Related Experiment Video
Updated: Jun 9, 2026

Surface Mapping of Earth-like Exoplanets using Single Point Light Curves
Published on: May 10, 2020
Kepler-9: a system of multiple planets transiting a Sun-like star, confirmed by timing variations
Matthew J Holman1, Daniel C Fabrycky, Darin Ragozzine
1Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. mholman@cfa.harvard.edu
Abstract:
The Kepler spacecraft is monitoring more than 150,000 stars for evidence of planets transiting those stars. We report the detection of two Saturn-size planets that transit the same Sun-like star, based on 7 months of Kepler observations. Their 19.2- and 38.9-day periods are presently increasing and decreasing at respective average rates of 4 and 39 minutes per orbit; in addition, the transit times of the inner body display an alternating variation of smaller amplitude. These signatures are characteristic of gravitational interaction of two planets near a 2:1 orbital resonance. Six radial-velocity observations show that these two planets are the most massive objects orbiting close to the star and substantially improve the estimates of their masses. After removing the signal of the two confirmed giant planets, we identified an additional transiting super-Earth-size planet candidate with a period of 1.6 days.
Related Concept Videos
Kepler's Second Law of Planetary Motion
While in an elliptical orbit, the total energy of the planet is conserved. Therefore, the planet slows down when it is at apogee and...
Kepler's Third Law of Planetary Motion
Kepler's First Law of Planetary Motion
Polish astronomer Nikolaus Copernicus put forth a theory that stated a heliocentric model for the solar system. According to this heliocentric theory, all the planets, including Earth, orbit the Sun in circular orbits.
On the other hand,...
Acceleration due to Gravity on Other Planets
Astronomical observations are thus used to measure the acceleration due to gravity on other planets. This can be determined by observing the effect of a planet's gravity on objects close to it. The crucial factor that helps in this...
Circular Orbits and Critical Velocity for Satellites
Nicolaus Copernicus (1473-1543) first suggested that the Earth and all other planets orbit the Sun in...
Detection of Black Holes
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...

