Distributed astronomy

Recently, news sources all over the place have been reporting on the imaging of a black hole, or  more precisely, the immediate vicinity of a black hole.  The black hole itself, more or less by definition, can't be imaged (as far as we know so far).  Confusing things a bit more, any image of a black hole will look like a black disc surrounded by a distorted image of what's actually in the vicinity, but this is because the black hole distorts space-time due to its gravitational field, not because you're looking at something black.  It's the most natural thing in the world to look at the image and think "Oh, that round black area in the middle is the black hole", but it's not.

Full disclosure: I don't completely understand what's going on here.  Katie Bouman has done a really good lecture on how the images were captured, and Matt Strassler has an also really good, though somewhat long overview of how to interpret all this.  I'm relying heavily on both.

Imaging a black hole in a nearby galaxy has been likened to "spotting a bagel on the moon".  A supermassive black hole at the middle of a galaxy is big, but even a "nearby" galaxy is far, far away.

To do such a thing you don't just need a telescope with a high degree of magnification.  The laws of optics place a limit on how detailed an image you can get from a telescope or similar instrument, regardless of the magnification.  The larger the telescope, the higher the resolution, that is, the sharper the image.  This applies equally well to ordinary optical telescopes, X-ray telescopes, radio telescopes and so forth.  For purposes of astronomy these are all considered "light", since they're all forms of electromagnetic radiation and so all follow the same laws.

Actual telescopes can only be built so big, so in order to get sharper images astronomers use interferometry to combine images from multiple telescopes.  If you have a telescope at the South Pole and one in the Atacama desert in Chile, you can combine their images to get the same resolution you would with a giant telescope that spanned from Atacama to the pole.  The drawback is that since you're only sampling a tiny fraction of the light falling on that area, you have to reconstruct the rest of the image using highly sophisticated image processing techniques.  It helps to have more than two telescopes.  The Event Horizon Telescope project that produced the image used eight, across six sites.

Even putting together images from several telescopes, you don't have enough information to precisely know what the full image really would be and you have to be really careful to make sure that the image you reconstruct shows things that are actually there and not artifacts of the processing itself (again, Bouman's lecture goes into detail).  In this case, four teams worked with the raw data independently for seven weeks, using two fundamentally different techniques, to produce the images that were combined into the image sent to the press.  In preparation for that, the image processing techniques themselves were thoroughly tested for their ability to recover images accurately from test data.  All in all, a whole lot of good, careful work by a large number of people went into that (deliberately) somewhat blurry picture.

All of this requires very precise synchronization among the individual telescopes, because interferometry only works for images taken at the same time, or at least to within very small tolerances (once again, the details are ... more detailed).  The limiting factor is the frequency of the light used in the image, which for radio telescopes is on the order of gigahertz. This means that images from the telescopes have to be recorded on the order of a billion times a second.  The total image data ran into the petabytes (quadrillions of bytes), with the eight telescopes producing hundreds of terabytes (that is, hundreds of trillions of bytes) each.

That's a lot of data, which brings us back to the web (as in "Field notes on the ...").  I haven't dug up the exact numbers, but accounts in the popular press say that the telescopes used to produce the black hole images produced "as much data as the LHC produces in a year", which in approximate terms is a staggering amount of data.  A radio interferometer comprising multiple radio telescopes at distant points on the globe is essentially an extremely data-heavy distributed computing system.

Bear in mind that one of the telescopes in question is at the south pole.  Laying cable there isn't a practical option, nor is setting up and maintaining a set of radio relays.  Even satellite communication is spotty.  According to the Wikipedia article, the total bandwidth available is under 10MB/s (consisting mostly of a 50 megabit/second link), which is nowhere near enough for the telescope images, even if stretched out over days or weeks.  Instead, the data was recorded on physical media and flown back to the site where it was actually processed.

I'd initially thought that this only applied to the south pole station, but in fact all six sites flew their data back rather than try to send it over the internet (just to throw numbers out, receiving a petabyte of data over a 10GB/s link would take about a day).   The south pole data just took longer because they had to wait for the antarctic summer.

