The Dwarf Planet Known as Eris is More Massive than Pluto, New Data Shows

PASADENA, Calif.—Die-hard Pluto fans still seeking redemption for their demoted planet have cause for despair this week. New data shows that the dwarf planet Eris is 27 percent more massive than Pluto, thereby strengthening the decree last year that there are eight planets in the solar system and a growing list of dwarf planets.

According to Mike Brown, the discoverer of Eris, and his graduate student Emily Schaller, the data confirms that Eris weighs 16.6 billion trillion kilograms. They know this because of the time it takes Eris's moon, Dysnomia, to complete an orbit.

"This was Pluto's last chance to be the biggest thing found so far in the Kuiper belt," says Brown, a professor of planetary astronomy at the California Institute of Technology. "There was a possibility that Pluto and Eris were roughly the same size, but these new results show that it's second place at best for Pluto."

Eris was discovered in 2005 with Palomar Observatory's 48-inch Samuel Oschin Telescope, an instrument specially adapted to do comprehensive searches for objects in the sky.

When it became apparent that Eris was similar in size if not larger than Pluto, Brown and others called for the International Astronomical Union to rule on its planetary status. The end result was demotion of Pluto and the redesignation of it and other Kuiper-belt objects as dwarf planets.

Schaller says that the new results, obtained with Hubble Space Telescope and Keck Observatory data, indicate that the density of the material making up Eris is about two grams per cubic centimeter. This means that Eris very likely is made up of ice and rock, and thus is very similar in composition to Pluto. Past results from the Hubble Space Telescope had already allowed planetary scientists to determine that its diameter is 2,400 kilometers, also larger than Pluto's.

"Pluto and Eris are essentially twins—except that Eris is slightly the pudgier of the two," says Brown. "And a little colder," adds Schaller.

The reason for Eris's blustery surface conditions is its sheer distance from the sun. Currently 97 astronomical units from the sun (an astronomical unit being the distance between the sun and Earth), Eris hovers at temperatures well below 400 degrees Fahrenheit and is pretty dark.

However, things get a little better on Eris now and then. Orbiting the sun on a highly elliptical 560-year journey, Eris sweeps in as close to the sun as 38 astronomical units. But at present it is nearly as far away as it ever gets.

Pluto's own elliptical orbit takes it as far away as 50 astronomical units from the sun during its 250-year revolution. This means that Eris is sometimes much closer to Earth than Pluto, although never closer than Neptune.

Based on spectral data, the researchers think Eris is covered with a layer of methane that has seeped from the interior and frozen on the surface. As in the case of Pluto, the methane has undergone chemical transformations, probably due to the faint solar radiation, causing the methane layer to redden. But the methane surface on Eris is somewhat more yellowish than the reddish-yellow surface of Pluto, perhaps because Eris is farther from the sun.

As for Dysnomia, the tiny satellite remains the only moon discovered orbiting Eris so far. Dysnomia is about 150 kilometers in diameter, is about 37,000 kilometers from Eris, and has a lunar "month" that lasts 16 days.

"But every year is 560 Earth-years," says Brown. "So on Eris they have a lot more months in their calendar."

Like the Earth-moon system, Eris-Dysnomia probably formed about 4.5 billion years ago following a massive collision.

Brown and Schaller are the authors of a paper, "The Mass of Dwarf Planet Eris," appearing in the June 15 issue of the journal Science.

The search for new planets and other bodies in the Kuiper belt is funded by Caltech and NASA. For more information on the program, see the Samuel Oschin Telescope's website at http://www.astro.caltech.edu/palomarnew/sot.html.

For more information on Mike Brown's research, see http://www.gps.caltech.edu/~mbrown.

To learn more about Eris, see http://www.planeteris.com.

An Eris image is available at http://www.gps.caltech.edu/~mbrown/planetlila/moon/hst.jpg

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Caltech Astrophysicist Peter Goldreich Wins $1 Million International Shaw Prize

PASADENA, Calif.—Peter Goldreich, the Lee A. DuBridge Professor of Astrophysics and Planetary Physics, Emeritus, has been named winner of the 2007 Shaw Prize for astronomy by the Shaw Prize Foundation of Hong Kong. The announcement was made Tuesday, June 12, at foundation headquarters in Hong Kong.

Goldreich is one of four winners of the prize, which is awarded each year in the fields of astronomy, life sciences and medicine, and the mathematical sciences. This year's other recipients are Robert Lefkowitz of Duke University Medical Center, Robert Langlands of the Institute for Advanced Study, and Richard Taylor of Harvard University.

