Wednesday, March 31, 2010

Astro101: Telescopes and Observatories

Today I return to my (very) occasional series Astro101, in which I talk about some of the most basic concepts in the science of astronomy.  Since today is the deadline for proposals to use the telescopes available through Kitt Peak and other national observatories, I thought that a natural topic would be telescopes and observatories. Just as a caveat, here I will be defining the two words as they are most often used in present-day astronomy.  As is often the case, there are exceptions, and the definitions have changed over time.  But those are discussions for another day.

Saturday, March 20, 2010

Science bloggers lay claim to the periodic table

David Bradley is a British science writer.  Among other things, he authors and maintains the Sciencebase website and blog, he twitters, and he maintains a list of several hundred scientists on Twitter he calls "Scientwists".  Anyway, you should follow him and read up on his stuff.

Yesterday I noticed Bradley had developed a fun little project he calls the Periodic Table of Science Bloggers.  As you hopefully remember from chemistry class, the periodic table is a way of arranging the known elements such that vertical columns show you elements with similar chemical properties, and from left to right and top to bottom you go to heavier elements.  Each element has a one or two letter abbreviation.  My favorite version of the periodic table ever is the Periodic Table Table.  Warning: you can spend hours exploring that site.

The Periodic Table of Science Bloggers contains (as I write this) about 100 different science blogs, listed in most cases under the element whose abbreviation could conceivably be an abbreviation for the blog.  For example, I'm under "At" (for "Astatine" or "Astronomy"), element 85, near the lower right.  Some interesting facts about astatine I learned after choosing "my" element: all of its isotopes are highly radioactive.  At any given time, there are only about 30 grams of astatine in the entire crust of the Earth.  The astatine on Earth was not produced in stars or supernovae, but from the radioactive decay of uranium (which was produced, probably, by supernovae).  This isn't to say that astatine isn't created in supernovae or in stars, but astatine is so short-lived (just a few hours) that it would not be incorporated in to planets or other stars.

The only "problem" I have with the Periodic Table of Science Bloggers is that it is not periodic; that is to say, the different columns do not have anything to do with the topic of a blog.  But that would be a lot of work which I'm not willing to do, so this isn't a complaint.

So, go peruse the Periodic Table of Science Bloggers.  You'll  find a lot of good reading and learn a lot about all kinds of science!  And, while you're at it, maybe you'll learn about the actual elements, too.

Friday, March 19, 2010

The rate of supernovae in the Large Magellanic Cloud

Supernova remnants and other nebulae in the Large Magellanic Cloud
Image Credit: C. Smith, S. Points, the MCELS Team and NOAO/AURA/NSF

The picture above is of the Large Magellanic Cloud, or LMC for short.  The LMC is one of the closest galaxies to our home galaxy, the Milky Way. (Read here if you need to remind yourself what a galaxy is).

One of the troubles with trying to understand the Milky Way is that we are in it (can't see the forest for the trees), and large portions of the Milky Way are blocked from our view by clouds of dust and gas.  We can see the entire LMC, on the other hand, and it is close enough that we can see fairly typical individual stars!  So, with the LMC, we can study both the forest and the trees.  There is another, smaller galaxy called the Small Magellanic Cloud (SMC) that is roughly the same distance away, in a slightly different direction, which is likewise useful for studying an entire galaxy along with the component stars.

Wednesday, March 17, 2010

The state of the astronomy job market

Image Credit: Anil Seth et al. 2009, "Employment and Funding in Astronomy"

The current job market for professional astronomers is, for those of us trying to navigate it, absolutely terrifying.  Finding jobs in astronomy is, in "normal" times, a highly uncertain and stressful process, and the Great Recession in the United States is having a profound impact on astronomy jobs, just like in most of the labor market.  But perhaps the largest source of terror comes from within, from a foreboding among young astronomers that there are fundamental problems with the astronomy career path in the United States, and that a large fraction of us currently on the job market are not going to realize our dream of becoming lifelong professional astronomers. 

Monday, March 15, 2010

Happy 50th Birthday to Kitt Peak National Observatory!

50 years of optical telescopes at Kitt Peak
Image Credit: NOAO / KPNO

Today marks the 50th anniversary of the official dedication of the Kitt Peak National Observatory, one of the world's largest collection of telescopes about 60 miles southwest of Tucson, Arizona.  Prior to the founding of Kitt Peak, most observatories were privately owned and operated by individual universities or organizations.   This meant that astronomers who wanted to use telescopes had to either be employed by the observatory or had to strike some sort of deal (like buying part of the telescope or building a new camera for the telescope).

Monday, March 08, 2010

Correlations and causation

Hubble Space Telescope picture of the cluster of galaxies Abell S0740
Image Credit: NASA, ESA, and the Hubble Heritage Team

Many people think that there have been a lot of big earthquakes in the past few months.  In early January, a magnitude 7.1 earthquake hit the Solomon Islands, causing a small tsunami.   One week later, a magnitude 6.5 earthquake hit just off the California coast.  Two days after that, a magnitude 7.0 earthquake in Haiti killed hundreds of thousands of people. The Chilean magnitude 8.8 earthquake on February 27th was the 5th largest earthquake ever recorded. A few days ago, a magnitude 6.4 earthquake hit Taiwan, and today a magnitude 6.0 earthquake hit Turkey.  (For a more detailed list of recent large earthquakes, see this list by the US Geological Survey.)  Is there a relation between these earthquakes?  Or are we just hypersensitized after the tragedy of Haiti?  Or are we having the same frequency of big earthquakes as normal?  More on this later in the post.

Friday, March 05, 2010

Dinosaurs, asteroids, and the scientific methods.

