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Welcome-To-The-Galaxy-Zoo.Pdf

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wo astronomers walk into a pub … Welcome to the This could set up any number of jokes, but in fact it describes the genesis of the Zoo project, a uniquely successful research partnership that has grown to involve over a Tquarter-million people from all walks of life, all over the GGALAXYALAXY world, at the forefront of scientific discoveries. This sample classification screen from One evening in early 2007, two spins. Lintott and Schawinski envisioned the original project shows off Oxford University astronomers wan- a system in which members of the public the simple, clean layout. The buttons eas- dered into The Royal Oak pub to unwind could help classify all of the nearly one ily allow users to classify any galaxy as clockwise spiral, anti- or counterclockwise a bit, a few blocks from the million in the SDSS main galaxy spiral, edge-on spiral, elliptical, merging, lab and within sight of the 18th-century sample — if not in full detail, certainly or “don’t know.” Galaxy Zoo Radcliffe Observatory tower. Graduate into broad categories that would be use- student and postdoc- ful for a range of scientific problems. toral researcher were pon- They sketched the first draft of the inter- dering ways to go beyond the scope of face and system design on a napkin. With Schawinski’s dissertation project. Some- that, Galaxy Zoo was born. how, he had to visually sort through Ordinary people classifying galaxies makes one of 50,000 galaxies from the Sloan Digital ZZOOO Sky Survey (SDSS) to identify samples of the world’s most enjoyable citizen projects interest. (Incidentally, Lintott is perhaps by William Keel better known as co-presenter of the long- also one of the most successful. running BBC television production , along with .) Inspired by the success of such proj- ects as NASA’s Stardust@Home, which invited the public to help find interstellar dust grains captured by the Stardust mis- sion, they soon found that some local cosmologists had thought of a similar way to improve our knowledge of other issues such as the similarity of galaxy

University of Alabama astronomer William Keel specializes in the study of galaxies, specifi- cally their history, interactions, and content. He is author of The Road to Galaxy Formation (Springer Praxis, 2002) and The Sky at Einstein’s The Royal Oak pub at Oxford is the site of the Galaxy Zoo’s genesis. After astronomers Kevin Feet (Springer Praxis, 2005). Schawinski and Chris Lintott came up with the idea over drinks, they sketched the first details on a cocktail napkin. William Keel

Alison Mackey They sketched the first draft of the interface and system design

Astronomy: on a napkin. With that, Galaxy Zoo was born.