Not sure if any carrier pigeons were involved.

Hats off to New Horizons

A few years ago, around the time of the New Horizons encounter with Pluto (or if you're really serious about the demotion thing, minor planet 134340 Pluto), I gave the team a bit of grief over the probe having to go into "safe mode" with only days left before the flyby, though I also tried to make clear that this was still engineering of a very high order.

Early on New Year's Day (US Eastern time), New Horizons flew by a Kuiper Belt object nicknamed Ultima Thule (two syllables in Thule: THOO-lay).  I'm posting to recognize the accomplishment, and this post will be grief-free.

The Ultima Thule encounter was much like the Pluto encounter with a few minor differences:

• Ultima Thule is much smaller.  Its long axis is about 1-2% of Pluto's diameter
• Ultima Thule is darker, reflecting about 10% of light that reaches, compared to around 50% for Pluto. Ultima Thule is about as dark as potting soil.  Pluto is more like old snow.
• Ultima Thule is considerably further away (about 43 AU from the sun as opposed to about 33 AU for Pluto at the time of encounter -- an AU is the average distance from the Sun to the Earth)
• New Horizons passed much closer to Ultima Thule than it did to Pluto (3,500 km vs. 12,500 km).  This requires more accurate navigation and to some extent increased the chances of a disastrous collision with either Ultima Thule or, more likely, something near it that there was no way to know about.  At 50,000 km/h, even a gravel-sized chunk would cause major if not fatal damage.
• Because Ultima Thule is further away, radio signals take proportionally longer to travel between Earth and the probe, about six hours vs. about four hours.
• Because Ultima Thule is much smaller, much darker and significantly further away, it's much harder to spot from Earth.  Before New Horizons, Pluto itself was basically a tiny dot, with a little bit of surface light/dark variation inferred by taking measurements as it rotated.  Ultima Thule was nothing more than a tinier dot, and a hard-to-spot dot at that.
• We've had decades to work out exactly where Pluto's orbit goes and where its moons are.  Ultima Thule wasn't even discovered until after New Horizons was launched.  Until a couple of days ago we didn't even know whether it had moons, rings or an atmosphere (it appears to have none).  [Neither Pluto nor Ultima Thule is a stationary object, just to add that little additional degree of difficulty.  The Pluto flyby might be considered a bit more difficult in that respect, though.  Pluto's orbital speed at the time of the flyby was around 20,000 km/h, while Ultima Thule's is closer to 16,500 km/h.  I'd think this would mainly affect the calculations for rotating to keep the cameras pointed, so it probably doesn't make much practical difference.]

In both cases, New Horizons had to shift from pointing its radio antenna at Earth to pointing its cameras at the target.  As it passes by the target at around 50,000 km/h, it has to rotate to keep the cameras pointed correctly, while still out of contact with Earth (which is light-hours away in any case).  It then needs to rotate its antenna back toward Earth, "phone home" and start downloading data at around 1,000 bits per second.  Using a 15-watt transmitter slightly more powerful than a CB radio.  Since this is in space, rotating means firing small rockets attached to the probe in a precise sequence (there are also gyroscopes on New Horizons, but they're not useful for attitude changes).

So, a piece of cake, really.

Seriously, though, this is amazing engineering and it just gets more amazing the more you look at it.  The Pluto encounter was a major achievement, and this was significantly more difficult in nearly every possible way.

So far there don't seem to be any close-range images of Ultima Thule on the mission's web site (see, this post is actually about the web after all), but the team seems satisfied that the flyby went as planned and more detailed images will be forthcoming over the next 20 months or so.  As I write this, New Horizons is out of communication, behind the Sun from Earth's point of view for a few days, but downloads are set to resume after that.  [The images started coming in not long after this was posted, of course --D.H. Jul 2019]

The Great American Eclipse (and a bit about the web).

Most of this post is probably better suited to the other blog, but Field Notes has been a bit quiet for the past, um, years, so why not?

