Next Hangout – Thursday March 6th, 12.00pm Taipei Standard Time
Several of the Galaxy Zoo science team are together in Taipei this week for the Citizen Science in Astronomy workshop. If we’ve been a bit quiet it’s because we’re all working hard to get some of the more recent Galaxy Zoo classifications together from all of your clicks into information about galaxies we can make publicly available for science.
Brooke (@vrooje), Kevin (@kevinschawinski) and Zooniverse developer Ed working hard in Taipei on improvements to the process of how we turn your clicks into science papers.
But we thought we’d take this opportunity of all being in the same place to run a live Hangout. We might end up talking a bit about the process of combining multiple clicks into classifications, as well as some of the recent Galaxy Zoo science results. And we’re of course happy to take questions, either as comments below, as Tweets to @galaxyzoo or via the Google+ interface.
We plan to do this during our lunch break – probably about 12.00pm Taipei Standard Time tomorrow (which is, if I can do my sums, 4.00am UK time, or Wednesday 5th March at 11.00pm EST, 8.00pm PST). As usual the video will also be available to watch later:
Evolutionary Paths In Galaxy Morphology: A Galaxy Zoo Conference
This week much of the team has been in Sydney, Australia, for the Evolutionary Paths In Galaxy Morphology conference. It’s a meeting centered largely around Galaxy Zoo, but it’s more generally about galaxy evolution, and how Galaxy Zoo fits into our overall (ever unfolding) picture of galaxy evolution.
There’s a lot to that legacy already, and it’s still being written.
The first talk of the conference was a public talk by Chris, fitting for a project that would not have been possible without public participation. Chris also gave a science talk later in the conference, summarizing many of the different results from Galaxy Zoo (and with a focus on presenting the results of team members who couldn’t be at the meeting). For me, Karen’s talk describing secular galaxy evolution and detailing the various recent results that have led us to believe “slow” evolution is very important was a highlight of Tuesday, and the audience questions seemed to express a wish that she could have gone on for longer to tie even more of it together. When the scientists at a conference want you to keep going after your 30 minutes are up, you know you’ve given a good talk.
In fact, all of the talks from team members were very well received, and over the course of the week so far we’ve seen how our results compare to and complement those of others, some using Galaxy Zoo data, some not. We’ve had a number of interesting talks describing the sometimes surprising ways the motions of stars and gas in galaxies compare with the visual morphologies. Where (and how bright) the stars and dust are in a galaxy doesn’t always give clues to the shape of the stars’ orbits, nor the extent and configuration of the gas that often makes up a large fraction of a galaxy’s mass.
Karen explains her simple and clear diagram showing different galaxy evolutionary processes.
This goes the other way, too: knowing the velocities of stars and gas in a galaxy doesn’t necessarily tell you what kinds of stars they are, how they got there, or what they’re doing right now. I suspect a combination of this kinematic information with the image information (at visual and other wavelengths) will in the future be a more often used and more powerful diagnostic tool for galaxies than either alone.
Overall, the meeting was definitely a success, and throughout the meeting we tried to keep a record of things so that others could keep up with the conference even if they weren’t able to attend. There was a lot of active tweeting about the conference, for example, and Karen and I took turns recording the tweets so that we’d have a record of each day of the Twitter discussion. Here those are, courtesy of Storify:
Also, remember at our last hangout when we said we’d have a hangout from Sydney? That proved a bit difficult, not just because of the packed meeting schedule but also because of bandwidth issues: overburdened conference and hotel wifi connections just aren’t really up to the task of streaming a hangout. We eventually found a place, but then it turned out there was construction going on next door, so instead of the sunny patio we had intended to run the hangout from we ended up in an upstairs bedroom to get as far away from the noise as possible. Ah, well. You can see our detailed discussion of how the meeting went below, including random contributions from the jackhammer next door (but only for the first few minutes):
(click here for the podcast version)
And now we’ll all return (eventually) to our respective institutions to reflect on the meeting, start work on whatever new ideas the conference discussions, talks and posters started brewing, and continue the work we had set aside for the past week. None of this is really as easy as it sounds; the best meetings are often the most exhausting, so it takes some time to recover. I asked our fearless leader Chris if he had a pithy statement to sum up his feeling of exhilarated post-meeting fatigue, and he took my keyboard and offered the following:
gt ;////cry;gvlbhul,kubmc ;dptfvglyknjuy,pt vgybhjnomk
I’m sure that, if any tears were shed, they were tears of joy. This is a great project and it’s only getting better.
