Archive | January 2008

The Mystery of the Voorwerp Deepens!

A couple weeks ago, I talked about the Voorwerp (“object”), the strange blue object that Hanny posted to the Galaxy Zoo forum. She asked if anyone knew what it was, and we sure didn’t. Part of the problem was that we didn’t have a spectrum for it, so it could have been literally anywhere from right next door in our galaxy to the edge of the universe. Our colleague Bill Keel took a spectrum, which he posted about here in the blog, and found that the Voorwerp is associated with the galaxy above it. We’ve since been looking around for other colleagues that can help us figure out what the Voorwerp is.

Thanks to Matt Jarvis, who was observing at the 4.2m William Herschel Telescope in La Palma, we’ve been able to get some better images. The William Herschel Telescope is bigger than the telescope that gathers images for the Sloan Digital Sky Survey (SDSS is 2.4 m; WHT is 4.2 m), and the images that Matt took are longer exposures, so we can see fainter features in them. The conditions were also quite good (good “seeing” in astronomer’s lingo) and so the image has very good resolution (it’s “sharper”) as the atmosphere didn’t blur things too badly.

So what kind of data did we get? We got three images in filters very similar to the SDSS ones. We got a g, r and i-band image. Those correspond roughly to green, red and infra-red for human eyes. Just to make things confusing though, we colour g in blue, r in green and i in red to stay consistent with the SDSS/GZ images. Without further ado, here are the original SDSS and new WHT images:


Original SDSS image


New WHT image

The WHT image is rotated with respect to the SDSS image; look at the orientation of the galaxy and the Voorwerp to see how they compare. Once you mentally rotate the images so they match, you can see clearly that the Voorwerp is quite a lot bigger than we initially thought, because so much of it was too faint to be visible in the SDSS image. This immediately makes us want to get an even deeper g-band (blue colour) image to see just how much bigger it is! For that, we will probably go to the world’s largest telescopes such as ESO’s Very Large Telescopes, Gemini or Keck.

To give you an idea just how big the Voorwerp is by now, look at the spiral galaxy next to it. This galaxy is a very massive spiral galaxy, likely as big or bigger than our own Milky Way! That’s really, really big!

If you look at the new WHT image of the Voorwerp, you can also see a huge, gaping hole. From the SDSS images, it wasn’t really clear whether the fuzzy structure there was anything real, but the WHT image makes it clear that this is a genuine hole. Again, just to put it into proportion, that hole has a diameter of something like 10 000 light-years. We have no good idea of what could punch such a large hole. One possibility is that a massive burst of star formation occurred there, causing a string of powerful supernova explosions, causing an expanding bubble. Such holes presumably caused by supernovae have been seen in other galaxies, but as far as we know, nothing anywhere near this size.

In his last post, Bill mentioned that the spectrum of the Voorwerp showed some very odd emission lines, in particular Helium II (HeII) and Neon V. HeII only really appears in spectra when there is something really hot around to excite the gas – something hotter than the hottest star. This could be an active galactic nucleus(i.e. gas falling into a supermassive black hole, and heating up as it falls), or perhaps some high velocity shocks. We’re busy analysing the spectrum to understand better what’s going on here.

By a luck coincidence, the Voorwerp turned out to be at a redshift where the HeII line “redshifted” into a common narrow-band filter. Such a filter blocks all light except in a very narrow wavelength range, and so lets us take an image focusing only on those areas which are emitting light in that wavelength range. Below is the image of the Voorwerp in the wavelength range of the HeII line:


The Voorwerp in HeII

The HeII emission clearly comes from a good chunk of the whole Voorwerp (again,a deeper image might show even more), so whatever is exciting the gas in the Voorwerp seems to do it over quite a large volume.

What’s next? We really still have no idea of what the Voorwerp really is. The more data we take on it, the stranger it gets. Many of us are busy trying to convince friends of ours on observing runs to take observations of the Voorwerp so we can figure out what it is.

