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Posts Tagged ‘guestblog’

How Many Dwarfs Are There?

15 Dec
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(Image courtesy Wikipedia)

Most people know by now that Pluto has been downgraded. Astronomers have decided that, conceptually, we should reserve the word "planet" for the small number of dominant bodies in the solar system. Pluto doesn't come close to making the cut. But it didn't just get shoved into the corner as "insignificant object," it got to be part of a brand new class of objects never before defined, the "dwarf planets."

Now, before you complain that, clearly, by virtue of the power of the English language, a "dwarf planet" must certainly be a planet first, a dwarf second, I would just like to mention two things. First all adjective noun combination in the English language are not noun first, adjective second. A matchbox car is, in fact, not a real car. It's OK if a dwarf planet is not a real planet. Second, though, I will acknowledge that the language is unfortunate and misleading. I preferred the term "planetoid" myself, rather than the (intentionally?) misleading "dwarf planet."

Still, forgetting the vagaries of language, we are left with dwarf planets which are not planets. How many are out there besides Pluto? And what is a dwarf planet? The International Astronomical Union (the group responsible for all astronomical nomenclature) has officially declared there to be five dwarf planet (in order of mass: Eris, Pluto, Makemake, Haumea, Ceres), and we are likely in for a dry spell on new dwarf planets. The preliminary searches of the sky are all but complete, and (as far as I know) no one has any new objects the size of Haumea hiding in their back pockets. We'll probably be at five official dwarf planets for a while.

Now is a good time, then, to remind ourselves what a dwarf planet really is.


When the final vote on the definition of "planet" was made, and the eight dominant bodies in the solar system were declared (quite rationally) a class separate from the others, a new class of objects was defined. The "dwarf planets" are all of those objects which are not one of the eight dominant bodies (Mercury through Neptune) yet still, at least in one way, resemble a planet. The best description I can come up with is that a dwarf planet is something that looks like a planet, but is not a planet. The official definition is that dwarf planets are bodies in the solar system which are large enough to become round due to their own gravitational attraction.


Why do astronomers care about round? If you place a boulder in space it will just stay whatever irregular shape it is. If you add more boulders to it you can still have an irregular pile. But if you add enough boulders to the pile they will eventually pull themselves into a round shape. This transition from irregularly shaped to round objects is important in the solar system, and, in some ways, marks the transition from an object which is geologically dead and one which might have interesting processes worthy of study.


[Haumea is, of course, not round, but that is only because it is spinning so fast. If you stopped it spinning it would become a sphere. That still counts.]


So how many dwarf planets are there? Five, of course. The IAU says so.


But let's ask the more scientifically interesting question: how many (non-planet) objects in the solar system are large enough to be round due to their own gravitational pull?


Still five, right?


Well, no. Here is where the IAU and reality part ways.

There are many more objects that precisely fit the definition of dwarf planet but that the IAU chosen not to recognize. But if the category of dwarf planet is important, then it is the reality that is important, not the official list. So let's examine reality.


So how many dwarf planets are there? Ceres is still the only asteroid that is known to be round. Vesta, the next largest, is close, but has a large crater blasted out of its side that makes it distinctly oblong. After that it gets complicated. All of the rest of the new dwarf planets are in the distant region of the Kuiper belt, where we can't actually see them well enough to know for sure if they are round or not.


While we can't see most of the objects in the Kuiper belt well enough to determine whether they are round or not, we can estimate how big an object has to be before it becomes round and therefore how many objects in the Kuiper belt are likely round. In the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round, so somewhere around 900 km is a good cutoff for rocky bodies like asteroids. Kuiper belt objects have a lot of ice in their interiors, though. Ice is not as hard as rock, so it less easily withstands the force of gravity, and it takes less force to make an ice ball round.