Goldreich, who spends half his time at the Institute for Advanced Study, was cited by the Shaw Prize Foundation for his "lifetime achievements in theoretical astrophysics and planetary sciences." A native of New York, Goldreich joined the Caltech faculty in 1966 and took emeritus status in 2002, although he remains active in research.

Goldreich once described himself as a "general-purpose theoretician in astrophysics." His work has involved fundamental research into phenomena such as the dynamics of planetary rings, pulsars, masers, the spiral arms of galaxies, the rotation of planets as well as their orbital resonances, and the oscillations of the sun. His past papers have covered a range of topics, from why Saturn's rings have sharp edges, to how stars send out coherent microwaves, or masers, in a manner similar to lasers on Earth, to how the moon Io affects the radio bursts of Jupiter.

His current research is focused on planet formation and turbulence in magnetized fluids.

Among Goldreich's past honors is the 1995 National Medal of Science, which is generally regarded as America's highest scientific honor.

The Shaw Prize is an international award to honor individuals who are currently active in their respective fields and who have achieved distinguished and significant advances, who have made outstanding contributions in culture and the arts, or who in other domains have achieved excellence. The award is dedicated to furthering societal progress, enhancing quality of life, and enriching humanity's spiritual civilization. Each recipient of the Shaw Prize receives an award of $1 million.

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Caltech Seismologist Hiroo Kanamori Awarded Kyoto Prize by Inamori Foundation

PASADENA, Calif.—Hiroo Kanamori, one of the world's leading authorities on earthquakes, has been awarded the 23rd annual Kyoto Prize by the Inamori Foundation of Japan. The announcement was made today in Kyoto.

According to the Inamori Foundation, Kanamori is being awarded the honor for his "significant contributions to understanding the physical processes of earthquakes and developing seismic hazard mitigation systems to protect human life."

Kanamori is the John E. and Hazel S. Smits Professor of Geophysics, Emeritus, at the California Institute of Technology. A former director of the Seismological Laboratory at Caltech, he is widely known among earthquake scientists for a variety of important contributions. In 1977 he devised a moment-magnitude scale for determining the magnitudes of very large earthquakes, based on the amount of energy they release. Known as energy magnitude measurements, the method accounted for the effect of seismic waves with very long periods that were not accounted for by earlier methods.

Using the improved method, scientists were able to obtain more precise measurements of the energy of large earthquakes that occurred in the past, such as the 1960 Chilean earthquake and the 1964 Alaskan earthquake, as well as a better means of studying and analyzing seismic events when they occur.

Kanamori has also worked on the nature of tsunamis, particularly the relationship between ground motion and generation of giant sea waves that can have devastating consequences for coastline habitation. These "tsunami earthquakes" release most of their energy in very long-period seismic waves that do not necessarily cause precipitous shaking, but can nonetheless create huge ocean waves. He has also been a longtime advocate of automated early-warning systems to let populations know when a seismic event has occurred that could result in a tsunami.

Kanamori earned his doctorate in geophysics at the University of Tokyo in 1964. He came to Caltech as a postdoctoral researcher the following year, and after stints at MIT and the University of Tokyo, returned to Caltech as a full professor in 1972.

He is a member of the American Academy of Arts and Sciences, a past president of the Seismological Society of America, and winner of the National Academy of Sciences Day Prize and the Japan Academy Prize.

Kanamori will share this year's Kyoto Prize with Pina Bausch, director and choreographer of the Tanztheater Wuppertal Pina Bausch, and Hiroo Inokuchi, a materials scientist who has made fundamental contributions to organic molecular electronics. Kanamori, Inokuchi, and Bausch will each receive a cash gift of 50 million yen (approximately $410,000 at the current exchange rate), a Kyoto Prize Medal of 20-karat gold, and a diploma, and will be feted at a special weeklong event at Kyoto beginning November 9.

The Inamori Foundation was established in 1984 by Kazuo Inamori, founder and chairman emeritus of Kyocera and KDDI Corporation. The prize was created in 1985, in line with Inamori's belief that individuals have "no higher calling than to strive for the greater good of society," and that humanity's future "can be assured only when there is a balance between our scientific progress and our spiritual depth."

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Astronomers Find Their Third Planet With Novel Telescope Network

PASADENA, Calif.—Astronomers using the Trans-atlantic Exoplanet Survey (TrES) network of small telescopes are announcing today their discovery of a planet twice the mass of Jupiter that passes in front of its star every 31 hours. The planet is in the constellation Hercules and has been named TrES-3 as the third planet found with the TrES network.

