Monday, December 17, 2007

Reflecting on StarStuff

It's now been more than a year since I started this blog. I've had a great time with it, and I hope that I've been able to entertain and inform a few people along the way. A few months after I started, I began tracking visits using Google Analytics to help me get some sense of my audience -- and I discovered that I didn't have much of an audience. Even so, I decided to continue posting for at least a year.

I'm glad I did. If I hadn't continued, I would have missed the one remarkable event in the first year of this blog. On August 22, newspapers around the world carried an announcement by Google that the latest version of its popular "Earth" application also included the Sky -- turning any computer into a virtual telescope. One of my early posts to this blog speculated that such a feature might be coming soon, and during the final week of August that post attracted hundreds of users who were looking for the new software. In fact, about half of the visitors to this blog over the last 9 months came during those few days. Most didn't stay long. They were looking for something else.

Aside from that week in August, Google Analytics tells me that during a typical week about 15 unique visitors view this blog. Roughly 80 percent are new visitors, meaning that only 3 visitors per week are coming back for another look -- and the average time spent browsing the site is less than a minute, suggesting that most visitors aren't even reading a post. At this point, I have to ask myself whether I can justify the time I spend on this blog, even if it isn't much time.

Six months ago, I disabled the comments feature since I was essentially the only one making any comments (sometimes following up on the topics raised in the original post). Today, I'm turning the comments back on -- and I'm asking for your feedback: Should I continue posting to After the new year, based on the comments you leave or email, I'll either continue for another year or hang up my blogging hat. In either case, it's been a great experience, and the archive is here for everyone to enjoy.

Tuesday, December 11, 2007

Telescope Philanthropy

In the early history of astronomy, pioneers like Tycho Brahe depended on the generosity of kings to fund their science. Since the mid-20th century, this role has largely been supplanted by the government, through agencies like the National Science Foundation and NASA. Recently, with the federal budget slumping under the weight of excessive military expenditures and declining tax revenues, government funding for science has stagnated. But at the same time, a new class of philanthropists has emerged to help fill the gap.

Last week, Intel founder Gordon Moore announced that his foundation would donate $200 million to help build an enormous telescope with a mirror thirty meters (100 feet) in diameter. Imaginatively called the "Thirty Meter Telescope" (TMT), the California-led project is one of several competing efforts to build the next generation of large telescopes for astronomy research -- including the "Giant Magellan Telescope" (GMT) and an even larger European project called the "OverWhelmingly Large" (OWL) telescope, with a 100-meter mirror. All of these projects seek to produce the sharpest images ever obtained from a ground-based observatory (10 times sharper than images from the Hubble Space Telescope), offering new insights into the history and fate of the universe.

Moore's grant to the TMT project is just one example of a growing trend toward private funding for astronomy research. Last January, Google announced a partnership with the Large Synoptic Survey Telescope (LSST), which plans to image the entire sky every three nights beginning in 2013, and Microsoft co-founder Paul Allen is funding the latest efforts by the Search for Extra-Terrestrial Intelligence (SETI). Several global telescope networks have also received private funding, including the Whole Earth Telescope (from the DuPont Foundation), the Stellar Oscillations Network Group (from Danish beer giant, the Carlsberg Foundation) -- as well as the Las Cumbres Observatory Global Telescope Network, which was recently endowed by a retired silicon valley technology guru.

While most funding for science continues to come from government sources, it is encouraging to see the entrepreneurial spirit blossom among astronomers -- and to see it rewarded with the patronage of new donors who hold a special place in their hearts for the stars.

Thursday, November 29, 2007

Adopting a Star

Whenever the holiday shopping season rolls around, I consider the idea of setting up an "Adopt a Star" website to help fund scientific research. A quick Google search persuades me to abandon the idea -- the Internet is already full of such sites, and most of them are far more sophisticated than anything I would have time to create. Anyone who cares to fork out $19.95 can name a star "Lula", after their cute Bichon Frise puppy -- they even get a certificate with a star map and the vital statistics of their stellar namesake. But what are they really buying?

The International Astronomical Union (IAU) is the only "internationally recognized authority for naming celestial bodies... and names are not sold". In fact, with the exception of a few bright stars that have ancient traditional names, most of the stars in the sky only have boring old catalog numbers. The IAU does name comets after the discoverers, and astronomers who find new planets or asteroids in our solar system are allowed to suggest names for them (though they can only be named after people who have been dead for more than 100 years, which obviously limits the commercial possibilities). None of the websites that allow you to "buy" or "adopt" a star are affiliated with, or endorsed by, the IAU. So what are these businesses selling?

It's important to distinguish between companies that allow you to "adopt a star" and those that say you can "buy a star name". Although both are engaged in essentially the same business, the representation of the transaction as an "adoption" is more intellectually honest. When you "adopt a highway" it's understood that you do not thereby own a section of a public road. Instead, you agree to keep the adopted stretch free from garbage in exchange for a blue sign on the roadside acknowledging your effort (and possibly persuading drivers to stop at your coffee shop). In the case of stars, your only responsibility is to pay the $19.95 -- the company then lists your name beside the chosen star on their website, and maybe sends you a glossy certificate. One of the best operations I discovered recently is actually run by scientists to support their research. The website resembles the vision I had for "Google Sky", which I wrote about last December, and cleanly separates the commercial portion of the site from the main section that is meant to be a tool for astronomers and the general public.

Allowing anyone to adopt a star is fairly harmless, and most people probably realize that astronomers around the world do not subsequently publish scholarly articles detailing their in-depth decades-long study of "Lula" the puppy star. For those who don't realize that it's just a novelty gift, I have some very nice real estate on the Moon that promises to be really hot property in a few years...