You may be aware that there was recently a total eclipse of the sun in the United states.   If you've never seen a total eclipse, I highly recommend it.   If you happen to be near the path of totality when one occurs in your area, don't be lulled into thinking that seeing a 95% eclipse or whatever is 95% as good as seeing a total eclipse.  The difference is, literally, night and day.  During totality, the sun is not so much covered as replaced by a black hole surrounded by the corona, about as bright as the full moon.  And then, before you know it, there's an impossibly bright spot at the very edge and you have to look away.  Seconds later the light is already a thousand times brighter and it feels like day again -- a weirdly dim, clearly-lit day, to be sure, but definitely day.  Miss totality and that last part, the strange light, is about all you get.  So if you get the chance ...

There are two main concerns in getting a good view of an eclipse: traffic and weather.  Some people are able to bypass traffic by booking a train, or flying into the zone, or even being in the air during totality, but most of us will end up taking to the road.  If enough people decide to do this, things can get hairy.  A rule of thumb in traffic engineering is that one lane of highway can handle about 2000 cars an hour.  If your main route into the zone is a four-lane highway, that is, two lanes each way, that's about 4000 cars an hour.  If it's an hour before totality and you have 5000 cars between you and the zone, your chances are not looking good.

It would be nice to have some idea of what to expect, something like "If you live here, you should try to go here (assuming good weather).  Leave at this time and expect the trip to take this long."  But the problem is, nobody really had a good idea how many people would be trying to go where, when.  I'm not a total umbraphile, but I'm sure I paid a lot more attention to this eclipse than most of the population.  My personal attitude of "Yeah, gotta try to see that" was probably not typical.  Typical attitudes were probably more like  "Sounds kinda cool ... but I've got work on Monday.  Maybe I should take a look on my lunch break."  So not everyone is going to hop on the freeway or book a hotel months in advance.

Furthermore, a certain number of people who were thinking about it will hear reports of possible gridlock and think the better of it, or try to find an alternate route, or whatever.  In this internet-connected age people will be telling each other where they are and how conditions are, and watching real-time traffic, or at least trying to.

This sort of uncertainty makes projections a bit difficult, and there's not really any relevant historical data.  The last time an eclipse went all the way across the continental US, in 1918, there was no interstate system, much less an internet (though telegraphs were very much in use).  Even in 1979, the last time a total eclipse was visible in the contiguous US, the picture was still considerably different from today, if only because there were only 70% as many people in the country.

None of this stopped people from trying to project.  One such effort calculated the "drivesheds", analogous to watersheds, to show which locations on the centerline of the eclipse were closest, by road, to the highest number of people.  The top three were Santee, SC, where I-95 meets the centerline,  Idaho Falls, ID, where I-15 meets the centerline, and Sabetha, KS, where US 75 meets the centerline.

The first sounds pretty likely.  I-95 gets a lot of traffic to begin with, and it runs from the Canadian border in Maine through Boston, New York, Philadelphia and Washington,  DC on its way to Jacksonville and Miami.  The second seems plausible.  It's the closest point for Phoenix, Salt Lake City and, perhaps surprisingly, San Diego and from the looks of it most of LA.

The third ... well, it seems to assume that anyone in Texas wanting to see the eclipse is going to head up I-35 toward the Kansas City metro, a chunk of which is directly in the path, then veer off onto two-lane local highways to get to the (technically) closest point on the centerline.

I don't think traffic works that way.


In the event, traffic was bad in a few places in the days leading up to the eclipse, but not too bad.  It looks like people trickled in from here and there over a period of days, and relatively few people headed into the zone of totality on the day, or even at all.  There are 25 million people in the driveshed for Salem, Oregon.  Officials in Oregon planned on one million.  It's not clear that there were even that many.

Coming home, on the other hand, was a different matter.  There was no particular schedule for getting to the zone of totality, but the show ended at a very precise time, and suddenly there was no reason to stick around.  Hours-long delays were common across the country.  This seems obvious in hindsight, but in the run-up to the event the main concern was "will I be able to make it in time?" Most people were probably not really concerned about getting home at any particular time.

As far as I can tell, Sabetha, Kansas saw the same thing in miniature [Toward the bottom of the page it mentions that Sabetha's Sixth Street Park had a crowd of ... about 200 people --D.H.].