That’s how an observational science like astrophysics works: you find something new, you don’t know what it is, so you take more data to try and understand it better and form some hypothesis about what’s actually going on and then you confirm it with more data. But we’re still at the very start of this process. The mystery deepens… *cue scary music.

Tell the story of Galaxy Zoo yourself!

A couple weeks ago, Chris and I attended the meeting of the American Astronomical Society in Austin, Texas. At the end of the meeting, I uploaded the poster I had presented there:

Galaxy Zoo public outreach poster

In a comment to that post, mushroom made a fascinating suggestion:

Could be a fun visual communication exercise to try to make another poster which conveys the same information without using any text.

This is a fascinating idea. I talked it over with the team, and we’re not sure how to go about telling the Galaxy Zoo story without text. But we’re sure that with your creativity, someone can figure it out! And, to phrase mushroom’s suggestion in a different, more general way:

How would you tell the story of Galaxy Zoo?

Here is your chance. We invite you to “remix” the Galaxy Zoo poster, telling the story of Galaxy Zoo in your own words and images. You can start from the original work, or strike out on your own. Here is the original poster, as a JPEG image and as a Word file:

Galaxy Zoo public outerach poster (JPEG)

Galaxy Zoo public outreach poster (Word)

I have created a topic in the Galaxy Zoo Latest News forum called “Remix the Galaxy Zoo poster!” Post your ideas in that thread, or in comments here on the blog. Post your creations there, or if they’re too big to be uploaded, E-mail them to me at raddick “at”

If any of you are wise in the ways of Photoshop, E-mail me, and I can send you the original Photoshop CS2 file.

We’re really looking forward to seeing what you come up with, and we hope this is fun for you too!

Have fun, and keep telling the story!


You may change anything you want about the poster, as long as you leave the following elements. You may move them around, but you should maintain them visibly on the poster:

1) The author names and institutions (“TeamMembers” in the Word file). This is in the standard format for scientific posters and papers.

2) The names of the volunteers, which now appear at the end of the poster. But, of course, feel free to add your own name to our randomly-chosen list!

3) The logos of the institutions involved with Galaxy Zoo.

4) The copyright statement, including the Creative Commons logo.

Random thoughts

A user on the forum asked me what I meant by the word ‘random’ in my previous blog post. A statistician could explain this more precisely, but I’ll give my understanding of it in an astronomy context.

A random process is one in which a variety of alternatives could occur, but beforehand we cannot know which alternative actually will occur. The alternatives need not be equally likely, and the probabilities of each alternative happening (the probability density function) may be known very well. If we repeat the process many times, the number of times each alternative occurs will be very close to the probabilities we might already know. But we don’t know which alternative will actually happen each time the process occurs.

A random system is one which arises as a result of random processes. Everything has some element of randomness in it, nothing is perfectly ordered, but some things have a lot more order to them than others. The chair you are probably sitting on while reading this is a highly ordered system. Even though the atoms in it are jiggling around randomly to some extent, their overall motions are generally very ordered. The random motions of the atoms are not very large compared with the order that was instilled in the chair when it’s materials were constructed, whether that was by metal cooling in a mould or wood slowly forming in a tree.

The motions of stars in a spiral galaxy disk have a lot of order to them, as they are mostly formed by relatively gentle physical processes that maintain information about the history of the system. The galaxy started rotating long ago, and the stars which formed in it are still rotating today. In an elliptical galaxy some process has happened, for example a merger of two galaxies, which disturbs that order. The random process at work is the multiple close interactions of pairs of stars. The motion of two stars after they have passed close by one another is very dependent on the exact values of their motion before the interaction. If each of those stars then interacts with other stars we quickly get to a state where we could never know the stars’ initial motions well enough to predict their motions at a later time. This is an example of a chaotic system, and it can even occur for three objects interacting through gravity, never mind the billions of stars in a typical galaxy. There are many alternative paths the stars could travel along, and beforehand we don’t know which paths the individual stars will take. Despite this, we can go part way to determining what the result will be overall, a big fuzzy ball. The stars in elliptical galaxies are not moving totally randomly, there are certain ranges of orbits that are more populated than they should be for a truly random system. This order is a ‘memory’ of the initial motions of the stars in the merging galaxies. However, most of the stars’ movements are dominated by random motions.

