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American Today


Space: Dust’s Final Frontier?

By Mike Unger

Photo: Physics Department Chair U.J. Sofia

Physics Department chair U. J. Sofia

Even space is dusty.

Small particles of solid matter, roughly the size of those in cigarette smoke, exist between stars. This interstellar dust is a particular nuisance to many astrophysicists, whose views of faraway stars are altered by cosmic grains, as it’s also known.

But to U. J. Sofia, this space dirt is his life’s work.

“In astronomy and astrophysics, you can’t take a piece of something and stick it under a microscope, or break it apart, or dissolve it in a solution,” said Sofia, chair of AU’s physics department. “We get all of our information from light. What interstellar dust does is distort light from a very distant object. If that light is distorted, it gives us a distorted view of the star. The reason NASA gives me money is because everyone else cares about the distortion. I care about the dust.”

For that astrophysicists are grateful. Sofia is one of only about 200 people in the world studying the topic, and his latest research, showing that there appears to be more carbon in the dust than previously thought, will be published in Astronomical Journal.

He gets almost all his data from the Hubble Space Telescope, which captures highly detailed images of light from stars.

“There will be some colors of light, some energies that are missing,” he said. “From that we can tell what gasses are composing the cloud. If we have an idea of what the cloud’s composition is as a whole, if we see less than that in the gas, we know that stuff that’s missing from the gas must be clumped together to form dust.”

Sofia’s research also has been used by scientists studying the overall abundances of elements in the universe. Interstellar dust must be taken into account when contemplating many questions about space.

“There are some fundamental things in the universe that dust could be screwing up,” he said. “In the past 20 years we’ve discovered that the universe seems to be expanding faster and faster and faster with time. Some people don’t believe those results because we’re using objects that are extremely far away to tell us this is happening. Some people believe there is some distortion from dust that’s causing it to look like it’s expanding faster when really it’s not.”

Sofia clearly is enamored with light. He’s teaming up with his father, Yale University astrophysicist Sabatino Sofia, for a new project in which he will attempt to measure the sun’s size and energy variation over time.

“The sun changes its size on minute time scales,” he said. “That’s not going to affect the climate. We’re looking at time scales of decades to centuries; that can affect weather on large scales. Our weather this past year was kind of crazy. People look at that and say the climate’s changing. Scientists look at that and say no, that was a couple of [random] snowstorms. When you look at the weather over the past 100 years, you’ll see that most of the big snowstorms were in the past 20 years. That’s climate, that tells you something.”

The Sofias are the only scientists in the United States who will have access to data from the French microsatellite Picard, which launched on June 15.

“The bottom line, and this is years off, is how much is carbon dioxide actually changing the temperature on the surface of the planet,” Sofia said. “Right now the models that are out there use a model of the sun that is not very precise. We’re trying to get a more precise model of the sun so we better understand what the carbon dioxide is doing.

“The main force of energy on the earth is the sun. If the sun is changing and we don’t know how it’s changing, then it’s hard to know what part of the change in temperature is due to the carbon dioxide and what part is due to the sun. Carbon dioxide per ton might [mean] much less than we think to the temperature on the earth, or it might be more. We just don’t know.”