San Diego Astronomy Association - SDAAdocs.sdaa.org/Newsletters/2014-10.pdf · San Diego Astronomy Association ... (TARO) proposal of substantial donated equipment and actions to

San DiegoAstronomy AssociationCelebrating Over 40 Years of Astronomical Outreach

http://www.sdaa.orgA Non-Profit Educational Association

P.O. Box 23215, San Diego, CA 92193-3215

October 2014

SDAA Business MeetingNext meeting will be held at:3838 Camino del Rio North

Suite 300San Diego, CA 92108October 14th at 7pm

Next Program Meeting October 15th, 2014 at 7pmMission Trails Regional Park

Visitor and Interpretive Center1 Father Junipero Serra Trail

CONTENTSOctober 2014, Vol LII, Issue 10Published Monthly by the San Diego Astronomy Association$2.50 an issue/$30.00 yearIncorporated in California in 1963October Program Meeting.. . . . . . . . . .1Nominat ing Committee. . . . . . . . . . . . . .2S D A A B B Q . . . . . . . . . . . . . . . . . 2S e p t e m b e r M i n u t e s . . . . . . . . . . . . . . 3Te r r y A r n o l d D o n a t i o n . . . . . . . . 5October Calendar.. . . . . . . . . . . . . . . . . . . . . . . .6SDAA Contac t s. . . . . . . . . . . . . . . . . . . . . . . 7TDS, KQ, & Heise Schedules... . . .8We b O n l y - - - - - - - - - - - - - - - - - - - - - -I m a g e G a l l e r y . . . . . . . . . . . . 9P r o j e c t A s t r o . . . . . . . . . . . 1 0Space Place Partners’ Article.. . . .11As t ro Shor t . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Newsletter DeadlineThe deadline to submit articles

for publication is the15th of each month.

October Program Meeting

Date: October 15th, 2014Speaker: Jon Kaufman Topic: BICEP2

Dr. Kaufman is an experimental cosmologist studying the Cosmic Microwave Background, the glowing remnant of the Big Bang, searching for clues as to the origins of our Universe. He has done design, testing, integration, and data analysis for the BICEP1 and BICEP2 microwave telescopes located at the South Pole, which we believe have found the imprint of gravitational waves created during Inflation, the exponential expansion of our early Universe some 10-36 seconds after the Big Bang. This exponential expansion created a viable Universe and planted the seeds for all the stars and galaxies that we see today.

He currently works as a postdoc for Professor Brian Keating at UCSD with the BICEP2 and POLARBEAR telescopes.

San Diego Astronomy Association (SDAA) sponsors speakers on a wide range of astronomy topics on the third Wednesday of every month at the Mission Trails Regional Park Visitors Center. The program meeting begins at 7pm. Each attendee receives one free door prize ticket. After announcements and a small amount of business, the audience is treated to the featured presentation. At the close of the meeting the door prizes are presented. The event is open to the public. The Mission Trails Regional Park Visitors Center is at One Fr. Junipero Serra Trail, San Diego CA 92119. Call the park at 619-668-3281 for more information or visit http://www.mtrp.org.

http://www.sdaa.org

http://www.mtrp.org

http://www.mtrp.org

San Diego Astronomy Association

Page 2 SAN DIEGO ASTRONOMY ASSOCIATION NEWS AND NOTES, OCTOBER 2014

SDAA Business – Nominating Committee

Every year each of the Directors and at least two of the Officers must run for election. These elections are important for the effective management of the Association, its assets, and focus. This year, the following board positions are open: president, vice-president, and corresponding secretary.

The SDAA By-Laws State in part, ”There shall be a nominating committee consisting of three members, one of which shall be elected by the Board of Directors from its body, and two elected by the membership at the regular meeting in October. The President shall appoint one of the three to serve as Chairman of the Committee. The purpose of this committee is to solicit and accept nominations for the position[s] open to election.”

The Board of Directors has named Kin Searcy to serve on the committee and is soliciting volunteers from the membership to complete its membership. Anyone interested in serving the association in this committee membership capacity is urged to contact him at [email protected]. In accordance with the by-laws, the committee slate will be presented to the membership for affirmation at its October program (regular) meeting.

