Andrew Howard: Exploring New Worlds

Extrasolar planets, the newly discovered denizens of the Universe, have opened a new era in astronomy. Since the first exoplanet orbiting a Sun-like star was discovered in 1995, more than 3,500 other worlds have been found orbiting nearby stars. Hundreds more await confirmation.

Andrew Howard studies the formation and evolution of such planetary systems and is particularly interested in the diversity of smaller planets.

Stars outshine planets by factors of a few thousand to a few billion, making the dim light of planets very difficult to see. To avoid this problem, NASA’S Kepler Space Telescope detects planets by looking for the faint dimming that occurs when a distant planet crosses in front of its parent star, causing the star’s light to fade slightly. The smaller the planet, the weaker the dimming, so brightness measurements must be exquisitely precise.

Artist’s impression of the first Earth-sized rocky exoplanet, discovered by Andrew Howard and his collaborators. Art by Karen Teramura

In 2013, Howard’s team found the first Earth-sized planet with a density like that of Earth—albeit uninhabitable since it has a temperature between 3500 and 5000 degrees F. The planet was discovered using a combination of data from the Kepler spacecraft and analysis of its spectrum by the Keck Telescope’s HIRES spectrograph on Maunakea.

Based on Kepler’s space mission data, astronomers estimate that there could be as many as 40 billion rocky Earth-size exoplanets orbiting in habitable zones of Sun-like stars and red dwarfs within the Milky Way. It is estimated that 11 billion of these planets may be orbiting Sun-like stars. The nearest Earth-sized planet was recently found just 4 light years away.

“One in five stars like our Sun has planets approximately the size of Earth in an orbit warm like our Earth, and with a surface temperature conducive to life. People have been asking if there is life out there for thousands of years: we are now living in an age when we may actually answer that question.” – Andrew Howard