© 2010 Kalmbach Publishing Co. This material may not be reproduced in any form without permission from the publisher. www.Astronomy.com 30 Astronomy • September 2010 Alvin555 | Dreamstime.com, www.Astronomy.com 31 Birth pains Fortunate timing led to a quick boost Less than 3 years after the initial computer crashes, from news stories on the BBC’s website. So many users tried to sign up and take nearly a quarter of a million participants have provided part that it damaged the computer origi- nally serving the data. The quick work of more than 60 million total classifications. a team at Johns Hopkins University in Baltimore saved the day, and probably the project; Galaxy Zoo thus learned to Zooites started posting interesting be ready to respond quickly when public galaxies for comment, questions about interest is high. classification, and science musings. This Galaxy Zoo began modestly enough is about the time I joined the Zoo, and as a way to expand the number of galax- eventually became part of the science COUNTERCLOCKWISE SPIRAL CLOCKWISE SPIRAL ies a single graduate student could exam- team after noticing that some possible ine. It not only has yielded a series of galaxy mergers were more likely to be hitherto-unavailable science results, how- non-interacting galaxies that appear to ever, but it also became a pathfinder for “overlap” despite their great distance. participatory in the Inter- Some of the Zoo’s popularity traces to net age. In this it goes beyond projects smart decisions, and a bit of luck, in its such as Stardust@Home — like zombies, setup. The classification interface is clean the Zoo is interested in your brains. The and needs only limited comprehension original idea was simple and, in execu- of English. Wondering whether the next tion, habit-forming. galaxy will be a big, beautiful spiral or a Volunteer participants see one of a teeming cluster creates some of the sus- Besides accomplishing significant science by helping astronomers classify galaxies, the Galaxy million galaxies from the SDSS and clas- pense of a video game and keeps Zooites Zoo project has also created a “galaxy font” using actual galaxies. SDSS, Galaxy Zoo Team sify it as elliptical, one of three spiral clicking for more. The Zookeepers dis- orientation classes, a merging system, or covered how important these features something else. Hoping for a few thou- were when moving to Zoo 2, which asks The human element informed of project activities, and all EDGEON SPIRAL sand participants to finish looking at all more detailed questions about the As Zooites have learned about galaxies projects should have genuine research these galaxies over perhaps a year, the brightest galaxies. Incorporating new (as well as stars, clusters, and nebulae), goals rather than including simple busy- project’s immediate success left the team lessons about the interfaces with feed- the Zookeepers have learned about deal- work (“no clicks wasted”). Dealing with a scrambling to keep adequate computing back from users, and doing so before ing with Zooites. Several guiding prin- wide range of people in the forum also resources available. Less than 3 years many Zooites lose interest, proves to be a ciples emerged: Zooites are collaborators, has proven instructive, and the team after the Zoo’s initial computer crashes, sometimes tense challenge. not “users.” They should be kept fully leaders compare it to a crash course in nearly a quarter of a million participants applied psychology. have provided more than 60 million Why not just let a computer do all total classifications. this? The SDSS data were all evaluated The project team was initially flooded automatically to find objects, separate with too many e-mail queries to answer. stars from galaxies, and quantify the So they set up a discussion forum hoping match between each image and various users could help each other when the kinds of galaxy structures. Astronomers team couldn’t respond. This forum not and computer-science specialists have only has served as a venue to share expe- put considerable effort into automating ELLIPTICAL MERGING riences and help newcomers, but it also the assessment of objects in astronomical As these images demonstrate, the general galaxy classifications of counterclockwise spiral, has been a source of additional scientific images, both to make the process imper- clockwise spiral, edge-on spiral, elliptical, and merging are relatively easy to distinguish. (From results and a way to form a tight-knit sonal and to survey the ever-larger data top left to bottom right: M51, M83, NGC 4710, NGC 1132, and NGC 6670.) Most galaxies, however, community of users (“Zooites,” as they sets that the new instruments delivered. don’t fit so cleanly into these categories. NASA/ESA/S. Beckwith (STScI)/The Hubble Heritage Team (STScI/AURA); European South- came to call themselves, in distinction to Still, for many of these tasks, software ern Observatory; NASA/ESA/P. Goudfrooij (STScI); NASA/ESA/Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; NASA/ESA/Hubble Heritage (STScI/ the “Zookeepers” who run the project). leaves much to be desired. AURA)-ESA/Hubble Collaboration/A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University) Identifying fragmentary spiral pat- terns, distinguishing galaxies distorted by interaction from those only overlapping The original idea was simple and, in execution, habit-forming. along the line of sight, and identifying which distinct objects in an image might The used New Mexico’s to map more than a quarter of the sky, including several sights still unseen by human eyes. The Galaxy Zoo project aims be parts of a single galaxy — all are tasks to have human volunteers classify many of the galaxies in these images, helping astronomers find for which people have proven more accu- interesting objects and phenomena to do follow-up research on. Fermilab Visual Media Services, www.sdss.org rate after just brief practice. In fact, the

32 Astronomy • September 2010 www.Astronomy.com 33 up observations began only after a group of Zooites gathered the SDSS data and made the case to the Zookeepers. Further “What’s the blue stuff below? Anyone?” — Hanny van Arkel projects of this kind involve irregular gal- axies and nearby high-velocity stars. The depth of interest has been amaz- ing: Some volunteers have learned data- base query protocols and scripting languages to be able to winnow through the SDSS database on their own for these programs, and have even been co-authors on science papers reporting the results. The ownership Zooites show in the entire project has been another impressive, and mostly unexpected, outcome, reflected in the number of research papers (11) that include Zooites as authors.

