in Mesopotamia. and Jupiter suits Caesar Augustus’s
It is often depicted above Augustus’s
Jesus’ birth propaganda perfectly.
head (e.g. on the Gemma Augustea, cf.
Jesus’ birth falls in the era of Caesar Zanker, 2009: Fig.182, p.233), or holding 4.2 The context of Matthew’s story
Augustus in Rome. As he, Octavian, was the globe of the Earth between his front Jesus was murdered ~30 years later
only a nephew of the earlier Caesar legs (on several coins). and Matthew wanted to convince people
Gaius Julius, he systematically built
Augustus’ goddess ancestor. Gaius of the deification of Jesus. As explained
a case to legitimize his claim as the
rightful ruler of the Roman empire. Julius had already established a myth in the literature, the Jewish religion
In the biography of Augustus, ancient around his legitimacy as ruler of Rome requires the messiah to appear together
historian Sueton reports that Octavian, due to his family’s patrons. The Julian with a star – as is the case in many
at ag 18 a year before Gaius Julius’ family was considered to be founded cultures. Furthermore, there is a strong
murder, had been in Apollonia with by the goddess Venus herself (Zanker, legitimacy lent by the family tradition
his friend Agrippa and visited the 2009: 46). This tradition was continued (Continued on pg. 22)
astrologer Theogenes (Augustus, 8, by Augustus when he also imprinted
September 2021 Vol. 50, No. 3 Planetarian 11PLANETARIUM RESEARCH
JAWAHARLAH NEHRU PLANETARIUM
IN A NEW AVATAR
By Pradmod G. Galgali
Aerial View of Jawaharlal Nehru Planetarium (JNP), Bengaluru
Jawaharlal Nehru
(Bangalore), was established three decades ago by
Planetarium,
Bengaluru, India. Bangalore City Corporation. It is now administered
The planetarium by Bangalore Association for Science Education
dome is on the left (BASE). JNP is a non-profit organization, fully
side and the dome funded by the Karnataka State Government. It
on the right houses
a Zeiss 150 mm conducts six planetarium shows every day barring
Coudé Refractor. Monday, which is the weekly day off. The first two
shows are preferentially reserved for schools on
prior arrangement, who need to book the entire
theatre of 200 seats. Students make up 50 percent
of our annual visitors, and a large percentage of Above: Students escorted by teachers waiting for their show. Below:
those come from neighboring, rural areas. Under- Viewing of Partial Eclipse at JNP.
privileged students, children from orphanages,
Non-formal science activities cater to students
children of migrant laborers, and physically
of varied levels: Science Education for Early
challenged persons are admitted to the planetarium
without an entry fee. Every year, over 5,000 such Development (SEED) for primary school students,
persons make use of our facility. Science Over Weekends (SOW) for high school
students, and Research Education Advancement
JNP has two objectives: the popularization of Program (REAP) for undergraduate students. More
science, and non-formal science education. Our than 135 students who attended JNP’s non-formal
popularization activities, apart from sky-theater science education programs, such as REAP, have
shows, include a visit to Science Park, monthly proceeded to complete their Ph.D.s and have
sky-gazing program, and viewing of astronomical joined different Research Institutes as faculty in
events. During eclipses, transits, and conjunctions, India and abroad.
JNP becomes the place to go for the citizens of
Bangalore. Thousands of people, and a large The long journey from the opto-mechanical
amount of print and electronic media, assemble at era to hybrid systems
JNP to view such events. Arrangements made by JNP
In the beginning, the sky-theater had an opto-
benefit a large number of on-campus visitors, and
mechanical projector, RFPDP with its three
also the numerous people watching the event on
television from the comfort of their homes. These standard auxiliary projectors (orrery, Jupiter with
celestial events, especially the eclipses, not only 4 moons, and shooting stars) manufactured by
arouse people’s interest in science but give us the Carl Zeiss, Jena (of erstwhile GDR). JNP opened to
opportunity of debunking the age-old myths and the public in December of 1989 with an in-house,
superstitions associated with eclipses. pre-recorded sky-theater show, “Our Sun & his
12 Planetarian Vol. 50, No. 3 September 2021we replaced our stars, constellations, and the zodiac
video projectors were discussed, and digital video was
with three new projected from the Mirror Dome System
ones. Evolution to illustrate some phenomenon.
was also taking Our show operating engineers
place with audio became so dexterous with the manual
system technology. control of RFPDP and Mirror Dome
In the beginning, System that it gave viewers the
JNP played back impression of some kind of automation
its show-audio system in action. Some of these shows
through a 1/2” were hearing impaired friendly. For
Revox spool deck. this, we produced special shows with
In just five years, Kannada and English subtitles.
the first transition
came, and the The Mirror Dome System was
The Zeiss RFPDP projector, a video projector stands entertainment upgraded in 2012 to a new version with
near the center, seating is concentric - a few years industry began to move to Digital higher resolution.
before modernization.