Carnival of Space

Galaxy Zoo features in this week’s Carnival of Space, a collection of all the best space blog writing from the past seven days. This week it’s in a 50s detective story format…and it’s definitely worth a look.

Do galaxies care where they live?

Does where we live make a difference to the kind of person we are? This is a question that has been addressed many times by social scientists, and certainly with more refined thought than the following example, but it will serve our purposes.

Consider one person, Victor, living in a small countryside village, and another, Claire, who lives in the centre of a city. The nearest shops to Victor are many miles away. When he has a sudden biscuit craving and opens the cupboard to find, to his horror, that his wife finished off the last packet the previous evening, it is a great effort for him to travel to the shops to get another. Claire, on the other hand, has merely to stroll to the corner of her road to satisfy her craving for something crunchy. However, while Claire often finds herself nipping out for a packet of biscuits, Victor rarely has the need. He always makes sure he buys plenty of biscuits on his regular weekly shopping trip, and there is always the packet hidden at the back of the other cupboard that his wife hasn’t noticed. Victor is very organised, while Claire clearly isn’t, at least when it comes to biscuits. Does this have anything to do with where they live?

Of course, biscuit buying habits, although important, aren’t the only thing one can say about an individual. Each person is complex and unique, imperfectly describable even by a very large number of personality traits. However, there are simple and obvious ways of crudely dividing up the population. Although we have so far confined ourselves to biscuits, the chances are that Victor is generally more organised than Claire. Perhaps there is a way of dividing people into groups by how organised they are. I’ve no idea, but there are small number of general personality traits, like introvert and extrovert, that describe how many specific personality traits tend to group together, such that you can give reasonably good description of someone by just a few words.

By now you are sure to be wondering what the hell this has got to do with galaxies. Well, to date there has been very little research into the biscuit hoarding characteristics of different galaxies, but like people, galaxies are extremely complex objects. There are so many processes simultaneously going on inside them that we just can’t fully describe each one, never mind understand how those processes go towards forming the properties of the individual as a whole. However, one thing about galaxies, that you can’t help noticing when you’ve looked at a enough of them, is how cleanly they can be split into two different types: spirals and ellipticals. Spirals are, at least in some respects, very organised. Most of their stars are travelling in circles around the galaxy centre in an ordered manner. Ellipticals, on the other hand, are in disarray. Their stars move around on many different, random orbits. (It is interesting how the appearance of order, a nice smooth elliptical galaxy, appears when many unorganised things happen at once, but that is a whole other topic.)

Example galaxies

We’ve made the distinction between spirals and ellipticals completely obvious in Galaxy Zoo by only giving you those two options, along with “star/don’t know”. Even so, if we’d just sat each of you at a table with a pile of galaxy pictures to sort, without giving you any instructions about how to do it, most of you would probably have arrived at the same way of dividing them up. Those of you who value simplicity would have formed two or three piles. The pickier ones amongst you would probably be surrounded by lots of neat little stacks, containing galaxies with two sprawling spiral arms, with many tightly wound arms, big blobs, small blobs, red, blue, and so on. Nevertheless, the main distinction, the difference between all the galaxies on your left and those on your right, would probably be whether they possess a disk, often containing spiral arms, or whether they are just a big, smooth elliptical.

Of course, as many of you will have noticed, not all galaxies do fit into a nice category. So, as well as your stacks of spirals and ellipticals, you would be likely to have a collection of weird objects. However, these only form a small fraction of the whole population of galaxies. Whether you choose to hide your pile of odd galaxies away to one side, or display it smack right in front of you, again depends on your character. The projects examining blue ellipticals or Hanny’s Voorwerp belong to the latter class – confronting the occasional odd object to see what secrets it can tell us. The analysis I have been working on has more of the former character: as most objects are elliptical or spiral, let’s ignore the few weird ones and study how the majority behaves. One problem with working with the majority is that this is very many objects, hundreds of thousands of galaxies. To analyse a dataset this large we have to use statistics, for example we consider the fraction of objects that are elliptical, and how that changes when we only look at galaxies with certain properties.