The new planet is the 15th transiting planet discovered so far-in other words, it is a planet that passes directly in front of its home star as seen from Earth. Three of these transiting planets have been found with the TrES global network of small telescopes utilizing mostly amateur-astronomy components and off-the-shelf four-inch camera lenses.

When a transiting planet passes directly between Earth and the star, the result is a slight reduction in the light in a manner similar to that caused by the moon's passing between the sun and Earth during a solar eclipse. According to Francis O'Donovan, a graduate student in astronomy at the California Institute of Technology, "When TrES-3 is in front of the star, it blocks off about 2.5 percent of the star's light, which is an effect we can observe with our TrES telescopes."

"TrES-3 is an unusual planet as it orbits its parent star in just 31 hours," says Georgi Mandushev, Lowell Observatory astronomer. "That is to say, the year on this planet lasts less than one and a third Earth days." This means it is very close to the star—much closer than Mercury is to the Sun—and so is heated by the intense starlight to about 1,500 degrees Kelvin. The planet is about 1,500 light-years from Earth.

To look for transits, the small telescopes are automated to take wide-field timed exposures of the clear skies on as many nights as possible. When an observing run is completed for a particular field—usually over an approximate two-month period—astronomers measure very precisely the light from every star in the field in order to detect the possible signature of a transiting planet.

In order to accurately measure the size and other properties of the planet, astronomers also made follow-up observations of the planet with one of the 10-meter Keck telescopes atop Mauna Kea, Hawaii; with the telescopes at Lowell Observatory and the Fred L. Whipple Observatory in Arizona; and with the Las Cumbres Observatory Global Telescope in Hawaii.

These observations were made by members of the TrES and the Hungarian Automated Telescope Network (HATNet) teams. Francis O'Donovan praised the teamwork between TrES and HATNet: "The search for extrasolar planets is an exciting and competitive field. I was happy to see that cooperation between separate teams led to a rapid confirmation of this planet."

Francis O'Donovan's paper about the discovery of this extrasolar planet, "TrES-3: A Nearby, Massive, Transiting Hot Jupiter in a 31-hour Orbit," has been accepted for publication by the Astrophysical Journal. The paper's other authors are Georgi Mandushev of the Lowell Observatory; Gaspar Bakos, David Latham, Alessandro Sozzetti, Robert Stefanik, David Charbonneau, and Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics; Timothy Brown, Nairn Baliber, and Marton Hidas of the Las Cumbres Observatory Global Telescope; Geza Kovacs of the Konkoly Observatory in Hungary; Mark Everett and Gilbert Esquerdo of the Planetary Science Institute; Markus Rabus, Hans Deeg, and Juan Belamonte of the Instituto de Astrofisica de Canarias in Tenerife, Spain; and Lynne Hillenbrand of the California Institute of Technology.

This research is funded by NASA through the Origins of Solar Systems Program. The paper is available online at http://arxiv.org/abs/0705.2004.

 

 

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Some Earth-like Worlds May Have Foliage of Colors Other Than Green, Researchers Say

PASADENA, Calif.—In the next decade, when scientists are able to study Earth-sized worlds around other stars, they may find that foliage on some of the planets is predominantly yellow—or orange, or red. It all depends on the color of the star the planet orbits and the stuff that makes up the planet's atmosphere.

That's the conclusion of researchers from the Virtual Planetary Laboratory, a NASA-funded initiative at the California Institute of Technology, who are announcing today results from a series of comprehensive computer models for guiding the future search for plant life on other worlds. Two related papers on what to expect out of photosynthesis are being issued in the journal Astrobiology.

Determining the range of possible colors is important because scientists need to know what to look for when they begin getting spectra of light from faraway Earth-sized planets, says lead author Nancy Kiang, a biometeorologist at NASA's Goddard Institute for Space Studies, and currently a visitor at Caltech's Spitzer Science Center.

"The dominant color of photosynthesis could be yellow, or orange, or maybe red," Kiang explains. "I think it is unlikely that anything will be blue—and, of course, green plants are also a possibility, since that's what we have here."

"What makes this study unusual is the highly interdisciplinary method by which planetary scientists, atmospheric scientists, biologists, and others have pooled their efforts in modeling the possible spectra of light available to plants on Earth-like planets orbiting around other stars," says Vikki Meadows, an astrobiologist at Caltech and lead scientist of the Virtual Planetary Laboratory. Because the study requires data about everything from the type of photons given off by a main-sequence star in a particular stage of its life, to the depth of water that an aqueous plant might prefer, a huge variety of information is required.