The best estimate for how big an icy body needs to be to become round comes from looking at icy satellites of the giant planets. The smallest body that is generally round is Saturn's satellite Mimas, which has a diameter of about 400 km. Several satellites which have diameters around 200 km are not round. So somewhere between 200 and 400 km an icy body becomes round. Objects with more ice will become round at smaller sizes while those with less rock might be bigger. We will take 400 km as a reasonable lower limit and assume that anything larger than 400 km in the Kuiper belt is round, and thus a dwarf planet. We might be a bit off in one direction or another, but 400 km seems like a good estimate.


How many objects larger than 400 km are there in the Kuiper belt? We can't answer this question precisely, because we don't know the sizes of more than a handful of Kuiper belt objects, but, again, we can make a reasonable guess. If we assume that the typical small Kuiper belt object reflects 10% of the sunlight that hits its surface we know how bright a 400 km object would be in the Kuiper belt. As of now, about 50 objects this size or larger are known in the Kuiper belt (including, of course, Eris, Pluto, Makemake, and Haumea). Our best estimate is that a complete survey of the Kuiper belt would double this number, so there are roughly 100 dwarf planets in the Kuiper belt, of which 50 are currently known.


The new dwarf planets in the solar system are very different from the previous 8 planets. Most are so small that they are smaller across than the distance from Los Angeles to San Francisco. They are so small that about 30,000 of them could fit inside the earth.


Does it matter how many dwarf planets we say there are?


I think the answer is "yes." If you believe that there are only 4 dwarf planets in the Kuiper belt then you place an oversized importance on those 4 objects and you get an exceedingly warped picture of what the outer solar is like. The important thing about the Kuiper belt is that beyond Neptune there are many many many objects with hundreds being large enough to be round. The four "IAU Dwarf Planets" in the outer solar system are all fascinating objects -- hey! I discovered 3 of them, I must think there are at least a little interesting -- but it would be a gross exaggeration to think of them as the only objects, or even the only important objects, in the fascinating region of space beyond Neptune.


I love dwarf planets. All hundred of them or so.




 
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Look Up!

11 Dec
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Did anybody catch Mercury for the first time last night? I had just enough hazy cloud on my western horizon last night that Mercury was lost in the much. If you missed it, keep trying. And if you still can't find it, don't fret: your assignment for tonight is much, much easier.

The planets all travel around the sun in flat disk. Since we sit inside this disk too, when we go outside and look for planets they will all lie along one giant circle around us. Planets move slowly, so waiting for one of them to trace out the giant circle can take a while, but the Moon takes only a month to circle around us, so we can use it to trace the paths of the planets in the sky.

If you've been watching the moon the last few days, you have seen it climbing in the evening sky still growing towards its first quarter (which comes up on Monday - so quickly! Wasn't it a tiny sliver just days ago?).

The earthshine is fading away, as the view of the Earth from the Moon is also moving from full to third quarter.

As the moon has moved eastward, it might have been hard for you not to notice the incredibly bright star that the moon has been getting closer and closer to. It will be at its very closest on Monday night. That star is a great marker for helping you really visualize how fast the moon is moving across the sky. On Monday night, if you look right and sunset and then again a few hours later, you will even be able to notice the different positions in a single night.


That super bright star, though, is more than just a convenient sign post. And it's not a star. It's Jupiter. Jupiter! I think so many of us have gotten used to the fact that NASA and others provide us so many beautiful pictures of planets from spacecraft and telescope that we have forgotten that these things are really there, up in the sky, night after night after night.


Now that you know where Jupiter is (and, again, don't worry if you don't see it tonight; it is going to be the brightest thing gracing our evening skies for the rest of the year) you have a chance to see one of the most spectacular sights in the sky. Go back in and grab some binoculars. If you don't have binocular go back in and call your favorite present-giver and remind him or her that binoculars really would make the perfect present for you. Go back outside with your binocular and find a place where you can hold them good and steady. I like to lean against a wall, but you can try lying on the ground or setting them on a fence or anything that works for you. Now find Jupiter.


If you can get your binoculars steady enough, the disk of Jupiter will come into view. And it will clearly be a disk. Strung out in a line beside the disk will be four little orbs. Stars? Nope. Moons. These are the four moons of Jupiter that were first discovered by Galileo.