If you did the galaxy sorting exercise described above you would be reproducing work performed by many astronomers over the past ninety years, including Hubble, de Vaucouleurs and Sandange. This subject is called morphology, literally the study of the ‘forms’ that galaxies take. Strictly morphology doesn’t include a description of the colours of galaxies, but rather their shape or appearance in greyscale.

The distinction between spirals and ellipticals was noted even before it was fully accepted that these objects reside outside our own galaxy. It was also noticed, almost immediately, that spirals and ellipticals are distributed differently on the sky. They all tend to cluster together in groups, rather than being evenly or randomly arranged, but ellipticals cluster much more strongly than spirals. Ellipticals live in galaxy cities, alongside many others, whereas spirals prefer the villages and isolation of the cosmos’ countryside.

To use more scientific language, ellipticals are concentrated in high density regions, where many galaxies are located in a small volume of space. Spirals, on the other hand, are usually found in low density environments, where galaxies are separated from others by large distances. As mentioned earlier, the dependence of galaxy morphology on the density of surrounding galaxies was noticed early in the 20th century. However, it wasn’t until the 1980’s that it was well quantified in two landmark papers by Dressler (1980), looking specifically at large galaxy clusters, and Postman and Geller (1984), who extended the relationships to lower density environments around clusters and smaller groups. These studies tried to classify galaxies as ellipticals, spirals, or lenticulars. This last type is a galaxy morphology somewhere between a spiral and an elliptical: with a disk, but with no spiral arms. Lenticulars are tricky to classify, and so in Galaxy Zoo so far we haven’t asked the classifiers to try and identify them. Galaxy Zoo “ellipticals” will contain normal ellipticals, and most of the lenticulars. This issue will be discussed more in future posts.

PG84 morphology density relation

This figure shows the morphology-density relation from Postman and Geller (1984) and Dressler (1980), based on around 9000 galaxies. The lines show the fraction of ellipticals (red), lenticulars (orange), and ellipticals + lenticulars (purple) versus a measurement of local density. The different lines of the same colour just indicate three different sources. You can see that as local density increases, going from left to right in the figure, the fraction of ellipticals and lenticulars increases.

With the latest Galaxy Zoo data provided to me by Anze, I set to work analysing how a galaxy’s morphology depends on the environment it lives in. The initial thing I had to do was carefully measure and correct for any biases in the morphological classifications. This in itself is interesting, although it tells us more about people and the telescope than about galaxies, so I won’t discuss it further here. The next thing to do was to find out about the environments of the galaxies – specifically the local galaxy density. These were kindly provided by Ivan Baldry, an astronomer at Liverpool John Moores University who has done lots of work on the variation of galaxy colours with environment.

When I had my corrected dataset, with measurements of environment added in, the first thing I looked at was the relationship between the fraction of galaxies that are elliptical and local galaxy density.

Galaxy Zoo morphology-density relation

This figure shows the morphology-density relation for nearby galaxies from Galaxy Zoo, based on 100733 objects. The light shading indicates the very small uncertainties on the relation.

It is difficult to directly compare the Galaxy Zoo morphology-density relation with that by Postman & Geller (1984) shown further above. This is because the local density was measured in a different way, and they include lenticular galaxies separately. However, it is easy to see that the overall behaviour is the same. In regions of high density the fraction of elliptical galaxies increases. The Galaxy Zoo relation is much more accurate, as it is based on more than ten times the number of galaxies, and very clearly defined, which will enable future studies and models to easily compare with it. It shows clearly that morphology depends smoothly on local galaxy density over all environments. Even in the lowest density regions there is some dependence.