Tuesday, November 13, 2007

Alien Solar Systems

Last week a team of scientists in California announced the discovery of the fifth planet orbiting a distant star similar to our sun. The star is known as "55 Cancri", and is located 41 light years away in the constellation Cancer. This star now holds the record for hosting the largest known planetary system outside of our own. Only one other star (called mu Arae) is known to host four planets, while triple-planet systems have been documented around another half-dozen stars.

Since 1995, more than 220 planets have been discovered in orbit around other stars. The overwhelming majority of these planets have been found by their gravitational influence on the star that they orbit. We tend to think of a planet as simply moving around its star -- but even small planets exert a gravitational tug on the star that causes it to wobble around slightly in space. Astronomers can measure this wobble, essentially by passing the light from the star through a prism to spread it out into all of its colors (think of the famous Pink Floyd album cover) and then carefully measuring the positions of dark lines that appear where different chemical elements like hydrogen and helium absorb light near the surface of the star. The color corresponding to the position of these dark lines moves around as the star wobbles -- basically for the same reason that the pitch of an ambulance siren sounds different when it is moving towards you or speeding away (the effect is known as the Doppler shift).

The team has been monitoring 55 Cancri for more than 18 years. Since the wobbles caused by the five planets are all happening at the same time, and with different orbital periods, it took a long time to isolate the wobbles caused by each planet individually. The outermost planet in the system is about four times the size of Jupiter, and it takes 14 years to orbit the star. The other previously known planets are similar in size to Neptune, Jupiter, and Saturn, but they orbit the star relatively close in -- circling every 3, 15, and 44 days (all much faster than Mercury orbits the Sun). The newly discovered planet falls somewhere in between, orbiting the star in about 260 days. Since 55 Cancri is a little fainter than the Sun, this places the new planet inside an Earth-like "habitable zone" where liquid water can theoretically exist. Although the planet is roughly the size of Saturn, it could have large Earth-like moons where water and potentially life could survive (Saturn's largest moon "Titan" is bigger than the planet Mercury).

It's only a question of time before astronomers discover more and larger planetary systems around distant stars. The longest running surveys have been operating for less than 20 years, so even in the best case we would not be able to detect Saturn, Uranus, or Neptune if we were watching the Sun from a distance. As the technology improves we should also begin finding smaller planets, closer to the size of the Earth. In the future, people might wonder what all the fuss was about over this little five-planet system around 55 Cancri.

Friday, October 26, 2007

Splitting the Sky

Now that the Intergovernmental Panel on Climate Change (IPCC) and Al Gore have been awarded the Nobel Peace prize, the debate about global warming can shift from whether or not the human population is primarily responsible, to how we should design a solution. The idea that is currently most popular with politicians involves setting a cap on carbon emissions, distributing free permits to corporate polluters, and then allowing them to trade the permits amongst themselves. Since it establishes a free market for pollution rights, this "cap and trade" system is supposed to lead to the most efficient reduction in carbon emissions -- allowing the companies that learn how to reduce their pollution to profit by selling their permits to companies that have more trouble.

It sounds like a reasonable system, and it has even been used successfully in the past to reduce sulphur-dioxide emissions -- the leading cause of acid rain. But it suffers from a fatal flaw: the polluters do not pay the costs of the efficiency improvements, but instead transfer the burden to consumers. A slight modification of this system, popularized by the book "Who Owns the Sky?", divides the pollution permits equally among the population and forces the polluters to purchase them from us! Again the costs are eventually transferred back to us through products and services -- but the average person comes out about even. This has the advantage that it also establishes an incentive for individuals to reduce their pollution-generating consumption: if you drive an efficient car or reduce your overall energy use, you can can earn more from selling your carbon permits than you pay back to the polluters.

On a national level, this modified system seems pretty workable -- but how do we divide pollution rights between countries? The most obvious answer would be to split the sky evenly among the entire population of the planet -- every person gets an equal share. But the obvious answer may not be the best answer, because it effectively rewards countries with large populations -- and population is a major factor in the growth of global warming emissions. What really matters for each country is the relationship between its biocapacity (the natural resources within its borders, and how they are used) and the product of population and consumption (the total drain on those resources). Some countries have more biocapacity than their population consumes, while others have ecological deficits. If the global distribution of carbon permits were based on biocapacity, it would force countries that are far out of balance (whether due to consumption, population, or both) to purchase permits from countries that manage their resources more responsibly. This establishes the right incentives for both consumption and population.

With the right system, we can transform our societies and bring them back towards a balance with the resources of the planet. If we start reasonably soon, we might even avoid the most unpleasant consequences of pushing the limits of nature.

Friday, October 5, 2007

Science and Politics

During the U.S. election season, which seems to stretch on forever compared to most modern democracies, it's more difficult than usual to find science in the headlines. I'm fairly certain that good science continues to be produced, with press releases diligently prepared, while presidential hopefuls give stump speeches along the campaign trail. But most of the time, science just doesn't seem to make the cut. The exception to this general rule occurs when science and politics collide -- when the candidates begin to address the issue of government interference in research, where policymakers lose access to unbiased information.

This week, on the 50th anniversary of the launch of the Russian sputnik satellite, one high-profile candidate delivered a speech blasting the current administration's "war on science", and outlined strategies to shield government scientists from political pressure. Recent examples of scientific research being either suppressed or distorted by government managers -- many of whom were appointed more for their loyalty to an ideological agenda than for any expertise in the relevant discipline -- are most obvious in the area of climate change research. But other research areas have also been politicized, including the science of food safety, air quality, and forest management, to name just a few.

As with many issues, politicians are following rather than leading public opinion. The campaign to restore "scientific integrity" to decision making has recently been championed by the Union of Concerned Scientists. This grassroots organization has sponsored surveys of government scientists and circulated a petition, now with more than 12000 signers, to keep politics out of science. On the specific issue of embryonic stem cell research, which has had limited federal funding imposed by the current administration since August 2001, several prominent celebrities have also played an active role. One of the current group of candidates promises a return to "evidence-based decision-making" in the next administration, something most scientists would undoubtedly welcome.