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On the left, close together are the oddly magnetic Ganymede and the icy ocean filled Europa, close on the right is Io, the most volcanically active place in the solar system, and furthest of all on the right is Callisto, which is, well, just Callisto.


Come back tomorrow and everything is different. There are only three moons. Io and Europa have swapped places, Callisto hasn't moved much, and Ganymede is now so close to Jupiter that you probably won't be able to see it. The next night? All different again.


If you have been paying extra close attention you might even notice that the line that the four moons make basically points in the same direction as the line that our moon is tracing across our sky. Those moons of Jupiter are in the same disk as the planets of the solar system.


This amazing sight - Jupiter and its moons dancing across the sky - is, to my mind, one of the most wonderful things you can see in the solar system, on par with the Grand Canyon or Iguazu Falls or eruptions on Kilauea. Chances are you've never seen it, but it's just outside your door. It's free. Go outside. Look up!





 
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Chrome Lets You Remove Your Flash and Have It, Too

04 Nov
John Gruber at Daring Fireball has a clever workaround for when you want to have Flash available on demand on a Mac, but don't want it installed by default in all your browsers. John formerly used ClickToFlash with Safari to let him selectively control which Flash content displayed; there's a similar add-on called Flashblock for Firefox. Instead, John removed Flash from the various plug-in directories shared by browsers. He notes that Web sites now feed him alternative content, like static ads, since his browser no longer pretends it can accept Flash only to ignore it. A YouTube extension forces HTML5-compatible video to load, too. When he needs Flash, John launches Google Chrome, which has integral Flash support (it can be disabled, but you can't whitelist or blacklist specific sites). When he's done, he quits Chrome to prevent Flash from chewing cycles in the background.

 
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Privatized prisons in Arizona helped draft laws to send people to prison

28 Oct
news-releases.jpg The story of industries paying lobbyists to influence legislation that benefits their business is nothing new—but what about when that industry is a privately-owned and operated prison system?

NPR reports that Arizona Senate Bill 1070 (PDF), the immigration bill that requires anyone who can't produce papers proving they are in the country legally to be arrested, was drafted with the help and influence of Arizona's private prison companies.

"According to Corrections Corporation of America reports reviewed by NPR, executives believe immigrant detention is their next big market. Last year, they wrote that they expect to bring in "a significant portion of our revenues" from Immigration and Customs Enforcement, the agency that detains illegal immigrants."
Prison Economics Help Drive Ariz. Immigration Law - NPR

 
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Why natural history museum collections rock!

31 Aug
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Photo: Tom Goskar. Used with permission.

So far, it's been a very interesting experience in the month and a bit into my sabbatical at London's Natural History Museum. First off, there was that element of giddiness: coming back to an iconic institution that takes me back to my time as a kid in awe of dinosaurs, blue whales and all the sparkly stuff in the mineral exhibits. Next came, a weird sort of pride - like as if being in the museum's great hall, looking up at the beautiful ceiling, and standing in between a Diplodoccus skeleton and a statue of Darwin, made me feel privileged to be a scientist. I felt as if I was in the best-club-ever: one that carried on the work of so many pioneers whose efforts are housed in this museum. But then a strange feeling of discomfort settled in. This was because the science that goes on here, by and large, is quite foreign to the medically genetic driven projects of my own background. In other words, the bench tops here do not always require pipettemans and overpriced electronics. However, after having had the privilege of meeting some lovely people at the museum and viewing a few of these collections, I've come to really appreciate the importance of biological curation.

1. The collections serve as the physical and open portal to specimens needed for biodiversity research.

Here, the collections tackle the old adage that "people only really care about things they know." They provide a place for specimens to have a formal and accessible presence. In other words, when a new species is shared and characterized in the world of science (i.e. via a scientific paper), one of the required acts in this scientific culture is that multiple specimens of the new species must be deposited in a few institutions like the museum. Here, they are invaluable as a resource for making sense of the huge variety of form and function of the organisms on our planet (i.e. taxonomic studies). This can be done from the point of view of morphology, but also as a sort of tissue bank, so that people can perhaps later classify a specimen genetically.

