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Two Atoms Populate on a Dust Grain

I enjoy days where we get to use questions from the public to meander our way through the Universe. Our latest live hangout saw us discussing the latest update to the Galaxy Zoo site — made based on your clicks! — and doing a live, collective classification on a few example objects from our Hubble sample that we hope represent the kind of things you’ll be seeing more of from now on.

We debated, for example, whether this galaxy’s central “feature” was a bulge or a bar:

bar versus bulge? overlap versus merger?

We also discussed whether these galaxies are merging or overlapping.

Whether this relatively featureless galaxy’s blue smudge indicates a voorwerp:

GDS_13741

Depending on the redshift, a voorwerp in Hubble could be blue, green or red.

And how many spiral arms this galaxy has:

GDS_13741

Also, these two galaxies may have roughly the same proportions between them as between the Milky Way and the Large Magellanic Cloud.

We also talked about the origin and importance of dust in galaxies, and just what a green pea would look like in the Hubble data. Green peas are galaxies with incredibly high rates of star formation. They’re rare in the local Universe, but how rare do we think they were billions of years ago, at the epoch we’re looking back to with Hubble?

GDS_4792

Thing is, a “green pea” at redshift z=2 would be bright red.

And, for that matter, what were the stars like then? Astronomers very broadly group stars into three populations depending on their composition. The very earliest stars were made from the primordial elements forged during the Big Bang — almost entirely Hydrogen and Helium, nearly devoid of anything else (we call “anything else” a metal, including elements like Carbon and Oxygen). The next generation of stars had some metals, but the Universe has been around long enough that those stars (even the lower-mass ones that live for a long time) are past their prime and a new generation, one with compositions generally like our Sun, are now in their heyday.

Naturally, though, since the Sun is our First Star, we call its generation Population I. The slightly older stars, many of which are still around and living in our galaxy and others, are Population II; and the very massive rockstars of the early universe that have all died out are called Population III. So “Pop III” were the first stars — a slight reversal, but labels and names that seemed like a better idea at the time than with hindsight are nothing new in Astronomy. (Exhibit A: the magnitude system. Exhibit B: “planetary nebula“.)

Bonus: green peas, voorwerpjes, and planetary nebulae are just three of the phenomena that (at least in part) glow green to human eyes because of one particular frequency of light emitted by Oxygen at a certain temperature, an atomic transition seen only rarely on Earth but fairly often in the Universe.

Planetary Nebula IC 1295 - ESO

This VLT image shows the planetary nebula IC 1295 in ghostly green. Image Credit: ESO

Also, did you know that dust grains are the singles bars of the atomic universe, allowing atoms to meet and combine into molecules and cooling the gas clouds they live in — which in turn helps new stars form? Heating and cooling, gravity and pressure, and the interplay between atoms, molecules, and radiation are all a part of what gives us this amazingly diverse Universe. We understand quite a lot of it given that we are such a tiny part of it, but what we know is dwarfed by what we don’t. And that’s just the way astronomers like it… we love a challenge and we’re glad to have as much help as possible sorting things out.

Here’s the hangout video:

And click here to listen to the mp3 podcast version.

Next GZ Hangout: Wednesday, 10th April, 19:00 GMT

We’re trying a new time for our hangouts to make it easier for those of our viewers in North America to tune in live. Our next live hangout will be on Wednesday the 10th of April at 7 pm GMT. That’s 9 pm in Europe, 8 pm in the UK, 3 pm EDT and 12 pm PDT. Even if you live in Hawaii you won’t have to skip your morning cuppa to hang out with us (9 am HST)!

Update: The video link and the summary post (also with a video link) are here.

If you have any questions you’d like the science team to answer live on the air, please feel free to leave a comment below, or tweet them directly @galaxyzoo. During the hangout, if we use a term you’re not familiar with, you can use the jargon gong by tweeting at us too. For example, “@galaxyzoo GONG laser guide star” would have been perfectly appropriate during the last hangout. Go on… gong us! We like it!

Blood Oranges are just like Hubble Galaxies

Hubble CANDELS zoom

Astronomers always want better images. Sometimes it’s possible right away; other times doing better requires new technology and/or waiting for the next generation of telescopes. We have both kinds of “fuzzy blobs” in Galaxy Zoo, and during this hangout we showed several examples. For a couple of hangouts now we’ve been meaning to address some of the most frequently asked questions about the faintest, most distant galaxies we ask volunteers to classify:

  • what are they?
  • why are the images so fuzzy?
  • can we get better images of them now or in the future?

Given the data we have, the short answer to the first question is that we don’t yet know for sure — and, perhaps most importantly, we don’t need to know all the details. We can learn quite a lot from classifying even faint, fuzzy objects. Some of the faint galaxies on Galaxy Zoo are among the most distant galaxies ever imaged by the Hubble Space Telescope, and we don’t necessarily expect them to look like galaxies we see more nearby, so classifications from our volunteers are helping us to understand them even when we don’t have all the information we might want.