Like oil and water, science and politics simply do not mix. The government might shake things up for awhile, but -- honoring the finest traditions -- science will eventually rise to the top.

Friday, September 28, 2007

Astronomy Career Paths

The American Astronomical Society (AAS) and the American Institute of Physics (AIP) recently sent out the first survey of a planned 10 year “longitudinal study” that will follow astronomy and astrophysics graduate students registered in 2006-2007 throughout their early careers. The idea is to better understand not only the wide variety of career outcomes, but also the motivations underlying the decisions that lead to each path. This will hopefully allow the study to identify any factors in the culture of astronomy that might discourage some sectors of the initial student population from pursuing long-term careers in the field. Although certainly not as scientific as a formal survey, individual graduate programs could get a sort of “sneak preview” of this longitudinal study by finding everyone from their incoming class of 1996-1997 and asking what they are doing now. I performed an informal survey for one such class, which began with eleven incoming students in a large astronomy graduate program at a major public university. The sample consisted of seven males and four females, including seven domestic and four international students (one of them female).

At the end of the first year of graduate study, one female domestic student was asked to leave the program for academic reasons, and one male international student left the program to pursue a graduate degree in computer science at another university. The current status of these two students is not known, although the absence of recent scientific publications suggests that neither of them are presently doing astronomy research. After finishing coursework in the second year, four students ultimately decided to leave the program with a Master's degree, including three males (one of them international) and one female. The male international student transferred into the computer science graduate program at the same university and went on to work as a software developer for a local company. One male domestic student immediately obtained a software engineering and management job at a local startup, and eventually took a similar position out of state, closer to his family. Another male domestic student began teaching astronomy at a nearby community college, where he continued working on the tenure track for 6 years while also earning a Master's degree in a related science. He was recently given tenure and became chair of the department. The female domestic student stayed in the program for 2 more years before becoming a high school teacher. She took some graduate courses in mathematics prior to leaving, allowing her to obtain certification in math and physics through an alternative program that ran concurrently with her first year of teaching. She taught math in nearby public high schools for 4 years, and is now teaching physics at a private high school where she eventually expects to teach an astronomy course as well.

Only five of the eleven incoming students ultimately earned a Ph.D. through the program: three males and two females with one international student of each gender. One male domestic student took a series of postdoctoral fellowships over nearly 5 years before obtaining a tenure-track research position at a national laboratory. The female international student was awarded prestigious back-to-back postdoctoral fellowships, providing a total of 7 years of support, and is currently beginning her sixth year as a postdoc. The female domestic student worked as an associate editor for a popular astronomy magazine and in an instructional support position for an undergraduate program at a private university before recently accepting a non-tenure-track position at a small teaching college. Another male domestic student worked for several years through a postdoctoral fellowship at an international observatory before being hired as a tenure-track instrument scientist with both research and support responsibilities. The male international student worked in a postdoctoral position at a public university for almost 3 years before becoming a faculty member at a university in his home country, with a continuing adjunct appointment at his postdoctoral institution.

This “anecdotal” longitudinal study suggests that it might be difficult to define a “standard career path” in astronomy, if such a thing even exists. The wide variety of outcomes for this one small sample of students certainly did not reveal any systemic problems in the culture of the field, since both male and female as well as domestic and international students were proportionally represented along each major career path. More than a decade after entering a graduate program in astronomy, the experience appears to have led most of these students to interesting and fulfilling careers that they each shaped through their personal choices. Future students can take comfort in knowing that graduate study in astronomy only seems to multiply their possible career options.

Thursday, September 13, 2007

Extreme Exoplanet

About 5 billion years from now, the Sun will begin to exhaust its primary source of energy -- the hydrogen near the center that fuels nuclear fusion. The remnant helium core will begin to contract, and the surrounding shell of hydrogen will start to burn hotter. Our star will slowly bloat to 100 times its former size, becoming a "red giant" and possibly destroying some of the inner planets of our solar system. An unsettled question among astronomers is: could the Earth make it through such a catastrophic event?

New evidence in this longstanding debate surfaced this week, when an Italian-led group of scientists announced the discovery of the first planet around a distant star that appears to have survived this phase of stellar evolution. "The future of the Earth is to die with the Sun boiling up the oceans, but the hot rock will survive", said Don Kurtz, one of the coauthors of the investigation. The study focused on a star called V391 Pegasi, which is estimated to be about 10 billion years old and appears to have already gone through the red giant phase. This particular star is special: the light coming from its surface exhibits very regular pulsations, a kind of continuous "star-quake" that provides a window into its interior structure. The astronomers have been monitoring these pulsations for more than 6 years, and they noticed something interesting.

As expected, the period of the pulsations are increasing slightly over time -- a consequence of the continuing evolution of the star, which slowly modifies the interior conditions that determine the regularity of the pulsations. But in addition to the expected changes, the pulsations sometimes arrived a few seconds sooner or a few seconds later than predicted, in a pattern that suggests the star is wobbling around in space from the gravitational pull of an orbiting planet. This is the same technique that led to the discovery of the very first planets detected outside of our solar system in 1992, which were orbiting a distant pulsar. As it turns out, the planet around V391 Pegasi is close enough to the star right now that its orbit was probably the same size as the Earth's orbit around the Sun at the time the star became a red giant. The fact that the planet is still there suggests that close planets can, at least in some circumstances, survive this phase of stellar evolution.

Of course, more research is needed to determine whether or not V391 Pegasi represents a typical outcome for close planets. But, as Kurtz succinctly stated, "It is psychologically interesting to think that the Earth will survive." Even if all that's left is a hot rock.

