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Faculty Profile: Exoplanet Hunter Joins IfA Faculty

Andrew Howard
Andrew Howard   

Andrew Howard is the newest member of the IfA faculty. He comes to Hawai‘i from the University of California, Berkeley, where he worked with renowned planet hunter Geoff Marcy on the California Planet Survey, which searches for exoplanets (those orbiting a star other than our Sun). In a March 2011 public talk in California, Howard explained how he searched for exoplanets on the Keck I telescope on Mauna Kea using remote observing equipment in the basement of the Berkeley astronomy building. He lamented that while this setup “is nice for having dinner with my wife and kid,” it is “not so good if you want to go to Hawai‘i often.” Well, now he is here.

The subject of Howard’s dissertation was optical SETI (search for extraterrestrial intelligence). He says that “SETI, the search for extrasolar planets, and astrobiology are all ways of answering a common set of questions about our origins, how common planets like Earth are, and our place in the Universe.”

His current research focuses on the origin and evolution of a particular subgroup of exoplanets. “I am especially interested in figuring out the diversity of origins, of compositions, of structures of this new intermediate group of planets between the size of Earth and Neptune.” There are none in our solar system, but scientists are beginning to uncover them in great numbers in other solar systems. Their differences in composition could tell us about their origins.

Howard has been involved with the Kepler mission, a space telescope that is surveying a portion of the sky to find Earth-like planets that eclipse (or “transit”) their stars. His role is to analyze the deluge of Kepler-discovered planets to find patterns in the planet properties and to interpret those patterns in the context of planet formation, migration, evolution, and how common planets of a particular size are.

While Kepler is good at finding large numbers of planets, most of them are much too distant to be studied in detail. For that, Howard and colleagues use the Keck telescope. They look at a smaller number of nearby stars to detect planets and determine their masses and orbits using the radial velocity method, which measures how much an orbiting planet causes its star to wobble. This method is complementary to the work with Kepler, which measures the radius (size) of planets. A very small number of the planets found by the radial velocity method also happen to transit their stars, so Howard and colleagues are able to measure both the radius and mass. With these two measurements they can compute the planet’s density, which tells them what the planet is made of (gas, rock, water, etc.). Sometimes they are able to do “transmission spectroscopy”: As the planet eclipses its host star, the star acts like a giant searchlight shining through the planet’s atmosphere. This enables them to determine what elements and molecules are present in the planet’s atmosphere.

Howard and his wife Sarah have two children, an 11-month-old daughter and a four-year-old son. Time permitting, he enjoys photography and cycling, and would like to take advantage of the opportunities in Hawai‘i to go snorkeling and hiking.