Artist's Conception of the Asteroid Impact that May Have Killed Off the Dinosaurs
Artwork Credit: NASA / Don Davis

I like space.  I like dinosaurs.  I own a very well-written book called "T. rex and the Crater of Doom".  So you'd think I would be happy about a news story titled "It's official: An asteroid wiped out the dinosaurs".  But I'm not; in fact, I'm quite grumpy about it.  Why?  Because many of the versions of this story that I've read, whether from internet news, traditional media, or even Scientific American, imply that this is a decision and the final word on the subject.  But that's wrong.  That's not how science is done.  And, to be fair, the original press release does not make any such statement.  Let's look into the topic, what happened, why the news outlets got it wrong, and why it matters.

Monday, March 01, 2010

Earthquakes, tsunami, and astronomy

Image Credit: USGS Real-Time Seismogram Displays

Saturday morning, I awoke to news of the magnitude 8.8 earthquake that occurred 200 miles southwest of Santiago, Chile.  That news snapped me awoke instantly.  Magnitude 8.8 is a monstrous earthquake, roughly 500 times the strength of last month's disastrous quake in Haiti.  The amount of energy released in the Chilean quake is roughly equal to the amount of sunlight that hits the Earth in a three tenths of a second, or roughly one hour's worth of the average energy usage of humans, all focused into a small region of the planet.  The picture above is output from an electronic seismograph near San Jose, California.  The green signal and the wavy behavior in the rest of the graph is energy from the Chilean earthquake, easily detected nearly 10,000 kilometers away.

My thoughts immediately drifted to the many large observatories in Chile.  The United States operates the Gemini South Telescope and the Cerro Tololo Inter-American Observatory; these facilities are 700 km north of the earthquake epicenter.  After short interruptions to power up generators and to check for damage, these facilities were able to continue their work with no damage.  Other observatories located even further away from the earthquake suffered similar or no interruptions, and I haven't heard of any damage.

More important is the well-being of the observatory staff and their families.  I know many of the staff at many of the observatories, and I have friends and colleagues with Chilean roots or family.   Many of these people live in Santiago, which suffered moderate to severe damage from the earthquake.  The vast majority of these people are safe, thank goodness.  But the towns south of Santiago are in very bad shape and need aid desperately.  (Consider donating through a reputable agency; my personal favorite is the Red Cross).

As most people know after the horrible Indian Ocean tsunami five years ago, big earthquakes can trigger a tsunami, a series of waves that can cross oceans at hundreds of miles per hour and cause damage and destruction thousands of miles away from the earthquake.  A Chilean earthquake in 1960 caused a tsunami that devastated Hilo, Hawaii.  The Pacific Ocean has numerous buoys that can sense a tsunami, and one of those buoys detected a tsunami less than an hour after Saturday's earthquake.  The entire Hawaiian shoreline was evacuated (as were many shorelines around the Pacific rim), but the largest waves were about three feet, toward the small end of what had been predicted.  Thankfully!  Little damage was done, and no lives were lost on Hawaiian soil. 

Since this time, I've seen news stories asking how the scientists got it wrong.  I'm scratching my head, asking myself how people can consider that the scientists were wrong, when they predicted the arrival time of waves within a few minutes of the actual arrival, and the wave heights were within the predicted range. 

I watched live coverage of the Hawaiian wave arrival via an online feed of a Hawaiian TV station.  That station showed a live video feed of an inlet into Hilo Bay.  When the tsunami arrived, the nature of the ocean visibly changed, with strong surges of water entering what had been a very quiet bay.  Any swimmers on the beach on this otherwise warm, sunny weekend day would have been swept out to sea.  The evacuations undoubtedly saved lives, and while the Hawaiian shoreline was not destroyed by towering waves, people were safe and secure.

A precise prediction of the height of tsunami waves requires data we do not have -- accurate maps of ocean floors, understanding of the propagation of waves across this seafloor, and precise details of exactly what happened on the undersea fault that caused the earthquake (how much did the ocean floor lift or sink? Were there any additional underwater landslides to help push water?  Where and what direction?).  The mere fact that computer models based on a paucity of information came close to predicting (not just matching later) exact wave heights and arrival times is a triumph!  Data from many fields of science -- seismology, geology, oceanography, fluid dynamics, computer science, etc. -- was quickly synthesized and disseminated in order to protect lives and property.

Now, these data were not all collected on Saturday morning.  They have been collected over decades of research, over dozens upon dozens of research projects across numerous disciplines.  Most of these projects do not have titles like "Computational tsunami prediction" (though some might).  They'd be much more esoteric, like "Improved discretization for CFD via refined finite element analysis" or "Bathymetric constrains on strain release mechanisms in thrust faulting along the Nazca-South American subduction zone".  Even astronomical research, such as observations of supernovae or planet formation, can provide constraints that on computer models and methods that are used for both astronomical and ocean simulations, can provide improvements to methods and simulations used in geological and tsunami calculations.  It is the sum of these little pieces that have brought about our ability to predict tsunamis, and maybe one day the ability to predict the earthquakes themselves.

We scientists are often asked what use our research is, and sometimes we are attacked viciously for wasting money.  A computer scientist working on improving models of stellar atmospheres or the breaking processes in solids may not expect or realize that her methods may be a crucial part of vastly different projects, such as earthquake models and tsunami prediction.  Yet in science, these far-flung fields are often interrelated in intricate and unexpected ways.  This is why I believe it is short-sighted to spend money only on research specific to an obvious problem.    The "pure research" project in quantum physics may produce a key advance that helps solve the energy crisis, improve weather prediction, or even help to develop a new antibiotic drug.    Or maybe predict an earthquake, and allow us to minimize human tragedies like those in Haiti and Chile.