Annual SDAA Barbecue at Tierra Del Sol, Saturday, October 25thMark your calendar

Come for food and friends, stay for the stars. Master chef Dave Woods will be cooking up burgers, brats and chicken tenders about 5pm. Bring a desert or salad to share.

mailto://[email protected]


Page 3SAN DIEGO ASTRONOMY ASSOCIATION NEWS AND NOTES, OCTOBER 2014

San Diego Astronomy Association (SDAA) Board of DirectorsMonthly Business Meeting Minutes

September 9, 2014 – Unapproved and Subject to Revision

1. Call to order. The meeting was called to order at 7:08pm with the following board members in attendance: Michael Vander Vorst, President; Mike Chasin, Vice President; Ed Rumsey, Treasurer; Dennis Ritz, Treasurer, Mike Finch, Director; Dave Wood, Director, and SDAA member Pat Boyce.

2. Approval of Last Meeting Minutes. Minutes of the August meeting were approved. 3. Priority/Member Business. SDAA Member Pat Boyce was present to present and discuss alterations to the standard SDAA Private Pad lease for the Roboscope. Dennis

pointed out leasing to an organization, rather than as a member of the SDAA presented difficulties with the BOE-267 application #7 and read the section for the Board, especially in view of proposed change #11. Ed verified that no pad leases were to organizations, only SDAA members and pointed out that the standard private pad lease was reviewed by an attorney and has been well vetted. Mike Finch said the three year term could be accomplished by simply paying 3 years in advance rather than modifying several places in the standard lease. Proposed change #9 regards real estate and personal property delineation, Dennis pointed out these are well defined and did not need further delineation. He suggested having an attorney review the standard lease and proposed changes may be illustrative. The Board unanimously agreed to offer the standard lease to Pat Boyce and son as members of the SDAA.

• Michael V, Mike C, and Dave W provided a Terry Arnold Robotic Observatory (TARO) proposal of substantial donated equipment and actions to be accomplished, including installation of TARO equipment at TDS in a Pier Tech observatory, training and education of SDAA members and Rising Stars secondary school students in remote operations and onsite training and star parties at TDS. Particular attention to be paid to the student mentoring responsibilities. It was motioned and unanimously agreed the Board should accept the Terry Arnold Robotic Observatory proposal.

4. Approval of Treasurer's and Membership Report Treasurer’s and Membership Report. Membership=516

Ed is working on updating the records and reviewed the books. Was a problem with Quicken and Chase On Line Banking wiping out transactions. He is recreating items and preparing for tax submission which deadline the 15th day of the 5th month after fiscal year end, i.e. Nov 15, also the due date for filing with the CA Attorney General charitable organizations. Ed distributed and reviewed the Monthly Treasurers Report for Sept 9, 2014, and noted the membership is up. Following a motion and second, Board unanimously Approved the Treasurer’s report.

5. Standard Reports.

a. Site Maintenance Report. Bill plans to repair downed private pad area power outlets by Public night 9/20/14. b. Observatory Report. Observatory good, the ProDome has been erected.

c. Private Pad Report. There is nobody on the waiting list (in fact, this is the only summer in a long time where nobody has requested a pad). We show five pads available. d. Program Report. Next week UCSD Professor Dusan Keres, PhD will present Galactic Ecosystems at Mission Trails. In October Dr. Kaufman will update news of BICEP CMB microwave polarization detection from the South Pole, and November is Gadget Night. SDAA members with fun, interesting and useful gadgets are encouraged to bring them November 19.

September 17 Dusan Keres - Galactic Ecosystems October 15 Jon Kaufman - Current Research on the Cosmic Microwave Background using BICEP2 November 19 SDAA Member Gadget Night

e. Roboscope. See Member Priority notes above.

f. TDS Network. Tachyon has repaired the satellite gear and will continue to host free internet coverage at the site for as long as the equipment holds out. Dave W doesn’t have a schedule yet for when he can re-install but will need a new fan in the cabinet.

g. AISIG Report.