So much for traffic.  The eternal concern for eclipse chasers everywhere, whether on the I-95 corridor or Mongolia, is the weather.  Personally, I've seen two total eclipses (this one and the Great European Eclipse of 1999), and in both cases sheer dumb luck brought a break in the clouds in time to see the corona and the diamond ring.

I followed weather forecasts closely in the days leading up to the eclipse.  Unlike 18 years ago, there were a number easily available online.  Weather forecasting has advanced significantly.  Live radar is available on any number of sites, as are recent satellite images.  If there's a hole in the cloud cover, it doesn't seem like it should be too hard to find.

If you've got an internet connection.

I gave up trying to get online and our party ended up just picking a spot.  My guess is that if we'd had to make an emergency call it would have had priority and it would have been connected.  Data, not so much.  It's almost as though there were more people in town than usual and they were all trying to get on the web at the same time.

We thought about trying to move toward what looked like a clearer spot, but in the time it took to try to figure it out the clouds shifted and a beautiful blue gap opened up with about 30 minutes to go.  Then closed again as the encroaching moon shut the light down by bit.  Then the sky abruptly darkened more.  The eclipsed sun was up there somewhere.  The clouds above were dark, but the horizon was dusk (or dawn, if you prefer) in all directions.  It looked like some of the low clouds were moving away from where the sun must have been, but it was hard to tell.

And then the clouds shifted and there was the silvery ring of the corona a minute or more into totality.  A little washed out, like the full moon through high clouds, but there.  Then, after what seemed like no time at all, an incredibly bright pinpoint of light widening into a slim maybe-crescent.  Time to look away.

A mile down the road, people saw nothing but clouds.  On the way back, through what had been overcast and rain, the sun was out.  Would live radar really have helped?  Who knows.

The two eclipses I've seen happened to be part of the same Saros series, a set of eclipses at 18-year intervals with nearly identical geometry.  The latitude was similar.  The duration was similar.  As it happens, the weather was similar.  In theory, technology would have played a much larger role in this one than the last one, but in practice, not really.

"What was that bright light in the sky last night?"

While looking for information on comet ISON, I ran across an interesting project by NASA: the All Sky Fireball Network, a network of (currently) 12 black-and-white video cameras able to image the whole night sky.  The images from these cameras are processed by ASGARD (All Sky and Guided Automatic Realtime Detection), developed for a similar effort in Canada.  These astro folks sure love their acronyms.

A "fireball" is any meteor brighter than venus.  These are not rare events.  There are several on most nights, and nights with a dozen or two are not uncommon.   As there is deliberately quite a bit of overlap in the cameras' fields of view, most fireballs are caught on multiple cameras, making it possible to calculate the three-dimensional trajectory of the meteor, and from that determine its orbit.  Spaceweather.com posts a graphic of the night's calculated orbits.  I believe they produce that themselves from the raw data on the NASA site, which just seems to show the orbital elements as text.

It's pretty easy to see why this data is of interest to NASA.  Not only does it provide information about the composition of the Solar System, it's of practical use in designing satellites.  But even without that, it's a just plain neat hack.

Straight dope on Comet ISON

In a few days, a highly unusual comet will pass within a million miles or so of the Sun's surface.  That in itself is not unusual.   Comets pass that closely reasonably often and thousands such are known.  However, this comet is a "dynamically new" comet, meaning it has never been close to the Sun before, and no dynamically new comet has come so close to the Sun in at least 200 years.

This rare combination offers an unprecedented chance for astronomers to observe an object which has basically been sitting in a deep freeze since the formation of the Solar System react to close contact with the heat of the Sun.  That in turn will reveal much about what the comet is made of and thus offer clues about how the Solar System itself was formed.  Dozens of major observatories, on Earth and in space, will be watching.

As I write, the comet is visible to the naked eye in the pre-dawn sky, but only if you're in a dark place and know just where to look.  It's a little point of light, not your classic image of a comet.  At least not yet.

