University of Rochester

Astronomer's Baby Planet Makes RedNova Top Ten Science List

January 6, 2005

In a look back at the major space discoveries of 2004, the work of the Mars rovers certainly tops the list, but astronomers at the University of Rochester have made the 2004 RedNova list with a planet discovery of their own. In June, Dan Watson, professor of physics and astronomy at the University, detected the youngest planet ever discovered, orbiting a star more than 420 light years away. The discovery was made using the new infrared Spitzer Space Telescope, which was partially developed by University of Rochester astronomers. is a science web site dedicated to astronomy news.

The planet cannot be seen directly, but Spitzer's Infrared Spectrograph instrument clearly showed that an area of dust in the disk was missing, strongly suggesting the presence of a planet. The dust in the disk is hotter in the center near the star and so radiates most of its light at shorter wavelengths than the cooler outer reaches of the disk. The research team found that there was an abrupt dearth of light radiating at all short infrared wavelengths, strongly suggesting that the central part of the disk was absent. Scientists know of only one phenomenon that can tunnel such a distinct "hole" in the disk during the short lifetime of the star—a planet at least 100,000 years old.

CoKu Tau 4, the million-year-old star around which the new planet circles, is a baby by stellar standards. By comparison, our sun is roughly 4.5 billion years old. The presence of a planet around so young a star challenges the leading theories of how planets form, most of which suggest the process takes at least several million years.

The baby planet so disrupted the current models of planet formation that many scientists assumed its discovery was an error, but in November, Adam Frank, professor of physics and astronomy at the University, showed that there was a sound model to explain the planet's formation. Intriguingly, working from the original team's data, Rochester researchers revealed that the planet was likely smaller than most extra-solar planets discovered thus far—about the size of Neptune—and that it is also about the same distance from its parent star as our own Neptune is from the Sun. Most extra-solar planets discovered to date are much larger and orbit extremely close to their parent star.

The critical infrared "eyes" of the infrared telescope were designed in part by physics and astronomy professors Judith Pipher, William Forrest, and Watson, a team that has been among the world leaders in opening the infrared window to the universe. It was Forrest and Pipher who were the first U.S. astronomers to turn an infrared array toward the skies. In 1983, they mounted a prototype infrared detector onto the University telescope in the small observatory on top of the Wilmot Building on campus, taking the first-ever telescopic pictures of the moon in the infrared, a wavelength range of light that is invisible to the naked eye as well as to most telescopes. The effort attracted colleagues and supporters, culminating 20 years later in the launch of the Spitzer Space Telescope and the discovery of the toddler planet.

RedNova's list of 2004 achievements in space science can be seen at