• Dave Wood reports the AISIG Meeting with Craig Stark went over very well. Even Craig thought it went great. The entire presentation is posted on my YouTube channel and the link has been published on the AISIG yahoo group. https://www.youtube.com/channel/UCZ1sxMp8JKNkpS7yNqaNhgQ

• Richard Wright of Software Bisque will present on Paramount operation on the 26th. It will be streamed and posted to Dave's YouTube channel. Riverside Astronomy GMARS is hosting a Software Bisque Paramount workshop Nov 15 and 16, details here: http://www.bisque.com/sc/blogs/seeker_blog/archive/2014/08/12/free-paramount-workshop.aspx

• Hoping for a Tony Hallas presentation for January or February. • Dave W is working with the MTRP staff to upgrade their AV system.



h. Governing Documents. Open i. Newsletter. Great as always. j. Website. Webmaster report: Lots of last minute updates, but no significant issues on the JSF site. Still need list of 2014 JSF volunteers. When there are dates for JSF2015 I can update the site in advance. Before next year someone should update the information on the Town of Julian web page.

For the SDAA site, repeating request from June: There are a couple of pages on the SDAA site that are out of date. Please provide updates if possible:

1. The AISIG page still has 2013 meetings. Please send an updated schedule. 2. The Second Site page still has older information about the Border Patrol problem. I updated the page to the current Congressman for the area (Vargas), but the text should be revised to be more current. 3. AISIG Yahoo! Group link is bad: AISIG Yahoo! Group.

4. SDAA web site page footers need updated to 2014 copyright notice. Says 2011. k. Outreach Committee Report.

• Schools are back in session. • Thanks to the members (3) who took telescopes to the Japanese/American Friendship group. Yahoo SDAA group doing very well communicating the outreach

needs. KQ donations are down since the recession, but perhaps a Banquet donor/sponsor this year. • Still looking for a South Bay star party coordinator and will have to curtail presentations in the south bay without a local coordinator. If you are in the South Bay

and can help out, contact Kin Searcy.

l. Merchandise. Sold lots of SDAA merchandise at JSF. Square credit card processing worked really well, PayPal also for PayPal accounts. No numbers available yet.

m. New Member Mentor. Dan Kiser sent out New Member Mentor packages to 40 new members from July to September: Contributing-17, Contributing Family Members-7, Basic-12, Basic Family Members-4.

• Dennis asked if JSF was beneficial to membership. Dave W said a number of memberships were received from the SCAE booth, in addition to the basic memberships raffled. Ed ran the new numbers for September: Twenty-one new members which is a very large number for the period. Hard to attribute all of these to JSF, but it is likely the event had a very positive impact to our membership

n. Julian StarFest - Was a great success, a good time was had by all. Merchandise sold well at JSF, financial information not yet finalized. This was a successful event in that we had a record number of campers, day use attendees and a public star party attendees (CERT parked approximately 420 cars. Full report to follow.

• The Board unanimously moved and approved to support the JSF for 2015 with A BIG THANK YOU to all the hard workers and organizers for this fantastic event.

6. Old Business.

a. Annual Banquet Martha Baker and Daphne Zay have agreed to coordinate and are contacting hotels, speakers, sponsors, etc. b. Treasurer's website evaluation - Ed has it in hand presently but will revisit the need when running from Treasurer next year. c. Speeding at TDS - Signs have been placed advertising speed limit. d. Insurance review. Brian out, nothing to report.

e. Call for any other Old Business. None.

7. New Business.

a. Fall BBQ TDS Oct 25th Michael V will make flyers. Jim T and Dennis R can distribute to neighbors, fire and border patrol. Dave W will cook. b. Nominating Committee: Kin will head the 3 member nominating committee to present a slate of Board members for 2015 per our articles and bylaws. c. Call for New Business: Michael Vander Vorst, President, will appoint Jerry Hilburn to the Grants and Fundraising committee chair currently vacant. d. Document retention system: documents are scattered among the various Board members, online central storage may present a better solution to locating needed documents. To be discussed later. e. Call for any other New Business. None.