Left to Right: Tom, Kevin, Bob, Amit, Ed, Chris S, Bill, Kyle, Chris L, Ivy, Brooke, Karen, Julie
What is a Galaxy? …the return
The first time I gave a public talk, I spent an hour describing why galaxy classification is fundamentally important to the study of the Universe, the origins of Galaxy Zoo, the amazing response of the volunteers and the diverse results from their collective classifications of a million galaxies near and far. I showed many gorgeous galaxy images, a few dark matter simulations and even a preview of the Hubble image of Hanny’s Voorwerp.
As I finished my talk and the Q&A began, I braced myself for the inevitably interesting and challenging questions (I seem to get a lot of questions about black holes and spacetime).
A brief pause, and then the first question echoed from somewhere in the darkened auditorium: …”What’s a galaxy?”
Oops. Apparently I’d forgotten that little detail at the start of the talk. So I described a typical galaxy (if there is such a thing): a collection of stars, gas, dust, dark matter, all gravitationally bound together. Then I made a joke about scientists forgetting to define their terms, and we moved on to the next raised hand.
Turns out, though, it’s not such an easy question. Even though my casual definition works fine for most galaxies, it’s not at all an agreed-upon standard. We’ve discussed this on the blog before, and even in the short time (astronomically speaking) since Karen wrote that very nice post, more work has been done to find galaxies that push the boundaries and force us to re-think what it really means to be a galaxy.
The circled stars (plus a lot of dark matter you can’t see) are Segue 1, one of the smallest galaxies we know about. To read more on this, click the image.
So, spurred by a very broad interpretation of a question left for us in the comments on the post announcing this hangout, we decided to re-visit the discussion, covering the various properties a galaxy must have, should have, could have, and can’t have. We discussed the smallest galaxies, found by counting and measuring each of their individual stars. We discussed the biggest, brightest galaxies in the universe, living in rich environments and grown fat by eating other galaxies. And everything in between.
Note: when we talk about Segue 1 and 2, I say that these galaxies are unique because they have low mass-to-light ratios. Despite the pause that indicated I was trying to keep from inverting numerator and denominator… that’s exactly what I did. The galaxies have very few stars compared to the amount of dark matter in them, so their mass is high and their light is low, so their mass-to-light ratios are high. Oops (again)!
Galaxy Zoo Quench – Experience the Full Scientific Process
Experience Science from Beginning to End! Classify, Analyze, Discuss, and Collaboatively Write an Article!
Galaxy Zoo and other Zooniverse projects have given thousands the opportunity to contribute to scientific research. It’s time to take the role of volunteers to the next level. For the next two months*, this new Galaxy Zoo Quench project provides the opportunity to take part in the ENTIRE scientific process – everything from classifying galaxies to analyzing results to collaborating with astronomers to writing a scientific article!
Galaxy Zoo Quench will examine a sample of galaxies that have recently and abruptly quenched their star formation. These galaxies are aptly named Post-Quenched Galaxies. They provide an ideal laboratory for studying how galaxies evolve from blue, star-forming spiral galaxies to red, non-star-forming elliptical galaxies. Using the more than a million galaxies in the Sloan Digital Sky Survey, we identified ~3000 post-quenched galaxies. By classifying these galaxies and analyzing the results, we will explore the mechanisms that quenched their star formation and investigate the role of post-quenched galaxies in galaxy evolution.
