Florida Tech Leads Study of Rare Orbital Configuration Surrounding Kepler-80

The unusual planetary array highlighted in the study deepens the ongoing examination of similar systems known as STIPs – Systems with Tightly-spaced Inner Planets – and contributes to the understanding of how Earth formed.

The findings will be published soon in the Astronomical Journal and are currently available by CLICKING HERE.  MacDonald and Ragozzine gratefully acknowledge the support of 11 coauthors.

Located about 1,100 light years away, Kepler-80, named for the NASA telescope that discovered it, features five small planets orbiting in extreme proximity to their star. MacDonald and Ragozzine determined the nature of the exoplanetary system through measurements taken with the telescope.

As early as 2012, Kepler scientists found that all five planets orbit in an area about 150 times smaller than the Earth’s orbit around the Sun, with “years” of about one, three, four, seven and nine days.

The planets’ close proximity to each other and their star allowed the Kepler Space Telescope to detect tiny variations (about 0.001 percent) in the length of their “years” due to their mutual gravitational interactions.

Analysis by MacDonald and her collaborators revealed that the outer four planets had masses about four- to six-times that of Earth, though they shared Earth’s rocky composition.

All four planets have masses similar to one another, though the two outermost planets are almost twice as big. This was attributed to a very puffy hydrogen/helium atmosphere.

Kepler measures the brightness of stars. The data will look like an EKG showing the heart beat. Whenever a planet passes in front of its parent star as viewed from the spacecraft, a tiny pulse or beat is produced. From the repeated beats we can detect and verify the existence of Earth-size planets and learn about the orbit and size of the planet. (NASA Image)

These properties are not uncommon for exoplanets, but having precise compositional estimates for multiple planets in the same planetary system is rare.

Another rare attribute of the Kepler-80 system is that its planets have “synchronized” orbits. “The outer four planets return to almost exactly the same configuration every 27 days,” said Ragozzine. This effect is known as a “resonance” and helps the system remain gravitationally stable.

The study also explained the origin of the synchronized orbits in general – and possibly the tightly-spaced configuration. In a process called migration, the orbits of these planets shrank over time while they were forming.

Simulations clearly showed that this migration effect caused the planets to lock into synchronized orbits just like those seen with Kepler-80.