Tuesday, August 28, 2007

Teachers in Space

I will never forget the morning I entered my seventh grade science class and our teacher, Mr. Harshfield, quietly played a video recording of that morning's launch of the Space Shuttle Challenger. It was the 28th of January 1986, and 73 seconds after liftoff the classroom fell into a stunned silence as we witnessed the disaster that claimed the lives of seven astronauts, including Christa McAuliffe who would have been the first teacher launched into orbit under a new NASA program. The tragedy was later traced to a design flaw in the "O-ring" seal on one of the solid rocket boosters, leading to a fuel leak which ultimately broke up the entire shuttle.

The dream of sending a teacher safely into space was finally realized last week, when the Space Shuttle Endeavour successfully returned home after 13 days in orbit. Former elementary school teacher Barbara Morgan, who served as NASA's backup astronaut to McAuliffe for the ill-fated Challenger mission in 1986, said "the flight was absolutely wonderful" and "the shuttle program gets an A-plus". There were initially some concerns about the safety of the crew after a small gouge was discovered in the protective heat shield on the underside of the shuttle. The gash was apparently caused by a collision during liftoff with a baseball-sized chunk of insulating foam from the external fuel tank, similar to the damage that caused the Space Shuttle Columbia to disintegrate during re-entry in February 2003, but considerably less severe and in a less vulnerable location on the spacecraft.

Engineers from NASA determined that the risk posed by the gouge was not significant enough to justify an unrehearsed spacewalk to repair the damage from the International Space Station, where the shuttle was docked for most of the mission. Given the tragic potential of the damage, as exemplified by the Columbia disaster, it must have been a difficult decision for the engineers to make and for the astronauts to accept. But knowing the extreme risks of an impromptu spacewalk to the underside of the shuttle -- a procedure that has never been attempted before, and one that would normally require extensive training and practice in enormous dive tanks to simulate the weightless environment -- and considering the unknown effectiveness of the proposed repair work, NASA's decision is understandable.

Thankfully, it all worked out in the end. The space agency is now planning to implement several modifications to the foam-covered fuel tanks to prevent future damage to the shuttle's heat shield. These modifications are expected to be complete in time for the next mission to the International Space Station, in April 2008.

Friday, August 10, 2007

Cosmic Fireworks

This weekend, one of the best annual displays of shooting stars will light up the night sky. The Perseid meteor shower has its peak activity during August 11-12 every year, but it promises to be a particularly good show this year since it coincides with new moon -- ensuring dark skies if you're away from the city lights.

Contrary to their name, "shooting stars" aren't stars at all -- they are tiny pieces of dust from outer space that run into the Earth's atmosphere and burn up from the friction of moving at thousands of miles per hour. Most of the streaks of light that we see are caused by particles no larger than a grain of sand. When they burn up in the atmosphere, somewhere between 30 and 80 miles above the surface of the Earth, scientists call them "meteoroids". Only the very rare chunks of rock that are larger than a car have any chance of striking the ground, and these so-called "meteorites" are typically no bigger than your fist by the time they hit the surface. On average, only about 8000 meteorites weighing more than a few ounces make it to the ground every year (with another 16000 falling into the oceans). That's a little more than 1 per day for an area the size of the continental United States.

Meteors are streaking through the sky all the time, but sometimes the Earth moves through a dense cloud of dust that was left behind by a comet and we have a "meteor shower". Meteor showers are named for the constellation where all of the streaks of light appear to originate, which is roughly the direction that the Earth is moving in its orbit around the Sun as we intersect a particular cloud of comet dust. During the Perseid meteor shower you can trace most of the shooting stars back to the constellation Perseus, which rises in the northeast sky after sunset. Comet Swift-Tuttle, named after the astronomers who discovered it in 1862, is the source of the Perseid meteor shower. It orbits the Sun every 130 years, and most recently crossed the orbit of the Earth in 1992 -- leaving behind fresh debris for our viewing pleasure every August.

So find a spot away from the city lights, spread out a blanket or set up your reclining lawn chairs facing the northeast, and just look up. Give your eyes about 30 minutes to adjust to the dark, and keep your flashlights off or covered in red plastic. You can expect to see a Perseid meteor shoot across the sky about once or twice minute, with the show getting better and better after midnight when you are on the side of the Earth that is blasting through the dust cloud. Happy skywatching!

Monday, July 23, 2007

Water Worlds

Earlier this month, astronomers announced the first clear detection of water in the atmosphere of an alien world orbiting a distant star in the constellation Vulpecula, "the Fox". The star is formally known as HD 189733, and the planet -- which is slightly larger than the planet Jupiter in our solar system -- is affectionately called HD 189733b. Like the detection earlier this year of an extrasolar planet not much larger than the Earth, finding evidence of water from a distance of 63 light years is a landmark in the search for habitable worlds outside of our solar system.

This particular planet is special -- the alignment of its orbit causes it to pass directly in front of its parent star as seen from the Earth. As a consequence, the planet causes a tiny eclipse during each orbit as it blocks a few percent of the starlight from reaching us. How much starlight it blocks depends on the size of the planet, including its atmosphere. That atmosphere acts as a kind of filter -- allowing some colors of light through easily, while blocking some others. The scientists exploited this fact, along with the known absorption properties of water, to measure the size of the planet in several different colors of infrared light. The pattern of absorption in these colors matched the pattern expected for water, and could not be explained by any other common atmospheric molecule.

After the planet stops blocking any starlight, it swings around to the back side of the star. During this segment of its orbit, the planet exhibits phases just like the moon -- showing a crescent until it reaches the largest separation, and then gradually becoming fully illuminated before it slides out of view behind the star. Although astronomers cannot observe the phases directly, they can monitor the tiny changes in reflected light during this part of the orbit. In this way, it was also recently possible to reconstruct a map of the temperature difference between the day and night sides of HD 189733b. The day side of the atmosphere turned out to be more than 200 C degrees hotter than the night side, and the hottest spot actually occurred slightly before noon local time on the planet.