The future Zoo The Zoo is now in its second phase, with participants contributing more refined classifications of bright galaxies. At a broader level, it has expanded its scope to the “,” embracing additional A 2009 meetup in Greenwich, England, brought 40 Zooites together, 0.016 percent of the total. Hanny’s Voorwerp (Dutch for “Hanny’s Object”) may be Galaxy Zoo’s most famous discovery. When a Dutch schoolteacher saw unusual “blue stuff” Despite few actually having careers in science, these volunteers have advanced astronomy signifi- below galaxy IC 2497 (at left), she posted the picture and asked for feedback. Despite more intricate observations from Kitt Peak National Observato- astronomical projects. cantly, sometimes even co-authoring papers in scientific journals. William Keel ry’s 3.5-meter WIYN telescope (at right), its remains mysterious. SDSS; William Keel and Anna Manning A new application, Merger Zoo, allows users to compare simulations of merging galaxies to actual images (another task at the action practically as it’s happening, extending this approach to the distant next round of upgrades has used the Gal- asked simply, “What’s the blue stuff virtually turned off within the past which people still prove to be much bet- picking out supernovae from false posi- using the rich Hubble Space axy Zoo results to help train the software below? Anyone?” 80,000 to 100,000 years. Either conclu- ter than software). The participants zero tives before large telescopes follow up Telescope archive, as has Moon Zoo, to be even faster and more accurate, The Zookeepers collected available sion has a strong impact on how we in on the best matches before performing with spectroscopic analysis, while Solar which uses Lunar Reconnaissance completing the next step in the spiral of information to constrain speculation on think about and their occur- more detailed, and time-consuming, sim- Storm Watch lets users track any solar Orbiter images to map the history of the the human-machine partnership. its nature until it was clearly time for new rence in galaxies. ulations to unravel the galaxies’ physical outbursts seen by the twin STEREO Moon via counts of craters and boulders. data. Colleagues from the U.K. to Cali- The nearest analogs to Hanny’s Voor- properties. Supernova Zoo puts people in spacecraft. Hubble Zoo has gone live, As part of the Citizen Science Alli- Science at your fingertips fornia obtained light measurements that werp are giant ionized gas clouds occa- ance, the Zoo team is also investigating The Zooites have by now exceeded all of showed this to be a cloud of gas tens of sionally seen on the outskirts of active non-astronomical applications of its the Zoo’s original science goals. They thousands of light-years in extent, illumi- radio galaxies, where powerful methodology and information infra- have identified red spirals and blue ellip- nated by an unseen (the super- radiation encounters unusually dense gas. structure — discussions have included ticals, outliers to the general rules con- energetic centers of some galaxies). These Zoo participants have proven able to pick animal behavior and papyrus recon- necting galaxy form and content. The measurements set off further programs these out by their unusual colors in the struction. Looking ahead within as- Zoo has shown differences in the growth aimed at examining it in other wave- SDSS images, adding considerably to the tronomy, it has become clear that the history of massive black holes between lengths, from radio to X-ray. known sample and strengthening the human-machine partnership will have to spiral and elliptical galaxies, and contrib- By now, Hanny’s Voorwerp (the Dutch points of comparison for Hanny’s Voor- change shape yet again with future uted to the known characteristics of word for object, albeit not usually used in werp. Some participants worked with me projects such as the Panoramic Survey merging galaxies. this context) has undergone examina- to set up a “Voorwerpje hunt” (the Dutch SDSS 0914 SDSS 1145 Telescope & Rapid Response System Additional science results have arisen tions from additional ground-based opti- diminutive form of Voorwerp), in which (Pan-STARRS) and the Large Synoptic from objects posted by participants for cal telescopes, a continent-wide network at least 10 people examined 15,000 active Survey Telescope (LSST). With such discussion on the project forum — these of European radio telescopes, the Wester- galaxy candidates within a 6-week period. mammoth surveys, more intense than include overlapping galaxies suitable for bork and MERLIN radio arrays, Kitt This sort of screening approach, with any that have come before, Galaxy Zoo’s measuring dust absorption and the giant Peak’s WIYN telescope, the Hubble Space objects culled for further inspection by efforts will be best used to train and ionized gas cloud known as Hanny’s Telescope, the GALEX spacecraft, the the science team, has proven to be a pow- check on automated routines, as well as Voorwerp, the signature discovery of the Swift and Suzaku X-ray telescopes, and erful specialty of Galaxy Zoo. examine oddities flagged automatically. Zoo. Although several dozen users had the XMM-Newton X-ray observatory. Some projects have arisen strictly It’s fun and it’s educational, so why earlier seen the galaxy IC 2497 for clas- The current data allow two possibili- because of interest among Zooites, inde- SDSS 1442 UGC 5769 not join us on a field trip to the Zoo and sification, it drew special attention only ties, both unprecedented — either the pendent of the science team. Most nota- Galaxy Zoo volunteers, or “Zooites,” have helped classify these galaxies, a type known as “back- see for yourself? after a couple of weeks when Dutch ele- nearest quasar lies behind so much ble so far has been identifying a class of lit” galaxies and of particular interest to astronomers. Galaxy Zoo brought the number of such gal- mentary school teacher Hanny van obscuring gas and dust that even X-ray compact galaxies with extremely high axies from a few dozen to more than 2,000. William Keel and Anna Manning Read “Making sense of galaxies” Arkel posted its image on the forum and surveys have failed to find it, or it has star-formation rates, the “Peas.” Follow- online at www.Astronomy.com/toc.

34 Astronomy • September 2010 www.Astronomy.com 35

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