Smallest planet in the solar system

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Mercury: The Smallest Planet in the Solar System

Mercury is the smallest planet in our solar system, with a diameter of about 4,880 km, which is only about two-fifths the size of Earth. In fact, some moons, such as Ganymede and Titan, are even larger than Mercury. Mercury is also the closest planet to the Sun, making it unique in both size and position among the solar system's planets .

Comparison with Other Small Planets and Moons

While Mercury is the smallest planet, it is still larger than Mars, which is also significantly less massive than Earth. However, both Mercury and Mars are considered "sub-Earths" due to their smaller size and mass compared to our planet. These sub-Earths are important for understanding the diversity of planetary bodies in our solar system and beyond .

Exoplanets Smaller than Mercury

Recent discoveries have shown that planets even smaller than Mercury exist outside our solar system. For example, the exoplanet Kepler-37b is significantly smaller than Mercury, with a size similar to Earth's Moon. This demonstrates that while Mercury is the smallest planet in our solar system, it is not the smallest planet known in the universe 28.

The Prevalence of Small Planets

Studies of exoplanets reveal that small, rocky planets are very common around Sun-like stars. Many of these exoplanets are similar in size to Mercury or even smaller, and advances in detection methods have allowed astronomers to find and study these tiny worlds. The Kepler mission, in particular, has discovered dozens of confirmed or candidate sub-Earths, expanding our understanding of planetary sizes beyond what is found in our solar system 38.

Conclusion

Mercury holds the title of the smallest planet in our solar system, but ongoing research and discoveries of exoplanets show that even smaller planets exist elsewhere in the universe. These findings help scientists learn more about planet formation and the variety of worlds that exist beyond our solar neighborhood 1238.

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Most relevant research papers on this topic

Mercury the Sunshine Planet

Mercury is the smallest planet in our solar system, with a diameter of 2/5 of that of the Earth, and is the closest to the Sun, named after the Roman god of dealers and thieves.

2015·

0citations

·J. Benkhoff

A sub-Mercury-sized exoplanet

Kepler-37b, a sub-Mercury-sized exoplanet, is likely rocky and without atmosphere or water, similar to Mercury.

Highly Cited

2013·

175citations

·T. Barclay et al.

Occurrence and core-envelope structure of 1–4× Earth-size planets around Sun-like stars

Small, 1–4 Earth-size planets are extremely common around Sun-like stars, with 26% having them with orbital periods under 100 days, and 11% receiving 1–4 the incident stellar light that warms our Earth.

Highly Cited

2014·

83citations

·G. Marcy et al.

The HARPS survey for southern extra-solar planets. II. A 14 Earth-masses exoplanet around μ Arae

A 14 Earth-mass exoplanet has been discovered orbiting the star mu Ara, with a mass slightly smaller than Uranus, and may be considered an ice giant or super-earth planet depending on core-accretion and migration models.

Highly Cited

2004·

181citations

·N. Santos et al.

Kepler-78 and the Ultra-Short-Period planets

Ultra-short-period planets, like Kepler-78b, are common and often smaller than 2 R, often found in compact multi-planet systems, and may be the exposed rocky cores of "gas dwarfs".

Highly Cited

2018·

70citations

·J. Winn et al.

Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST

The James Webb Space Telescope can potentially detect the atmospheres of nine Earth-sized planets, allowing for the first time to probe the formation and evolution processes of terrestrial planetary atmospheres beyond our solar system.

Highly Cited

2017·

221citations

·C. Morley et al.

It's a Small World After All

Japanese astronomers have successfully photographed a new planet, the least massive ever captured on camera, about three times as big as Jupiter.

2020·

24citations

·Module Layout

Below One Earth: The Detection, Formation, and Properties of Subterrestrial Worlds

Advances in astronomical instrumentation and space missions have made it possible to discover and study sub-Earths, with potential implications for planet formation and evolution.

2013·

8citations

·E. Sinukoff et al.

TESS Hunt for Young and Maturing Exoplanets (THYME) XI: An Earth-sized Planet Orbiting a Nearby, Solar-like Host in the 400Myr Ursa Major Moving Group

HD 63433d is the smallest confirmed exoplanet with an age less than 500 Myr, and the nearest young Earth-sized planet.

2024·

1citation

·Benjamin K. Capistrant et al.

Discovery and spectroscopy of the young jovian planet 51 Eri b with the Gemini Planet Imager

The Gemini Planet Imager has discovered a Jupiter-like planet orbiting a young star, offering a new insight into solar system origins and a new era in next-generation planetary imaging.

Highly Cited

2015·

455citations

·B. Macintosh et al.

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