The entire process of classifying, analyzing, discussing, and writing the article will take place over an 8 week period*, beginning July 18th. After classifying the galaxies, volunteers will use the tools available within Zooniverse to plot the data and look for trends. Through reading articles and interaction in Talk, volunteers will gain background information. Throughout, they’ll discuss with the science team their interpretation of the results. At the end of the process, volunteers and the science team will collaboratively write a 4-page Astrophysical Journal article.
What causes the star formation in these galaxies to be quenched? How do interactions impact galaxy evolution? What is the fate of our Milky Way? Join us this Summer (or Winter if you’re below the equator!) in exploring these questions, being a part of the scientific process, and contributing to our understanding of this dynamic phase of galaxy evolution!
CLICK HERE TO PARTICIPATE!
We’ll be sharing more details about this project during the next Galaxy Zoo Hangout, on Monday, July 15th at 14:00 CST / 19:00 GMT / 20:00 BST. Have questions about the project? Post them here or tweet at us (@galaxyzoo). Just before the Hangout starts, we’ll embed the video here so you can watch from the blog.
The best way to send us a comment during the live Hangout is through twitter (@galaxyzoo). You can also leave a comment on this blog post, or on Google Plus, Facebook or YouTube. See you soon!
Update: here’s the hangout (and the mp3 version)!
*Note: science timelines often subject to a factor of two uncertainty. We’ll do our best to keep on track, at the same time expecting the unexpected (all part of the fun of doing science!).
Clicking 10 Billion Years Into The Past
Astronomers use funny units. We have the light-year, which sounds like a time but is actually a distance. There’s the parsec, a historical (but still used) unit of distance that was famously mis-used as a time in Star Wars. And then there’s redshift, which is actually a velocity — distance divided by time — but which, because of the expansion of the universe, astronomers get to use as a proxy for distance.
While it may be convenient for us to use distance units where we set a mind-blowingly large number equal to 1, it doesn’t really help us communicate our work to the public. If I note that the galaxy images from CANDELS look a little different from the galaxies in the SDSS because the CANDELS galaxies are typically at a redshift of 2, that’s pretty meaningless. But it’s a little different to think of the fact that, when you classify a galaxy from CANDELS, you may be looking three-quarters of the way to the edge of the visible universe, and seeing the galaxy as it was 10 billion years ago.
Okay, that’s kinda cool.
During this hangout, we announced that your clicks and classifications of the CANDELS galaxies have been moving at such an impressive rate that the first round is finished. Every galaxy has enough classifications for us to get a very good sense of what its morphology is. It may be that, for some of the galaxies where there are clearly more details to flush out, we will ask for a few more classifications per galaxy. And there will probably be future CANDELS images from survey fields that are still being completed. So, don’t worry, there will still be plenty of opportunities to classify galaxies as they were 10 billion years ago!
In the meantime, though, we’re getting ready not just to do the scientific analysis, but to share Galaxy Zoo results with our colleagues around the world. The summer conference season is upon us, and many of us have given and are giving talks and posters at various meetings in various cities. This includes not just the recent meeting highlighting the importance of galaxy morphology in the era of large surveys at the Royal Astronomical Society and the upcoming ZooCon in Oxford and Galaxy Zoo meeting in Sydney, but also several more general conferences, including the 222nd American Astronomical Society meeting and the upcoming UK National Astronomy Meeting. Spreading the word about the scientific results we’re finding with Galaxy Zoo is one of the most important parts of our job — and it doesn’t hurt that in order to do that we have to visit some very interesting places. During the hangout we chatted a bit about that and also took some of your questions:
Note: although it was a beautiful sunny day in Oxford, the variable audio quality is not because I was occasionally distracted looking out the window. I don’t think it was the new microphone, either. We’ll look into it, but in the meantime I’ve tried to equalize the podcast version with some after-editing, so hopefully that is slightly better.