While ISON's orbit is known quite precisely, it's not at all clear what happens next.  On November 28th it will reach perihelion, its closest point to the Sun's center.  It will be moving at about 400 km/s, or about 900,000 mph, and experiencing intense heat and significant tidal stress that may or may not destroy it.  If it survives, it may reappear as anything from a point of light to a real spectacle.

If you've seen reports of a "comet of the century" likely to be "brighter than the full moon", this would be it.  The press has a habit of taking the "this could maybe happen if we're really lucky" scenario and running with it.  If you prefer to know what actual astronomers are saying and seeing and what the comet is up to, along with informative discussions of why we don't really know what the comet will do, you'll want to check out CIOC, NASA's Comet ISON Observing Campaign.

CIOC is a coordinating group.  It's not performing the actual observations, but it is a serious scientific collaboration, promoting research and gathering results for all the net.world to see.  This is classic Web, the kind of thing TimBL had in mind, I have to think, when putting up the first HTTP server way back when.

You may be wondering: What kind of a name is Comet ISON anyway?  It's named after the International Scientific Optical Network, a collection of 30 or so telescopes in about 20 countries that has been used in quite a bit of research, including but definitely not limited to detecting the comet in the subject line, formally known as C/2012 S1 (ISON).

UPDATE: Comet ISON appeared to disintegrate just before perihelion, and when it dropped behind the occluding discs of the SOHO (SOlar and Heliospheric Observatory) cameras that have been the main source of images for it in the past few days, the consensus was that there was a good chance that nothing would come out the other side.  When the SDO (Solar Dynamics Observatory) and PROBA (PRoject for On Board Autonomy) scopes that had been pointed at what should have been ISON's path failed to detect anything, the folks at CIOC did the only reasonable thing and declared it dead, vaporized in the heat of the sun (around 2800℃/5000℉).  And then it re-appeared.  At this writing, it is a fuzzy blob headed away from the sun, nowhere near as bright as it had been, but possibly bright enough to be seen with the naked eye when it gets far enough away from the sun.  We shall see.

UPDATE:  ... and it's gone.  On December 18th, the Hubble telescope was pointed at where Comet ISON ought to have been.  We can be quite sure of the location since anything solid remaining would have continued to follow the original orbit -- a solid object moving that fast is not going to be affected significantly by outgassing, the solar wind or other such effects.  The HubbleSite ISON blog has the full details, including photographs annotated to point out things you might think could be comet remains but definitely aren't.  Cosmic rays, stars streaking because the telescope is moving to follow the orbit of the comet, reflections on the lens and so forth.  Plenty of that, no comet.

What's twice as big as the internet?

(Yikes ... I went 0 for March!)

I've mentioned before that telescopes can generate a lot of data.  IBM seems inclined to drive the point home by collaborating with ASTRON (the Netherlands Institute for Radio Astronomy) to put together "exascale" computing horsepower behind the world's largest radio telescope.

The telescope is actually (or rather, will be) an array of millions of antennas spread out over a square kilometer, from which the name SKA, for Square Kilometer Array.  This array is expected to produce on the order of an exabyte of data per day.  This is an absolutely ridiculous amount of data by today's standards.  Think one million terabyte disk drives, or twenty million feature film's worth of Blu-ray, or ... according to IBM, twice the daily volume currently carried on the internet.

I'm a little skeptical as to exactly how one measures that, but hey, you've got to trust a press release, right?


So where do you put an exabyte a day worth of data?  Well, you don't.  You're certainly not going to upload it to the web.  Particle physicists are faced with the same problem of having to figure out what portion of a huge data set to keep for later analysis, and a large part of running an experiment is setting up the "trigger" criteria by which the software collecting the data will decide what to keep and what to throw.  IBM and ASTRON's system will be dealing with the same problem, but on an even larger scale.

Or I suppose you could sign up two million people and somehow stream an equal share of the data to each at Blu-ray resolution all day every day, but somehow I doubt that kind of crowdsourcing will help much.