"No single astronomer or biologist or atmospheric scientist could have attacked this problem individually to get the simulation," says Meadows, who is herself an astrobiologist whose original academic training was in astronomy. "So these papers are truly interdisciplinary pieces of work."

The researchers focused on the way plants use light for energy to produce sugar—which is pretty much the definition of photosynthesis—because photosynthetic pigments must be adapted to the available light spectrum. The available light spectrum at a planet's surface is a result of both the light from the parent star and filtering effects of gases in the atmosphere. For example, ozone absorbs ultraviolet light, so that not much reaches Earth's surface.

"It turns out that the spectrum of the number of particles of light is what is important, and on Earth there are more particles in the red," Kiang explains. "This could explain why plants here on Earth are mainly green."

On Earth, plants absorb blue light because it is energetic, and red light because the photons are plentiful. There is more than enough energy from the blue and red in sunlight, so plants do not really need more. Therefore, they reflect away relatively more green light, which is why plants appear green to us.

A planet orbiting a star with the size and temperature roughly like our sun, and with Earth's particular mix of oxygen and what-have-you, would tend to have plants that like to soak up light in blue and red and less in green. But the situation could be different on other planets, where other colors of the spectrum might predominate. In those cases, another color like red might not be so useful, and the plants would mostly appear red.

There are many other factors, such as the role not only ozone plays but also carbon dioxide and water vapor, how the stellar radiation creates chemical reactions in the atmosphere, whether the star is prone to solar flares, how much water is on the planet, how much light gets to the surface, what gases are produced by the plants themselves, and so on. This is why a complex computer model was necessary.

Also, one might wonder what things could live on a planet with very little ozone, for example, where radiation would be a daily assault on living organisms, and energetic particles from solar winds would be like deadly microscopic bullets. Meadows says the modelers have taken such scenarios into consideration, and they think that there might be a "sweet spot" a few to tens of feet below the surface of the water where life is protected from UV radiation.

"We found that the sweet spot could be up to nine meters underwater for a planet orbiting a star significantly cooler than our sun, and photosynthesis could still take place," she says. "Something with a floatation capability could be protected from solar flares and still get enough photons to carry on."

In short, the new model provides a powerful tool for looking for life on other worlds, Meadows says.

"We once thought that planets around other stars were exceedingly rare," she explains. "But every time telescopes have gotten better, we've been able to find more and more Jupiter-sized planets. So there's no reason to think that there aren't a huge number of Earth- sized planets out there as well.

"We may not find anything like ourselves, but it's possible that bacterial life is prevalent on these Earth-like planets," Meadows adds. "If we have the environment for life to exist, then we think that it's likely that life will emerge in these conditions."

The other authors of the two papers are Antigona Segura-Peralta, Giovanna Tinetti, Martin Cohen, Janet Siefert, and David Crisp, all of the Virtual Planetary Laboratory, Govindjee, of the University of Illinois, and Robert Blankenship, of Washington University.

The Virtual Planetary Laboratory was formed as part of the NASA Astrobiology Institute, which was founded in 1997 as a partnership between NASA, 12 major U.S. teams, and six international consortia. NAI's goal is to promote, conduct, and lead integrated multidisciplinary astrobiology research and to train a new generation of astrobiology researchers.

For related images, please visit

http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html.

 

 

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Caltech's Planet Hunter Mike Brown Wins Annual Feynman Prize for Teaching

PASADENA, Calif.—On a campus where scientific research can be pretty challenging for the uninitiated, Mike Brown's search for new bodies in the outer solar system is as refreshingly straightforward as, well, the brightly colored marble spheres that sit on his shelf. Each sphere represents a Kuiper-belt object he has found in the last few years, including Eris, which led to the demotion of Pluto to the status of "dwarf planet."

Brown's approach to science is obviously to the taste of California Institute of Technology students as well, because they recently threw their support behind his nomination for the annual Feynman Prize, which is Caltech's most prestigious teaching honor. The prize is given to a faculty member each year for "exceptional ability, creativity, and innovation in both laboratory and classroom instruction," and is in honor of the Nobel Prize-winning physicist Richard Feynman, a favorite teacher and still a powerful influence on campus 19 years after his death.