8. Adjournment. Adjournment at 9:05pm was approved.



Donation by Terry Arnold of Robotic Observatory to SDAA

Terry Arnold and his wife Susi Kniel are graciously donating a fully equipped robotic observatory to SDAA. Due to illness, Terry can no longer pursue his astro-imaging obsession. The observatory will be available for use by fully trained and pre-qualified SDAA members through the SDAA AISIG group; and also by the new Rising Stars Educational Program that Terry and Susi are establishing, initially through Preuss High School and UCSD. The Terry Arnold Robotic Observatory (TARO) will be located at our dark sky site at Tierra del Sol. TARO will be an astro-imagers dream system. The observatory will be housed in a new Pier Tech roll of roof observatory. Inside will be a Paramount ME mount with two astrographs: a Deep Sky Instruments 14.5-inch RC with Paul Jones quartz optics and two Takahashi refractors. Cameras include an Apogee U16M, an SBIG ST2000XM and an SBIG ST10, loaded with visual and narrow band filters. Remote control will be done over the internet using the ACP Observatory Control Software. David Wood, the AISIG chairman, will lead the effort to get TARO up and running. There is a lot to do: pouring a new pad, installing equipment, software integration, production of training materials, and ongoing maintenance and training.

We plan to have TARO up and running by the fall of 2015. We will need your help. Michael Vander Vorst, our president, will be the liaison between SDAA and the Rising Stars Program at Preuss High School. Preuss is impressive. It is located near Scripps Hospital off Genesee Ave. All the students are low income, with parents who have not attended college. The kids are bused in from all over San Diego. Most students start in the 6th grade and continue through 12th, 800 students total. They are chosen by lottery from qualified applicants. The school has an excellent reputation with nearly 80% of graduates accepted to 4 year universities. Few students drop out. The details of the Rising Stars Program at Preuss are being worked out. The most likely scenario is that Preuss will weave an astronomy module into their science curriculum. TARO and also be used in student's projects for the San Diego Science Fair. The module will most likely be taught by UCSD graduate students from the Astro-Physics department. SDAA volunteers will assist with after-school mentoring on campus and with using TARO. SDAA will also sponsor star parties at TDS for the students. This is an incredible gift from Terry and Susi. We owe them a debt of gratitude and support. TARO will take our outreach in significant new directions and to new groups in the coming years. We also thank our corporate supporters, Eric Blackhurst and Chris Hendren of OPT and Mike Fowler of Orange County Telescopes in performing the appraisal of Terry's equipment. We will provide updates on the TARO's progress and how you can support this endeavor in future newsletters.



October 2014 Sunday Monday Tuesday Wednesday Thursday Friday Saturday

1

Stars in the Park

2

3

Birney Elementary

4

Heise

5

6

7

8

Moon Walk

Full Moon

9

10 Stars at Mission

Trails

11

12

13

14

SDAA Business Meeting

15

SDAA Program Meeting

16

17 Stars at

Sycamore Canyon

18

KQ Ranch Public Star Party

TDS

19

20

21

Miller Elementary

22

AISIG Meeting

23 McKinley

Elementary New Moon

Nightfall

24

Nightfall

25 SDAA BBQ

Member Night TDS

Nightfall

26

27

28

29 Rancho Del Rey Middle School

30

31

1

St Pius Fall Festival



SDAA ContactsClub Officers and Directors

President Michael Vander Vorst [email protected] (858) 755-5846Vice President Mike Chasin [email protected] (858) 210-1454Recording Secretary Dennis Ritz [email protected] (619) 890-7480Treasurer Dave Wood [email protected] (858) 735-8808Corresponding Secretary Kin Searcy [email protected] (858) 586-0974Director Alpha Ed Rumsey [email protected] (858) 735-8808 Director Beta Brian McFarland [email protected] (619) 462-4483Director Gamma Michael Finch [email protected] (760) 440-9650Director Delta Jim Traweek [email protected] (619) 207-7542