Crowdsourcing the sky

Astronomy has been likened to watching a baseball game through a soda straw.  For example, the Hubble Deep Field, assembled from 342 images taken over the course of ten days, covers about 1/500,000th of the sky, or about the size of a tennis ball seen a hundred yards away.  It's quite possible to survey large portions of the sky, but there are trade-offs involved since you can only collect so much light so fast.  To cover a large area and still pick up faint objects, you need some combination of a big telescope and a lot of time.  The bigger the telescope (technically, there's more to it than sheer size) the faster you can cover a given area down to a given magnitude (how astronomers measure faintness).

The Large Synoptic Survey Telescope (LSST) is designed to cover the entire sky visible from its location every three days, using a 3.2 gigapixel camera and three very large mirrors.  In doing this, it will produce stupefying amounts of data -- somewhere around 100 petabytes, or 100,000 terabytes, over the course of its survey.  So imagine 100,000 terabyte disk drives, or over 2 million two-sided Blu-ray disks.  Mind, the thing hasn't been built yet, but two of its three mirrors have been cast, which is a reasonable indication people are serious.  Even if it's never finished, there are other sky surveys in progress, for example the Palomar Transient Factory.

Got a snazzy 100 gigabit ethernet connection?  Great!  You can transfer the whole dataset in a season -- start at the spring equinox and you'll be done by the summer solstice.  The rest of us would have to wait a little longer.  My not-particularly-impressive "broadband" connection gets more like 10 megabits, order-of-magnitude, so that'd be more like 2500 years, assuming I don't upgrade in the meantime and leaving aside the small question of where I'd put it all.

Nonetheless, the LSST's mammoth dataset is well within reach of crowdsourcing, even as we know it today:

• Galaxy Zoo claims that 250,000 people have participated in the project.  Many of them are deadbeats like me who haven't logged in for ages, but suppose there are even 10,000 active participants.
• The LSST is intended to produce its data over ten years, for an average of around 2-3Gbps.  Still fairly mind-bending -- about a thousand channels worth of HD video, but ...
• Divide that by our hypothetical 10,000 crowdsourcers and you get 200-300Kbps, not too much at all these days.  Each crowdsourcer could download a 3GB chunk of data in under an hour in the middle of the night or spread it out through the day without noticeably hurting performance.
• Assuming you kept all the data, you'd need a new terabyte disk every few months, so that's not prohibitive either.
• The hard part is probably uploading a steady stream of 2-3Gbps (bittorrent wouldn't help here, since each recipient gets a unique chunk of data).  As far as I can tell the bandwidth is there, but at that volume I'm guessing the cost would be significant.
• In reality, there would probably be various reasons not to ship out all the raw data in real time, but instead send a selection or a condensed version.

Bottom line, it's at least technically possible with today's technology, to say nothing of that available when the LSST actually goes online, to distribute all the raw data to a waiting crowd of amateur astronomers.

Wikipedia references a 2007 press release saying Google has signed up to help.  As usual I don't know anything beyond that, but it does seem like a googley thing to do.

It's a whole Zooniverse now

Almost two years ago now (has it really been that long?), I learned about the Galaxy Zoo. At the time it looked like an interesting approach to try -- invite the general public to classify galaxies, a task which is

• useful (to astronomers, at least)
• reasonably easy for humans
• not at all easily or well handled by computers
• able to be split into millions of independent pieces

Given those characteristics, the original project had at least a chance of succeeding, and indeed it has succeeded handsomely. Last April, it announced the 60 millionth classification, and as a result of all this work it now has "an incredibly robust, well-defined and scientifically valid catalogue of Sloan Digital Sky Survey galaxies." It has also produced some significant results, with more in the pipeline.

Along with all that, it's given hundreds of thousands of people (myself included) a chance to participate in real scientific research and see the same images working astronomers see. If that's not a clear win I don't know what is, and it simply couldn't have happened without the web.

As it became clear how well things were working, a second project was launched, aimed at spotting supernovas, again with good results. That project has since been joined by others and the whole crowd has overflowed the original galaxyzoo.org domain into the Zooniverse.

The latest addition, Moon Zoo, is aimed at classifying craters and other features in the heaps and heaps of data from the Lunar Reconnaissance Orbiter. The problem looks to fit all four criteria above and so have every bit as good a chance of success as its predecessors.

