Tightly spaced planets inside an alien solar system known as Kepler-80 boast a rare orbital configuration. Mariah MacDonald, an undergraduate, and Darin Ragozzine, an assistant professor of physics and space sciences, both at Florida Institute of Technology, led the study.
The unusual planetary array deepens the ongoing examination of similar systems known as STIPs (Systems with Tightly-spaced Inner Planets) and contributes to understanding how Earth formed. MacDonald and Ragozzine gratefully acknowledge the support of 11 coauthors.
Credit: Third Party Reference
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 Kepler Space 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’ 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.
Credit: Third Party Reference
These properties are not uncommon for exoplanets, but having precise compositional estimates for multiple planets in the same 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 the same configuration every 27 days,” said Ragozzine. This effect is known as a “resonance” and helps the system remain gravitationally stable.
The study explained the origin of the synchronized orbits 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 in the Kepler-80 system.
Credit: Third Party Reference
Kepler has discovered hundreds of other STIPs, which consist of three to seven relatively small and closely packed planets that complete orbits in 1 to 100 days. This new form of planetary system, quite different from our own solar system, is changing the way scientists think about how planets form, including the Earth. With all the knowledge gained by the analysis of Kepler-80, this system is granting important insight into how STIPs formed.
Reference: https://phys.org/journals/astronomical-journal/