"I'm thrilled," Brown said after the award was announced. "I never interacted with Feynman, but the people who have won the award in the past are the teachers I have a huge amount of respect for. So it's a fantastic honor."

Brown becomes the fourteenth recipient of the Feynman Prize, which carries a $3,500 award and an equal raise in salary. Brown is also probably one of the few recipients thus far who didn't personally know Richard Feynman.

Nonetheless, Brown structures his classroom methods in a manner reminiscent of the award's namesake, who was also noteworthy for his fresh and original approach to teaching. Brown says that paying close attention to methodology, and to coming up with the best educational outcome for his students, is the only way to go.

"Teaching is terrifying," he says. "It's the most stressful thing I do. I have given countless presentations over the years about my research, but talking at the Air and Space Museum [which he did in mid-March] is nothing like the classroom experience."

One challenge in teaching is the Caltech culture itself, Brown says. A difficult school for everyone, especially undergraduates, Caltech is legendary for the sheer amount of homework and the high expectations on students. Not surprisingly, the students in turn are themselves very astute and quite capable of discriminating between really effective teaching strategies and mediocre ones.

"Around here, you always feel like you're just keeping your head above water when you lecture students," he says. "You can't teach and not have some off days, and you know all too well when you're having one-it's easy to see when the students are engaged and when they're not.

"I guess that's why I try so hard to teach well—I hate that feeling of knowing the students realize I'm having an off day."

According to Caltech provost Paul Jennings, who announced Brown's receipt of the award at a recent faculty meeting, Brown has been singled out for the award because of "his extraordinary teaching ability, his skill in exciting his students, and his evident caring about his students' learning.

"Mike is first recognized for his contribution to Geology 1, Earth and Environment, which he has taught since spring 2005," said Jennings. "Although he himself is an astronomer, well-known for his discovery of a large object in the outer solar system with a diameter greater than Pluto, the possible 'tenth planet,' he volunteered to teach Ge 1 because he wanted to learn the geology material himself."

Brown says that one of his innovations in teaching the Ge 1 course was a type of homework assignment that required students to travel to nearby Eaton Canyon in order to answer homework problems by observation. One of the students who supported his nomination added that his lecture style is also memorable: "Attending a fun and engaging lecture to break the monotony of core classes was the best part of our day."

In his graduate-level course, "Formation and Evolution of Planetary Systems," Brown is also credited by students for making them feel as if they are part of the scientific process. "We could watch the formation of the solar system unfold in front of us, like a good book that we couldn't put down," a graduate student wrote.

Brown says he loves teaching both the graduate and undergraduate classes. Another assumption he bases his preparations for Ge 1 on is that Caltech's science students can benefit intellectually from a different type of lab experience than the ones they encounter in their major courses.

"Ge 1 is a class for nonmajors," he explains. "At a state university, you often find 'rocks for jocks' courses, which are designed for people who aren't going into science but are just trying to get their degrees. Here, we don't have any nonscientists, so the question is what is going to expand their horizons."

The answer Brown has come up with is that geology for scientists who are not themselves geologists should focus on the field as an observational science. "In geology, you take what you're given-you can't drill to the center of Earth to see what's there, or go back in time to see what happened, so the laboratory experience is different from the one in chemistry or physics or biology."

As for the graduate course, the class is designed to give geologists a bit more physics than they may have had as undergraduates. But like the undergraduate course, Brown has also worried about precisely what experience is likely to be of the most intellectual benefit to scientists working in other fields.

"The graduate course is probably the most intuitively taught physics class on campus," he says. "For me, if you can't talk the equation out, you don't really understand it, so everything in the class is aimed at making the physics accessible to geologists who don't need to get heavily into the theoretical aspects, but really need to understand certain equations to do their work."

The son of a NASA engineer, Brown grew up in Huntsville, Alabama, where the nearby presence of the Marshall Space Flight Center and its legendary director Werner von Braun, as well as the Redstone Arsenal, whetted his appetite for all things space-related. Brown attended Princeton University as an undergraduate, and then changed coasts for a doctorate in astronomy from Berkeley.

As for Brown's reputation as a researcher, one need only read the news to find his name associated with a major discovery. In mid-March, Brown and his graduate students Kristina Barkume, Darin Ragozzine, and Emily Schaller reported in the journal Nature that one of the Kuiper-belt objects Brown previously discovered, 2003 EL61, shows evidence of having been struck by a smaller body 4.5 billion years ago. The discovery is important because it reveals new insights into the dynamics of solar-system formation—knowledge that could help us better understand our own home system as well as systems in those galaxies far, far away.