For a bonus, some lucky classifiers will run across human artifacts, from orbiters to footprints of astronauts. Take the resolution needed for that times the surface area of the moon and you've got some idea how ridiculously much data is involved.

Not every bright idea on the web makes a significant impact on the outside world, but some do. If you accept that basic research is significant to the world at large, then the Zooniverse has to rank as a major success story.

Lost in a web of stars

The day job is less busy now. In the inevitable letdown period, my attention has wandered skyward, to the Astronomy Picture of the Day. Along with the Galaxy Zoo and other random sites, the APOD largely satisfies my desire to learn a little astronomy without, um, actually going out and looking at the sky. Besides, I learn more this way, or at least I learn things that just looking up at the sky gives little hint of. That's why they have all those telescopes and high-tech instruments, after all.

For example, while you'll often see pretty posters of the Orion nebulae or the Trifid nebula, it's another thing entirely to see them in context and realize that, were our eyes sufficiently sensitive (and our surroundings sufficiently dark) even a clear, dark sky would be cloudy. And of course, Van Gogh's Sterrennacht springs to mind.

In the night sky most places we see very little beyond local stars. In major cities it can be hard to see even that much. This limited view reveals very little about the universe at large. Recent theories hold that the universe was born out of some sort of quantum foam and still reflects that structure. What are they talking about? If you zoom out far enough, it starts to make sense.

How can astronomers develop theories of how stars and galaxies form when the timescales involved are much, much longer than anyone's lifetime? They look at lots and lots and lots of stars and galaxies. On a clear, dark night the unaided eye can pick out a few thousand stars. Galaxies have stars by the billion, and there are plenty of galaxies. The Hubble Deep Field, for example, covers about two millionths of the night sky and comprises about 3,000 galaxies. Even the Galaxy Zoo's original million are only a small sample of what's out there.

From common experience, stars (except our sun, of course) are little pinpricks of light. Science tells us that's because they're mind-bogglingly far away. Only objects in the solar system are close enough to appear as anything more than points [well ... you have the Sun, the Moon, the Andromeda galaxy, the Magellanic clouds and the occasional comet ... but let's just agree that you'll see a lot more with a telescope, especially a big one or one in space --D.H. Dec 2015]. But with a good telescope, you can not only tell stars from points of light, you can not only see that stars are round, you can see one that isn't and pick out individual stars in a galaxy far, far away (well, actually a pretty close one by galactic standards).

With special equipment astronomers can see colors the eye can't, as in this lovely image of the Andromeda galaxy in ultraviolet (make sure your cursor isn't over the picture), or pick out otherwise hidden features and reveal the complexity of the processes at work in a nebula, or even show us what's right in front of our faces.

This is a really small sample of the APOD archive. Wander through it yourself and you'll find all kinds of wonders and not a few oddities. But beyond the pretty pictures, the real value lies in the descriptions, written by professional astronomers. It's one thing to read in a science article about this or that theory or process, quite another to see a principle illustrated by a real live picture from a real live observatory accompanied by a clear, concise paragraph rich in links to further pictures and other resources.

This is the kind of thing the web was made for. Certainly it's long been possible to subscribe to an astronomy magazine or go to the local library and get information of a similar quality, but the web enhances the experience considerably.

More fun from Galaxy Zoo

The Galaxy Zoo project has been so successful, it's been expanded. Along with classifying images of galaxies -- which is still ongoing -- you can help them screen candidates for supernovae. Astronomers are standing by in the Canary Islands to examine the likeliest ones. Evidently said astronomers are happy with the results so far, having confirmed several supernovae last night based on the Zoo's findings.

As with the galaxy classification, it's oddly fascinating and somewhat addictive. Betcha can't classify just one ...

Galaxy Zoo 2

In celebration of the 100 Hours of Astronomy event, Galaxy Zoo aims to get one million galaxies classified before the hundred hours are up. At this writing, it looks like they'll easily meet that goal (well done, everyone!), but you can still try your hand at it any time you want. Who knows? You might even find your very own "voorwerp".