CommitteesSite Maintenance Bill Quackenbush [email protected] (858) 395-1007Observatory Director Jim Traweek [email protected] (619) 207-7542Private Pads Mark Smith [email protected] (858) 484-0540Outreach Kin Searcy [email protected] (858) 586-0974N. County Star Parties Doug McFarland [email protected] (760) 583-5436S. County Star Parties -Vacant- [email protected] E. County Star Parties Dave Decker [email protected] (619) 972-1003Central County Star Parties Kin Searcy [email protected] (858) 586-0974Camp with the Stars Doug McFarland [email protected] (760) 583-5436K.Q. Ranch Coordinator Michael Vander Vorst [email protected] (858) 755-5846Newsletter Andrea Kuhl [email protected] (858) 547-9887New Member Mentor Dan Kiser Mentor @sdaa.org (858) 922-0592Webmaster Jeff Stevens [email protected] (858) 566-2261AISIG Dave Wood [email protected] (858) 735-8808Site Acquisition -Vacant- [email protected] Field Trips -Vacant- [email protected] Grants/Fund Raising -Vacant- [email protected] Merchandising -Vacant- [email protected] Publicity -Vacant- [email protected] Loaner Scopes Ed Rumsey (858) 722-3846 Governing Documents TBDTDS Network Dave Wood [email protected] (858) 735-8808Amateur Telescope Making Peter De Baan [email protected] (760) 745-0925

Have a great new piece of gear? Read an astronomy-related book that you think others should know about? How about a photograph of an SDAA Member in action? Or are you simply tired of seeing these Boxes in the Newsletter rather than something, well, interesting?

Join the campaign to rid the Newsletter of little boxes by sharing them with the membership. In return for your efforts, you will get your very own by line or pho-tograph credit in addition to the undying gratitude of the Newsletter Editor. Just send your article or picture to [email protected].

SDAA Editorial StaffEditor - Andrea [email protected]

Assistant Editor: Craig Ewing













mailto:[email protected]









[email protected]




mailto:// [email protected]





MEMBERSHIP INFORMATIONSend dues and renewals to P.O. Box 23215, San Diego, CA 92193-3215. Include any renewal cards from Sky & Telescope or Astronomy magazine in which you wish to continue your subscription. The expiration date shown on your newsletter’s mailing label is the only notice that your membership in SDAA will expire. Dues are $60 for Contributing Memberships; $35 for Basic Membership; $60.00 for Private Pads; $5 for each Family membership. In addition to the club dues the annual rates for magazines available at the club discount are: Sky & Telescope $32.95 and Astronomy $34. Make checks payable to S.D. Astronomy Assn. PLEASE DO NOT send renewals directly to Sky Publishing. They return them to us for processing.

KQ and Heise Star Party 2014 Schedule

KQ Ranch Heise

10/18 10/4

2014 TDS SCHEDULE

DATE MOON DATA SUNSET

OCT 18 R- 3:03A 18% 6:08P PUBLIC25 S- 7:33P 3% 6:01P

NOV 15 R-12:46A 33% 4:44P PUBLIC22 S- 5:15A 0% 4:41P

DEC 13 R-11:28P 60% 4:41P PUBLIC20 S- 3:55P 3% 4:44P



Image Gallery

Submitted by William Carter

Here is an image of M16 The Eagle Nebula (HaRGB) and was taken with an Atik 460EXM camera (guided by PHD) mounted on an AT8”RC OTA at f/5.6 (with an AP CCD.67 Reducer) on an AP Mach1 mount. It was post-processed with CCD Stack and Photo-shop. This was imaged at the Julian Starfest.



CALLING ALL ASTRONOMY ENTHUSIASTS - PROJECT ASTRO SAN DIEGO NEEDS YOU!

Be a visiting astronomer in a San Diego County school.

- Project ASTRO will provide you with free training, materials, and a rewarding way to help our local schoolchildren and teachers.

Project ASTRO is a program of the Astronomical Society of the Pacific to create partnerships between 3rd-10th grade teachers and local astronomers and space scientists. If you have ever wondered how you can best share your enthusiasm for space and astronomy, AND help your local schools improve their science education, then Project ASTRO is for you.

With a minimum commitment of one training workshop (the next is Saturday NOVEMBER 1, 2014 at R. H. Fleet Science Center) and only 4 classroom visits during the school year, you can make a BIG difference in the education of our next gen-eration of scientists and explorers. And you’ll have FUN - with the most inquisitive and appreciative audience you can find.

Project ASTRO provides all the training and educational materials that you will need, and ongoing support and equipment loan throughout the year.

This is a great opportunity to help kids learn science hands-on, as well as work with a dedicated teacher who desperately needs your knowledge of basic astronomy and space science in the classroom.