The ultimate goal of such research is to find water and other possible signs of life on a distant Earth-like planet, motivated by the age old question: "Are we alone in the Universe?". With the demonstration of these powerful techniques to study the atmospheres of alien worlds, we are on our way to finding the answer.

Friday, June 15, 2007

The Would-Be 10th Planet

Today, astronomers at the California Institute of Technology announced new measurements of a Pluto-like object in the outer solar system, which under different circumstances could have been identified as the 10th planet. The object, officially named Eris, belongs to the new class of "dwarf planets" that now includes Pluto. Earlier measurements had securely determined that Eris was physically larger than Pluto, which was one factor in the decision to demote Pluto from planethood and create the new category. The new observations show that Eris is also 27 percent more massive than Pluto -- making the would-be 10th planet the currently undisputed king of the dwarf planets.

In 2005, a tiny moon called Dysnomia was discovered in orbit around Eris. Using both the Hubble Space Telescope and the largest telescope in the world on top of Mauna Kea in Hawaii, the scientists measured the position of Dysnomia on six different nights as it traveled around Eris in a 15-day orbit. There is a simple relation between the size of a moon's orbit and the mass of the planet it circles, formulated in the 16th century by Johannes Kepler. This allowed the CalTech astronomers to calculate the mass of Eris directly from the observations.

This discovery adds further support to the reclassification of objects like Pluto and Eris as "dwarf planets" instead of traditional planets like the other 8 in our solar system. Without the new definitions, there would probably already be 8 Pluto-like planets for school children to memorize in the sequence after Neptune, with hundreds of others likely to be discovered in the coming years. Pluto has made its mark in history, but 50 years from now it will be as anonymous as a random chunk of rock in the asteroid belt.

Tuesday, June 5, 2007

Images of Distant Stars

Last week, astronomers from the University of Michigan announced that they have successfully obtained the first image of a distant Sun-like star. Using a technique known as optical interferometry, the scientists combined the light from a group of four small telescopes scattered across the top of a mountain in California -- effectively creating one huge telescope more than 200 meters across. The resulting image is about 100 times sharper than the view from the Hubble Space Telescope.

Astronomers have been making images of the nearest star (our Sun) since the time of Galileo, but other stars are so far away that even the most powerful telescopes see them as single points of light. In 1995, the Hubble Space Telescope obtained the first direct image of a distant star -- the supergiant Betelgeuse in the constellation Orion, which is so enormous that it would span the orbit of Jupiter in our solar system. The technique of interferometry -- combining the signals from many individual telescopes to produce a sharper image -- has been used in radio astronomy for a long time, most famously in New Mexico at the Very Large Array that was featured in the movie Contact, with Jodie Foster. Recent advances in technology have now made it possible to do a similar thing with optical telescopes.

The target of the University of Michigan study was Altair, the brightest star in the constellation Aquila, which is about 80% more massive than the Sun and spins about 60 times faster. It's rotation is so fast -- more than 600,000 miles per hour at the equator -- that Altair bulges out around the middle. The new image not only reveals this flattened shape, it also shows that the star is much cooler around the equator than near the pole. Although this feature was expected, the predictions do not match the observations exactly -- suggesting that astronomers may need to improve the theory.

There are several arrays of telescopes around the world that are designed for this type of imaging. As the technology continues to improve, imaging of distant Sun-like stars will become routine. This is just the beginning of an exciting era for interferometry.

Friday, May 25, 2007

Book Review

"Survival Skills for Scientists" by Federico Rosei and Tudor Johnston is the best career guide to be published since Peter Feibelman's "A Ph.D. Is Not Enough!". Because the authors work in an academic environment, as opposed to a government laboratory, they offer a different perspective of the optimal career path. By co-authoring the work, they combine the time-tested wisdom of a senior researcher (Johnston) with the more recent experience of a junior faculty member (Rosei) who has direct knowledge of the current job climate. Drawing from their own interactions in Europe, North America, and Asia, they also provide a more international outlook.

The authors begin with the First Law of Scientific Survival, which is "Know thyself". Their simple recommendation is that you figure out what kind of scientist you want to be by carefully considering the kind of person you actually are. Obviously this includes an assessment of your strengths and weaknesses, but it also means understanding what role you want to play in research, and how you want to spend your time on a day to day basis. They don't try to conceal their preference for an academic career, and this could slightly alienate the reader who prefers another path. But everyone can benefit from the self-reflection that the authors promote by asking the right questions.

The bulk of the book is devoted to the Second Law: "Know your tradecraft". This begins with a very honest and pragmatic critique of postdoctoral experience, and outlines the essential factors to consider when choosing a position at various stages of your career. While admitting that intelligence and hard work are the foundation of a successful career in science, they go on to summarize other advantageous character traits that anyone can develop over time. They continue with a broad overview of the landscape of the science profession, and the metrics that will be used throughout your career to judge your productivity. Among the many unique themes that emerge from the text is the concept of being your own "agent", boosting your prospects for a successful career. The authors point out that publications in scholarly journals are the primary way other scientists learn about your research, and that generously citing the work of others will help get their attention. They finish by detailing all of the ways you communicate your work to others, including specific advice about journal papers, your thesis and curriculum vitae, as well as conference talks and posters.

The book closes with the Third Law: "Know thy neighbor". Unlike Feibelman's book, which begins with a series of anecdotes to illustrate how a scientific career can be derailed, Rosei and Johnston place this section in the back of their book. The authors also try to keep it positive by including success stories in addition to the failures.

Overall, this book fills a niche that nicely complements the material contained in other popular career guides. It is logically organized, and is filled to the brim with candid advice that you are unlikely to find anywhere else. Some readers may be frustrated by the many parenthetical remarks, footnotes, and clearly labeled "diversions" that make the text less concise than it could be. To others, these features will simply add humor, depth, and humanity to an otherwise serious discussion. "Survival Skills for Scientists" may not replace your copy of Feibelman's "A Ph.D. Is Not Enough!", but it certainly deserves to sit alongside it on your bookshelf.