Audio Tape (DAT) players. At JNP, we The new Hybrid Avatar
family.” The show was successful, and updated our audio system from spool
to DAT, DAT to CD, then into DVD, and Finding spares for our aging RFPDP
its appeal drew from a good amount of projector becoming impossible, and
finally to digital audio recorded on
science interspersed with references of growing popularity and availability of
computer disk drives. Haven’t we all
the star, Sun, and its family in Indian undergone this process? the new paradigm of computerized
culture and history. The illustrations, projection systems prompted us to
cartoons, and music used in the show Mirror Dome Projection System go for a whole-hog revamp of our
all had local flavor. So far, JNP has sky-theater in 2016.
produced over 25 shows on diverse We opted for a Hybrid
Projection System: a
topics in two languages, English for
ZKP4 opto-mechanical
cosmopolitan visitors and in the state
projector and
language of Kannada. With every six-channel fulldome
passing year, the planetarium has Velvet Digital Projector
gradually gained popularity among the System, both from Carl
public, and the current (pre-pandemic) Zeiss, Germany.
annual attendance was over 300,000.
The occasion
Before the video and digital era, provided an
the special effect projectors (mostly opportunity for a
slide projectors) were very important complete overhaul
for illustrating themes of the show, of everything in
and every show demanded a new the sky-theater:
The author (right) in dialogue with Dr. Paul Bourke as the latter installs a
set of unique special effects. These new Mirror Dome projection system in 2012. projectors, audio system,
were designed and fabricated at the seats, sound-absorbing
planetarium and our stock steadily material, electrical
grew. The availability of small, In 2007, we had a major up-gradation wiring. Everything was dismantled
fractional rpm motors and a variety in the form of an additional Mirror and replaced, including the central
of lenses was a game-changer; over Dome Projection System. It was air-conditioning system. Only the old
a period of time, we fabricated more conceived of by Dr. Paul Bourke of projection dome was retained and
than 100 special effect projectors. And Swinburne University, Australia. We repainted. The seating arrangement
then, in the mid-nineties when 3-gun used it for all-video shows, like Hubble in the sky-theater was changed from
RGB video projectors became easily Vision-2 by Loch Ness Productions and all-on-one level concentric seating to
available, we installed one and added our own biographical show “Acharya unidirectional tiered seating with a
another a few years later to show Jagadish Chandra Bose”, “Mars – The slope of 90. Normally, it is expected
animated videos relevant to the show Red Planet”, and others. For some that a transition from concentric to
theme. Apart from using off-the-shelf, shows, the Mirror Dome system was unidirectional brings a reduction in
commercially available video clips, we used along with the opto-mechanical seats, however, we have squeezed in
created our own content as well. The RFPDP projection system, such as, and retained the same number of seats
video projection technology changed “Our Solar System.” These shows were – 210. We are a little cramped but so
and improved with time, so in 2007 made of an initial star-talk where far no one has complained. Since we
September 2021 Vol. 50, No. 3 Planetarian 13PLANETARIUM RESEARCH
In the meantime, so far are “Dawn of the Space Age,”
JNP introduced “Exploring the Universe,” “Stars,” and
another piece of “To Worlds Beyond – Journey through
customization: the Solar System.”
installing unique JNP regularly conducts live night sky
artwork of observation sessions in the sky-theater.
constellations by a These are followed by viewing of planets
renowned local artist, and lunar craters through telescopes.
Mr. Chandranath It is an enthralling experience, for
Acharya, in the new both the viewers and the presenters. A
digital system. Now visit to the planetarium is considered
JNP has two sets of incomplete without a walkthrough of
constellation figures, the science park, which has over 45
the line drawings hands-on exhibits to enjoy and learn
provided by Carl Zeiss science. Our ‘Anti-gravity Cottage’
in ZKP4, and our own is a big draw; it gives visitors an
constellation artwork unforgettable experience of skewed
in digital format. gravity, like water flowing up, wayward
The new system pendulum, and visitors precariously
projects stars and leaning while standing on a platform.
planets with good ····· ····· ····· ····· ····· ····· ····· ·····
image definition
by the ZKP4 star Jawaharlal Nehru Planetarium,
projector and Bengaluru – timeline & milestones
seamless immersive • Website: www.taralaya.org
video through
the high contrast, • Opened: December 1989
six-channel velvet • System: Zeiss RFPDP
video system.
