Related Experiment Video
Updated: May 6, 2026

06:48
Surface Mapping of Earth-like Exoplanets using Single Point Light Curves
Published on: May 10, 2020
3.0K
A rocky composition for an Earth-sized exoplanet.
Andrew W Howard1, Roberto Sanchis-Ojeda, Geoffrey W Marcy
1Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA.
Nature
|November 1, 2013
Summary
Researchers measured the mass of Earth-sized exoplanet Kepler-78b using Doppler spectroscopy. Its density is similar to Earth's, suggesting a rocky composition, providing insights into exoplanet diversity.
Area of Science:
- Exoplanetary Science
- Stellar Astrophysics
- Planetary Dynamics
Background:
- Super-Earths and mini-Neptunes (1-4 Earth radii) are common around Sun-like stars.
- Transit photometry determines exoplanet size but not mass or density.
- Mass measurements are crucial for inferring exoplanet composition.
Purpose of the Study:
- To measure the mass and density of the Earth-sized exoplanet Kepler-78b.
- To determine the composition of Kepler-78b.
- To expand mass-density studies to smaller exoplanets.
Main Methods:
- Utilized Doppler spectroscopy to measure the radial velocity shifts caused by Kepler-78b's gravitational pull.
- Combined mass measurements with previously determined radius (1.20 ± 0.09 Earth radii) from transit data.
- Calculated the planet's mean density.
Main Results:
- Kepler-78b has a mass of 1.69 ± 0.41 Earth masses.
- The calculated mean density is 5.3 ± 1.8 g/cm³.
- This density is comparable to Earth's density.
Conclusions:
- Kepler-78b is likely composed of rock and iron, similar to Earth.
- This study demonstrates the feasibility of characterizing Earth-sized exoplanets.
- The findings contribute to understanding the diversity of planetary compositions.
Related Concept Videos
Conditions on Early Earth
2.5K
2.5K
Conditions on Early Earth
67.1K
Around 4 billion years ago, oceans began to condense on earth while volcanic eruptions released nitrogen, carbon dioxide, methane, ammonia, and hydrogen into the primordial atmosphere. However, organisms with the characteristics of life were not initially present on earth. Scientists have used experimentation to determine how organisms evolved that could grow, reproduce, and maintain an internal environment.
67.1K
Minerals
1.7K
Minerals are essential nutrients that the human body needs in small amounts to work properly. They play a vital role in many bodily functions, such as building strong bones and transmitting nerve impulses. Some minerals are needed for hormone production or to maintain a normal heartbeat. Major minerals include calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium, while trace minerals include iron, manganese, copper, iodine, zinc, cobalt, fluoride, and selenium.
Major...
Major...
1.7K
The Soil Ecosystem
17.5K
Plants obtain inorganic minerals and water from the soil, which acts as a natural medium for land plants. The composition and quality of soil depend not only on the chemical constituents but also on the presence of living organisms. In general, soils contain three major components:
17.5K
Acceleration due to Gravity on Other Planets
3.4K
The gravitational acceleration of an object near the Earth's surface is called the acceleration due to gravity. It can be measured by conducting simple experiments on Earth. However, such an experiment is impossible to conduct on the surface of 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...
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...
3.4K
Kepler's First Law of Planetary Motion
4.9K
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.
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,...
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,...
4.9K