I actually saw this facet in action, having had the chance to visit the museum's arachnid collection (spiders!), which was very cool. I asked the curator, Jan Beccaloni, how many spider specimens there were exactly, and she told me that they weren't entirely sure, but that it was something in the millions, or at least equivalent to "the number of legs you can count divided by eight!" She also described how specimens were always coming in and going out, like packets with legs, stored with things to discover. It was marvelous!


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Imagine multiple rooms filled with shelves of spiders like these. The one on the right is a Theraphosidae specimen (Tarantula type).

2. The collections have huge historical value: not only from a humanities angle, but also as a scientific record of the past.

Many of the collections at the museum are very old and/or span a huge timeline. In fact, they very nicely reflect aspects of the scientific process of different times in history, and therefore offer a wonderful window into the history of science. Here, I also had a chance to talk to Mark Spencer, curator of British and European herbariums, and in particular, he was kind enough to grant me an up close look at the Sloane Herbarium.


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Coolest book shelves ever! (and possibly one of the most expensive)

In case you didn't know, Sir Hans Sloane (1660-1753) was a fellow, a physician, a scientist who had amassed a massive collection of plants, many of which are impressively bound in the 265 volumes that are housed in a very cool book room within the museum (I should also mention that Sloane was an avid collector of many things - in fact his collections are essentially the initial core of what would be become the Natural History Museum as well as the British Museum).

As a small example of the historic relevance of the collection, let's consider Sloane's connection to chocolate:

While in Jamaica, Sloane was introduced to cocoa as a drink favoured by the local people. He found it 'nauseous' but by mixing it with milk made it more palatable. He brought this chocolate recipe back to England where it was manufactured and at first sold by apothecaries as a medicine. Eventually, in the nineteenth century, it was being taken up by Messrs Cadbury who manufactured chocolate using Sloane's recipe. (NHM website)

Essentially, Sloane had a key role in the popularity of "milk" chocolate. In fact, one of the original cocoa (Theobroma cacao) specimens first brought over to England can be seen in the Sloane Herbarium.

These historical collections also provide a scientific snapshot of the past, a sort of biodiversity record book. For this aspect, Johannes Vogel, Keeper of Botany at the museum, provided a great example of this. Here, I was told that the peregrine falcon eggs used to suggest DDT effects on eggshell breakage and population loss are primarily housed at the museum. This was largely work done by Derek Ratcliffe in the 1960s, that was eventually part of the argument used by Rachel Carson in her book "Silent Spring."

Furthermore, in his 1970 paper, "Changes attributable to pesticide in egg breakage and eggshell thickness in some British birds," Derek went on to provide a very nice study that confirmed this link. i.e. population numbers were closely attune to egg breakage within the nest of these birds; which was best explained by the apparent thinning of the eggshells; which closely correlated to the introduction and prevalence of synthetic organic chemicals such as DDT; which was verified by accessing the actual amounts of the synthetics in the various egg shells. Basically, this type of work could not have been done had there not been a collection available, a collection that house various Peregrine eggs from different points in time.

Finally, I should point out that this sort of example is particularly prevalent today. As climate change alters ecosystems and the geochemistry of our planet, these collections, especially ones that stretch far back in time, are providing valuable data on the past. Which is important: as it is this sort of data that helps us more effectively examine the present, as well as provide a possible window into the future.



 
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Postcard from Language Camp

28 Jul
langcamp.jpg Greetings from one of the best places in the world to learn foreign languages! DLI, CIA University? No, a small town in Vermont that hosts an annual summer language institute: Middlebury. To call the Middlebury language schools a camp is like calling a hurricane a rain shower.

At the core of the language program here is the contractual agreement of all participants to only use their language of study for the duration of their stay. The "language pledge" is in effect 24-7 and contributes to the full-immersion environment. In many ways, you are exposed to more of the language than in a country where it is spoken. There is simply no escape from the language outside of withdrawal from the program, resulting in a strange environment in this small Vermont town near the Green Mountain National Forest. Pictured above is Sunday morning at the library where students pore over word lists, prepare for the upcoming week, and listen to audio files to improve their listening comprehension.