Wednesday, May 2, 2007

Sister Earth?

Last week, a group of European astronomers announced that they had discovered the "most Earth-like planet yet" around a star in the constellation Libra. The planet, known as GL581c, is the first of more than 200 planets discovered outside our solar system that is apparently in the so-called "habitable zone" of its star -- the range of orbital distances where liquid water can theoretically exist. In this sense, the discovery is a landmark in the search for life elsewhere in the Universe.

But if you examine the details more closely, you will discover a planet that is very different from the Earth. First of all, it is at least 5 times the mass of the Earth -- and it orbits the star every 13 days (instead of our leisurely 365 days), at less than 1/5 the distance from the Sun to the sweltering planet Mercury. The only reason the planet isn't burnt to a crisp is that its parent star is much cooler than the Sun -- a tiny red dwarf. As a consequence, it is likely that the surface of this planet has the right temperature for liquid water to exist.

But I wouldn't want to live there, even if I could breath whatever atmosphere might exist. Red dwarf stars give off most of their radiation in the form of infrared light -- basically heat, like what you see with night vision goggles -- and almost no visible light. So it might be warm, but it would always be dark to human eyes. Finally, although it is among the 100 nearest stars to the Sun, even the fastest spacecraft ever built by humans would take more than 90,000 years to get there. So don't count on this planet offering us a safe haven in case we wreck our own.

It's an exciting discovery -- and one that we will undoubtedly see more of in the near future. As technology improves and allows astronomers to find ever-smaller planets around other stars, we will eventually find a true Sister Earth, and maybe even life. But we're not there yet.

Monday, April 9, 2007

Sustainable Planet

A report issued Friday from the UN-sponsored Intergovernmental Panel on Climate Change (IPCC) has once again prompted debate about how to respond to global warming. Perhaps one of the biggest obstacles to meaningful progress on this issue comes from the perception that changing our consumption levels will drastically reduce our standard of living. This kind of hysteria is fueled by the commonly quoted phrase: "if everyone consumed like North Americans, we'd need five planets to support us". But if you consider the natural resources, population, and consumption patterns of the U.S. by itself, how unsustainable are we, really?

This is similar to the question raised by popular "ecological footprint" calculators, but it takes into account the fact that our nation has more natural resources and a lower population density than most of the rest of the world. So in a sense, it's more fair. Basically, "sustainability" is a careful balance of three factors: (1) the available natural resources, often lumped into a quantity called "biocapacity", (2) the average consumption level of those natural resources, known as our "footprint", and (3) the total size of the population. Since total biocapacity is fairly constant, any increase in population erodes the available footprint per person. So if we want to maintain a certain standard of living, we need to either control population growth or decrease our footprint over time.

As you can imagine, the average footprint in the U.S. is actually growing slowly over time, mostly from energy use (the inability of the environment to absorb all of the carbon dioxide we release). The last time we were in balance with the available resources was around 1969. As it stands today, the average footprint is about twice the available biocapacity per person. So we only need two planets to be sustainable as a nation, not five. The reason is simple: it's harder for Africa to be locally sustainable because they don't have enough arable land, and it's harder for China because they have too many people. We should certainly help them address these problems, but those challenges are distinct from the challenge of sustainability at home.

Even so, the average footprint in the U.S. is still twice as high as it needs to be if we want to live a sustainable lifestyle. So you might ask: when in history was the standard of living in the U.S. half of what it is today? Even if you use a traditional economic measure of the standard of living, like "real GDP per capita" (which is adjusted for inflation and population growth), you find that to be sustainable we would need to adopt the lifestyle of the mid-1960's. That doesn't seem like such a sacrifice, and it's close to the "1969" balance mentioned above because improvements in (agricultural and energy) efficiency have basically made up for all of the population growth since then.

The average U.S. footprint is currently about 24 acres, while the locally sustainable level is around 12. Something to shoot for.

Monday, April 2, 2007

Blaming the Sun for Global Warming

In recent weeks, skeptics of the notion that global warming is caused by humans have been promoting alternative theories. One of the most plausible explanations asserts that global warming is part of a natural cycle caused by changes in the temperature of the Sun. It's undeniable that the Earth experiences natural variations in climate due to the Sun and other factors, but the warming over the past 100 years has a fundamentally different character, and is unprecedented in the 600,000 year climate history that scientists have reconstructed from ice cores and tree rings.

One way to quantify the relative importance of natural variations compared to those caused by people is to calculate the climate "forcing" of each factor individually. In this way, scientists have shown that changes in the concentration of carbon dioxide (CO2) in the Earth's atmosphere are at least 5 times more important to global warming than any changes in the Sun. The skeptics argue that the atmospheric CO2 concentration is changing because of temperature changes on the Earth, rather than the other way around. In fact, scientists have shown that changes in the Earth's orbit over thousands of years lead to natural changes in global temperature (periodic ice ages) that also cause natural changes in the CO2 concentration. But this predictable effect cannot explain the extraordinary warming that the Earth has experienced in recent times.

Another point raised by skeptics is that for several decades after 1945, global temperatures were falling even though the atmospheric CO2 concentration was rising. This is true, but there is a very simple explanation: in addition to the warming effect of CO2, common pollution in the form of particulate matter called "aerosols" has a cooling effect on the climate. Prior to the clean-air legislation enacted in the 1960's and 1970's, the cooling from aerosols overwhelmed the warming from additional CO2. As developing countries such as China and India adopt similar clean-air measures, this may actually accelerate global warming in the future.

By raising plausible doubts about the responsibility of humans for global warming in modern times, skeptics are trying to confuse the public into inaction. If climate scientists successfully communicate these subtle effects to the public, the skeptics will ultimately fail.