(Top) Overhauled sky-theater with new ZKP4 and velvet projectors,
• Projection dome: 15 meter
The 5.1 audio-
unidirectional tiered seating arrangement. (Above) Constellation artworks by perforated aluminum dome
renowned artist Mr. Chandranath Acharya.
system enhances
the experience. • Seats (concentric): 210
decided to retain our old aluminum, Planetary bodies with • Addition of Video Projectors: Began
15-meter projection dome, we did not vivid details, floating in the starry sky in mid 90s
disturb it from its horizontal alignment projected with the video projectors, give
• Addition of Mirror Dome System:
as this would have entailed making the feel of space travel. The Powerdome
2007 and its up-gradation in 2012
drastic changes to the dome structure III Zeiss proprietary software integrates
and perhaps even building a new outer smooth control of the star and video • Closed in March 2016 for 9 months
structural dome. projectors. Another addition to the for overhaul of the sky-theater
sky-theater is the LED cove lights with • New Hybrid Avatar: December 2016
Retrofitting the new hybrid system
many hues and features.
into the existing building necessitated • System: Zeiss ZKP4 and 6-channel
several modifications. A service In keeping up with its tradition of Velvet projection system, 90
corridor along the periphery of the in-house show production, JNP has tilted floor, horizontal dome, 210
dome was created to house the digital produced two shows for the new unidirectional seats.
velvet projectors. The flooring tiles hybrid system. They are, “Celestial
of the sky-theater were removed to Fireworks,” which covers explosions ····· ····· ····· ····· ····· ····· ····· ·····
reduce the burden on the supporting on various scales like a meteor burst,
structure, and also to make room for supernovae, and the big bang (if
the additional load of the steel structure that can be called an explosion), and
required for tiered seating. another show on a popular theme
All these jobs, and installation and entitled “Our Solar System”.
commissioning of hybrid system, were The new computer powered
completed in a nine-month period projection system, unlike the earlier
between March and November 2016. system, is compatible with other digital
After tests and trial runs, JNP was systems. This feature has enabled JNP
ready for operation in its new avatar in to screen excellent shows produced by
December 2016. other producers. Such shows screened
14 Planetarian Vol. 50, No. 3 September 2021the image
makes the
experience
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September 2021 Vol. 50, No. 3 Planetarian 15PLANETARIUM RESEARCH
SURFACE VS. VOLUME
NEBULAE, TAKE 2
By Nico Koning & Wolfgang Steffen
Figure 1: Different views of ilumbra’s volumetric model of the Ant
Nebula are shown as captured from an interactive visualization. The
view at the top-right is as seen from Earth, whereas the views on the
left are during a flight into the nebula. At the bottom right, the virtual
camera is inside the nebula, looking outwards (Image: ilumbra.com).
again, that is true only for the optical emission that
comes from the outer shockwave.
An important aspect of most supernovae
is x-ray emission. It provides proof that the
interior is still a very hot gas. This emission is
distributed throughout the volume enclosed
by the optical bubble, and therefore requires a
volumetric representation. Omitting the x-ray
emission from a model would be withholding a
key piece of information for the understanding
of the phenomenon. Although the x-ray emission
is not visible to the human eye, it has become
customary to include it in images as a light-blue
glow. Volumetric, 3-D models can take care of this,
while a surface representation will not allow a filled
interior of the bubble to be visualized correctly.
Supernova remnants, such as the Crab Nebula
(M1) or Cassiopeia A, have more complex
In Take 1 of this discussion of surface versus filaments throughout much of their volume, even
volume rendering for interactive visualization for the optical emission. This makes a surface
of astronomical objects in planetarium live- representation unsuitable if the planetarium
presentations, we found that surface rendering presenter endeavours to fly around or even through
wins big over volumetric modeling for the solar the nebula.
system. Surfaces rule in the solar system, and they Planetary nebulae are similar to supernova
allow efficient and realistic rendering of most remnants in that they are ejecta from a star and
objects in our solar neighborhood. often have a mixture of filaments and shells. In this
What about further out? This time, we will discuss case, it is a star with a mass similar to the sun that
surface and volumetric rendering for supernovae, is running out of hydrogen fuel. Usually, planetary
planetary nebulae, and star forming regions. nebulae are more complex than supernova
remnants, having several shells in addition to
Nebulae from stellar ejecta complex bi- or multipolar structures that may
Supernova remnants are the ejecta from the penetrate each other. These cannot be considered
explosion of a massive star after it runs out of thin surfaces.
thermonuclear fuel and collapses onto its core. The Ant Nebula (Menzel 3) is a beautiful example.
