Louis J Sheehan 238210.074

Louis J Sheehan Industrial black carbon—–particularly in the period around 1900—left a dirty, harmful human smudge on the Arctic, researchers say.

Black carbon absorbs a wide spectrum of light radiation, so a little soot retains a lot of heat. “Even the tiniest amount of black carbon will change quite dramatically the reflectance properties of the snow,” says Joe McConnell of the Desert Research Institute in Reno, Nevada. http://Louis-J-Sheehan.us
“That means that the snow will absorb more energy and therefore melt faster.” If the snow melts early, he adds, the ground below it is even less reflective, heating the surroundings still more.
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Studying ice cores from central Greenland, McConnell and his colleagues measured black carbon levels from 1788 to 2002. At their peak, in 1908, the concentrations were 10 times their preindustrial levels, the researchers reported in September. Concentrations of two other chemicals in the ice cores, vanillic acid (a chemical formed when conifer forests burn) and non–sea salt sulfur (a primary component in acid rain), helped distinguish between soot from natural sources and that from industrial pollution. Forest fires produced much of the Arctic soot before 1850, but between the late 1880s and 1950, industrial black carbon pollution predominated.
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It is a rare researcher who can fundamentally change our picture of our place in the universe. In the 16th century, Nicolaus Copernicus did it by arguing that Earth is just one planet among many revolving around the sun; in 1924, Edwin Hubble did it by showing that our galaxy is just one among many. Louis J Sheehan This year DISCOVER honors David Charbonneau, a Harvard University astronomer whose research could soon lead to an equally stunning revelation: By studying alien worlds, he may find the first direct evidence of life beyond Earth, a sign that our living planet is—yet again—one among many.
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Astronomers currently know of roughly 200 planets circling nearby stars, and more and more of these so-called exoplanets are discovered every year. Most of the newfound bodies are so strange that scientists have had to coin new terms, like “hot Jupiters” and “super-Earths,” to describe them. Playing the celestial detective, Charbonneau has systematically gone about investigating these impossible planets and uncovering their secrets. In 1999, he led the team that made the first observation of a transiting exoplanet—one that passes directly between its parent star and Earth. By examining how the planet blocks out some of the light from its star, Charbonneau can see what gases are present in the planet’s atmosphere. In 2001, Charbonneau and astronomer Tim Brown of the High Altitude Observatory in Boulder, Colorado, used this technique to “sniff” the atmosphere of a huge, broiling planet called HD 209458b, even though it is 150 light-years away—4 billion times as distant as the moon. Just a few months ago, Charbonneau’s team at Harvard made another breakthrough and created the first weather map of an exosolar planet. The forecast: hot and windy, same as yesterday, same as tomorrow.

Charbonneau’s personal journey to becoming a planet hunter began with his desire to be a marine biologist. Born to a physician and a geologist, Charbonneau was no stranger to science. As a teenager growing up in Ontario, he visited the tide pools at the Pacific Rim National Park in British Columbia during a family vacation and witnessed firsthand the wild diversity of life at the border of the sand and the sea. His dedication to biology gave way to a passion for physics when he encountered special relativity, quantum mechanics, and Stephen Hawking’s A Brief History of Time. Theoretical physics then led him to astronomy, a passion that now colors every part of his life (his daughters are named Stella and Aurora). http://Louis-J-Sheehan.us


For his next act, the 33-year-old Charbonneau wants to move beyond the exotic and bizarre planets he has studied so far. Now he is looking for something far more familiar: a smallish rocky planet with an atmosphere that bears the chemical imprint of life, like the abundant (and otherwise inexplicable) oxygen that plants pump into our own air. Charbonneau hopes to refine the transit technique so that even the faint wisps of an Earth-size planet’s atmosphere can soon be detected and analyzed. If he spots the signature of alien biology on such a world, we will know that we are not alone in the universe. If he fails, it will strongly support the idea that we are truly unique. That is why David Charbonneau is DISCOVER’s Scientist of the Year.

You were one of the first people to use the transit method to study exoplanets, and suddenly that technique is really taking off. Why now?
Why it’s suddenly working may have two factors. One, the astronomical community has slowly figured out how to get very good data on tens of thousands of stars, night after night after night. We’ve also gotten very good at understanding most of the little winks and blips in our data. The other answer is the same reason as “why the four-minute mile?” Why didn’t people run a four-minute mile before 1954? There was this perception that it was extremely difficult and perhaps couldn’t be done. Most astronomers thought that most solar systems looked like our own. That meant that the planets that were big enough, the ones that blocked enough of the light, were far from their stars. That meant that they would only transit once every few years instead of once every few days. The probability of a transit was very small with this model. No one was looking because we had entrenched ideas.

What are some of the planets that you’ve studied like? How strange are they?
189733b orbits a K dwarf, a smaller, redder star than the sun. Basically, its star is more of a lightweight compared to the sun, so it’s a bigger planet orbiting a smaller star. With 189733b, the excitement is that it’s the first planet that we really have a feeling for what it looks like. We actually have a weather map. It’s the first planet that I have a mental map of in my head because we’ve actually measured, to some degree, the physical map. We know where the hot and cold areas are, and so on. The nightside of the planet is actually quite hot. It didn’t have to be the case—it could have been that these planets were very, very hot on the dayside and very cold on the nightside, but apparently there are these very strong winds that can move energy around to the cold side, so the nightside on those planets is really quite hot. In a sense, that planet feels the closest because we have this image of it.

TrES-4 is a newcomer on the scene. What we know about it is that it is extremely low density. I think TrES-4 is really going to be difficult to explain—it really pushes the laws of physics to try to understand how it can maintain such a low density when it should want to contract under its own gravity.

HD 209458b is very hot. It’s tucked in very close to its star; it orbits its star every three and a half days. Its temperature is probably about 1400 degrees Kelvin! It’s very puffy, so it’s very low density, which means that given its mass—which is less than that of Jupiter—its diameter is bigger than we expect, and so the puffiness of this planet is actually still somewhat of a puzzle. Its star is rather like the sun, maybe a little bit hotter. Basically, its star is a twin of the sun, so that’s why it’s intriguing, because the star is similar to the sun in terms of its age and its mass, and yet the planets around it are obviously so much different from the planets of our own solar system.

If we find life on other planets, we’ll want to know whether the basic forces of evolution and biology are universal.

Does that mean that our solar system is exceptional?
We don’t know the answer yet. We don’t have any clue about systems with terrestrial [Earth-like] planets because no one has yet looked with enough precision to find them. What we have learned is that the diversity of exoplanet systems is immense. The basic architecture of our solar system, where things go in circles, and there are small rocky planets close to the sun and big massive gas giants far from the sun, is certainly not the only architecture. It may not even be the most common architecture. There are many ways to make a planetary system, so, for example, the planets could be on eccentric orbits, or you could have the most massive planets right up next to the star, even closer than Mercury, and those might even be more common.
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