Next GZ Hangout: Thursday, June 6th, 15:00 GMT
It’s been a while since we’ve had a hangout — how about this Thursday?
8:00 PDT, 11:00 EDT, 15:00 GMT, 16:00 BST, 17:00 CET, 18:00 CAT. Have questions? Post them here or tweet at us (@galaxyzoo). Just before the hangout starts, we’ll embed the video here so you can watch from the blog.
The best way to send us a comment during the live hangout is to tweet at us, but you can also leave a comment on this blog post, or on Google Plus, Facebook or YouTube, which we’ll also try to keep an eye on. See you soon!
Using Space Warps to Discover and Weigh Galaxies
John Wheeler once summarized General Relativity as “Matter tells space how to curve, and space tells matter how to move.” While that is a handy description, and while there have been many textbooks written, lectures given and websites constructed to explain this, the quote itself doesn’t address what happens to the light streaming through the universe as it encounters the warped space curved by matter.
The simple answer is: it curves too, and Einstein’s equations provide predictions for exactly how it works. In fact, observations of the bending of starlight around the Sun were one of the first implemented tests of General Relativity, and it passed with flying colors. On the scale of the Universe, the Sun isn’t that massive, but it’s massive enough to bend the light just a little, and by exactly the amount the equations predicted.
Those equations say that more matter in the same place is more likely to produce a strong lens effect, distorting and magnifying a background source. So what happens when you have a *lot* of matter, say, in a big galaxy or a cluster of galaxies?
From left to right: a) an Einstein cross (credit: NASA/ESA); b) an example from the Space Warps dataset; c) a known lens in CANDELS that Galaxy Zoo users spotted.
Some pretty impressive configurations, which are rare but which humans are best at finding — hence Space Warps, the Zooniverse’s newest project and our astronomical project sibling. Co-lens-experts Phil Marshall and Aprajita Verma joined us during this hangout to describe how they use gravitational lenses to weigh galaxies. In particular, they can tell the difference between Dark Matter and “matter that’s dark” — the former being the exotic particles that are very different from stars and gas and planets and people, and the latter being normal matter that isn’t bright, such as brown dwarf “stars” that never actually ignited.
Note: Google+ was feeling a bit out of sorts, so the first minute or so of the broadcast was cut off, during which time Bill Keel showed us the first known image of a gravitational lens, from 1903. We went on to talk about all of the above, and more besides, including the importance of simulated lenses, why the images Space Warps uses are specially tuned to help us find lenses, and how the science team (which includes citizen scientists from Galaxy Zoo!) plan to turn our clicks into discoveries.
(or download the podcast mp3 here)
Notice my swapping of pronouns to “we” — I’m not on the Space Warps science team, but I’ve done nearly 100 classifications now myself! I can’t wait to see the results start to come in from this project.
Next GZ Hangout: Thursday, May 9th, 15:00 GMT – with special guests!
Our next hangout will be this Thursday, the 9th of May, at 15:00 GMT, which is 8:00 PDT, 11:00 EDT, 16:00 BST, 17:00 CET, 18:00 CAT… and midnight in Japan.
Why Japan? Does that have anything to do with the special guest participant(s)? And why is there an image of a gravitational lens on this blog post?
You’ll have to tune in to see!
The best way to send us a comment during the live hangout is to tweet at us (@galaxyzoo), but you can also leave a comment on this blog post, or on Google Plus, Facebook or YouTube, which we’ll also try to keep an eye on. See you soon!
Oh, Sweet Spiral Of Mine
See the video of our latest hangout here (or, if you prefer, click to download the podcast version):
Spiral galaxies are seemingly endless sources of fascination, perhaps because they’re so complex and diverse. But why does spiral structure exist? Why do some spiral galaxies have clearly defined spiral arms and others have flocculent structure that barely seems to hold together? What’s the difference between a 2-arm spiral and a 3-arm spiral? How many kinds of spirals do we actually observe? And what is happening to the stars and gas in spiral galaxy disks?