A faculty member at Caltech since 1997, Brown is currently a professor of planetary astronomy. Among the other classes he has taught are Applications of Physics to the Earth Sciences, Observational Planetary Astronomy, Planetary Interiors, and Introduction to the Solar System.

The Feynman Prize is endowed through the generosity of Ione and Robert E. Paradise, with additional contributions from Mr. and Mrs. William H. Hurt, to annually honor a professor who demonstrates, in the broadest sense, unusual ability, creativity, and innovation in undergraduate and graduate classroom or laboratory teaching. Winners are selected by a committee of students, former winners, and other faculty.

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Kuiper-belt Object Was Broken up by Massive Impact 4.5 Billion Years Ago, Study Shows

PASADENA, Calif.—In the outer reaches of the solar system, there is an object known as 2003 EL61 that looks like and spins like a football being drop-kicked over the proverbial goalpost of life.

Still awaiting a more poetic name, 2003 EL61 largely escaped the media hubbub during last year's demotion of Pluto, but new findings could make it one of the most important of the Kuiper-belt objects for understanding the workings of the solar system. In this week's Nature, the original discoverer of the body, Mike Brown, announces with his colleagues that an entire family of bodies seems to have originated from a catastrophic collision involving 2003 EL61 about the time Earth was forming.

Brown and his team base their assumptions on similar surface properties and orbital dynamics of smaller chunks still in the general vicinity. They conclude that 2003 EL61 was spherical and nearly the size of Pluto until it was rammed by a slightly smaller body about 4.5 billion years ago, leaving behind the football-shaped body we see today and a couple of moons, as well as many more fragments that flew away entirely.

"Some of these chunks are still in orbit around the sun and very near the orbit of 2003 EL61 itself," says Brown, a professor of planetary astronomy at the California Institute of Technology. "The impact made a tremendous fireball, and large icy chunks of the big object split off and went flying into space, leaving behind a huge ice-covered rock spinning end over end every four hours.

"It spins so fast that it has pulled itself into the shape of an American football, but one that's a bit deflated and stepped on," Brown adds.

A significant part of the finding is that the collision occurred in a region of space where orbits are not very stable. "In most places, things go around the sun minding their own business for 4.5 billion years and nothing happens," says Brown. "But in a few places, though, orbits go crazy and change and eventually objects can find themselves on a trajectory into the inner solar system, where they would be what we would then call comets."

As a consequence, many of the shards probably made their way to the inner solar system, and a few have undoubtedly hit Earth in the past. The study thus provides new ideas about how the solar system evolves, and how comets fit into the big picture.

Brown adds that 2003 EL61 will put on quite a show in about a billion years, if anyone is still around to enjoy it.

"It's a long time to wait, but 2003 EL61 could become by far the largest comet in eons," Brown says. "It will be something like 6,000 times brighter than Hale-Bopp a few years ago."

The other authors of the paper are Kristin Barkume, Darin Ragozzine, and Emily Schaller, all graduate students in planetary science at Caltech.

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Astronomers Puzzled by Spectra of Transiting Planet Orbiting Nearby Star

PASADENA, Calif.—A team of astronomers led by Carl Grillmair of the California Institute of Technology has discovered some puzzling things about a Jupiter-sized planet that passes in front of a nearby star in the constellation Vulpecula.

Both the Grillmair team and groups from NASA's Goddard Space Flight Center and NASA's Jet Propulsion Laboratory are reporting today on their independent findings about two transiting exoplanets. These are the first spectra from planets outside our own solar system, and have been made possible by the NASA Spitzer Space Telescope's unexpectedly keen ability to study nearby stars.

According to Grillmair, an astronomer at Caltech's Spitzer Science Center, the planet studied by his group is named HD 189733b. The planet is about 62 light-years, or 360 trillion miles away from Earth, is about 10 percent larger than Jupiter, and has a "year" that lasts only two days. It orbits the star HD 189733, which is somewhat smaller and slightly redder than our own sun. And unexpectedly, the data doesn't show the presence of water.

"It's surprising," says Grillmair. "According to what the theoreticians tell us, we had expected to see a very structured spectrum that would have a particular shape because of the presence of water in the planet's atmosphere. But what we actually see is a very flat spectrum."

Spectral data is good for determining what's in a star—or planet, for that matter—because different substances can look very different when the light from them is split into separate colors by a prism. Scientists in the 19th century discovered that burning a substance and then looking at its light through a prism was an excellent way of figuring out what was being burned, and roughly the same procedure has been used ever since for finding out about the light-emitting things in the universe.