For more information, and an application form so that we can match you with a nearby school, please contact the local coor-dinators for Project ASTRO: Dr. Philip Blanco ([email protected]), or Dr. Ron Angione ([email protected]) at (619) 594-6183. or visit the San Diego Project ASTRO Website: http://mintaka.sdsu.edu/projectastro/index.html where you will find further details for volunteers and a FAQ list.

Please apply before NOVEMBER 1 in time for the workshop. (If you cannot make the workshop this year, you may still volunteer).

http://mintaka.sdsu.edu/projectastro/index.html



Space Place partner’s article September 2014

Twinkle, twinkle, variable star By Dr. Ethan Siegel

As bright and steady as they appear, the stars in our sky won't shine forever. The steady brilliance of these sources of light is powered by a tumultuous interior, where nuclear processes fuse light elements and isotopes into heavier ones. Because the heavier nuclei up to iron (Fe), have a greater binding energies-per-nucleon, each reaction results in a slight reduction of the star's mass, converting it into energy via Einstein's famous equation relating changes in mass and energy output, E = mc2. Over timescales of tens of thousands of years, that energy migrates to the star's photosphere, where it's emitted out into the universe as starlight. There's only a finite amount of fuel in there, and when stars run out, the interior contracts and heats up, often enabling heavier elements to burn at even higher temperatures, and causing sun-like stars to grow into red giants. Even though the cores of both hydrogen-burning and helium-burning stars have consistent, steady energy outputs, our sun's overall brightness varies by just ~0.1%, while red giants can have their brightness’s vary by factors of thousands or more over the course of a single year! In fact, the first periodic or pulsating variable star ever discovered—Mira (omicron Ceti)—behaves exactly in this way. There are many types of variable stars, including Cepheids, RR Lyrae, cataclysmic variables and more, but it's the Mira-type variables that give us a glimpse into our Sun's likely future. In general, the cores of stars burn through their fuel in a very consistent fashion, but in the case of pulsating variable stars the outer layers of stellar atmospheres vary. Initially heating up and expanding, they overshoot equilibrium, reach a maximum size, cool, then often forming neutral molecules that behave as light-blocking dust, with the dust then falling back to the star, ionizing and starting the whole process over again. This temporarily neutral dust absorbs the visible light from the star and re-emits it, but as infrared radiation, which is invisible to our eyes. In the case of Mira (and many red giants), it's Titanium Monoxide (TiO) that causes it to dim so severely, from a maximum magnitude of +2 or +3 (clearly visible to the naked eye) to a minimum of +9 or +10, requiring a telescope (and an experienced observer) to find! Visible in the constellation of Cetus during the fall-and-winter from the Northern Hemisphere, Mira is presently at magnitude +7 and headed towards its minimum, but will reach its maximum brightness again in May of next year and every 332 days thereafter. Shockingly, Mira contains a huge, 13 light-year-long tail -- visible only in the UV -- that it leaves as it rockets through the interstellar medium at 130 km/sec! Look for it in your skies all winter long, and contribute your results to the AAVSO (American Association of Variable Star Observers) International Database to help study its long-term behavior! Check out some cool images and simulated animations of Mira here: http://www.nasa.gov/mission_pages/galex/20070815/v.html Kids can learn all about Mira at NASA’s Space Place: http://spaceplace.nasa.gov/mira/en/



Space Place partner’s article September 2014

Images credit: NASA's Galaxy Evolution Explorer (GALEX) spacecraft, of Mira and its tail in UV light (top); Margarita Karovska (Harvard-Smithsonian CfA) / NASA's Hubble Space Telescope image of Mira, with the distortions revealing the presence of a binary companion (lower left); public domain image of Orion, the Pleiades and Mira (near maximum brightness) by Brocken Inaglory of Wikimedia Commons under CC-BY-SA-3.0 (lower right).



