Researchers Discover New Earth-Sized Planet

Kepler 78b is a fiery planet with an orbit so much smaller than average that it may alter existing planetary theory.

A team of scientists, including Harvard Lecturer in Astronomy David W. Latham, discovered Kepler 78b, a planet outside of our solar system that is a “virtual twin of Earth by astronomical standards,” wrote unaffiliated University of Maryland Astronomy professor L. Drake Deming in a commentary to the science journal Nature.

Kepler 78b’s density of 0.2 pounds per cubic inch is equivalent to the density of the Earth, which suggests that the 3,500 to 5,000 degree Fahrenheit planet and Earth have similar iron and rock compositions.

Dimitar D. Sasselov, a Harvard professor of astronomy who worked on the project, wrote in an email to The Crimson that the research indicates that “planets made of rock and metals are common in the range [of] Earth's size.”

Sasselov said that the discovery opens many doors to new astronomical theory.

“We want to know how common Earth analogs are in order to evaluate habitability and origins of life,” he said.

Deming echoed Sasselov’s point, arguing that the discovery of Kepler 78b “foreshadows leaps forward in the search for life beyond the Solar System.”

But Kepler 78b is also significant for its differences from Earth—and from all other known planets.

“What is unusual about Kepler-78b is its orbit—it will require changes to the existing ideas [and] theories on planet formation,” Sasselov said.

Kepler-78b’s orbit is less than one million miles and takes 8.5 hours to complete.

The short orbiting period has left many astronomers baffled as to how the planet formed or arrived at its current location, said Sasselov.

NASA’s Kepler spacecraft has identified over 150 other planets, including a new class of planets with star orbit periods of under 12 hours, a category under which Kepler 78b falls. With data from the HARPS-N instrument on the Galileo National Telescope of Italy, the mass and density of Kepler 78b was calculated, making it the first of these new planets with a calculated mass.

“Our imagination and scientific prediction power was limited with only one solar system as an example,” said Sasselov.

This article has been revised to reflect the following correction:

CORRECTION: Nov. 8, 2013

An earlier version of this article misattributed Dimitar D. Sasselov’s quotation about imagination and scientific prediction power to astronomy lecturer David W. Latham.