The problem with exoplanets, however, has been that the light of the star can be billions of times brighter than the planet itself. As a result, astronomers have previously been unable to study the spectra of planets outside our solar system due to the sheer distance and their inability to distinguish planet light from starlight.

"Normally, trying to see a planet next to a star is like trying to see a firefly next to an airport searchlight several miles away," Grillmair explains. "But in the case of our planet and the one being reported by the other teams, you can take the combined spectrum of the star and planet, and then when the planet passes behind the star, take another spectrum. By subtracting the second spectrum of just the star from the first, you can divine the spectrum of the planet itself."

Another key element to this discovery is that the observations are done in the infrared. The contrast between the star and the planet isn't as large in the infrared, so researchers can tease out the infrared spectrum of the planet. It remains impossible, with current technology, to do this in the visible light, even for transiting planets.

As for the apparent lack of water, Grillmair says there are at least four possibilities. First of all, there could really be no water, which he feels is not very likely. Second, there could be some other chemicals in the planet's atmosphere that emit radiation just where water absorbs it, thereby effectively camouflaging the signature of the water. This too seems unlikely. Third, the water could be hidden underneath an opaque cloud layer the Spitzer telescope can't see through. Fourth, a theoretical model suggests that, if the planet is in tidal lock (in other words, is so close to its sun that the same side always faces the same way), the atmospheric temperature profile on the day-side of the planet could be such that spectral features are suppressed.

But whatever the case, Grillmair thinks that a healthy collection of additional data during the Spitzer's final year or two of life could settle the matter—and teach us much about the worlds beyond our solar system.

"We really need more data to hammer this thing and knock down the noise," he says. "There will be 17 eclipses during the next year that will be visible to Spitzer, and I'd really like to look at every one of them."

So far, Grillmair and his team have been able to observe the planet for a total of 12 hours during two eclipses. A nearly tenfold increase in data would allow positive identifications of individual chemical elements, which has not been possible with the data returned so far.

"This type of data will undoubtedly be one of Spitzer's greatest legacies," Grillmair says. "Transiting extrasolar planets hadn't even been discovered when the Spitzer Space Telescope was designed, so this was all unanticipated."

NASA's Jet Propulsion Laboratory, located in Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA.

The other members of Grillmair's team are David Charbonneau of the Harvard-Smithsonian Center for Astrophysics; Adam Burrows of the Steward Observatory; Lee Armus, John Stauffer, Victoria Meadows, and Deborah Levine, all of the Spitzer Science Center; and Jeffrey Van Cleve of Ball Aerospace and Technologies Corp.

The Grillmair team's results will be published in an upcoming issue of Astrophysical Journal Letters. A report on the Goddard Space Flight Center team's study of the transiting exoplanet HD 209458b is being published this week in the journal Nature.

A separate paper by the JPL-led team on HD 209458b has been submitted to the Astrophysical Journal Letters. The JPL team, led by Mark Swain, also includes Caltech's Rachel Akeson and Chas Beichman

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Geologists Provide New Evidence for Reason Behind Rise of Life in Cambrian Period

PASADENA, Calif.—Geologists have uncovered evidence in the oil fields of Oman that explains how Earth could suddenly have changed 540 million years ago to favor the evolution of the single-celled life forms to the multicellular forms we know today.

Reporting in the December 7 issue of the journal Nature, researchers from MIT, the California Institute of Technology, and Indiana University show that there was a sudden change in the oxygenation of the world's oceans at the time just before the "Cambrian explosion," one of the most significant adaptative radiations in the history of life. With a increased availability of oxygen, the team speculates, single-celled life forms that had dominated the planet for the previous three billion years were able to evolve into the diverse metazoan phyla that still characterize life on Earth.

"The presence of oxygen on Earth is the best indicator of life," says coauthor John Grotzinger, the Fletcher Jones Professor of Geology at Caltech and an authority on sedimentary geology. "But it wasn't always that way. The history of oxygen begins about two and a half billion years ago and occurs in a series of steps. The last step is the subject of this paper."

The key insight was derived when Grotzinger's student Dave Fike, who is lead author of the paper, analyzed core samples and drillings taken at a depth of about three kilometers from oil wells in Oman, which are known to have the oldest commercially viable oil on the planet. The results of carbon and sulfur isotopic analyses from the material led the team to the conclusion that the oceanic conditions that laid down the deposits originally in Oman were quite different from conditions of today.