And what would it take to give us the information we want? What’s the future of astronomy after Hubble? How can we get better data than we have right now? Do we need to go into space to do it? (And what else are we working on right now, anyway?) Answers given in the video:

This is a great time to be working on Galaxy Zoo: there’s plenty to classify and analyze, and — of course — plenty to discuss. So stay tuned for next time!

Note: for those who prefer audio only, here’s a link to the podcast version.

Next GZ Hangout: Friday, 22nd March, 15:30 GMT

Next Galaxy Zoo Hangout: Friday, the 22nd of March, 2013, 3:30 p.m. GMT (time zones are currently weird since the US has sprung forward but Europe has not, so that’s 4:30 p.m. Central European Time, 11:30 a.m. Eastern Daylight Time, 8:30 a.m. Pacific Daylight Time).

Want to contribute for our next hangout? Post your questions & comments below and/or feel free to tweet them @galaxyzoo or post them on Facebook.

During the chat, if we use a science term you aren’t familiar with, please use the Jargon Gong by tweeting us with a GONG (example: “@galaxyzoo GONG SPS template fitting“); we’ll be happy to explain!

Update: view the video here!

Jargon Alert: Your IMF Just Messed With My SPS!

I remember going to a lecture as an undergraduate wherein my professor compared what astronomers do to a hypothetical alien crew on a fast-moving ship that can only take one photo of the Earth as it passes by. We can assume they have a special camera that can see through buildings, but otherwise they just get one photo of, say, a major city, and from that they have to try and learn as much as they can about the human race. How hard would it be to discover that our species has two genders? Or that both of them are required to propagate the species, but only one gives birth? Would it be possible to figure out the whole human life cycle? To discover what disease is? To distinguish between genetics and culture (nature and nurture)? Just having one picture is limiting, but with careful study you can learn more than you think.

H-R Diagram

One of the most fundamental plots in astronomy.

The professor was drawing an analogy with the Hertzsprung-Russell diagram in particular, which we’ve talked about before on our hangouts: to make it, you record the color and the luminosity of all the stars you can and plot them up against each other, one point per star. The stars group together in interesting ways in particular areas of the diagram, and it turns out that from this diagram alone you can recover an enormous amount about the life cycles of a population of stars (for example, in a star cluster, a neighborhood of our own galaxy, or a nearby galaxy). You can learn even more if you couple the diagram with spectra of stars from different parts of it. Studying stellar populations has helped us understand the fundamentals of what kinds of stars exist, how they are born and die, and how many stars of any given mass are likely to develop in a galaxy in relation to stars of different masses. That last thing is called the Initial Mass Function (IMF for short). Essentially it says that, when stars form in groups, more low-mass stars form than high-mass stars. Put that together with what we know about how much brighter high-mass stars shine and how much faster they die than low-mass stars, and you can start to understand how whole populations of stars in galaxies form and evolve.

And we can apply our studies of nearby galaxies and groups of stars to galaxies we observe much farther away. It’s a good thing, too, since most galaxies are far enough away that our current telescopes can’t resolve individual stars. We just get the sum of the light from all the stars. That combined light is sometimes made up of multiple populations of stars that formed in groups at different times and now all live together in a particular galaxy. Taking that single picture combining the light from billions (often hundreds of billions) of stars and using it to learn about the stars’ masses, ages and histories is an important process, and there are several ways to do it: one way combines models of stellar populations made by forming and evolving many stars in a computer simulation. This is sometimes called Stellar Population Synthesis, or SPS.

On today’s live Hangout, we once again let your questions guide us as we talked about IMFs and what they have to do with SPS and measuring the stellar masses of galaxies. The work that laid the foundations for today’s study of galaxy stellar populations was done in large part by women (Bill mentioned Beatrice Tinsley, for example), which is fitting since today is International Women’s Day. We talked about that too, and about diversity in general in astronomy. Just as you can learn a lot from even one snapshot of a galaxy, you can do a lot with just a bit of mindfulness about being an ally for diversity (Kyle noted on Twitter that World Day for Cultural Diversity is May 21), be it equality for women or for any other minority groups in science, or indeed any field.

Here’s the audio-only version of the Hangout: click to listen to mp3 version.

And the video:

We’ll post about our next hangout soon; in the meantime, keep those questions coming!

Next GZ Hangout: Friday, 8th March, 15:30 GMT

Next Galaxy Zoo Hangout: Friday, the 8th of March, 2013, 3:30 p.m. GMT

Want to contribute for our next hangout? Post your questions & comments below and/or feel free to tweet them @galaxyzoo or post them on Facebook.