Now is a good time to think back to Victor and Claire. Like Victor, organised spiral galaxies tend to live in areas of low density. Disorganised ellipticals are found where many galaxies cluster together, somewhat comparable to the city Claire lives in. But is Victor organised because he lives in such an isolated place, and is forced to be; or is he just an intrinsically organised person, and so living in the countryside didn’t seem such a problem? Likewise, is Claire disorganised because of where she lives? Do the plethora of nearby shops make biscuit hoarding unnecessary? Or is she simply a disorganised person, and so chose to live in the city to avoid having to be organised? If Victor moved to the city, would be become more disorganised? Would the place he lives change his personality?

Obviously galaxies don’t choose where they live, in the sense that Victor and Claire can, but the analogy is still strong. Are there more ellipticals in clusters because that’s where ellipticals happen to be, or because something about where they live has turned them into ellipticals? If otherwise identical galaxies form in areas of different densities, would they be the same, or is there something happening in dense regions that changes galaxies into ellipticals? Maybe something about dense regions turns organised galaxies into disorganised ones.

One of the powers of Galaxy Zoo is the staggering number of galaxies we have data for. It is possible to divide up our sample by a variety of galaxy properties, such as their mass and colour, and still have enough galaxies in each slice to see how environment affects that particular subsample. Each of these different properties tells us something different about a galaxy, and enables us to go someway to disentangling their intrinsic properties from recent changes. I’ll discuss the things we’ve learned by doing this in future posts.

More on the Voorwerp

Kevin asked whether I could provide an entry on our efforts to figure out just what Hanny’s Voorwerp might be. This is definitely a guest blog – I am not a ZooKeeper, but they have been gracious enough to let me feed some of the less delicate animals on occasion.

As a reminder, Hanny posted this object on back on August 13 (I can’t believe it was that long ago now, but apparently the topic scrolled way down in the forum until early December). It showed up on the SDSS color rendition as a deep blue, irregular cloud, just south of the spiral galaxy IC 2497. Pulling out the brightness measurements from the Sloan data in all five filters gave a very unusual result. This thing looked so blue in the color images (made from the gri images) because it puts out almost ten times as much light coming into the g filter as any of the others, and isn’t even detected in the very-far-red z band. That suggests that there is a very strong emission line somewhere in the wavelength range of that filter, about 4200-5500 Angstroms. The SDSS images do show a small object at the north tip of the blob with a more continuous distribution of light; the location is suspicious, but we don’t have direct evidence yet whether it belongs to the Voorwerp. The blob does show structure in the g image, like shells or loops.

Archive searches turned up a radio source in IC 2497, and nothing else helpful (the object just appears on the old Palomar Sky Survey blue-light photographs). A single emission line in that wavelength range could be almost anything, although it was a bit odd that no other emission line was bright enough to produce much light in the other filters. It might be some kind of small nebula in our own galaxy (really small so its dust didn’t block our view of IC 2497 just to the north), some kind of ionized gas cloud associated with IC 2497 itself (redshift z=0.05), or something like the “Lyman α blobs”, gigantic glowing gas clouds seen only in the early Universe (z=3 or so). A spectrum would tell which (if any) of these was correct. So I started emailing friends who use appropriate telescopes pretty regularly, and mostly ended up grumbling about the shortage of spectrographs on 1-3 meter telescopes these days. Meanwhile, I was able to do some measurements with the SARA 0.9-meter telescope, which our university operates remotely as part of a consortium. (In fact, I did these measurements sitting at home, assisted by one of our cats who finds a logbook in front of a monitor the most comfortable place in the house). It takes a pretty long time for a telescope that size to surpass the quick-look Sloan image, but these data were able to narrow down where that strong emission line could be. I used a different set of filters, the classic BVRI set which were designed to be optimized for certain measurements of stars (rather than galaxies), but are helpful here because they’re different. The bright peak made it into the V filter but not the others. The V band runs more or less from 5000-5900 Angstroms, so the wavelength we seek is in the overlap between v and [i]g[/i] between 5000-5500 Angstroms. Alas, that didn’t help us much, since the strong [O III] emission line at 5007 Angstroms would land in that range for something very nearby or at the redshift of IC 2497.