"You need a very different ocean for these conditions to exist—more like the Black Sea of today, with an upper oxidized layer and lower reduced layer with very little oxygen," says Grotzinger. "The ocean today is pretty well oxidized at all layers, but the ocean before the Cambrian period must have been very different."

When organic matter falls into an ocean that doesn't stir, it becomes deprived of sufficient oxygen and cannot survive as multicellular forms. For this reason, with a limited amount of oxygen, life continued in its single-celled form for the first three billion years.

But about 550 million years ago, according to the team's geologic evidence, the deep ocean began mixing its contents with the shallow ocean, resulting for the first time in a fully oxidized deep ocean.

Characterizing the study as paleoceanography, Grotzinger says the evidence is persuasive because it is so clearly evident in the rock record. Geologists have long believed that the rise of oxygen was a key element involved in the Cambrian radiation, so this discovery really helps solidify that hypothesis.

The oxygen trigger helps account for how life 500 million years ago could have gone from its single-celled existence to the emergence just 10 to 15 million years later of all the metazoan phyla we know today. In short, an abrupt increase in the availability of oxygen may have led to the diversity and complexity of life.

Fike is a graduate student at MIT who is currently in residence at Caltech to work with his professor, Grotzinger, who himself came to Caltech from MIT last year. The other authors of the paper are Lisa Pratt of Indiana University and Roger Summons of MIT.

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Robert Tindol
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Anticipating Another Sumatran Tsunami

PASADENA, Calif.—Research by the California Institute of Technology, the University of Southern California, and Indonesian scientists indicates that within the next few decades another big tsunami could flood densely populated sections of western coastal Sumatra, south of those that suffered from the tsunami of December 2004.

Four researchers at Caltech and USC have modeled the dynamics of past and plausible future tsunamis.

They hope that such detailed calculations of tsunami characteristics will speed preparations that could save lives. Their work will appear in the Proceedings of the National Academy of Sciences (PNAS) on December 4.

Kerry Sieh, a professor of geology at Caltech and one of the participants in the study, explained, "When we tell people living along this 700-kilometer section of the Sumatran coast that they will likely experience a big tsunami within the next 30 years, they ask for details. How much time after the earthquake will they have before the tsunami strikes? How big will the waves be? How far inland should they be prepared to run? What areas are likely to suffer tsunami damage? This paper is our first attempt to answer these important questions."

The same big fault, or megathrust, that caused the tsunami of 2004 extends much farther southeastward, beneath the Indian Ocean, just off the southwest coast of Sumatra. Rupture of this section of the megathrust, under the Mentawai Islands, produced two great quakes and tsunamis in 1797 and 1833. Such events appear to recur on average every 230 years.

Samples of coral from the islands show how much these previous quakes lifted the seafloor. The patterns of uplift gave the scientists the information they needed to do computer simulations of the historical tsunamis. Costas Synolakis, director of the USC Viterbi School of Engineering's Tsunami Research Center, says that the impact of the computed 1797 and 1833 tsunamis is consistent with historical accounts.

This consistency increased the scientists' confidence in using the same model to evaluate worst-case scenarios for future tsunamis, which, according to Jose Borrero, lead author of the study, "confirm a substantial exposure of coastal Sumatran communities to tsunami surges." For example, two river valleys near Bengkulu, a coastal city of about 350,000 people, experience flooding that extends up to several kilometers inland.

In the models of future tsunamis, offshore islands appear to shield the larger city of Padang somewhat, but even there the 1797 tsunami reportedly carried a 200-ton English ship into the town, approximately a kilometer upstream, and smaller vessels were carried yet further.

"The population of Padang in 1797 and 1833 was a few thousand," Sieh says. "Now it is about 800,000, and most of it is within a few meters of sea level. We hope that these initial results will help focus educational efforts, emergency preparedness activities, and changes in the basic infrastructure of cities and towns along the Sumatran coast," Adds Synolakis, "The message of the 2004 tsunami has not been lost in the research community. We are trying to be proactive and help prevent a disaster like Aceh in 2004."

This tsunami study is the work of four Southern California researchers. Jose Borrero is a scientist at USC's Tsunami Research Center. Kerry Sieh is the Robert P. Sharp professor of geology at Caltech. Mohamed Chlieh is a postdoctoral scholar at Caltech's Tectonics Observatory. Costas Synolakis is a professor in the department of civil and environmental engineering in the USC Viterbi School of Engineering and director of its Tsunami Research Center.

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John Avery
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