Shortly before the hangout starts, we’ll embed the video in this post so you can watch from here. And during the chat, if we use a science term you aren’t familiar with, please use the Jargon Gong by tweeting us with a GONG (example: “@galaxyzoo GONG forbidden [OIII] atomic transition” — not that I’m quoting the last hangout or anything); we’ll be happy to explain!

Update: video now available at the hangout summary post!

Green Valley: The Town Too Good To Die

Galaxies of different colors

I swear we are consistently trying to keep our live hangouts to about 15 minutes. We have so far failed at keeping to time, but hopefully also succeeded in the sense that we only run over because there’s so much to discuss.

We had a number of good questions from Twitter, Facebook and the blog about various types of galaxies — from red spirals to green peas and blue ellipticals — and I rather arbitrarily decided this was an indication that our hangout should have a color theme. That is, what exactly does “color” mean in the context of astronomy? What is going on physically when a galaxy is one color versus another, or has multiple colors? Is color information always telling us the same thing? We tried to address all those questions, as well as show some examples of different galaxies in the above queried categories. As a bonus, we learned how galaxy colors are related to the town my grandparents retired to. (This post’s title is a quote from the Green Valley Chamber of Commerce’s official website.) That was as much a surprise to me as it was to the viewers!

We also talked about what’s currently going on in Galaxy Zoo behind the scenes. Earlier today, Kyle sent around a really nice draft of the Galaxy Zoo 2 data paper for the team to read and comment on (you’ll have to watch the video to get a sneak peek at some of the figures).

And it’s that time again: Hubble Space Telescope proposals are due in about a week. We talked about the proposal process from concept to submission to review, discussing both specifics of certain telescopes and the general practices that (we hope) help lead to a successful proposal. Here’s a hint: it may not be what you think!

We covered all this and some other questions, too. No wonder we ran a little over…

And here’s the podcast version:

Download MP3 file

GZ4 merger or overlap set

Is it a triple merger? A double overlap? A hybrid?

Spiral Colors

A blue(ish) and red spiral.

Elliptical colors

A red and blue elliptical.

Green pea

A tiny green pea galaxy, and zoomed-in at right.

Live Chat: Galactic Rings, Secular Evolution and The Good Old Days

GdV 3D morphological classification

It’s amazing what happens when you actually publicize your live chat in advance. We got so many questions, we decided to spend the entire chat just discussing them, and we still didn’t finish!

Partly that’s because we had a surprise guest appearance from the esteemed Ron Buta, who came in just after we had talked about some of the details covered in his Galaxy Morphology article (his Figure 3 is shown in the image). Ron worked with Gérard de Vaucouleurs — aka GdV — and told us some amusing stories about trying to take photometric* observations of dwarf galaxies, and about how GdV’s wife used to disagree with his morphologies, at one point looking over his shoulder and proclaiming, “no, there’s no ring”. I rather liked that story as it’s a reminder that anyone can spot patterns in galaxy images.

We’ll try to answer those questions on the previous blog post that we didn’t get to there — but in the meantime, here’s the video:

Left to right: Ron Buta & Bill Keel, Karen Masters, Kevin Schawinski, Brooke Simmons (me). Toward the end (not shown on the thumbnail), Kyle Willett arrived just in time to answer a question about the status of the latest Galaxy Zoo classification set.

We made ample use of the jargon gong on ourselves, but we may not have managed to define all the terms Ron used. We’ll try to do so in this post — if we’ve missed any please say so in the comments!

*photometry = precise quantitative measurements of the brightness of objects in the sky. You need very good observing conditions to take photometric measurements, which many (but not all) astronomical projects require.

Update: Now in podcast form:

Download MP3 file

Spiral Galaxies and the Future of Citizen Science: a Live Chat

Last week Karen Masters suggested that we start doing Galaxy Zoo live chats a little more often. I thought that sounded like a great idea, and we figured we’d just have an informal chat about whatever galaxy/Zooniverse topic we felt like discussing that day.

We were joined by Kyle Willett and Kevin Schawinski, and the four of us started talking about this paper, which presents an automated system for classifying and measuring spiral arms. It compares to Galaxy Zoo 2 data within the text, and we talked about what the fact that the computers did pretty well means for the future of Galaxy Zoo. We didn’t prepare anything in advance, and I didn’t even start reading the paper until about 20 minutes before we got going. So my favorite part of the chat is where I put forward a few definitions of pitch angle and get them all wrong. Science in action!

We also introduced the jargon gong, which we used on each other whenever one of us said something in insider-speak. I think this is a feature worth keeping, and we also plan to invite viewers to gong us themselves via Google+ or Twitter for the next chat.

When will the next chat be? We’re not sure yet, but hopefully soon — I promise I’ll even try to make a blog post before we start next time!

Update: We’ve now extracted the audio into an mp3 file and started a podcast:

Download MP3 file