Clockwise from top right: X-ray, UV, optical, near-IR, mid-IR, far-IR, radio
All of the above questions are related to a question we got right at the end of our last hangout: what is the significance of the number of spiral arms? Determining how many spiral arms a galaxy has is hard, and is often subjective — so why bother?
It’s a good question. Part of the reason spiral arm classification & count is a challenge is that it often depends on the wavelength at which you observe a galaxy. New stars tend to form along the spiral arms, whereas older stars have time to spread out into more uniform orbits. So ultraviolet observations of a galaxy, which tend to pick out the new and bright stars, often highlight the spiral arms much more strongly than longer-wavelength observations, which see more light from older stars.
It’s not quite that simple, though. As you get to longer and longer wavelengths, you start to pick up the heat radiated by clouds of gas and dust, which are often stellar nurseries — and often trace spiral arms. At a wavelength of 21 centimeters you can detect neutral Hydrogen, which provides raw material for the cooling and condensation of gas into cold, dense molecular clouds that form stars in their densest pockets. Each wavelength you observe at provides a glimpse at a different targeted feature of a spiral galaxy.
A map of neutral Hydrogen in the Milky Way — complete with yellow “you are here” arrow.
Including our own, of course: we live in a spiral galaxy (though how many arms it has, and whether it’s flocculent, is a matter of debate), and it provides the best means of studying star formation up close. When studying other galaxies, it’s easy to get caught up in the race to discover the biggest, the smallest, the farthest and the most extreme, and forget that our own Universal neighborhood is pretty amazing too.
Herschel sees much longer wavelengths than HST, so its resolution isn’t as high even though it has a bigger mirror. (Click to see a larger version.) Credit: ESA/NASA
For example, one of the most famous nebulae in the world was recently imaged by one of the most famous telescopes in the world — again — but this time in the near-infrared. The Horsehead Nebula is a well-known feature in the Orion star-forming complex, and the new Hubble images provide a great opportunity to learn even more about this region that has been studied for hundreds of years. How thick and cold is the gas and dust in the nebula? How long will it take for it to dissipate under the harsh radiation of the bright, young stars near it? What’s going on behind it?
The near-infrared view from HST is sort of the sweet spot in this spectacular space — the wavelengths aren’t so long that the resolution suffers, but they are long enough that you see through a bit more of the clouds than in the optical. So you see more of the structure of the cloud itself, and more of where it’s thin and thick. If you zoom in, you can even see distant galaxies peeking through! And not just on the edges: in some parts you can see galaxies through the middle of the nebula. Wow. This image alone contains spiral galaxy insights big and small, near and far, from the very distant universe and right in our own backyard.
Note: right at the end of the hangout, we again got another great question from a viewer that we didn’t have time to answer. So stay tuned for the next hangout when we just might have a thing or two to say about dark matter, dark energy and new projects!
Next GZ Hangout: Thursday, April 25th, 18:30 GMT
Our next hangout will be on Thursday the 25th of April at 6:30 p.m. GMT, which is 11:30 a.m. Pacific Daylight Time, 2:30 p.m. Eastern Daylight Time, 7:30 p.m. British Summer Time, 8:30 p.m. Central European Time and 9:30 p.m. Central African Time.
Just before the hangout we’ll update this post with the embedded video, so you can watch it live from here. Last time we had some great live tweets from volunteers during the hangout. If you’re watching live and want to jump in on Twitter, please do! we use a term you’ve never heard without explaining it, please feel free to use the Jargon Gong by tweeting us. For example: “@galaxyzoo GONG big bang nucleosynthesis“.
In the meantime, please feel free to leave a question in the comments section below. See you soon!
Update: view the summary and video here!
Galaxy Zoo 