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Kepler's First Law of Planetary Motion

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In the early 17th century, German astronomer and mathematician Johannes Kepler postulated three laws for the motion of planets in the solar system. He formulated his first two laws based on the observations of his forebears, Nikolaus Copernicus and Tycho Brahe.
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Updated: Jun 28, 2026

Surface Mapping of Earth-like Exoplanets using Single Point Light Curves

Surface Mapping of Earth-like Exoplanets using Single Point Light Curves

Published on: May 10, 2020

Direct imaging of multiple planets orbiting the star HR 8799.

Christian Marois¹, Bruce Macintosh, Travis Barman

¹National Research Council Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada. christian.marois@nrc-cnrc.gc.ca

Science (New York, N.Y.)

|November 15, 2008

Summary

Directly imaging exoplanets is challenging but reveals Jupiter-like planets. Observations of the HR 8799 system show three planets with masses 5-13 times Jupiter

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Last Updated: Jun 28, 2026

Surface Mapping of Earth-like Exoplanets using Single Point Light Curves

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Area of Science:

Astronomy and astrophysics
Exoplanetary science
Direct imaging techniques

Background:

Direct imaging of exoplanets is crucial for characterizing atmospheres and finding Earth-like planets.
Challenges include small angular separation and high luminosity contrast between planets and stars.

Purpose of the Study:

To demonstrate the capability of direct imaging for detecting and characterizing exoplanets.
To analyze the HR 8799 system, a benchmark for high-contrast imaging.

Main Methods:

Utilized high-contrast imaging observations from Keck and Gemini telescopes.
Analyzed multi-epoch data to track orbital motion.

Main Results:

Successfully imaged three planets orbiting the star HR 8799 at projected separations of 24, 38, and 68 astronomical units.
Observed counter-clockwise orbital motion for all three planets.
Estimated planetary masses between 5 and 13 Jupiter masses based on luminosity and system age.

Conclusions:

The HR 8799 system serves as an excellent analogue for scaled-up outer solar system architectures.
Direct imaging is a viable method for studying gas giants in wide orbits.
Further characterization of exoplanetary atmospheres is enabled by this technique.