Stars are born in groups or clusters when a cold giant molecular cloud collapses under its own gravita-tional force. If many stars form all at once—that is, if star formation efficiency is high—they will stay to-gether as a gravitationally bound open cluster (like the Pleiades) or a globular cluster (like M13 in Hercules). For more than a decade, it has been known that any two stars that are members of the same gravitationally bound star cluster always show the same pattern of chemical abundances. Stars are made mostly of hydro-gen and helium, but they also contain traces of other elements: carbon, oxygen, iron, and even more exotic substances. By carefully measuring the wavelengths

(colors) of light com-ing from a star, as-tronomers can deter-mine how abundant each trace element is. “The pattern of abundances is like a DNA fingerprint, where all the mem-bers of a family share a common set of genes,” said Mark Krumholz, associate professor at Universi-ty of California, Santa Cruz. The pattern of abundances, set at birth, is consistent regardless of an indi-vidual star’s spectral type. But most stellar families don’t stay together: stars don’t form fast enough for

them to remain gravitationally bound, and so groups of stars drift apart, eventually even ending up on op-posite sides of a galaxy. That is likely what happened with our Sun. Thus, astronomers have long wondered whether it might be possible to tell if two stars now on opposite sides of the galaxy were born billions of years ago from the same cloud. In fact, they wondered, might it be possible to find our own Sun’s long-lost siblings? Why such family resemblance? Just one big problem: “Although we see that mem-ber stars of a long-lived star cluster today are chemi-cally identical, we had no good reason to think that this would also be true of stars that were born together but then dispersed immediately,” explained Krumholz.

After all, in a cloud where stars formed rapidly over a light-year apart, might the cloud not have had enough time to homogenize thoroughly, and form stars at the same time but not uniform in chemical composition? “We didn’t really know why stars are chemically homogeneous,” he said. “Without a solid understand-ing of the physical mechanism that produces uniformi-ty, everything was at best a speculation.” So Krumholz and his graduate student Yi Feng ran a fluid dynamics simulation on UCSC’s Hyades super-computer. They simulated two streams of interstellar gas converging to form a cloud that, over a few mil-lion years, collapses under its own gravity to make a cluster of stars. In the simulation, they added red trac-er dye to one stream and blue tracer dye to the other. Fast, early mixing “We found that, as the streams came together, they became extremely turbulent, very effectively mixing the red and blue tracer dyes,” Krumholz recounted. By the time the cloud started to collapse and form stars, everything was purple—and the resulting stars were purple as well. “This was a surprise,” Krumholz exclaimed. “I thought we’d get some blue stars and some red stars, instead of getting all purple stars. I didn’t expect the turbulence to be as violent as it was, and so I didn’t expect the mixing to be so rapid or efficient.” In other runs of the simulation, Krumholz and Feng observed that even clouds that do not turn much of their gas into stars—as the Sun’s parent cloud proba-bly didn’t—still produce stars with nearly-identical abundances. Their findings have given the “chemical tagging” method a boost. “We’ve provided the missing physical explanation of how and why chemical mixing works, and shown convincingly that the chemical mixing pro-cess is very general and rapid even in an environment which did not yield a star cluster, like the one in which the Sun must have formed,” said Krumholz. “This is good news for prospects for finding the Sun’s long-lost siblings.” –Trudy E. Bell, M.A.

Separated at Birth: Finding our Sun’s Long-Lost Siblings?

AstroShort

Two 11-second movies at http://hipacc.ucsc.edu/PressRelease/sibling-stars_videos.html shows face-on and head-on views of a computation-al simulation of a collision of two converging streams of interstellar gas, leading to collapse and for-mation of a star cluster at the center. The simulation reveals that the gas streams are thoroughly homogenized well before stars begin forming. Credit: Mark Krumholz/University of California, Santa Cruz

The University of California High-Performance AstroComputing Center (UC-HIPACC), based at the University of California, Santa Cruz, is a consortium of nine University of California cam-puses and three affiliated Department of Energy laboratories (Lawrence Berkeley Lab, Law-rence Livermore Lab, and Los Alamos National Lab). UC-HiPACC fosters collaborations among researchers at the various sites by offering travel and other grants, co-sponsoring conferences, and drawing attention to the world-class resources for computational astronomy within the University of California system. More information appears at http://hipacc.ucsc.edu

Further reading: The paper “Early turbulent mixing as the origin of chemical homogeneity in open star clusters” is published in the August 31 online issue of Nature. A UC-HiPACC press release is at http://hipacc.ucsc.edu/PressRelease/sibling-stars.html and a UCSC press release is at http://news.ucsc.edu/2014/08/star-formation.html.