Giving up English for 7-10 weeks has a strange, Kafkaesque effect on the brain. You live in a heterotopian space, one that makes you question where and when you exactly are, and how you came to be there. Time seems to stand still in this environment as the new language permeates you, even as an instructor. The frustration of not being able to express yourself in English either gives way to creative uses of the new language, or a bout of 'language breakdown' when students are incapable of any form of communication. This intense committment to staying in the language has resulted in the occasional call from the local hospital asking for a translator for an injured student who is 'stuck' in the language.

I am teaching beginning German this summer to students who have had almost no exposure to the German language. They too sign away English for seven weeks, and of course they often make the most progress of all students. It is a testament to the hard work of the students and to the human brain's ability to acquire languages.

Middlebury started with a school of German in 1915, when Vassar professor Lilian Strobe thought that Middlebury's isolated geography would make an ideal place to allow students to focus on language learning. Today, Middlebury teaches 10 languages and on any Friday night, the town pub becomes an even more surreal place. As you walk in you can hear a table of German speakers, a table of French, a table of Spanish, etc. If you passed through town accidentally and did not know what was going on, you might question where in the world you were. If you try to speak to the students, you would only get a strange look or an answer in the language they study. The motto of the Language Schools is "No English Spoken Here".

Teaching a language without the aid of any English explanations or translations is an interesting challenge, but the challenge forces both me and the students to strain our minds to comprehend and communicate. It forces a more efficient, comprehensive teaching and learning style that manages to promote quick and effective language acquisition.

Students from a variety of backgrounds come here, including many graduate students who need a language for their research, government types whose first phrase in the language is "I'm not permitted to tell you what I do for a living," and students who are preparing to move abroad and need to learn as much of a language as possible in a short period of time.

The program runs from June-August only and is roughly the equivalent of two years of instruction. The real trick is the constant immersion and steady interaction with other speakers. Contrary to popular belief, there is no way to 'pick up' a language quickly with self-study. Languages are spoken among people and that spoken interaction is critical to learning. Here, students only sit in classes 3-4 hours daily. The rest of the day is spent doing other activities involving high frequency vocabulary such as working out, playing teams sports, yoga, singing in a choir, eating, drinking, putting on a play, playing billiards, and hiking in the nearby forests; all in the target language. Often, these seemingly superfluous interactions outside of the classroom prove to be the most beneficial way to solidify what one has learned in the classroom earlier that morning.

I have long lamented the state of language education in the United States, but I see change and improvement in foreign language education every year. Middlebury reflects this trend and has shown a steady increase in demand. Overall applications for admission to the program have increased 120% over a ten-year period. For Arabic, applications are up 375% and this increase has prompted the program to move the Arabic school to Mills College in Oakland, California. For my passion, German, applications are up a significant 75% with steady enrollments over a ten- year period, countering the trends of decreasing interest after the fall of the Berlin wall.

For a realistic look at the amount of progress made, you can view the before and after videos on the Middlebury web site.



 
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Home-made life insurance, the Apollo way

27 Jul
apollocovers.jpgOf all the places I never expected to learn anything cool about the Apollo astronauts, number one would have to be the blog run by ukinsurance.net. ("For many years we have provided buildings and contents insurance for home owners, landlords and business premises.") I mean, it doesn't exactly promise a light, zippy read, does it? But it delivers one, and this week's post on "The Apollo Astronauts' Fascinating Insurance Covers" actually is fascinating. It details the extraordinary measures taken to provide financial security for families of the Apollo crews, who were literally uninsurable: Before every flight, from 11 to 16, the crews would autograph and leave behind a number of commemorative post cards, the idea being that, should the flight end in an untimely fashion, the cards' value would skyrocket. ("No pun intended," ukinsurance.net notes brightly.) It's a weird, unexpected look into a neglected corner of our history in space. (Via Coudal.)

 
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