The rebounding shock wave hurls much of the In Figure 1, there are several views of ilumbra´s
star’s material into interstellar space, replenishing volumetric model of this nebula. The reason for
it with gas enriched in heavier elements that were this complexity and variety is that a planetary
synthesized during the lifetime of the star. nebula is not the result of a single explosion, but
The structure of the supernova ejecta varies a lot. rather a sequence of ejection events and stellar
The cases where surface models might be adequately wind interactions at different times and velocities.
employed are the few supernovae remnants that Bipolar structures, such as those in the Ant
are similar to soap bubbles with an emitting shell Nebula, are thought to be caused by the changing
of gas that is very thin compared to its diameter. An interaction between two stars in a gravitationally
example is the “Red Bubble” (SNR 0509-67.5). Then bound binary central star system.
16 Planetarian Vol. 50, No. 3 September 2021antialiasing corrections by the graphics
cards, alleviate this issue. Future
advancements in graphics card capacity
will greatly reduce these problems.
New methods are under
development at ilumbra that will allow
small-scale details to be incorporated
into the model landscape without
substantially increasing the memory
and processing footprint. These are
prospects for amazing interactive
“rides” through interstellar landscapes
in the not-too-distant future of live
presentations in planetariums.
While surface models have fewer
problems with spatial resolution,
their key challenge is that most of
the volume of star forming regions is
filled with absorption from dust and
emission from gas at various densities.
Modeling this with surface methods, in
a way that is convincing from different
viewpoints in an interactive show, is
not really possible. There will always
Figure 2: A rendering of a volumetric model of a becomes visible to observation in be sharp edges in the wrong place and
generic star forming region with multiple bubbles
an optical telescope. In the form of regions without appropriate emission
and a popular color scheme frequently used by
astrophotographers (Image: ilumbra.com). beautifully structured dust filaments or absorption.
and gas, excited by the young stas to
Hence, a surface model does not work
Unless the planetarium presenter emit in a characteristic pink color, a
at all in this case if the camera view is
does not move the virtual camera too new star forming region appears in the
to change substantially during a live
far from Earth’s line of sight, a suitable landscape of interstellar space.
presentation. The incredibly complex
representation with a surface model is The complexity of structure in physical and structural situation
hopeless and volumetric 3-D models are star forming regions, along with the in a star forming region requires a
the only real option. highly variable transparency of dust volumetric model, since filling the space
What about nebulae such as the filaments, results in several challenges with structured gas and dust is part of
Orion Nebula and other cradles of that apply to both volumetric and the requirement.
star formation? surface models. First of all, there is
In conclusion, in the realm of
important structure to be shown at all
Star forming regions supernovae, planetary nebulae, and
spatial scales. The spatial resolution
star forming regions, it is a clear win for
Star forming regions are highly of the model sets the limit to which volumetric, 3-D models over surface
complex clouds of gas, dust, and stars. details can be appreciated. This might modeling methods.
The radiation and the stellar winds prevent important phenomena, such
of fast tenuous gas, that young stars as stellar jets or the so-called proplyds, At this stage, you will probably be
eject, interact with the very cloud from from being suitably included in tempted to ask how we, at ilumbra,
which they formed. The combination volumetric models. figure out the structure along the
of stellar winds and radiation creates line of sight that can not be extracted
high pressures on the inner region of Currently, volumetric models have from images? In Take 3 of this series
the cloud, which causes it to expand. limited resolution for depicting this of articles, we will look at “the line-
Eventually the young star emerges from amount of detail on conventional of-sight problem,” providing a more
its shroud by blowing out a cavity in its commercial graphics cards. A secondary detailed explanation of how we
environment through a mechanism consequence of this is potential aliasing determine the structure in the depth
known as “champagne flow”. It is like a problems in regions with sharp edges direction, that in most cases is not
champagne bottle that suddenly opens, and high opacity, such as the famous directly accessible from photographic
and it blows away the cover of gas in dusty columns in the Eagle Nebula (M16) images of a nebula. Hint: astrophysics´
the weakest region of the environment. that are being evaporated by photons most powerful tool is key.
Thus, on this blown out side, the dust from nearby stars. Special algorithms
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shroud clears and the new star cluster in the modeling, together with
September 2021 Vol. 50, No. 3 Planetarian 17You can also read