Friday, March 23, 2007

The Magnetic Sun

This week, the recently launched "Hinode" satellite returned some stunning new photos and video of our Sun. Focusing near the edge of our star, the space telescope documents the turbulent boiling of the solar surface in exquisite detail. But look a little closer and you will notice that as the hot material flows away from the surface, it does not simply stream off in any direction. It follows the invisible lines of a pervasive and dynamic magnetic field.

Galileo was the first to point a telescope at the Sun, revealing the dark spots that litter the surface. We now know that these "sunspots" are areas where the magnetic field is stronger, inhibiting the boiling motion and keeping the surface cooler -- and thus darker -- than its surroundings. Each spot is enormous, typically the size of our entire planet. But sunspots are only the beginning of the story of our magnetic Sun.

If you watched the Sun closely over many years, and you counted the total number of sunspots regularly, you might notice an interesting pattern. Every 11 years, the Sun seems to show a few sunspots, then many more, and then fewer again. What's more, when there are only a few spots they seem to show up in two bands, about halfway between the Sun's equator and poles. Over the course of this 11 year "solar cycle" they increase in number, migrate toward equator, and gradually fade away.

As the decades go by, you would notice that some of the cycles are stronger than others -- generating far more sunspots during the peak. Best of all, you would undoubtedly notice the huge explosions on the Sun's surface that eject hot gas out into space, sometimes directly at the Earth. When there are many sunspots, these explosions are more frequent and more dangerous. They are powerful enough to threaten astronauts and orbiting satellites, disrupt our communications systems, and occasionally bring down electricity grids.

With this new eye in the sky, astronomers will study the underlying order in these patterns -- eventually helping us predict the explosions and protect ourselves from the boiling magnetic Sun.

Friday, March 9, 2007

Astronomer Surplus

This week, as part of my work with the American Astronomical Society's Committee on Employment, I've been digging up statistics on the relative rates of training and employment of young astronomers. As in many sciences, the production rate of new Ph.D. astronomers by universities is completely decoupled from the global demand for trained scientists. This has created a huge surplus of young astronomers -- there are now about 3 new Ph.D. recipients annually for every new tenure-track job in astronomy.

The job market has responded by creating more and more temporary (2-3 year) "postdoctoral" positions -- a sort of holding pattern for young scientists who are seeking an academic or research career. In the long term, there appears to be no easy solution to the problem, since the incentive of the university system is to use as many graduate students as possible for cheap skilled labor, without regard to their long-term job prospects. Essentially, overproduction appears to be built into the system -- making the mathematical formulation of surplus production of astronomers similar to that for industrial pollution models, an unintended side-effect of the production process.

What I found in the numbers surprised me. Although the current situation is clearly unsustainable, it was much worse a decade ago -- with nearly 7 times as many Ph.D. recipients in 1995 than new tenure-track jobs. While the number of new "permanent" positions steadily increased throughout the late-1990's, the number of new Ph.D. astronomers gradually declined. After the turn of the century, something else happened. The number of new astronomers being produced by the system leveled off, but new postdoctoral positions grew dramatically. With fewer graduate students around, all of those new university professors had to hire postdocs to get the work done.

Of course this only tells part of the story. There has also been recent growth in the number of non-tenure-track lecturer, research, and support positions. This is just one example of the larger cultural shift to temporary employment that is happening throughout society -- it is not unique to astronomy. It may not be in the best interests of science, but there it is.

Wednesday, February 28, 2007

Pluto and Planethood

Today NASA's "New Horizons" mission, launched just over 13 months ago, will fly past Jupiter on its way to Pluto. The giant planet will provide a gravitational boost to the spacecraft, helping it reach the edge of our solar system by 2015. Over the past few decades, NASA satellites have visited Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune -- but this is the first mission ever to visit Pluto. Meanwhile, astronomers have decided that Pluto should no longer be considered a planet.

To the average person, it probably seemed ridiculous when the International Astronomical Union announced last August that Pluto would henceforth be known as a "dwarf planet" -- the prototype of a new class of objects in the outer solar system. It even led to a satirical headline reading "NASA Launches Probe To Inform Pluto Of Demotion". However, there were legitimate scientific developments that compelled astronomers to adopt a new definition of planet -- it was just unfortunate that this new definition removed Pluto from the list.

Starting in 1992, astronomers began to discover many small icy objects outside the orbit of Neptune that appeared similar to comets, but which never came close enough to the Sun to evaporate and develop tails. As time went by and the technologies for detecting these objects improved, surveys began to identify some larger examples. In the last few years, astronomers found several that are comparable in size to Pluto -- and even one that is larger! Theories suggested that there were likely to be hundreds or thousands of such objects in the outer solar system, so classifying them all as new planets could create real problems for school children trying to remember them all.

Since Pluto appeared to be just one of the larger members of this class of objects, it fell victim to the new classification scheme. Like many political decisions, the available choices were limited to bad (define planet in a way that excludes Pluto) or worse (bestow the title of planet on hundreds of new objects). Conspicuously absent was an alternative proposal to adopt a new definition of planet that would avoid such proliferation, while honoring the historical status of Pluto as an exception to the new rule. When the IAU meets again 3 years from now, I suspect that such an alternative will be considered by the astronomers -- with plenty of time to spare before "New Horizons" reaches its final destination.

Tuesday, February 20, 2007

Killer Asteroid Politics

This past weekend, a group of scientists and former astronauts met in San Francisco to discuss the possibilities for averting disaster if one of the hundreds of known potentially hazardous asteroids were found to be on a collision course with the Earth. They were motivated, in part, by the recent discovery that one such asteroid -- known as "99942 Apophis" -- will skim very close to the Earth in 2029, and has a significant chance of actually hitting the Earth seven years later. The central question is: if precise observations during the 2029 passage reveal that Apophis will hit in 2036, what should we do about it?