Bill’s cat helping astronomy

Finally, some of the UK zookeepers were able to find a colleague working at the 4.2-m William Herschel Telescope on the island of La Palma who was able to get a spectrum, while some of us were at the big meeting of the American Astronomical Society in Texas (just last week). The WHT is very well equipped for spectroscopy, and La Palma is a superb site (from which I’ve seen the sharpest images from any telescope I could put my hands on). We’ve got a quick-look screensnap of the spectrum, and it answers a couple of questions right away. The Voorwerp is at almost exactly the same redshift as IC 2497, and almost certainly associated with it. The strong and narrow emission lines are what one would see from a star-forming region. But there are some things about it that are strange, and need more work.

I’ve labelled some of the emission lines in the spectrum here. The spectrograph slit was oriented roughly north-south, running through IC 2497 as well, and is shown left-to-right. Wavelength increases from bottom to top; this is a slice of the violet-to-green region, from about 3400-5100 Angstroms in the reference frame of the object itself. We see the hydrogen series (labelled as H+Greek letters), produced when electrons join with free protons to make hydrogen atoms. There are also lines from heavier elements; the brackets denote so-called forbidden lines, radiation which arises from decay of energy levels excited by collisions between ions and electrons. Looking at what we can tell so far about the relative strengths of these features, there is funny business afoot. First, the gas is hot (even by the standards of ionized nebula). The ratio of [O III] lines between 4363 and 4959+5007 is sensitive to temperature (for those who really want to know why, here is an online lecture including details, with abundant thanks to the late Don Osterbrock for pounding this stuff into my thick head). To have the 4363 line even detectable, the gas has to be unusually hot, more like 15-20,000 K (exact numbers are pending getting the final calibrated spectrum from the observers). Even odder are some of the other lines. He II is produced when an electron joins a bare helium nucleus, and requires high enough temperature or radiation with enough energy to tear both electrons from helium (four times harder than for hydrogen). We don’t see this in star forming regions. The only stars hot enough to produce He II in surrounding nebulae are the central stars of planetary nebulae (which are the hottest stars known, but only for a few thousand years) and a handful of X-ray-bright stars usually associated with accretion onto black holes or neutron stars. On top of that, at the blue end of the spectrum is [Ne V]. If it’s hard to rip two electrons from helium, it’s that much harder to pull four from neon lights. This requires 97 electron volts (eV), compared to 54 to make He II and 13.6 to ionize hydrogen. [Ne V] does sometimes show up in planetary nebulae, but even there calculations suggest that it’s not the UV starlight that’s responsible, but that high-speed shock waves may be the culprit. This line is also common in the spectra of active galaxies – Seyfert nuclei and their kin, where we know that there are abundant X-rays interacting with the gas.


So the spectrum tells us where the Voorwerp is, and leaves us with a fascinating conundrum. (To quote an email from a ZooKeeper, “Hmm..that doesn’t make any sense! Excellent…” Not only do we see these high-ionization lines, but we can already see that they come from the whole cloud, not some small bright region. Are we dealing with shocks, or perhaps with radiation from an active nucleus in IC 2497 which is obscured from our point of view but shining full force toward the blob? Or something we haven’t thought of? All good questions. We’ll know more when we have the calibrated spectrum so we can do detailed numerical comparisons.

There are obviously a lot more observations we’d like to have. The gas is shining so brightly that it’s hard to tell what the stars are doing. We’re putting together a request to have the Swift orbiting observatory take a look with its UV camera and perhaps in X-rays as well. Swift was designed to follow up gamma-ray bursts, but they also take requests for where to point while sitting there waiting for a random burst to go off. And not too long from now, it will be the season to propose for Hubble imaging and spectroscopy with the Gemini telescope’s integral-field unit (which gives the spectrum not just along a line, but at every point within a small area of sky).