The new classification is more fun than the old, which was not bad to begin with. There are more questions, the interface is nicer, you can go back and review the galaxies you've classified and mark images as favorites. You can invert the image you're looking at, which both looks cool and can help you see features you might otherwise miss. If the galaxy you're looking at has a bar or spiral arms, you get to play "Galaxy Wars" (kinda cheesy name, but what the hey) to gauge whether the features are more or less prominent compared to some other galaxy.

If you think of a sequence from indistinct blob to disk with a blob in the middle to full-featured galaxy, you can imagine the galaxies actually form over stupefyingly long periods of time -- which is more or less the point of the whole exercise. [Actually, no. It turns out that Hubble was quite clear that his now-famous sequence of galaxy forms was meant as a taxonomic device and makes no claim about the forms through which galaxies evolve. Current theory holds that elliptical galaxies form via mergers of spiral galaxies.].

Oddly fascinating fun. Recommended.

Happy 2009!

As you're waiting for the ball to drop tonight (or whatever other marker you like), remember that 2008 will be hanging around for just a bit longer than the last few years. A leap second has been introduced for the first time since 2005 and only the second time this century.

Leap seconds are interesting (and somewhat problematic) to anyone interested in keeping a computer's clock exactly in sync with the official timekeepers because, unlike leap years, they do not follow a predetermined rule. Rather, the International Earth Rotation and Reference Systems Service (IERS) announces them based on observations of the earth's rotation. Despite what the name might suggest, the IERS does not actually cause the earth to rotate.

The Wikipedia link above has a good rundown. The official version is on the IERS site, but be advised that it's a bit technical. Evidently "How much is the accuracy of precession/nutation improved by MHB2000 and corrections to the precession constant and obliquity rate over the current IAU models?" is a frequently asked question.

Deja vu in the Galaxy Zoo

Hmm ... where have I seen this before?

Hunting the elusive voorwerp

Since it's been slashdotted and has appeared on the major news feeds, there's a good chance you've heard of Hanny's Voorwerp by now. It's a we-haven't-seen-anything-quite-like-this found by a Dutch schoolteacher named Hanny as part of the Galaxy Zoo project (I've seen voorwerp variously translated as "object" or "thing" -- the etymology suggests there might be a shade of meaning we're missing, so better not to translate).

The Galaxy Zoo is an interesting bit of crowdsourcing. Unlike SETI@home, GIMPS or similar projects it relies on human processing power rather than the idle cycles of millions of PCs. In the typical distributed-computing project, the algorithms are well-understood but require massive amounts of computing power. In this case, no one knows a good algorithm for classifying galaxies, but people can do it reasonably well, even with no training in astronomy.

Galaxy Zoo literally gives the rest of us a look at what kinds of things astronomers spend their time looking at, plus the chance of turning up something truly new. It also relieves the astronomers of the effort of taking a first look at millions and millions of images and turns up oddities, like the voorwerp, that would otherwise have gone unnoticed. Going by the entries on the Galaxy Zoo blog and the acknowledgments in the submitted papers, they're very grateful for the assist.

Apart from the human visual system's ability to recognize shapes, Galaxy Zoo takes advantage of another facet of human perception, namely its imprecision. While most people could easily distinguish a well-defined spiral galaxy from an elliptical one, many actual galaxies are harder to characterize.

In such cases a particular algorithm distributed to everyone's PC would always give the same answer, whether it's right or wrong. With some effort, you could distribute several different algorithms [or several versions of the same one, or one with some random "fuzz"] and look for discrepancies, but you'd have to write several different algorithms, or at least discover tuning parameters that made a significant difference. This not impossible, by any means, but you get it for free by having several people look at the same image (or, quite possibly, just from having the same person look at the image every so often).

Objects that produce varying answers are likely to be the interesting borderline cases, whether because there's more going on with them, or simply because we humans have more trouble figuring it out.

[Hanny's Voorwerp has since been identified as a "quasar ionization echo", but there's still plenty of research to be done.  Similar objects (voorwerpjes, or "little voorwerps") have been found elsewhere.  As usual, Wikipedia has a summary -- D.H. Dec 2018]