You might think that these astronomers are just being alarmist. After all, there have been several recent occasions when the news media report on an asteroid that might hit the Earth -- only to retract the claim a few days later, after additional observations rule out a collision. The primary source of these reports is a list maintained by the Minor Planet Center at the Harvard- Smithsonian Center for Astrophysics. Consider the position of the scientists. They are certainly aware that additional observations will often rule out a future impact -- but if they withhold the early predictions they are accused of a cover-up. So instead they update their predictions continuously, the newspapers report on an uncertain impact, and the astronomers are accused of fear-mongering. It's a no-win situation.

Considering the possible consequences of an asteroid impact, I would rather know about it as far ahead of time as possible. It's similar to the early predictions by meteorologists tracking the path of a hurricane. The uncertainties grow larger as they extrapolate the observations further from the storm's current location -- but the advance warning helps residents of the potentially affected areas to begin preparing for the worst. In the case of Apophis, this might mean placing the entire planet on alert, but at least we would have seven years to devise and execute a plan for avoiding doomsday.

The age of the dinosaurs came to a sudden end when a large asteroid struck near the Yucatan peninsula in the Gulf of Mexico. If humans are smart enough, we can avoid a similar fate.

Wednesday, February 7, 2007

Budget Uncertainties

More than 4 months into the current fiscal year, the U.S. government still hasn't passed a budget. The administration has already released its budget request for the next fiscal year, which begins in October. This is not the first time we've seen such long delays in the funding of government programs -- including scientific research and development -- and it probably won't be the last. But these annual delays undermine the ability of federal agencies to engage in the long-term planning that could improve the overall efficiency of government.

After the elections in November, the lame-duck Congress passed only 2 of the 11 appropriations bills needed to keep the government running. So, while the Departments of Defense and Homeland Security were fully funded, all other federal programs were asked to continue operating at last year's budget levels through mid-February. The idea was to force the newly elected Congress to spend its first weeks debating the unfinished business of the outgoing Congress. But it didn't work, and in late January the incoming Congress was poised to extend last year's funding levels through the end of this year.

This was a particularly unpleasant prospect for science funding, since several federal agencies (including the National Science Foundation) had been promised significant budget increases this year as part of the American Competitiveness Initiative announced in the State of the Union address in 2006. Without an appropriations bill, this extra funding would simply disappear. Fortunately, last week Congress included a last-minute provision to restore the promised budget increases for several agencies that support scientific research.

A typical grant from the NSF to an individual researcher lasts for 3-5 years, so this effectively sets a minimum planning timescale for the agency. Long annual budget delays create serious inefficiencies in the system -- inflation erodes the value of last year's budget dollar, forcing program cuts to make up any gap, and budget increases that arrive late need to be spent on a shorter timescale. There must be a better way to fund science.

Wednesday, January 31, 2007

Engineering the Climate

This week the media got a sneak preview of the most recent 5-year study from the Intergovernmental Panel on Climate Change -- a United Nations group of more than 500 scientists from around the globe. The report, which will officially be released this Friday, concludes that "humans have already caused so much damage to the atmosphere that the effects of global warming will last for more than 1,000 years." The good news is: we haven't reached the tipping point yet -- there's still time to reverse the damage we've done and avoid the most severe consequences of climate change.

But some scientists have already started to think about the worst case scenario. What if we don't have the political will to break our addiction to fossil fuels and overconsumption before it's too late? In this case, we might want to consider more drastic measures -- like devising a technological fix, as a last ditch effort to save ourselves.

One such idea, soon to be published in the Journal of the British Interplanetary Society, is to shade the Earth slightly for several decades by creating huge dust clouds in semi-stable orbits near the Moon. The dust could be obtained by deflecting a nearby comet to this region of space and then grinding it up -- but this has the disadvantage of possibly causing the comet to strike the Earth itself and destroy all life as we know it. The other potential source of dust is the Moon. There's plenty of dust there, but we would need to launch it into orbit. This is somewhat easier on the Moon, since the gravity is weaker and there is no atmospheric drag, but it is still a formidable challenge.

To obtain the necessary amount of lunar dust, the author estimates that we would need to launch "about 300 metric tons/s for 10 years" and that "the energy can be derived directly from the Sun". The amount of energy required is about 2% of the current global demand for energy, hundreds of times more solar power capacity than we currently have on Earth -- and we need it on the Moon! If we cannot manufacture solar panels on the Moon, then we would need to launch them from the Earth -- and this would cost about 300 times the current U.S. national debt. This is much more expensive than simply blanketing the Earth with solar panels now -- a technological fix to the climate problem before it gets out of hand.

Thursday, January 11, 2007

The Earth from Space

In a live conversation from the International Space Station last night, Indian-American astronaut Sunita Williams told a group of school children in India that "Space is an amazing place for all. Here there are no borders, and the world is very peaceful". Sunita traveled to the ISS aboard the space shuttle Discovery, and plans to work there for the next six months.

The view of a world without borders may be the greatest benefit of making space tourism more accessible to the people of Earth in the future. But with a current price tag of about $20 million, few people can afford the trip. Several entrepreneurs are developing concepts for bringing space travel to the masses, and they are already busy building "spaceports" in places like New Mexico and west Texas. Competition between these companies will help push the price down by a factor of 100, but there are still relatively few people who will be able to afford a $200,000 seat.

Fortunately, an ongoing project by NASA is bringing the view of our planet without borders (or even clouds!) to computer screens around the globe. No doubt you have already seen the impressive composite image of the Earth, pieced together from satellite data obtained at different times and places when there were no clouds to block the view. NASA's "Blue Marble" project is now generating such images every month, so we can watch the surface of the Earth changing over time. At the highest resolution, each pixel in these new images spans just 500 meters on the ground.

Maybe if more people see these images and begin to think of the Earth as a place without borders, we can all live in the peaceful world that Sunita was talking about.