Whatever this is, it’s rare. After I mentioned wanting to improve my SQL fu to check for more things in the SDSS with its odd colors, Chris Lintott did just that. There are no more things in the survey database which are not imaging artifacts and have colors within 15% of what we see here. There’s more work ahead to make sure that we include the possibility of, say, having H-alpha not fall between the r and i filters as it did here, but there can’t be many more of these. Rare objects suggest rare events, just the kind of thing that it takes a deep sky survey and careful winnowing to find. Dank U wel, Hanny!

AAS Talk

I suspect this is finally the last post relating to the AAS meeting, but I wanted to share the slides from my talk last Friday. Please note that these results are officially provisional! Talks at the AAS are just 5 minutes long (with so many astronomers it’s hard to find space) and I was definitely pushing my luck cramming this much in. As you’ll see, I’m not really one for lots of words on slides so I’ll write a brief commentary between them.


Obligatory title slide complete with names. Sorry Anze for missing out the Berkeley logo.


Pretty Sloan galaxies in need of classification; there were then a couple of slides showing the site design which I’ll presume you’re familiar with.


The picture is from BBC News ‘most emailed’. People seemed to find our competing articles funny.


Note that the first six hours showed nothing (as the server had melted). There was then a slide about the weightings, which Anze has already blogged about.


Look, it works!


The last sentence means that the result was statistically significant, although we now know that’s down to human bias and not the Universe.


I’m still very excited about getting observing time.


and about the blue ellipticals. The Milky Way forms stars at a rate of about 1 solar mass per year, so these things are really going some.


The next few slides have the provisional version on Steven’s results. This shows the fraction of galaxies which are elliptical at a range of densities, from the middle of nowhere on the left to the centre of galaxy clusters on the right.


Same thing, but showing red galaxies as well as ellipticals. People are surprised to be reminded that red doesn’t necessarily mean elliptical.


And the same thing, but for blue ellipticals and red spirals. It’s particularly interesting that red spirals seem to prefer a particular density.


And that’s it. There were some positive questions, mostly about future plans, and then it was on to the next talk.

All slides are copyright the Galaxy Zoo team and shouldn’t be used without permission.

Interview with Chris and Jordan

While we were at the AAS, Jordan and I were interviewed by Pamela Gay of Astronomy Cast. You can hear the results over at Star Stryder. (The good news is it’s audio, so you don’t have to worry about my shirt…)

Galaxy Zoo: the poster

The reason that Chris and I were at the meeting last week was to present results from Galaxy Zoo. On Thursday, I gave a scientific poster session about the public outreach results from Galaxy Zoo – how thousands of people have helped us classify galaxies, and how we hope we have helped you understand the process of science. On Friday, Chris gave a talk about Galaxy Zoo’s science results.

Today, I’ll write about the public outreach poster, and on Thursday, Chris or I will write about the science talk. At this point, two questions might be occurring to you:

1) What the heck is a “poster”?

2) What do we mean by “public outreach”?

There are two main ways of presenting scientific results at meetings. One is to give a talk. At AAS, these talks are 10 minutes, including time for questions – and it goes by quickly! The other way is to present a “poster” at a scientific “poster session.” In a poster session, authors write about their research and tack it up on a bulletin board 4 feet (120 cm) square. They leave the poster up all day, and stand in front of it at designated times, answering questions. Thus, posters are a good way to present “work in progress,” and get feedback from colleagues.

Here is a copy of our poster (it’s the entire poster as a 5 MB JPG image):

Galaxy Zoo public outreach poster

[Note: there is a section on how we are planning a social science study of Galaxy Zoo volunteers. Some of you may be worried about being a part of this experiment. The short answer is, don’t worry. We will not use any classifications in the study unless you explicitly give us permission to include yours, and no classification will be identifiable as coming from a specific person. For a more detailed answer, read the poster or the Galaxy Zoo Meets Social Science topic in the forum. You’re welcome to ask questions as (anonymous) comments here or by private message in the forum to zookeeperJordan.]

Here are three photos of Chris and I standing in front of the Galaxy Zoo poster (I’m the one in the hat).

Chris and I proudly posing in front of the poster:

.Chris and I proudly pose in front of the poster

A long shot of the poster hall, with us in front of our poster. You can see several other posters as well:

A long shot of the poster hall, including people looking at several posters

Chris and I answer questions from an unidentified astronomer:

Answering a question

The content of the poster was about how Galaxy Zoo has supported public outreach in science. Public outreach means many things to many people – it’s everything from creating formal lesson plans for use in schools (what I do with SDSS data) to developing museum exhibits to giving public talks to writings blogs (like Chris’s) and podcasts.

What we are doing with Galaxy Zoo is a new and innovative way of working with the public. Our inspiration was Stardust@Home, where volunteers searched through aerogels to find interstellar dust grains. That took some training and careful examination; Galaxy Zoo requires only a quick glance to classify a galaxy as spiral or elliptical. We’ve also tried to use the forum and this blog to give you some insight into the day-to-day process by which scientists work – an insight that scientists often aren’t able to give because of schedule constraints.

We were just one of maybe 100 posters presented on Thursday, but we got excellent response from the people that stopped by. The astronomy community is excited about what all of us are doing here at Galaxy Zoo. On Thursday, we’ll let you know what we told them about the new science that we are discovering.

AAS: index of zookeeper experiences

I’m back from the AAS meeting in Austin. Last week, Chris and I reported on some of our experiences at the meeting; I know many of you said you wished you could be there, so we wanted to give you a peek at what a scientific meeting was like. There were a lot of posts flying furiously, so this is an index of what we reported on, both here and on Chris’s blog. For more perspectives on the goings-on at the meeting, see the Astronomy Cast LIVE blog. The meeting went from Tuesday to Friday, so this is indexed by day.


Chris wrote about the search for extrasolar planets, both the progress being made and the postponement of some other missions.

Then, Chris posted some highlights of research presented on Tuesday, including three results that have implications for Galaxy Zoo: a study of the importance of classifying galaxies by eye, the discovery of a spiral galaxy that appears to rotate backwards, and the discovery of a voorwerp-like blue blob.


Chris posted some beautiful images of the infrared sky from the UKIRT.

Then, Jordan posted about his experiences at the Sloan Digital Sky Survey booth, answering questions about the survey while wearing a chef’s hat. The purpose of the hat was to advertise a session called “Cooking with Sloan,” which served up hot and fresh galaxy images like the ones you see on Galaxy Zoo.

Chris posted again, about how observers and theorists are both making important contributions to the study of extrasolar planets.

At the end of the day, Chris posted about a talk he went to with the intriguing title of How Astronomers Die.


Thursday was the day of the Galaxy Zoo poster presentation – much more about this tomorrow. We were busy in the morning, but several posts appeared in the afternoon.
First, Jordan posted about pub conversations with a researcher at the University of Alaska Anchorage about the role of scientific research in science education.

Next, Kate and Anze posted about the initial results of the Galaxy Zoo bias study, finding that the apparent excess of anticlockwise galaxies has something to do with human perception and not the universe. They also share some ideas about what we’re doing next.

Then, Chris posted twice in a row, about a study of a galaxy supercluster, then about an interview with him posted on Youtube.

Then, Jordan proudly noted that his chef’s hat had been complimented by a Nobel prize recipient, and later added a slightly embarrassing picture.


Friday was Chris’s talk about the science results from Galaxy Zoo – more on that tomorrow as well.

Then, Kevin posted about one of the fascinating and unexpected results of Galaxy Zoo – Hanny’s voorwerp.

We hope you enjoyed our coverage of AAS. The next meeting is in St. Louis in early June; whichever of us is going to that will try to provide you with coverage of that meeting too.